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Sun ONE Application Server 7, Enterprise Edition Developer's Guide to Web Applications

Chapter 1
Web Applications

This chapter describes how web applications are supported in the Sun™ Open Net Environment (Sun ONE) Sun ONE Application Server 7, Enterprise Edition, and includes the following sections:

Introducing Web Applications

Sun ONE Application Server 7 supports the Java™ Servlet 2.3 API specification, which allows servlets and JavaServer Pages™ (JSP™) pages to be included in web applications.

A web application is a collection of servlets, JavaServer Pages, HTML documents, and other web resources which might include image files, compressed archives, and other data. A web application may be packaged into an archive (a WAR file) or exist in an open directory structure.

The following figure illustrates details of the Java™ 2 Platform, Enterprise Edition (J2EE™ platform) environment. Web applications are in the presentation layer. Two web applications are running in the web container: one of them is part of a full application that includes Enterprise JavaBeans™ (EJB™) modules and connectors, while the other is an individually deployed web module.

Figure 1-1  Web applications in the J2EE environment

Figure shows detailed J2EE environment. Illustrates the contents and flow of the client layer, the presentation layer, the business logic layer, and the data access layer.

In addition, Sun ONE Application Server 7 supports SHTML and CGI, which are non-J2EE application components.

This section includes summaries of the following topics:

Servlets

Java servlets are server-side Java programs that application servers can run to generate content in response to a client request. Servlets can be thought of as applets that run on the server side without a user interface. Servlets are invoked through URL invocation or by other servlets.

Sun ONE Application Server 7 supports the Java Servlet Specification version 2.3.

Note

Servlet API version 2.3 is fully backward compatible with versions 2.1 and 2.2, so all existing servlets will continue to 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

For information about developing servlets in Sun ONE Application Server, see Chapter 2, “Using Servlets.”

JavaServer Pages

Sun ONE Application Server 7 supports JavaServer Pages (JSP) Specification version 1.2.

A JSP is a page, much like an HTML page, that can be viewed in a web browser. However, in addition to HTML tags, it can include a set of JSP tags and directives intermixed with Java code that extend the ability of the web page designer to incorporate dynamic content in a page. These additional features provide functionality such as displaying property values and using simple conditionals.

One of the main benefits of JSPs is that they are like HTML pages. The web page designer simply writes a page that uses HTML and JSP tags and puts it on their application server. The page is compiled automatically when it is deployed. What the web page designer needs to know about Java classes and Java compilers is minimal.

Sun ONE Application Server supports precompilation of JSPs, however, and this is especially useful for production servers.

JSP pages can access full Java functionality in the following ways:

Both beans and servlets are Java classes that need to be compiled, but they can be defined and compiled by a Java programmer, who then publishes the interface to the bean or the servlet. The web page designer can access a pre-compiled bean or servlet from a JSP page.

Sun ONE Application Server 7 supports JSP tag libraries and standard portable tags.

For information about creating JSPs, 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

For information about developing JSPs in Sun ONE Application Server, see Chapter 3, “Using JavaServer Pages.”

SHTML

HTML files can contain tags that are executed on the server. In addition to supporting the standard server-side tags, or SSIs, Sun ONE Application Server 7 allows you to embed servlets and define your own server-side tags. For more information, see Chapter 7, “Using Server-Parsed HTML.”

CGI

Common Gateway Interface (CGI) programs run on the server and generate a response to return to the requesting client. CGI programs can be written in various languages, including C, C++, Java, Perl, and as shell scripts. CGI programs are invoked through URL invocation. Sun ONE Application Server complies with the version 1.1 CGI specification. For more information, see Chapter 8, “Using CGI.”

Creating a Web Application

To create a web application:

  1. Create a directory for all the web application’s files. This is the web application’s document root.
  2. Create any needed HTML files, image files, and other static content. Place these files in the document root directory or a subdirectory where they can be accessed by other parts of the application.
  3. Create any needed JSP files. For more information, see Chapter 3, “Using JavaServer Pages.”
  4. Create any needed servlets. For more information, see Chapter 2, “Using Servlets.”
  5. Compile the servlets. For details about precompiling JSPs, see “Compiling JSPs: The Command-Line Compiler”.
  6. Organize the web application as described in “Web Application Structure”.
  7. Create the deployment descriptor files. For more information, see Chapter 6, “Assembling and Deploying Web Modules.”
  8. Package the web application in a WAR file if desired. This is optional. For example:

    9. jar -cvf module_name.war *

  9. Deploy the web application. For more information, see Chapter 6, “Assembling and Deploying Web Modules.”

You can create a web application by hand, or you can use Sun ONE Studio 4. For more information about Sun ONE Studio, see the Sun ONE Studio 4, Enterprise Edition Tutorial.

