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Sun GlassFish Enterprise Server v3 Prelude Developer's Guide

Chapter 7 Developing Web Applications

This chapter describes how web applications are supported in the Sun GlassFish Enterprise Server and includes the following sections:

For general information about web applications, see “Part One: The Web Tier” in the Java EE 5 Tutorial.

Packaging an EJB JAR File in a Web Application

The Enterprise Server supports the EJB 3.1 specification, which allows EJB JAR files to be packaged in WAR files. EJB classes must reside under WEB-INF/classes. For example, the structure of a hello.war file might look like this:

index.jsp
META-INF/
   MANIFEST.MF
WEB-INF/
   web.xml
   classes/
      com/
         sun/
            v3/
               demo/
                  HelloEJB.class
                  HelloServlet.class

For more information about EJB components, see Chapter 8, Using Enterprise JavaBeans Technology.

Note –

For GlassFish v3 Prelude, EJB modules are not supported unless the optional EJB container add-on component is downloaded from the Update Tool. For information about the Update Tool, see the Sun GlassFish Enterprise Server v3 Prelude Installation Guide.

For GlassFish v3 Prelude, only stateless session beans with local interfaces and entity beans that use the Java Persistence API are supported. Stateful, message-driven, and EJB 2.0 and 2.1 entity beans are not supported. Remote interfaces and remote business interfaces for any of the bean types are not supported.

Using Servlets

Enterprise Server supports the Java Servlet Specification version 2.5.

Note –

Servlet API version 2.5 is fully backward compatible with versions 2.3 and 2.4, so all existing servlets should work without modification or recompilation.

To develop servlets, use Sun Microsystems’ Java Servlet API. For information about using the Java Servlet API, see the documentation provided by Sun Microsystems at http://java.sun.com/products/servlet/index.html.

The Enterprise Server provides the wscompile and wsdeploy tools to help you implement a web service endpoint as a servlet. For more information about these tools, see the Sun GlassFish Enterprise Server v3 Prelude Reference Manual.

This section describes how to create effective servlets to control application interactions running on an Enterprise Server, including standard-based servlets. In addition, this section describes the Enterprise Server features to use to augment the standards.

This section contains the following topics:

Invoking a Servlet With a URL

You can call a servlet deployed to the Enterprise Server by using a URL in a browser or embedded as a link in an HTML or JSP file. The format of a servlet invocation URL is as follows:

http://server:port/context-root/servlet-mapping?name=value

The following table describes each URL section.

Table 7–1 URL Fields for Servlets Within an Application

URL element 

Description 

server:port

The IP address (or host name) and optional port number. 

To access the default web module for a virtual server, specify only this URL section. You do not need to specify the context-root or servlet-name unless you also wish to specify name-value parameters.

context-root

For an application, the context root is defined in the context-root element of the application.xml, sun-application.xml, or sun-web.xml file. For an individually deployed web module, the context root is specified during deployment.

For both applications and individually deployed web modules, the default context root is the name of the WAR file minus the .war suffix.

servlet-mapping

The servlet-mapping as configured in the web.xml file.

?name=value...

Optional request parameters. 

In this example, localhost is the host name, MortPages is the context root, and calcMortgage is the servlet mapping:

http://localhost:8080/MortPages/calcMortgage?rate=8.0&per=360&bal=180000

When invoking a servlet from within a JSP file, you can use a relative path. For example:

<jsp:forward page="TestServlet"/>
<jsp:include page="TestServlet"/>

Servlet Output

ServletContext.log messages are sent to the server log.

By default, the System.out and System.err output of servlets are sent to the server log, and during startup, server log messages are echoed to the System.err output. Also by default, there is no Windows-only console for the System.err output.

You can change these defaults using the Administration Console. Select the Enterprise Server component and the Logging tab. Then check or uncheck Write to System Log. If this box is checked, System.out output is sent to the server log. If it is unchecked, System.out output is sent to the system default location only.

For more information, click the Help button in the Administration Console from the Logging page.

Caching Servlet Results

The Enterprise Server can cache the results of invoking a servlet, a JSP, or any URL pattern to make subsequent invocations of the same servlet, JSP, or URL pattern faster. The Enterprise Server caches the request results for a specific amount of time. In this way, if another data call occurs, the Enterprise Server can return the cached data instead of performing the operation again. For example, if your servlet returns a stock quote that updates every 5 minutes, you set the cache to expire after 300 seconds.

Whether to cache results and how to cache them depends on the data involved. For example, it makes no sense to cache the results of a quiz submission, because the input to the servlet is different each time. However, it makes sense to cache a high level report showing demographic data taken from quiz results that is updated once an hour.

To define how an Enterprise Server web application handles response caching, you edit specific fields in the sun-web.xml file.

Note –

A servlet that uses caching is not portable.

For Javadoc tool pages relevant to caching servlet results, go to https://glassfish.dev.java.net/nonav/api/v3-prelude/index.html and click on the com.sun.appserv.web.cache package.

The rest of this section covers the following topics:

Caching Features

The Enterprise Server has the following web application response caching capabilities:

Default Cache Configuration

If you enable caching but do not provide any special configuration for a servlet or JSP, the default cache configuration is as follows:

Caching Example

Here is an example cache element in the sun-web.xml file:

<cache max-capacity="8192" timeout="60">
<cache-helper name="myHelper" class-name="MyCacheHelper"/>
<cache-mapping>
	<servlet-name>myservlet</servlet-name>
	<timeout name="timefield">120</timeout>
	<http-method>GET</http-method>
	<http-method>POST</http-method>
</cache-mapping>
<cache-mapping>
	<url-pattern> /catalog/* </url-pattern>
	<!-- cache the best selling category; cache the responses to
	   -- this resource only when the given parameters exist. Cache
	   -- only when the catalog parameter has 'lilies' or 'roses'
	   -- but no other catalog varieties:
	  -- /orchard/catalog?best&category='lilies'
	  -- /orchard/catalog?best&category='roses'
	  -- but not the result of
	   -- /orchard/catalog?best&category='wild'
	-->
	<constraint-field name='best' scope='request.parameter'/>
	<constraint-field name='category' scope='request.parameter'>
		<value> roses </value>
		<value> lilies </value>
	</constraint-field>
	 <!-- Specify that a particular field is of given range but the
	   -- field doesn't need to be present in all the requests -->
	<constraint-field name='SKUnum' scope='request.parameter'>
		<value match-expr='in-range'> 1000 - 2000 </value>
	</constraint-field>
	<!-- cache when the category matches with any value other than
	   -- a specific value -->
	<constraint-field name="category" scope="request.parameter>
		<value match-expr="equals" cache-on-match-failure="true">
       bogus
		</value>
	</constraint-field>
</cache-mapping>
<cache-mapping>
	<servlet-name> InfoServlet </servlet-name>
	<cache-helper-ref>myHelper</cache-helper-ref>
</cache-mapping>
</cache>

For more information about the sun-web.xml caching settings, see cache in Sun GlassFish Enterprise Server v3 Prelude Application Deployment Guide.

The CacheKeyGenerator Interface

The built-in default CacheHelper implementation allows web applications to customize the key generation. An application component (in a servlet or JSP) can set up a custom CacheKeyGenerator implementation as an attribute in the ServletContext.

The name of the context attribute is configurable as the value of the cacheKeyGeneratorAttrName property in the default-helper element of the sun-web.xml deployment descriptor. For more information, see default-helper in Sun GlassFish Enterprise Server v3 Prelude Application Deployment Guide.

About the Servlet Engine

Servlets exist in and are managed by the servlet engine in the Enterprise Server. The servlet engine is an internal object that handles all servlet meta functions. These functions include instantiation, initialization, destruction, access from other components, and configuration management. This section covers the following topics:

Instantiating and Removing Servlets

After the servlet engine instantiates the servlet, the servlet engine calls the servlet’s init() method to perform any necessary initialization. You can override this method to perform an initialization function for the servlet’s life, such as initializing a counter.

