Configuring Filters

You configure filters as part of a Web application, using the application's web.xml deployment descriptor. In the deployment descriptor, you specify the filter and then map the filter to a URL pattern or to a specific servlet in the Web application. You can specify any number of filters.


To configure a filter:

1. Open the web.xml deployment descriptor in a text editor or use the Administration Console. The web.xml file is located in the WEB-INF directory of your Web application.
2. Add a filter declaration. The filter element declares a filter, defines a name for the filter, and specifies the Java class that executes the filter. The filter element must directly follow the context-param element and directly precede the listener and servlet elements.


<context-param>Param</context-param>
<filter>
  <icon>
    <small-icon>MySmallIcon.gif</small-icon>
    <large-icon>MyLargeIcon.gif</large-icon>
  </icon>
  <filter-name>myFilter</filter-name>
  <display-name>My Filter
  <description>This is my filter</description>
  <filter-class>examples.myFilterClass</filter-class>
</filter>
<listener>Listener</listener>
<servlet>Servlet</servlet>
</code>

The icon, description, and display-name elements are optional.

3. Specify one or more initialization attributes inside a filter element. For example:


<filter>
  <icon>
    <small-icon>MySmallIcon.gif</small-icon>
    <large-icon>MyLargeIcon.gif</large-icon>
  </icon>
  <filter-name>myFilter</filter-name>
  <display-name>My Filter</display-name>
  This is my filter</description>
  <filter-class>examples.myFilterClass</filter-class>
  <init-param>
    <param-name>myInitParam</param-name>
    <param-value>myInitParamValue</param-value>
  </init-param>
</filter>

Your Filter class can read the initialization attributes using the FilterConfig.getInitParameter() or FilterConfig.getInitParameters() methods.

4. Add filter mappings. The filter-mapping element specifies which filter to execute based on a URL pattern or servlet name. The filter-mapping element must immediately follow the filter elements

• To create a filter mapping using a URL pattern, specify the name of the filter and a URL pattern. URL pattern matching is performed according to the rules specified in the servlet 3.0 specification at http://jcp.org/en/jsr/detail?id=315Opens a new window. For example, the following filter-mapping maps myFilter to requests that contain /myPattern/.

<filter-mapping> <filter-name>myFilter</filter-name> <url-pattern>/myPattern/*</url-pattern> </filter-mapping>

• To create a filter mapping for a specific servlet, map the filter to the name of a servlet that is registered in the Web application. For example, the following code maps the myFilter filter to a servlet called myServlet:


<filter-mapping> <filter-name>myFilter</filter-name> <servlet-hame>myServlet</servlet-name> </filter-mapping>

Configuring a Chain of Filters

WebLogic Server creates a chain of filters by creating a list of all the filter mappings that match an incoming HTTP request. The ordering of the list is determined by the following sequence:

● Filters where the filter-mapping element contains a url-pattern that matches the request are added to the chain in the order they appear in the web.xml deployment descriptor.
● Filters where the filter-mapping element contains a servlet-name that matches the request are added to the chain after the filters that match a URL pattern.
● The last item in the chain is always the originally requested resource.

In your filter class, use the FilterChain.doFilter() method to invoke the next item in the chain.

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