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Configuring WebLogic Server Web Components
This section discusses how to configure Web components. The following topics are covered:
In addition to its ability to host dynamic Java-based distributed applications, WebLogic Server is also a fully functional Web server that can handle high volume Web sites, serving static files such as HTML files and image files as well as servlets and JavaServer Pages (JSP). WebLogic Server supports the HTTP 1.1 standard.
You can configure the following HTTP operating parameters using the Administration Console for each instance of WebLogic Server (or for each virtual host):
For detailed information on setting these attributes, see Virtual Host .
Configuring the Listen Port
You can specify the port that each WebLogic Server listens on for HTTP requests. Although you can specify any valid port number, if you specify port 80, you can omit the port number from the HTTP request used to access resources in your Web Application. For example, if you define port 80 as the listen port, you can use the form http://hostname/myfile.html instead of http://hostname:portnumber/myfile.html.
You define a separate listen port for regular and secure (using SSL) requests. You define the regular listen port on the Servers node in the Administration Console, under the Configuration/General tab, and you define the SSL listen port under the Configuration/SSL tab.
HTTP and Web services are deployed according to the Servlet 2.2 specification from Sun Microsystems, which describes the use of Web Applications as a standardized way of grouping together the components of a Web-based application. These components include JSP pages, HTTP servlets, and static resources such as HTML pages or image files. In addition, a Web Application can access external resources such as EJBs and JSP tag libraries. Each server can host any number of Web Applications. You normally use the name of the Web Application as part of the URI you use to request resources form the Web Application.
For more information, see Deploying and Configuring Web Applications.
Web Applications and Clustering
Web Applications can be deployed in a cluster of WebLogic Servers. When a user requests a resource from a Web Application, the request is routed to one of the servers of the cluster that host the Web Application. If an application uses a session object, then sessions must be replicated across the nodes of the cluster. Several methods of replicating sessions are provided.
For more information, see Using WebLogic Server Clusters.
Designating a Default Web Application
Every server and virtual host in your domain has a special type of Web Application, called a default Web Application. The default Web Application responds to any HTTP request that cannot be resolved to another deployed Web Application. In contrast to all other Web Applications, the default Web Application does not use the Web Application name as part of the URI. Any Web Application targeted to a server or virtual host can be declared as the default Web Application. (Targeting a Web Application is discussed later in this section. For more information about virtual hosts, see Configuring Virtual Hosting)
If you do not declare a default Web Application, WebLogic Server creates a default Web Application for each server or virtual host when you start WebLogic Server. The default Web Application is named DefaultWebApp_servername, where servername is the name of the server you started, or in the case of a virtual host, DefaultWebApp_virtualHostName.
If you declare a default Web Application that fails to deploy correctly, an error is logged and the user will receive an HTTP 400 error message.
For example, if your Web Application is called shopping, you would use the following URI to access a JSP called cart.jsp from the Web Application:
http://host:port/shopping/cart.jsp
If, however, you declared shopping as the default Web Application, you would access cart.jsp with the following URI:
(Where host is the host name of the machine running WebLogic Server and port is the port number where the WebLogic Server is listening for requests.)
To designate a default Web Application for a server or virtual host, use the Administration Console:
Virtual hosting allows you to define host names that servers or clusters respond to. When you use virtual hosting you use DNS to specify one or more host names that map to the IP address of a WebLogic Server or cluster and you specify which Web Applications are served by the virtual host. When used in a cluster, load balancing allows the most efficient use of your hardware, even if one of the DNS host names processes more requests than the others.
For example, you can specify that a Web Application called books responds to requests for the virtual host name www.books.com., and that these requests are targeted to WebLogic Servers A,B and C, while a Web Application called cars responds to the virtual host name www.autos.com and these requests are targeted to WebLogic Servers D and E. You can configure a variety of combinations of virtual host, WebLogic Servers, clusters and Web Applications, depending on your application and Web server requirements.