When a servlet is removed from service, the servlet engine calls the destroy() method in the servlet so that the servlet can perform any final tasks and deallocate resources. You can override this method to write log messages or clean up any lingering connections that won’t be caught in garbage collection.

Request Handling

When a request is made, the Enterprise Server hands the incoming data to the servlet engine. The servlet engine processes the request’s input data, such as form data, cookies, session information, and URL name-value pairs, into an HttpServletRequest request object type.

The servlet engine also creates an HttpServletResponse response object type. The engine then passes both as parameters to the servlet’s service() method.

In an HTTP servlet, the default service() method routes requests to another method based on the HTTP transfer method: POST, GET, DELETE, HEAD, OPTIONS, PUT, or TRACE. For example, HTTP POST requests are sent to the doPost() method, HTTP GET requests are sent to the doGet() method, and so on. This enables the servlet to process request data differently, depending on which transfer method is used. Since the routing takes place in the service method, you generally do not override service() in an HTTP servlet. Instead, override doGet(), doPost(), and so on, depending on the request type you expect.

To perform the tasks to answer a request, override the service() method for generic servlets, and the doGet() or doPost() methods for HTTP servlets. Very often, this means accessing EJB components to perform business transactions, then collating the information in the request object or in a JDBC ResultSet object.

Using JavaServer Pages

The Enterprise Server supports the following JSP features:

For information about creating JSP files, see Sun Microsystem’s JavaServer Pages web site at http://java.sun.com/products/jsp/index.html.

For information about Java Beans, see Sun Microsystem’s JavaBeans web page at http://java.sun.com/beans/index.html.

This section describes how to use JavaServer Pages (JSP files) as page templates in an Enterprise Server web application. This section contains the following topics:

JSP Tag Libraries and Standard Portable Tags

Enterprise Server supports tag libraries and standard portable tags. For more information, see the JavaServer Pages Standard Tag Library (JSTL) page at http://java.sun.com/products/jsp/jstl/index.jsp.

Web applications don’t need to bundle copies of the jsf-impl.jar or appserv-jstl.jar JSP tag libraries (in as-install/lib) to use JavaServerTM Faces technology or JSTL, respectively. These tag libraries are automatically available to all web applications.

Options for Compiling JSP Files

Enterprise Server provides the following ways of compiling JSP source files into servlets:

Creating and Managing Sessions

This chapter describes how to create and manage HTTP sessions that allows users and transaction information to persist between interactions.

This chapter contains the following sections:

Configuring Sessions

This section covers the following topics:

HTTP Sessions, Cookies, and URL Rewriting

To configure whether and how HTTP sessions use cookies and URL rewriting, edit the session-properties and cookie-properties elements in the sun-web.xml file for an individual web application. For more about the properties you can configure, see session-properties in Sun GlassFish Enterprise Server v3 Prelude Application Deployment Guide and cookie-properties in Sun GlassFish Enterprise Server v3 Prelude Application Deployment Guide.

Coordinating Session Access

Make sure that multiple threads don’t simultaneously modify the same session object in conflicting ways.

This is especially likely to occur in web applications that use HTML frames where multiple servlets are executing simultaneously on behalf of the same client. A good solution is to ensure that one of the servlets modifies the session and the others have read-only access.

Saving Sessions During Redeployment

Whenever a redeployment is done, the sessions at that transit time become invalid unless you use the keepSessions=true property of the asadmin redeploy command. For example:


asadmin redeploy --properties keepSessions=true --name hello.war

For details, see the Sun GlassFish Enterprise Server v3 Prelude Reference Manual.

The new class loader of the redeployed application is used to deserialize any sessions previously saved. The usual restrictions about serialization and deserialization apply. For example, any application-specific class referenced by a session attribute may evolve only in a backward-compatible fashion. For more information about class loaders, see Chapter 2, Class Loaders.

Session Managers

A session manager automatically creates new session objects whenever a new session starts. In some circumstances, clients do not join the session, for example, if the session manager uses cookies and the client does not accept cookies.

Enterprise Server offers these session management options, determined by the session-manager element’s persistence-type attribute in the sun-web.xml file:

Note –

If the session manager configuration contains an error, the error is written to the server log and the default (memory) configuration is used.

For more information, see session-manager in Sun GlassFish Enterprise Server v3 Prelude Application Deployment Guide.

The memory Persistence Type

This persistence type is not designed for a production environment that requires session persistence. It provides no session persistence. However, you can configure it so that the session state in memory is written to the file system prior to server shutdown.

To specify the memory persistence type for a specific web application, edit the sun-web.xml file as in the following example. The persistence-type property is optional, but must be set to memory if included. This overrides the web container availability settings for the web application.

<sun-web-app>
...
<session-config>
	<session-manager persistence-type="memory" />
		<manager-properties>
			<property name="sessionFilename" value="sessionstate" />
		</manager-properties>
	</session-manager>
	...
</session-config>
...
</sun-web-app>

The only manager property that the memory persistence type supports is sessionFilename, which is listed under manager-properties in Sun GlassFish Enterprise Server v3 Prelude Application Deployment Guide. The sessionFilename property specifies the name of the file where sessions are serialized and persisted if the web application or the server is stopped. To disable this behavior, specify an empty string as the value of sessionFilename.

For more information about the sun-web.xml file, see Sun GlassFish Enterprise Server v3 Prelude Application Deployment Guide.

The file Persistence Type

This persistence type provides session persistence to the local file system, and allows a single server domain to recover the session state after a failure and restart. The session state is persisted in the background, and the rate at which this occurs is configurable. The store also provides passivation and activation of the session state to help control the amount of memory used. This option is not supported in a production environment. However, it is useful for a development system with a single server instance.

Note –

Make sure the delete option is set in the server.policy file, or expired file-based sessions might not be deleted properly. For more information about server.policy, see The server.policy File.

To specify the file persistence type for a specific web application, edit the sun-web.xml file as in the following example. Note that persistence-type must be set to file. This overrides the web container availability settings for the web application.

<sun-web-app>
...
<session-config>
	<session-manager persistence-type="file">
		<store-properties>
			<property name="directory" value="sessiondir" />
		</store-properties>
	</session-manager>
	...
</session-config>
...
</sun-web-app>

The file persistence type supports all the manager properties listed under manager-properties in Sun GlassFish Enterprise Server v3 Prelude Application Deployment Guide except sessionFilename, and supports the directory store property listed under store-properties in Sun GlassFish Enterprise Server v3 Prelude Application Deployment Guide.

For more information about the sun-web.xml file, see Sun GlassFish Enterprise Server v3 Prelude Application Deployment Guide.

Using Comet

This section explains the Comet programming technique and how to create and deploy a Comet-enabled application with the Sun GlassFish Enterprise Server.

Introduction to Comet

Comet is a programming technique that allows a web server to send updates to clients without requiring the clients to explicitly request them.

This kind of programming technique is called server push, which means that the server pushes data to the client. The opposite style is client pull, which means that the client must pull the data from the server, usually through a user-initiated event, such as a button click.

Web applications that use the Comet technique can deliver updates to clients in a more timely manner than those that use the client-pull style while avoiding the latency that results from clients frequently polling the server.

One of the many use cases for Comet is a chat room application. When the server receives a message from one of the chat clients, it needs to send the message to the other clients without requiring them to ask for it. With Comet, the server can deliver messages to the clients as they are posted rather than expecting the clients to poll the server for new messages.

To accomplish this scenario, a Comet application establishes a long-lived HTTP connection. This connection is suspended on the server side, waiting for an event to happens before being resumed. This kind of connection remains open, allowing an application that uses the Comet technique to send updates to clients when they are available rather than expecting clients to reopen the connection to poll the server for updates.