Deploying a Web Application

Web application deployment descriptor files are created by the Sun ONE Application Server Administration interface during deployment. You can also create these by hand. These descriptor files are packaged within Web Application aRchive (.war) files. They contain metadata, plus information that identifies the servlet or JSP and establishes its application role. For more information about these descriptor files, see Chapter 6, “Assembling and Deploying Web Modules.”

Debugging a Web Application

For information about debugging applications, see the Sun ONE Application Server Developer’s Guide.

Internationalization Issues

This section covers internationalization as it applies to the following:

The Server

To set the default locale of the entire Sun ONE Application Server, which determines the locale of the Administration interface, the logs, and so on, do one of the following:

Servlets

This section explains how the Sun ONE Application Server determines the character encoding for the servlet request and the servlet response.

For encodings you can use, see:

http://java.sun.com/j2se/1.4/docs/guide/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:

Servlet Response

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

To send non-ASCII characters in the response headers, set the useResponseCTForHeaders property, which is described in the section “sun-web-app”.

JSPs

For encodings you can use, see:

http://java.sun.com/j2se/1.4/docs/guide/intl/encoding.doc.html

To set the character encoding of a JSP, use the page directive. For example:

<%@ page contentType="text/html; charset=Shift_JIS" %>

The contentType attribute defines the following:

The default value is text/html; charset=ISO-8859-1.

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

Some JSP pages can deliver content using different content types and character encodings depending on the request time input. Dynamic setting of content type relies on an underlying invocation of response.setContentType(). This method can be invoked as long as no content has been sent to the response stream.

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 may serve content using the same or different host names, port numbers, or IP addresses. The HTTP service can direct incoming web requests to different virtual servers based on the URL.

When you first install Sun ONE Application Server, a default virtual server is created. (You can also assign a default virtual server to each new HTTP listener you create. For details, see the Sun ONE Application Server Administrator’s Guide.)

Web applications and J2EE applications containing web components can be assigned to virtual servers. You can assign virtual servers in either of these ways:

Using the Administration Interface

You can assign a virtual server to a web module during deployment as described in “Deploying Web Applications”. To use the Administration interface to specify a virtual server’s default web module:

  1. Deploy the web application or J2EE application as described in “Deploying Web Applications”.
  2. Open the HTTP Server component under your server instance.
  3. Open the Virtual Servers component under the HTTP Server component.
  4. Select the virtual server to which you want to assign the web application.
  5. Select the web application from the Default Web Module drop-down list.
  6. Select the Save button.
  7. Go to the server instance page and select the Apply Changes button.

For more information, see "Default Web Modules".

Editing the server.xml File

When a web module is deployed as part of an application, a j2ee-application element is created for it in server.xml during deployment. When a web module is deployed as an individual module, a web-module element is created for it in server.xml during deployment. The j2ee-application and web-module elements both have a virtual-servers attribute, which specifies a list of virtual server IDs. The virtual-servers attribute is empty by default, which means that the web application is assigned to all virtual servers.

Each virtual-server element in server.xml has a default-web-module attribute, which allows you to configure a default web module for each virtual server. A default web module for the default virtual server is provided at installation. For more information, see "Default Web Modules".

For more information about server.xml and virtual servers, see the Sun ONE Application Server Administrator’s Configuration File Reference.

Default Web Modules

You can assign a default web module to the default virtual server and to each new virtual server you create. For details, see "Virtual Servers". To access the default web module for a virtual server, point your 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 JSP content from its document root, which is usually instance_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

Servlet and JSP Caching

The Sun ONE Application Server has the ability to cache servlet or JSP results in order to make subsequent calls to the same servlet or JSP faster. The Sun ONE Application Server caches the request results for a specific amount of time. In this way, if another data call occurs the Sun ONE Application 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.

For more information about response caching as it pertains to servlets, see “Caching Servlet Results”. For more information about JSP caching, see “JSP Caching”.

Database Connection Pooling

Database connection pooling enhances the performance of servlet or JSP database interactions. There are several Java™ Database Connectivity (JDBC™) 2.0 compatible drivers that support connection pooling, for example Pointbase, Oracle 8i update, and CloudScape 3.0. For more information about JDBC, see the Sun ONE Application Server Developer’s Guide to J2EE Services and APIs.

Configuring the Web Container

You can configure logging in the web container for the entire server in these ways:

Web Application Examples

Sample web applications that you can examine and deploy are included in Sun ONE Application Server, in the install_dir/samples/webapps directory. Each sample has its own documentation.



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