For each virtual host that you define you can also separately define HTTP parameters and HTTP access logs. The HTTP parameters and access logs set for a virtual host override those set for a server. You may specify any number of virtual hosts.
You activate virtual hosting by targeting the virtual host to a server or cluster of servers. Virtual hosting targeted to a cluster will be applied to all servers in the cluster.
Virtual Hosting and the Default Web Application
You can also designate a default Web Application for each virtual host. The default Web Application for a virtual host responds to all requests that cannot be resolved to other Web Applications deployed on same server or cluster as the virtual host.
Unlike other Web Applications, a default Web Application does not use the Web Application name (also called the context path) as part of the URI used to access resources in the default Web Application.
For example, if you defined virtual host name www.mystore.com and targeted it to a server on which you deployed a Web Application called shopping. you would access a JSP called cart.jsp from the shopping Web Application with the following URI:
http://www.mystore.com/shopping/cart.jsp
If, however, you declared shopping as the default Web Application for the virtual host www.mystore.com, you would access cart.jsp with the following URI:
http://www.mystore.com/cart.jsp
For more information, see How WebLogic Server Resolves HTTP Requests.
To define a virtual host, use the Administration Console:
WebLogic Server can keep a log of all HTTP transactions in a text file, in either common log format or extended log format. Common log format is the default, and follows a standard convention. Extended log format allows you to customize the information that is recorded. You can set the attributes that define the behavior of HTTP access logs for each server or for each virtual host that you define.
You can also choose to rotate the log file based on either the size of the file or after a specified amount of time has passed. When either one of these two criteria are met, the current access log file is closed and a new access log file is started. If you do not configure log rotation, the HTTP access log file grows indefinitely. The name of the access log file includes a numeric portion that is incremented upon each rotation. Separate HTTP Access logs are kept for each Web Server you have defined.
Setting Up HTTP Access Logs by Using the Administration Console
To set up HTTP access logs use the Administration Console:
If you have not set up virtual hosting:
After the log file reaches the specified size, the next time the server checks the file size, it will rename the current log file as FileName.n and create a new one to store subsequent messages.
The default format for logged HTTP information is the common log format. This standard format follows the pattern:
host RFC931 auth_user [day/month/year:hour:minute:second
UTC_offset] "request" status bytes
Setting Up HTTP Access Logs by Using Extended Log Format
WebLogic Server also supports extended log file format, version 1.0, as defined by the W3C. This is an emerging standard, and WebLogic Server follows the draft specification from W3C. The current definitive reference may be found from the W3C Technical Reports and Publications page
The extended log format allows you to specify the type and order of information recorded about each HTTP communication. To enable the extended log format, set the Format attribute on the HTTP tab in the Administration Console to Extended. (See step 4. in Setting Up HTTP Access Logs by Using the Administration Console).
You specify what information should be recorded in the log file with directives, included in the actual log file itself. A directive begins on a new line and starts with a # sign. If the log file does not exist, a new log file is created with default directives. However, if the log file already exists when the server starts, it must contain legal directives at the head of the file.
Creating the Fields Directive
The first line of your log file must contain a directive stating the version number of the log file format. You must also include a Fields directive near the beginning of the file:
#Version: 1.0
#Fields: xxxx xxxx xxxx ...
Where each xxxx describes the data fields to be recorded. Field types are specified as either simple identifiers, or may take a prefix-identifier format, as defined in the W3C specification. Here is an example:
#Fields: date time cs-method cs-uri
This identifier instructs the server to record the date and time of the transaction, the request method that the client used, and the URI of the request for each HTTP access. Each field is separated by white space, and each record is written to a new line, appended to the log file.
Note: The #Fields directive must be followed by a new line in the log file, so that the first log message is not appended to the same line.
Supported Field identifiers
The following identifiers are supported, and do not require a prefix.
Note that the cached field defined in the W3C specification is not supported in WebLogic Server.
The following identifiers require prefixes, and cannot be used alone. The supported prefix combinations are explained individually.