The Grizzly Implementation of Comet

One limitation of the Comet technique is that you must use it with a web server that supports non-blocking connections in order to avoid poor performance. Non-blocking connections are those that do not need to allocate one thread for each request. If the web server were to use blocking connections then it might end up holding many thousands of threads, thereby hindering its scalability.

The GlassFish server includes the Grizzly HTTP Engine, which enables asynchronous request processing (ARP) by avoiding blocking connections. Grizzly's ARP implementation accomplishes this by using the Java NIO API.

With Java NIO, Grizzly enables greater performance and scalability by avoiding the limitations experienced by traditional web servers that must run a thread for each request. Instead, Grizzly's ARP mechanism makes efficient use of a thread pool system and also keeps the state of requests so that it can keep requests alive without holding a single thread for each of them.

Grizzly supports two different implementations of Comet:

Client Technologies to Use With Comet

In addition to creating a web component that uses the Comet APIs, you need to enable your client to accept asynchronous updates from the web component. To accomplish this, you can use JavaScript, IFrames, or a framework, such as Dojo.

An IFrame is an HTML element that allows you to include other content in an HTML page. As a result, the client can embed updated content in the IFrame without having to reload the page.

The example explained in this tutorial employs a combination of JavaScript and IFrames to allow the client to accept asynchronous updates. A servlet included in the example writes out JavaScript code to one of the IFrames. The JavaScript code contains the updated content and invokes a function in the page that updates the appropriate elements in the page with the new content.

The next section explains the two kinds of connections that you can make to the server. While you can use any of the client technologies listed in this section with either kind of connection, it is more difficult to use JavaScript with an HTTP-streaming connection.

Kinds of Comet Connections

When working with Comet, as implemented in Grizzly, you have two different ways to handle client connections to the server:

HTTP Streaming

The HTTP Streaming technique keeps a connection open indefinitely. It never closes, even after the server pushes data to the client.

In the case of HTTP streaming, the application sends a single request and receives responses as they come, reusing the same connection forever. This technique significantly reduces the network latency because the client and the server don't need to open and close the connection.

The basic life cycle of an application using HTTP-streaming is:

request --> suspend --> data available --> write response --> data available --> write response

The client makes an initial request and then suspends the request, meaning that it waits for a response. Whenever data is available, the server writes it to the response.

Long Polling

The long-polling technique is a combination of server-push and client-pull because the client needs to resume the connection after a certain amount of time or after the server pushes an update to the client.

The basic life cycle of an application using long-polling is:

request -> suspend --> data available --> write response --> resume

The client makes an initial request and then suspends the request. When an update is available, the server writes it to the response. The connection closes, and the client optionally resumes the connection.

How to Choose the Kind of Connection

If you anticipate that your web application will need to send frequent updates to the client, you should use the HTTP-streaming connection so that the client does not have to frequently reestablish a connection. If you anticipate less frequent updates, you should use the long-polling connection so that the web server does not need to keep a connection open when no updates are occurring. One caveat to using the HTTP-streaming connection is that if you are streaming through a proxy, the proxy can buffer the response from the server. So, be sure to test your application if you plan to use HTTP-streaming behind a proxy.

Grizzly Comet

The following sections describe how to use Grizzly Comet.

The Grizzly Comet API

Grizzly's support for Comet includes a small set of APIs that make it easy to add Comet functionality to your web applications. The Grizzly Comet APIs that developers will use most often are the following:

The way a developer would use this API in a web component is to perform the following tasks:

  1. Register the context path of the application with the CometContext object:

    CometEngine cometEngine = 
	CometEngine.getEngine();
CometContext cometContext = 
	cometEngine.register(contextPath)

  2. Register the CometHandler implementation with the CometContext object:

    cometContext.addCometHandler(handler)

  3. Notify one or more CometHandler implementations when an event happens:

    cometContext.notify((Object)(handler))

The Hidden Frame Example

This rest of this tutorial uses the Hidden Frame example to explain how to develop Comet-enabled web applications. You can download the example from grizzly.dev.java.net at Hidden example download. From there, you can download a prebuilt WAR file as well as a JAR file containing the servlet code.

The Hidden Frame example is so called because it uses hidden IFrames. What the example does is it allows multiple clients to increment a counter on the server. When a client increments the counter, the server broadcasts the new count to the clients using the Comet technique.

The Hidden Frame example uses the long-polling technique, but you can easily modify it to use HTTP-streaming by removing two lines. See Notifying the Comet Handler of an Event and Creating the HTML Page That Updates and Displays the Content for more information on converting the example to use the HTTP-streaming technique.

The client side of the example uses hidden IFrames with embedded JavaScript tags to connect to the server and to asynchronously post content to and accept updates from the server.

The server side of the example consists of a single servlet that listens for updates from clients, updates the counter, and writes JavaScript code to the client that allows it to update the counter on its page.

See Deploying and Running a Comet-Enabled Application for instructions on how to deploy and run the example.

When you run the example, the following happens:

  1. The index.html page opens.

  2. The browser loads three frames: the first one accesses the servlet using an HTTP GET; the second one loads the count.html page, which displays the current count; and the third one loads the button.html page, which is used to send the POST request.

  3. After clicking the button on the button.html page, the page submits a POST request to the servlet.

  4. The doPost method calls the onEvent method of the Comet handler and redirects the incremented count along with some JavaScript to the count.html page on the client.

  5. The updateCount JavaScript function on the count.html page updates the counter on the page.

  6. Because this example uses long-polling, the JavaScript code on count.html calls doGet again to resume the connection after the servlet pushes the update.

Creating a Comet-Enabled Application

This section uses the Hidden Frame example application to demonstrate how to develop a Comet application. The main tasks for creating a simple Comet-enabled application are the following:

Developing the Web Component

This section shows you how to create a Comet-enabled web component by giving you instructions for creating the servlet in the Hidden Frame example.

Developing the web component involves performing the following steps:

  1. Create a web component to support Comet requests.

  2. Register the component with the Comet engine.

  3. Define a Comet handler that sends updates to the client.

  4. Add the Comet handler to the Comet context.

  5. Notify the Comet handler of an event using the Comet context.

ProcedureCreating a Web Component to Support Comet

  1. Create an empty servlet class, like the following:

    import javax.servlet.*;

public class HiddenCometServlet extends HttpServlet {
	private static final long serialVersionUID = 1L;
private String contextPath = null;
	@Override
	public void init(ServletConfig config) throws ServletException {}

	@Override
	protected void doGet(HttpServletRequest req, 
	HttpServletResponse res) 
	throws ServletException, IOException {}

	@Override
	protected void doPost(HttpServletRequest req, 
	HttpServletResponse res)
	throws ServletException, IOException {);
}

  2. Import the following Comet packages into the servlet class:

    import com.sun.grizzly.comet.CometContext;
import com.sun.grizzly.comet.CometEngine;
import com.sun.grizzly.comet.CometEvent;
import com.sun.grizzly.comet.CometHandler;

  3. Import these additional classes that you need for incrementing a counter and writing output to the clients:

    import java.io.IOException;
import java.io.PrintWriter;
import java.util.concurrent.atomic.AtomicInteger;

  4. Add a private variable for the counter:

    private final AtomicInteger counter = new AtomicInteger();

ProcedureRegistering the Servlet with the Comet Engine

  1. In the servlet's init method, add the following code to get the component's context path:

    ServletContext context = config.getServletContext();
contextPath = context.getContextPath() + "/hidden_comet";

  2. Get an instance of the Comet engine by adding this line after the lines from step 1:

     CometEngine engine = CometEngine.getEngine();

  3. Register the component with the Comet engine by adding the following lines after those from step 2:

    CometContext cometContext = engine.register(contextPath);
cometContext.setExpirationDelay(30 * 1000);

ProcedureDefining a Comet Handler to Send Updates to the Client

  1. Create a private class that implements CometHandler and add it to the servlet class:

    private class CounterHandler 
	implements CometHandler<HttpServletResponse> {
	private HttpServletResponse response;
}

  2. Add the following methods to the class:

    public void onInitialize(CometEvent event) 
	throws IOException {}

	public void onInterrupt(CometEvent event) 
		throws IOException {
		removeThisFromContext();
	}
	
	public void onTerminate(CometEvent event) 
		throws IOException {
		removeThisFromContext();
	}

	public void attach(HttpServletResponse attachment) {
            this.response = attachment;
	}

	private void removeThisFromContext() throws IOException {
		response.getWriter().close();
		CometContext context = 
			CometEngine.getEngine().getCometContext(contextPath);
		context.removeCometHandler(this);
	}

    You need to provide implementations of these methods when implementing CometHandler. The onInterrupt and onTerminate methods execute when certain changes occur in the status of the underlying TCP communication. The onInterrupt method executes when communication is resumed. The onTerminate method executes when communication is closed. Both methods call removeThisFromContext, which removes the CometHandler object from the CometContext object.

ProcedureAdding the Comet Handler to the Comet Context

  1. Get an instance of the Comet handler and attach the response to it by adding the following lines to the doGet method:

    CounterHandler handler = new CounterHandler();
handler.attach(res);

  2. Get the Comet context by adding the following lines to doGet:

    CometEngine engine = CometEngine.getEngine();
CometContext context = engine.getCometContext(contextPath);

  3. Add the Comet handler to the Comet context by adding this line to doGet:

    context.addCometHandler(handler);

ProcedureNotifying the Comet Handler of an Event

  1. Add an onEvent method to the CometHandler class to define what happens when an event occurs:

    public void onEvent(CometEvent event) 
	throws IOException {
	if (CometEvent.NOTIFY == event.getType()) {
		int count = counter.get();
		PrintWriter writer = response.getWriter();
		writer.write("<script type='text/javascript'>" + 
			"parent.counter.updateCount('" + count + "')" +
			"</script>\n");
		writer.flush();
		event.getCometContext().resumeCometHandler(this);
	}
}

    This method first checks if the event type is NOTIFY, which means that the web component is notifying the CometHandler object that a client has incremented the count. If the event type is NOTIFY, the onEvent method gets the updated count, and writes out JavaScript to the client. The JavaScript includes a call to the updateCount function, which will update the count on the clients' pages.

    The last line resumes the Comet request and removes it from the list of active CometHandler objects. By this line, you can tell that this application uses the long-polling technique. If you were to delete this line, the application would use the HTTP-Streaming technique.

    • For HTTP-Streaming:

      Add the same code as for long-polling, except do not include the following line:

      event.getCometContext().resumeCometHandler(this);

    You don't include this line because you do not want to resume the request. Instead, you want the connection to remain open.

  2. Increment the counter and forward the response by adding the following lines to the doPost method:

    counter.incrementAndGet();
CometEngine engine = CometEngine.getEngine();
CometContext<?> context = 
	engine.getCometContext(contextPath);
context.notify(null);
req.getRequestDispatcher("count.html").forward(req, res);

    When a user clicks the button, the doPost method is called. The doPost method increments the counter. It then obtains the current CometContext object and calls its notify method. By calling context.notify, the doPost method triggers the onEvent method you created in the previous step. After onEvent executes, doPost forwards the response to the clients.

Creating the Client Pages

Developing the HTML pages for the client involves performing these steps:

  1. Create a welcome HTML page, called index.html, that contains: one hidden frame for connecting to the servlet through an HTTP GET; one IFrame that embeds the count.html page, which contains the updated content; and one IFrame that embeds the button.html page, which is used for posting updates using HTTP POST.

  2. Create the count.html page that contains an HTML element that displays the current count and the JavaScript for updating the HTML element with the new count.

  3. Create the button.html page that contains a button for the users to submit updates.

ProcedureCreating a Welcome HTML Page That Contains IFrames for Receiving and Sending Updates

  1. Create an HTML page called index.html.

  2. Add the following content to the page:

    <html>
	<head>
		<title>Comet Example: Counter with Hidden Frame</title>
	</head>
	<body>
  </body>
</html>

  3. Add IFrames for connecting to the server and receiving and sending updates to index.html in between the body tags:

    <frameset>
	<iframe name="hidden" src="hidden_comet" 
		frameborder="0" height="0" width="100%"></iframe>
	<iframe name="counter" src="count.html" 
		frameborder="0" height="100%" width="100%"></iframe>
<iframe name="button" src="button.html" frameborder="0" height="30%" widget="100%"></iframe>
</frameset>

    The first frame, which is hidden, points to the servlet by referencing its context path. The second frame displays the content from count.html, which displays the current count. The second frame displays the content from button.html, which contains the submit button for incrementing the counter.

ProcedureCreating the HTML Page That Updates and Displays the Content

  1. Create an HTML page called count.html and add the following content to it:

    <html>
	<head>
	</head>
		<body>
			<center>
				<h3>Comet Example: Counter with Hidden Frame</h3>
				<p>
				<b id="count">&nbsp;</b>
				<p>
			</center>
		</body>
</html>

    This page displays the current count.

  2. Add JavaScript code that updates the count in the page . Add the following lines in between the head tags of count.html:

    <script type='text/javascript'>
	function updateCount(c) {
		document.getElementById('count').innerHTML = c;
		parent.hidden.location.href = "hidden_comet";
	};
</script>

    The JavaScript takes the updated count it receives from the servlet and updates the count element in the page. The last line in the updateCount function invokes the servlet's doGet method again to reestablish the connection.

    • For HTTP-Streaming:

      Add the same code as for long-polling, except for the following line:

      parent.hidden.location.href = “hidden_comet”

      This line invokes the doGet method of CometServlet again, which would reestablish the connection. In the case of HTTP-Streaming, you want the connection to remain open. Therefore, you don't include this line of code.

ProcedureCreating the HTML Page That Allows Submitting Updates

  1. Create an HTML page called button.html and add the following content to it:

    <html>
	<head>
	</head>
		<body>
			<center>
				<form method="post" action="hidden_comet">
					<input type="submit" value="Click">
				</form>
			</center>
		</body>
</html>

    This page displays a form with a button that allows a user to update the count on the server. The servlet will then broadcast the updated count to all clients.

Creating the Deployment Descriptor

This section describes how to create a deployment descriptor to specify how your Comet-enabled web application should be deployed.

ProcedureCreating the Deployment Descriptor

  1. Create a file called web.xml and put the following contents in it:

    <?xml version="1.0" encoding="UTF-8"?>
	<web-app version="2.5"
		xmlns="http://java.sun.com/xml/ns/javaee"
		xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
		xsi:schemaLocation=
			"http://java.sun.com/xml/ns/javaee 
			http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd ">
			
		<servlet>
			<servlet-name>HiddenCometServlet</servlet-name>
			<servlet-class>
				com.sun.grizzly.samples.comet.HiddenCometServlet
			</servlet-class>
			<load-on-startup>0</load-on-startup>
		</servlet>
		<servlet-mapping>
			<servlet-name>HiddenCometServlet</servlet-name>
			<url-pattern>/hidden_comet</url-pattern>
		</servlet-mapping>
	</web-app>

    This deployment descriptor contains a servlet declaration and mapping for HiddenCometServlet. The load-on-startup attribute must be set to 0 so that the Comet-enabled servlet will not load until the client makes a request to it.

Deploying and Running a Comet-Enabled Application

Before running a Comet-enabled application in the Enterprise Server, you need to enable Comet in the server. Then you can deploy the application just as you would any other web application.

When running the application, you need to connect to it from at least two different browsers to experience the effect of the servlet updating all clients in response to one client posting an update to the server.