Creating Custom Field Identifiers
You can also create user-defined fields for inclusion in an HTTP access log file that uses the extended log format. To create a custom field you identify the field in the ELF log file using the Fields directive and then you create a matching Java class that generates the desired output. You can create a separate Java class for each field, or the Java class can output multiple fields. A sample of the Java source for such a class is included in this document. See Java Class for Creating a Custom ELF Field.
X-myCustomField. Where myCustomField is a fully-qualified class name. For more information on the Fields directive, see
Creating the Fields Directive.
weblogic.servlet.logging.CustomELFLogger In your Java class, you must implement the logField() method, which takes a HttpAccountingInfo object and FormatStringBuffer object as its arguments:
Note: Do not place this class inside of a Web Application or Enterprise Application in exploded or jar format.
Note: When writing the Java class that defines your custom field, you should not execute any code that is likely to slow down the system (For instance, accessing a DBMS or executing significant I/O or networking calls.) Remember, an HTTP access log file entry is created for every HTTP request.
Note: If you want to output more than one field, delimit the fields with a tab character. For more information on delimiting fields and other ELF formatting issues, see Extended Log Format.
Get methods of the HttpAccountingInfo Object
The following methods return various data regarding the HTTP request. These methods are similar to various methods of javax.servlet.ServletRequest, javax.servlet.http.Http.ServletRequest, and javax.servlet.http.HttpServletResponse.
For details on these methods see the corresponding methods in the Java interfaces listed in the following table, or refer to the specific information contained in the table.
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HttpAccountingInfo Methods |
Where to find information on the methods |
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Object getAttribute(String name); |
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Enumeration getAttributeNames(); |
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String getCharacterEncoding(); |
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int getResponseContentLength(); |
javax.servlet.ServletResponse. (this method gets the content length of the response, as set with the setContentLength() method) |
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String getContentType(); |
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Locale getLocale(); |
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Enumeration getLocales(); |
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String getParameter(String name); |
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Enumeration getParameterNames(); |
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String[] getParameterValues(String name); |
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String getProtocol(); |
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String getRemoteAddr(); |
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String getRemoteHost(); |
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String getScheme(); |
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String getServerName(); |
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int getServerPort(); |
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boolean isSecure(); |
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String getAuthType(); |
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String getContextPath(); |
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Cookie[] getCookies(); |
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long getDateHeader(String name); |
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String getHeader(String name); |
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Enumeration getHeaderNames(); |
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Enumeration getHeaders(String name); |
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int getIntHeader(String name); |
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String getMethod(); |
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String getPathInfo(); |
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String getPathTranslated(); |
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String getQueryString(); |
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String getRemoteUser(); |
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String getRequestURI(); |
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String getRequestedSessionId(); |
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String getServletPath(); |
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Principal getUserPrincipal(); |
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boolean isRequestedSessionIdFromCookie(); |
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boolean isRequestedSessionIdFromURL(); |
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boolean isRequestedSessionIdFromUrl(); |
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boolean isRequestedSessionIdValid(); |
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String getFirstLine(); |
Returns the first line of the HTTP request, for example: GET /index.html HTTP/1.0 |
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long getInvokeTime(); |
Returns the length of time it took for the service method of a servlet to write data back to the client. |
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int getResponseStatusCode(); |
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String |
Listing 7-1 Java Class for Creating a Custom ELF Field
import weblogic.servlet.logging.CustomELFLogger;
import weblogic.servlet.logging.FormatStringBuffer;
import weblogic.servlet.logging.HttpAccountingInfo;
/* This example outputs the User-Agent field into a
custom field called MyCustomField
*/
public class MyCustomField implements CustomELFLogger{
public void logField(HttpAccountingInfo metrics,
FormatStringBuffer buff) {
buff.appendValueOrDash(metrics.getHeader("User-Agent"));
}
}
Preventing POST Denial-of-Service Attacks
A Denial-of-Service attack is a malicious attempt to overload a server with phony requests. One common type of attack is to send huge amounts of data in an HTTP POST method. You can set three attributes in WebLogic Server that help prevent this type of attack. These attributes are set in the console, under Servers or virtual hosts. If you define these attributes for a virtual host, the values set for the virtual host override those set under Servers.