ProcedureEnabling Comet in the Enterprise Server

Before running a Comet-enabled application, you need to enable Comet in your application server by adding a special property to the http-listener element of the domain.xml file.

The following steps tell you how to add this property.

  1. Open domain-dir/config/domain.xml in a text editor.

  2. Add the following property in between the http-listener start and end tags:

    <property name="cometSupport" value="true"/>

  3. Save domain.xml and restart the server.

ProcedureDeploying the Example

These instructions tell you how to deploy the Hidden Frame example.

  1. Download grizzly-comet-hidden-1.7.3.1.war.

  2. Run the following command to deploy the example:

    as-install/bin/asadmin deploy grizzly-comet-hidden-1.7.3.1.war

ProcedureRunning the Example

These instructions tell you how to run the Hidden Frame example.

  1. Open two web browsers, preferably two different brands of web browser.

  2. Enter the following URL in both browsers:

    http://localhost:8080/grizzly-comet-hidden/index.html

  3. When the first page loads in both browsers, click the button in one of the browsers and watch the count change in the other browser window.

Bayeux Protocol

The Bayeux protocol, often referred to as Cometd, greatly simplifies the use of Comet. No server-side coding is needed for servers such as Enterprise Server that support the Bayeux protocol. Just enable Comet and the Bayeux protocol, then write and deploy the client as described in the following tasks:

ProcedureEnabling Comet

Before running a Comet-enabled application, you need to enable Comet in your application server by adding a special property to the http-listener element of the domain.xml file.

The following steps tell you how to add this property.

  1. Open domain-dir/config/domain.xml in a text editor.

  2. Add the following property in between the http-listener start and end tags:

    <property name="cometSupport" value="true"/>

  3. Save domain.xml and restart the server.

ProcedureConfiguring the web.xml File

To enable the Bayeux protocol on the Enterprise Server, you must reference the CometdServlet in your web application's web.xml file. In addition, if your web application includes a servlet, set the load-on-startup value for your servlet to 0 (zero) so that it will not load until the client makes a request to it.

  1. Open the web.xml file for your web application in a text editor.

  2. Add the following XML code to the web.xml file:

    <servlet>
   <servlet-name>Grizzly Cometd Servlet</servlet-name>
   <servlet-class>
      com.sun.grizzly.cometd.servlet.CometdServlet
   </servlet-class>
   <init-param>
      <description>
         expirationDelay is the long delay before a request is
         resumed. -1 means never.
      </description>
      <param-name>expirationDelay</param-name>
      <param-value>-1</param-value>
   </init-param>
   <load-on-startup>1</load-on-startup>
</servlet>
<servlet-mapping>
   <servlet-name>Grizzly Cometd Servlet</servlet-name>
   <url-pattern>/cometd/*</url-pattern>
</servlet-mapping>

    Note that the load-on-startup value for the CometdServlet is 1.

  3. If your web application includes a servlet, set the load-on-startup value to 0 for your servlet (not the CometdServlet) as follows:

    <servlet>
   ...
   <load-on-startup>0</load-on-startup>
</servlet>

  4. Save the web.xml file.

ProcedureWriting, Deploying, and Running the Client

The examples in this task are taken from the example chat application posted and discussed at http://weblogs.java.net/blog/jfarcand/archive/2007/02/gcometd_introdu_1.html.

  1. Add script tags to the HTML page. For example:

    <script type="text/javascript" src="chat.js"></script>

  2. In the script, call the needed libraries. For example:

    dojo.require("dojo.io.cometd");

  3. In the script, use publish and subscribe methods to send and receive messages. For example:

    cometd.subscribe("/chat/demo", false, room, "_chat");
cometd.publish("/chat/demo", { user: room._username, chat: text});

  4. Deploy the web application as you would any other web application. For example:


    asadmin deploy cometd-example.war

  5. Run the application as you would any other web application.

    The context root for the example chat application is /cometd and the HTML page is index.html. So the URL might look like this:


    http://localhost:8080/cometd/index.html
See Also

For more information about deployment in the Enterprise Server, see the Sun GlassFish Enterprise Server v3 Prelude Application Deployment Guide.

For more information about the Bayeux protocol, see Bayeux Protocol.

For more information about the Dojo toolkit, see http://dojotoolkit.org/.

For information about pushing data from an external component such as an EJB module, see the example at http://blogs.sun.com/swchan/entry/java_api_for_cometd. Using this Grizzly Java API for Cometd makes your web application non-portable. Running your application on a server that doesn't support Grizzly Comet will not work.

For information about RESTful (REpresentational State Transfer) web services and Comet, see RESTful Web Services and Comet.

Developing Grails Applications

This section shows you how to get started using Groovy on Grails on the Enterprise Server by covering the following topics:

Introduction to Groovy and Grails

Groovy is a dynamic, object-oriented language for the Java Virtual Machine, which builds on the strengths of Java but has additional features inspired by languages such as Python, Ruby, and Smalltalk. For more information about Groovy, see Groovy.

Grails is an open-source web application framework that leverages the Groovy language and complements Java web development. Grails is a stand-alone development environment that can hide all configuration details or allow integration of Java business logic. For more information about Grails, see Grails.

Installing Grails

To develop and deploy Grails applications on the Enterprise Server, first install the Grails plug-in module.

ProcedureInstalling the Grails Plug-in Module

  1. Install the Grails add-on component from the Update Tool.

    For information about the Update Tool, see the Sun GlassFish Enterprise Server v3 Prelude Installation Guide.

  2. Create a GRAILS_HOME environment variable that points to the Grails directory, as-install/grails.

  3. Add the as-install/grails/bin directory to the PATH environment variable.

Example 7–1 Setting UNIX Environment Variables

On Solaris, Linux, and other operating systems related to UNIX, use the following commands for steps 2 and 3:


set GRAILS_HOME=~/glassfish/grails
export GRAILS_HOME
cd $GRAILS_HOME
set PATH=$GRAILS_HOME/bin:$PATH
export PATH
chmod a+x $GRAILS_HOME/bin/*
Example 7–2 Setting Windows Environment Variables

On the Windows operating system, use the following commands for steps 2 and 3:


set GRAILS_HOME=C:\GlassFish\grails
set PATH=%GRAILS_HOME%\bin;%PATH%

Creating a Simple Grails Application

To create the helloworld application, perform both these tasks:

For more information on creating Grails applications, see the Grails Quick Start.

ProcedureCreating the helloworld Application

  1. Go to the as-install/grails/samples directory.

  2. Run the grails create-app helloworld command.

    The grails create-app command creates an application framework that you can modify.

ProcedureCreating the hello Controller

  1. Go to the as-install/grails/samples/helloworld directory.

  2. Run the grails create-controller hello command.

    The grails create-controller command creates a controller file that you can modify.

  3. Edit the generated HelloController.groovy file so it looks like this:

    class HelloController {

       def world = {
                render "Hello World!"
        }
    //def index = { }
}

Deploying and Running a Grails Application

To deploy and run your application, perform one of these tasks:

ProcedureRunning a Grails Application Using run-app

  1. Go to the application directory.

    For example, go to the as-install/grails/samples/helloworld directory.

  2. Run the grails run-app command.

    The grails run-app command starts the Enterprise Server in the background and runs the application in one step. You don't need to create a WAR file or deploy your application.

  3. To test your application, point your browser to http://host:port/app-dir-name.

    For example, point to http://localhost:8080/helloworld. You should see a screen that begins, “Welcome to Grails.” Selecting the HelloController link should change the display to, “Hello World!”

See Also

For details about the grails run-app command, see the Sun GlassFish Enterprise Server v3 Prelude Reference Manual.

ProcedureRunning a Grails Application Using Standard Deployment

  1. Go to the application directory.

    For example, go to the as-install/grails/samples/helloworld directory.

  2. Create the WAR file in one of the following ways:

    • Run the grails war command.

      This command creates a large WAR file containing all the application's dependencies.

    • Run the grails shared-war command.

      This command creates a small WAR file, but requires referencing of the Grails library JAR at deployment.

    In the helloworld application, this step creates the helloworld-0.1.war file.

  3. Deploy the WAR file in one of the following ways:

    • In the Administration Console, open the Applications component, go to the Web Applications page, select the Deploy button, and type the path to the WAR file.

      The path to the helloworld WAR file is as-install/grails/samples/helloworld/helloworld-0.1.war.

      If you used the grails shared-war command, specify the as-install/grails/lib/glassfish-grails.jar file in the Libraries field.

    • On the command line, use the asadmin deploy command and specify the WAR file. For example:


      asadmin deploy helloworld-0.1.war

      If you used the grails shared-war command, specify the libraries using the --libraries option. For example:


      asadmin deploy --libraries $GRAILS_HOME/lib/glassfish-grails.jar helloworld-0.1.war

  4. To test your application, point your browser to http://host:port/war-file-name. Do not include the .war extension.

    For example, point to http://localhost:8080/helloworld-0.1. You should see a screen that begins, “Welcome to Grails.” Selecting the HelloController link should change the display to, “Hello World!”

See Also

For details about the Administration Console, see the online help.

For details about the asadmin deploy command, see the Sun GlassFish Enterprise Server v3 Prelude Reference Manual.

For details about the grails war and grails shared-war commands, see the Grails Quick Start.

For general information about deployment, see the Sun GlassFish Enterprise Server v3 Prelude Application Deployment Guide.

Advanced Web Application Features

This section includes summaries of the following topics:

Internationalization Issues

This section covers internationalization as it applies to the following:

The Server's Default Locale

To set the default locale of the entire Enterprise Server, which determines the locale of the Administration Console, the logs, and so on, use the Administration Console. Select the Enterprise Server component, the Advanced tab, and the Domain Attributes tab. Then type a value in the Locale field. For details, click the Help button in the Administration Console.

Servlet Character Encoding

This section explains how the Enterprise Server determines the character encoding for the servlet request and the servlet response. For encodings you can use, see http://java.sun.com/javase/6/docs/technotes/guides/intl/encoding.doc.html.

Servlet Request

When processing a servlet request, the server uses the following order of precedence, first to last, to determine the request character encoding:

For details about the parameter-encoding element, see parameter-encoding in Sun GlassFish Enterprise Server v3 Prelude Application Deployment Guide.

Servlet Response

When processing a servlet response, the server uses the following order of precedence, first to last, to determine the response character encoding:

Virtual Servers

A virtual server, also called a virtual host, is a virtual web server that serves content targeted for a specific URL. Multiple virtual servers can serve content using the same or different host names, port numbers, or IP addresses. The HTTP service directs incoming web requests to different virtual servers based on the URL.

When you first install the Enterprise Server, a default virtual server is created. You can also assign a default virtual server to each new HTTP listener you create.

Web applications can be assigned to virtual servers during deployment. A web module can be assigned to more than one virtual server, and a virtual server can have more than one web module assigned to it.

If you deploy a web application and don't specify any assigned virtual servers, the web application is assigned to all currently defined virtual servers. If you then create additional virtual servers and want to assign existing web applications to them, you must redeploy the web applications. For more information about deployment, see the Sun GlassFish Enterprise Server v3 Prelude Application Deployment Guide.

For more information about virtual servers, see virtual-server in Sun GlassFish Enterprise Server v3 Prelude Administration Reference.

ProcedureTo Assign a Default Virtual Server

  1. In the Administration Console, open the HTTP Service component under the relevant configuration.

  2. Open the HTTP Listeners component under the HTTP Service component.

  3. Select or create a new HTTP listener.

  4. Select from the Default Virtual Server drop-down list.

    For more information, see Default Web Modules.

See Also

For details, click the Help button in the Administration Console from the HTTP Listeners page.

ProcedureTo Assign Virtual Servers

  1. Deploy the application or web module and assign the desired virtual servers to it.

    For more information, see Sun GlassFish Enterprise Server v3 Prelude Application Deployment Guide.

  2. In the Administration Console, open the HTTP Service component under the relevant configuration.

  3. Open the Virtual Servers component under the HTTP Service component.

  4. Select the virtual server to which you want to assign a default web module.

  5. Select the application or web module from the Default Web Module drop-down list.

    For more information, see Default Web Modules.

See Also

For details, click the Help button in the Administration Console from the Virtual Servers page.

Default Web Modules

A default web module can be assigned to the default virtual server and to each new virtual server. For details, see Virtual Servers. To access the default web module for a virtual server, point the browser to the URL for the virtual server, but do not supply a context root. For example:

http://myvserver:3184/

A virtual server with no default web module assigned serves HTML or JavaServer Pages (JSP) content from its document root, which is usually domain-dir/docroot. To access this HTML or JSP content, point your browser to the URL for the virtual server, do not supply a context root, but specify the target file.

For example:

http://myvserver:3184/hellothere.jsp

Class Loader Delegation

The Servlet specification recommends that a web application class loader look in the local class loader before delegating to its parent. To make the web application class loader follow the delegation model in the Servlet specification, set delegate="false" in the class-loader element of the sun-web.xml file. It’s safe to do this only for a web module that does not interact with any other modules.

The default value is delegate="true", which causes the web application class loader to delegate in the same manner as the other class loaders. Use delegate="true" for a web application that accesses EJB components or that acts as a web service client or endpoint. For details about sun-web.xml, see Sun GlassFish Enterprise Server v3 Prelude Application Deployment Guide.

Note –

For Prelude, the delegate value is ignored and assumed to be set to true.

For general information about class loaders, see Chapter 2, Class Loaders.

Using the default-web.xml File

You can use the default-web.xml file to define features such as filters and security constraints that apply to all web applications.

For example, you can disable directory listings for added security. In your domain's default-web.xml file, search for the definition of the servlet whose servlet-name is equal to default, and set the value of the init-param named listings to false. Then redeploy your web application if it has already been deployed.

<init-param>
   <param-name>listings</param-name>
   <param-value>false</param-value>
</init-param>

The mime-mapping elements in default-web.xml are global and inherited by all web applications. You can override these mappings or define your own using mime-mapping elements in your web application's web.xml file. For more information about mime-mapping elements, see the Servlet specification.

You can use the Administration Console to edit the default-web.xml file. For details, click the Help button in the Administration Console. As an alternative, you can edit the file directly using the following steps.

ProcedureTo Use the default-web.xml File

  1. Place the JAR file for the filter, security constraint, or other feature in the domain-dir/lib directory.

  2. Edit the domain-dir/config/default-web.xml file to refer to the JAR file.

  3. Restart the server.

Configuring Logging and Monitoring in the Web Container

For information about configuring logging and monitoring in the web container using the Administration Console, click the Help button in the Administration Console. Logging and Monitor tabs are accessible from the Application Server page.

Header Management

In all Editions of the Enterprise Server, the Enumeration from request.getHeaders() contains multiple elements (one element per request header) instead of a single, aggregated value.

The header names used in HttpServletResponse.addXXXHeader() and HttpServletResponse.setXXXHeader() are returned as they were created.

Configuring Valves and Catalina Listeners

You can configure custom valves and Catalina listeners for web modules or virtual servers by defining properties. A valve class must implement the org.apache.catalina.Valve interface from Tomcat or previous Enterprise Server releases, or the org.glassfish.web.valve.GlassFishValve interface from the current Enterprise Server release. A listener class for a virtual server must implement the org.apache.catalina.ContainerListener or org.apache.catalina.LifecycleListener interface. A listener class for a web module must implement the org.apache.catalina.ContainerListener, org.apache.catalina.LifecycleListener, or org.apache.catalina.InstanceListener interface.