Post time exceeded MaxPostTimeSecs.
POST size exceeded the parameter MaxPostSize.
An HTTP error code 413 (Request Entity Too Large) is sent back to the client.
If the client is in listening mode, it gets these messages. If the client is not in listening mode, the connection is broken.
Setting Up WebLogic Server for HTTP Tunneling
HTTP tunneling provides a way to simulate a statefull socket connection between WebLogic Server and a Java client when your only option is to use the HTTP protocol. It is generally used to tunnel through an HTTP port in a security firewall. HTTP is a stateless protocol, but WebLogic Server provides tunneling functionality to make the connection appear to be a regular T3Connection. However, you can expect some performance loss in comparison to a normal socket connection.
Configuring the HTTP Tunneling Connection
Under the HTTP protocol, a client may only make a request, and then accept a reply from a server. The server may not voluntarily communicate with the client, and the protocol is stateless, meaning that a continuous two-way connection is not possible.
WebLogic HTTP tunneling simulates a T3Connection via the HTTP protocol, overcoming these limitations. There are two attributes that you can configure in the Administration Console to tune a tunneled connection for performance. You access these attributes in the Servers section, under the Tuning Tab located under the Configuration tab. It is advised that you leave them at their default settings unless you experience connection problems. These properties are used by the server to determine whether the client connection is still valid, or whether the client is still alive.
Default is 45 seconds; valid range is 20 to 900 seconds.
Default is 40 seconds; valid range is 10 to 900 seconds.
Connecting to WebLogic Server from the Client
When your client requests a connection with WebLogic Server, all you need to do in order to use HTTP tunneling is specify the HTTP protocol in the URL. For example:
Hashtable env = new Hashtable();
env.put(Context.PROVIDER_URL, "http://wlhost:80");
Context ctx = new InitialContext(env);
On the client side, a special tag is appended to the http protocol, so that WebLogic Server knows this is a tunneling connection, instead of a regular HTTP request. Your application code does not need to do any extra work to make this happen.
The client must specify the port in the URL, even if the port is 80. You can set up your WebLogic Server to listen for HTTP requests on any port, although the most common choice is port 80 since requests to port 80 are customarily allowed through a firewall.
You specify the listen port for WebLogic Server in the Administration Console under the "Servers" node, under the "Network" tab.
Using Native I/O for Serving Static Files (Windows Only)
When running WebLogic Server on Windows NT/2000 you can specify that WebLogic Server use the native operating system call TransmitFile instead of using Java methods to serve static files such as HTML files, text files, and image files. Using native I/O can provide performance improvements when serving larger static files.
To use native I/O, add two parameters to the web.xml deployment descriptor of a Web Application containing the files to be served using native I/O. The first parameter, weblogic.http.nativeIOEnabled should be set to TRUE to enable native I/O file serving. The second parameter, weblogic.http.minimumNativeFileSize sets the minimum file size for using native I/O. If the file being served is larger than this value, native I/O is used. If you do not specify this parameter, a value of 400 bytes is used.
Generally, native I/O provides greater performance gains when serving larger files; however, as the load on the machine running WebLogic Server increases, these gains diminish. You may need to experiment to find the correct value for weblogic.http.minimumNativeFileSize.
The following example shows the complete entries that should be added to the web.xml deployment descriptor. These entries must be placed in the web.xml file after the <distributable> element and before <servlet> element.
<context-param>
<param-name>weblogic.http.nativeIOEnabled</param-name>
<param-value>TRUE</param-value>
</context-param>
<context-param>
<param-name>weblogic.http.minimumNativeFileSize</param-name>
<param-value>500</param-value>
</context-param>
For more information on writing deployment descriptors see Writing Web Application Deployment Descriptors.
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Copyright © 2000 BEA Systems, Inc. All rights reserved.
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