In the sun-web.xml file, valve and listener properties for a web module look like this:

<sun-web-app ...>
   ...
   <property name="valve_1" value="org.glassfish.extension.Valve"/>
   <property name="listener_1" value="org.glassfish.extension.MyLifecycleListener"/>
</sun-web-app>

In the domain.xml file, valve and listener properties for a virtual server look like this:

<virtual-server ...>
   ...
   <property name="valve_1" value="org.glassfish.extension.Valve"/>
   <property name="listener_1" value="org.glassfish.extension.MyLifecycleListener"/>
</virtual-server>

You can define these properties for a virtual server in one of the following ways, then restart the server:

Alternate Document Roots

An alternate document root (docroot) allows a web application to serve requests for certain resources from outside its own docroot, based on whether those requests match one (or more) of the URI patterns of the web application's alternate docroots.

To specify an alternate docroot for a web application or a virtual server, use the alternatedocroot_n property, where n is a positive integer that allows specification of more than one. This property can be a subelement of a sun-web-app element in the sun-web.xml file or a virtual-server element in the domain.xml file. For more information about these elements, see sun-web-app in Sun GlassFish Enterprise Server v3 Prelude Application Deployment Guide and virtual-server in Sun GlassFish Enterprise Server v3 Prelude Administration Reference.

A virtual server's alternate docroots are considered only if a request does not map to any of the web modules deployed on that virtual server. A web module's alternate docroots are considered only once a request has been mapped to that web module.

If a request matches an alternate docroot's URI pattern, it is mapped to the alternate docroot by appending the request URI (minus the web application's context root) to the alternate docroot's physical location (directory). If a request matches multiple URI patterns, the alternate docroot is determined according to the following precedence order:

For example, the following properties specify three docroots. The URI pattern of the first alternate docroot uses an exact match, whereas the URI patterns of the second and third alternate docroots use extension and longest path prefix matches, respectively.

<property name="alternatedocroot_1" value="from=/my.jpg dir=/srv/images/jpg"/>
<property name="alternatedocroot_2" value="from=*.jpg dir=/srv/images/jpg"/>
<property name="alternatedocroot_3" value="from=/jpg/* dir=/src/images"/>

The value of each alternate docroot has two components: The first component, from, specifies the alternate docroot's URI pattern, and the second component, dir, specifies the alternate docroot's physical location (directory).

Suppose the above examples belong to a web application deployed at http://company22.com/myapp. The first alternate docroot maps any requests with this URL:


http://company22.com/myapp/my.jpg

To this resource:


/svr/images/jpg/my.jpg

The second alternate docroot maps any requests with a *.jpg suffix, such as:


http://company22.com/myapp/*.jpg

To this physical location:


/svr/images/jpg

The third alternate docroot maps any requests whose URI starts with /myapp/jpg/, such as:


http://company22.com/myapp/jpg/*

To the same directory as the second alternate docroot.

For example, the second alternate docroot maps this request:


http://company22.com/myapp/abc/def/my.jpg

To:


/srv/images/jpg/abc/def/my.jpg

The third alternate docroot maps:


http://company22.com/myapp/jpg/abc/resource

To:


/srv/images/jpg/abc/resource

If a request does not match any of the target web application's alternate docroots, or if the target web application does not specify any alternate docroots, the request is served from the web application's standard docroot, as usual.

Redirecting URLs

You can specify that a request for an old URL is treated as a request for a new URL. This is called redirecting a URL.

To specify a redirected URL for a virtual server, use the redirect_n property, where n is a positive integer that allows specification of more than one. This property is a subelement of a virtual-server element in the domain.xml file. For more information about this element, see virtual-server in Sun GlassFish Enterprise Server v3 Prelude Administration Reference. Each of these redirect_n properties is inherited by all web applications deployed on the virtual server.

The value of each redirect_n property has two components, which may be specified in any order:

The first component, from, specifies the prefix of the requested URI to match.

The second component, url-prefix, specifies the new URL prefix to return to the client. The from prefix is simply replaced by this URL prefix.

For example:

<property name="redirect_1" value="from=/dummy url-prefix=http://etude"/>

Using a context.xml File

You can define a context.xml file for all web applications, for web applications assigned to a specific virtual server, or for a specific web application.

To define a global context.xml file, place the file in the domain-dir/config directory and name it context.xml.

Use the contextXmlDefault property to specify the name and the location, relative to domain-dir, of the context.xml file for a specific virtual server. Specify this property in one of the following ways:

To define a context.xml file for a specific web application, place the file in the META-INF directory and name it context.xml.

For more information about virtual servers, see Virtual Servers. For more information about the context.xml file, see The Context Container. Context parameters, environment entries, and resource definitions in context.xml are supported in the Enterprise Server.

Enabling WebDav

To enable WebDav in the Enterprise Server, you edit the web.xml and sun-web.xml files as follows.

First, enable the WebDav servlet in your web.xml file:

<servlet>
   <servlet-name>webdav</servlet-name>
   <servlet-class>org.apache.catalina.servlets.WebdavServlet</servlet-class>
   <init-param>
      <param-name>debug</param-name>
      <param-value>0</param-value>
   </init-param>
   <init-param>
      <param-name>listings</param-name>
      <param-value>true</param-value>
   </init-param>
   <init-param>
      <param-name>readonly</param-name>
      <param-value>false</param-value>
   </init-param>
</servlet>

Then define the servlet mapping associated with your WebDav servlet in your web.xml file:

<servlet-mapping>
   <servlet-name>webdav</servlet-name>
   <url-pattern>/webdav/*</url-pattern>
</servlet-mapping>

To protect the WebDav servlet so other users can't modify it, add a security constraint in your web.xml file:

<security-constraint>
   <web-resource-collection>
      <web-resource-name>Login Resources</web-resource-name>
      <url-pattern>/webdav/*</url-pattern>
   </web-resource-collection>
   <auth-constraint>
      <role-name>Admin</role-name>
   </auth-constraint>
   <user-data-constraint>
      <transport-guarantee>NONE</transport-guarantee>
   </user-data-constraint>
   <login-config>
      <auth-method>BASIC</auth-method>
      <realm-name>default</realm-name>
   </login-config>
   <security-role>
      <role-name>Admin</role-name>
   </security-role>
</security-constraint>

Then define a security role mapping in your sun-web.xml file:

<security-role-mapping>
   <role-name>Admin</role-name>
   <group-name>Admin</group-name>
</security-role-mapping>

If you are using the file realm, create a user and password. For example:


asadmin create-file-user --user admin --host localhost --port 4848 --terse=true 
--groups Admin --authrealmname default admin

Enable the security manager as described in Enabling and Disabling the Security Manager.

You can now use any WebDav client by connecting to the WebDav servlet URL, which has this format:


http://host:port/context-root/webdav/file

For example:


http://localhost:80/glassfish-webdav/webdav/index.html

You can add the WebDav servlet to your default-web.xml file to enable it for all applications, but you can't set up a security role mapping to protect it.

Using mod_jk

To set up mod_jk, follow these steps:

  1. Obtain and install Apache 2.0.x or 2.2.x HTTP Server (http://httpd.apache.org/).

  2. Configure the following files:

    Examples of these files are shown after these steps. If you use both worker.properties and glassfish-jk.properties files, the file referenced by httpd.conf, or referenced by httpd.conf first, takes precedence.

  3. Start httpd.

  4. Enable mod_jk using the following command:


    asadmin set server-config.http-service.http-listener.listener.property.jkEnabled=true

    For example:


    asadmin set server-config.http-service.http-listener.http-listener1.property.jkEnabled=true

    Or you can use the following deprecated command, provided for backward compatibility:


    asadmin create-jvm-options -Dcom.sun.enterprise.web.connector.enableJK=8009

  5. If you are using the glassfish-jk.properties file and not referencing it in httpd.conf, point to it using the following command:


    asadmin create-jvm-options 
-Dcom.sun.enterprise.web.connector.enableJK.propertyFile=domain-dir/config/glassfish-jk.properties

  6. Restart the Enterprise Server.

Here is an example httpd.conf file:

LoadModule jk_module /usr/lib/httpd/modules/mod_jk.so
JkWorkersFile /etc/httpd/conf/worker.properties
# Where to put jk logs
JkLogFile /var/log/httpd/mod_jk.log
# Set the jk log level [debug/error/info]
JkLogLevel debug
# Select the log format
JkLogStampFormat "[%a %b %d %H:%M:%S %Y] "
# JkOptions indicate to send SSL KEY SIZE,
JkOptions +ForwardKeySize +ForwardURICompat -ForwardDirectories
# JkRequestLogFormat set the request format
JkRequestLogFormat "%w %V %T"
# Send all jsp requests to GlassFish
JkMount /*.jsp worker1
# Send all glassfish-test requests to GlassFish
JkMount /glassfish-test/* worker1

Here is an example worker.properties or glassfish-jk.properties file:

# Define 1 real worker using ajp13
worker.list=worker1
# Set properties for worker1 (ajp13)
worker.worker1.type=ajp13
worker.worker1.host=localhost.localdomain
worker.worker1.port=8009
worker.worker1.lbfactor=50
worker.worker1.cachesize=10
worker.worker1.cache_timeout=600
worker.worker1.socket_keepalive=1
worker.worker1.socket_timeout=300

Using SSI

To enable SSI (server-side includes) processing for a specific web module, add the SSIServlet to your web.xml file as follows:

<web-app>
   <servlet>
      <servlet-name>ssi</servlet-name>
      <servlet-class>org.apache.catalina.ssi.SSIServlet</servlet-class>
   </servlet>
   ...
   <servlet-mapping>
      <servlet-name>ssi</servlet-name>
      <url-pattern>*.shtml</url-pattern>
   </servlet-mapping>
   ...
   <mime-mapping>
      <extension>shtml</extension>
      <mime-type>text/html</mime-type>
   </mime-mapping>
</web-app>

To enable SSI processing for all web modules, un-comment the corresponding sections in the default-web.xml file.

If the mime-mapping is not specified in web.xml, Enterprise Server attempts to determine the MIME type from default-web.xml or the operating system default.

You can configure the following init-param values for the SSIServlet.

Table 7–2 SSIServlet init-param Values

init-param 

Type 

Default 

Description 

buffered

boolean

false

Specifies whether the output should be buffered. 

debug

int

0 (for no debugging)

Specifies the debugging level.  

expires

Long

Expires header in HTTP response not set

Specifies the expiration time in seconds. 

inputEncoding

String

operating system encoding 

Specifies encoding for the SSI input if there is no URL content encoding specified. 

isVirtualWebappRelative

boolean

false (relative to the given SSI file)

Specifies whether the virtual path of the #include directive is relative to the content-root.

outputEncoding

String

UTF-8 

Specifies encoding for the SSI output. 

For more information about SSI, see http://httpd.apache.org/docs/2.2/mod/mod_include.html.

Using CGI

To enable CGI (common gateway interface) processing for a specific web module, add the CGIServlet to your web.xml file as follows:

<web-app>
   <servlet>
      <servlet-name>cgi</servlet-name>
      <servlet-class>org.apache.catalina.servlets.CGIServlet</servlet-class>
   </servlet>
   ...
   <servlet-mapping>
      <servlet-name>cgi</servlet-name>
      <url-pattern>/cgi-bin/*</url-pattern>
   </servlet-mapping>
</web-app>

To enable CGI processing for all web modules, un-comment the corresponding sections in the default-web.xml file.

Package the CGI program under the cgiPathPrefix. The default cgiPathPrefix is WEB-INF/cgi. For security, it is highly recommended that the contents and binaries of CGI programs be prohibited from direct viewing or download. For information about hiding directory listings, see Using the default-web.xml File.

Invoke the CGI program using a URL of the following format:


http://host:8080/context-root/cgi-bin/cgi-name

For example:


http://localhost:8080/mycontext/cgi-bin/hello

You can configure the following init-param values for the CGIServlet.

Table 7–3 CGIServlet init-param Values

init-param 

Type 

Default 

Description 

cgiPathPrefix

String

WEB-INF/cgi

Specifies the subdirectory containing the CGI programs. 

debug

int

0 (for no debugging)

Specifies the debugging level.  

executable

String

perl

Specifies the executable for running the CGI script. 

parameterEncoding

String

System.getProperty("file.encoding", "UTF-8")

Specifies the parameter's encoding. 

passShellEnvironment

boolean

false

Specifies whether to pass shell environment properties to the CGI program. 

To work with a native executable, do the following:

  1. Set the value of the init-param named executable to an empty String in the web.xml file.

  2. Make sure the executable has its executable bits set correctly.

  3. Use directory deployment to deploy the web module. Do not deploy it as a WAR file, because the executable bit information is lost during the process of jar and unjar. For more information about directory deployment, see the Sun GlassFish Enterprise Server v3 Prelude Application Deployment Guide.

Using PHP

To enable PHP, deploy the Quercus PHP interpreter to the Enterprise Server as a web module as follows:

  1. Download the Quercus interpreter from http://quercus.caucho.com/.

  2. Deploy the WAR file you downloaded to the Enterprise Server.

  3. To verify that your PHP engine is working, point your browser to the default PHP script that comes with the Quercus interpreter, which is http://localhost:8080/quercus-3.1.6/.

  4. The Quercus application directory is located at domain-dir/applications/quercus-3.1.6/. Place your PHP application in a subdirectory of the Quercus directory, for example domain-dir/applications/quercus-3.1.6/myapp/. To point your browser to the PHP application, enter http://localhost:8080/quercus-3.1.6/myapp/.

For more information about using the Quercus PHP interpreter, see the documentation at http://quercus.caucho.com/quercus-3.1/doc/quercus.xtp.

Using Scala and Lift

Scala is a general purpose programming language designed to express common programming patterns in a concise, elegant, and type-safe way. It smoothly integrates features of object-oriented and functional languages. It is also fully interoperable with Java. For details, see http://www.scala-lang.org/.

Lift is an expressive and elegant framework for writing web applications using Scala. Lift stresses the importance of security, maintainability, scalability and performance, while allowing for high levels of developer productivity. For details, see http://liftweb.net/.

It is common practice to start a Lift web application using Maven. Maven is a software project management and comprehension tool. Based on the concept of a project object model (POM), Maven can manage a project's build, reporting and documentation from a central piece of information. For details, see http://maven.apache.org/.

To create a new Lift project, use Maven interactively in one of these ways:


mvn archetype:generate -DarchetypeCatalog=http://scala-tools.org/

Or:


mvn org.apache.maven.plugins:maven-archetype-plugin:1.0-alpha-7:create \ 
 -DarchetypeGroupId=net.liftweb                             \
 -DarchetypeArtifactId=lift-archetype-blank                 \
 -DarchetypeVersion=0.7.1                                   \
 -DremoteRepositories=http://scala-tools.org/repo-releases  \
 -DgroupId=__my.liftapp__ -DartifactId=__liftapp__

Or:


mvn org.apache.maven.plugins:maven-archetype-plugin:1.0-alpha-7:create \ 
 -DarchetypeGroupId=net.liftweb                             \
 -DarchetypeArtifactId=lift-archetype-basic                 \
 -DarchetypeVersion=0.7.1                                   \
 -DremoteRepositories=http://scala-tools.org/repo-releases  \
 -DgroupId=__my.liftapp__ -DartifactId=__liftapp__

After coding your application, build the WAR file using the mvn package command. Then deploy the WAR file to the Enterprise Server as you would any other web application.