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| <div class="subTitle">javax.servlet</div> |
| <h2 title="Interface Filter" class="title">Interface Filter</h2> |
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| <dt>All Known Implementing Classes:</dt> |
| <dd><a href="../../javax/servlet/GenericFilter.html" title="class in javax.servlet">GenericFilter</a>, <a href="../../javax/servlet/http/HttpFilter.html" title="class in javax.servlet.http">HttpFilter</a></dd> |
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| <pre>public interface <span class="typeNameLabel">Filter</span></pre> |
| <div class="block"><p> |
| A filter is an object that performs filtering tasks on either the request to a resource (a servlet or static |
| content), or on the response from a resource, or both. |
| </p> |
| |
| <p> |
| Filters perform filtering in the <code>doFilter</code> method. Every Filter has access to a FilterConfig object from |
| which it can obtain its initialization parameters, and a reference to the ServletContext which it can use, for |
| example, to load resources needed for filtering tasks. |
| |
| <p> |
| Filters are configured in the deployment descriptor of a web application. |
| |
| <p> |
| Examples that have been identified for this design are: |
| <ol> |
| <li>Authentication Filters |
| <li>Logging and Auditing Filters |
| <li>Image conversion Filters |
| <li>Data compression Filters |
| <li>Encryption Filters |
| <li>Tokenizing Filters |
| <li>Filters that trigger resource access events |
| <li>XSL/T filters |
| <li>Mime-type chain Filter |
| </ol></div> |
| <dl> |
| <dt><span class="simpleTagLabel">Since:</span></dt> |
| <dd>Servlet 2.3</dd> |
| <dt><span class="simpleTagLabel">Examples (en):</span></dt> |
| <dd><a href="../../../../../tomee-8.0/examples/polling-parent.html">polling-parent</a></dd> |
| <dt><span class="simpleTagLabel">Examples (es):</span></dt> |
| <dd><a href="../../../../../tomee-8.0/es/examples/polling-parent.html">polling-parent</a></dd> |
| <dt><span class="simpleTagLabel">Examples (pt):</span></dt> |
| <dd><a href="../../../../../tomee-8.0/pt/examples/polling-parent.html">polling-parent</a></dd> |
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| <h3>Method Summary</h3> |
| <table class="memberSummary" border="0" cellpadding="3" cellspacing="0" summary="Method Summary table, listing methods, and an explanation"> |
| <caption><span id="t0" class="activeTableTab"><span>All Methods</span><span class="tabEnd"> </span></span><span id="t2" class="tableTab"><span><a href="javascript:show(2);">Instance Methods</a></span><span class="tabEnd"> </span></span><span id="t3" class="tableTab"><span><a href="javascript:show(4);">Abstract Methods</a></span><span class="tabEnd"> </span></span><span id="t5" class="tableTab"><span><a href="javascript:show(16);">Default Methods</a></span><span class="tabEnd"> </span></span></caption> |
| <tr> |
| <th class="colFirst" scope="col">Modifier and Type</th> |
| <th class="colLast" scope="col">Method and Description</th> |
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| <tr id="i0" class="altColor"> |
| <td class="colFirst"><code>default void</code></td> |
| <td class="colLast"><code><span class="memberNameLink"><a href="../../javax/servlet/Filter.html#destroy--">destroy</a></span>()</code> |
| <div class="block"> |
| Called by the web container to indicate to a filter that it is being taken out of service.</div> |
| </td> |
| </tr> |
| <tr id="i1" class="rowColor"> |
| <td class="colFirst"><code>void</code></td> |
| <td class="colLast"><code><span class="memberNameLink"><a href="../../javax/servlet/Filter.html#doFilter-javax.servlet.ServletRequest-javax.servlet.ServletResponse-javax.servlet.FilterChain-">doFilter</a></span>(<a href="../../javax/servlet/ServletRequest.html" title="interface in javax.servlet">ServletRequest</a> request, |
| <a href="../../javax/servlet/ServletResponse.html" title="interface in javax.servlet">ServletResponse</a> response, |
| <a href="../../javax/servlet/FilterChain.html" title="interface in javax.servlet">FilterChain</a> chain)</code> |
| <div class="block">The <code>doFilter</code> method of the Filter is called by the container each time a request/response pair is |
| passed through the chain due to a client request for a resource at the end of the chain.</div> |
| </td> |
| </tr> |
| <tr id="i2" class="altColor"> |
| <td class="colFirst"><code>default void</code></td> |
| <td class="colLast"><code><span class="memberNameLink"><a href="../../javax/servlet/Filter.html#init-javax.servlet.FilterConfig-">init</a></span>(<a href="../../javax/servlet/FilterConfig.html" title="interface in javax.servlet">FilterConfig</a> filterConfig)</code> |
| <div class="block"> |
| Called by the web container to indicate to a filter that it is being placed into service.</div> |
| </td> |
| </tr> |
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| <a name="init-javax.servlet.FilterConfig-"> |
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| <h4>init</h4> |
| <pre>default void init(<a href="../../javax/servlet/FilterConfig.html" title="interface in javax.servlet">FilterConfig</a> filterConfig) |
| throws <a href="../../javax/servlet/ServletException.html" title="class in javax.servlet">ServletException</a></pre> |
| <div class="block"><p> |
| Called by the web container to indicate to a filter that it is being placed into service. |
| </p> |
| |
| <p> |
| The servlet container calls the init method exactly once after instantiating the filter. The init method must |
| complete successfully before the filter is asked to do any filtering work. |
| </p> |
| |
| <p> |
| The web container cannot place the filter into service if the init method either |
| </p> |
| <ol> |
| <li>Throws a ServletException |
| <li>Does not return within a time period defined by the web container |
| </ol></div> |
| <dl> |
| <dt><span class="paramLabel">Parameters:</span></dt> |
| <dd><code>filterConfig</code> - a <code>FilterConfig</code> object containing the filter's configuration and initialization |
| parameters</dd> |
| <dt><span class="throwsLabel">Throws:</span></dt> |
| <dd><code><a href="../../javax/servlet/ServletException.html" title="class in javax.servlet">ServletException</a></code> - if an exception has occurred that interferes with the filter's normal operation</dd> |
| </dl> |
| </li> |
| </ul> |
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| <h4>doFilter</h4> |
| <pre>void doFilter(<a href="../../javax/servlet/ServletRequest.html" title="interface in javax.servlet">ServletRequest</a> request, |
| <a href="../../javax/servlet/ServletResponse.html" title="interface in javax.servlet">ServletResponse</a> response, |
| <a href="../../javax/servlet/FilterChain.html" title="interface in javax.servlet">FilterChain</a> chain) |
| throws java.io.IOException, |
| <a href="../../javax/servlet/ServletException.html" title="class in javax.servlet">ServletException</a></pre> |
| <div class="block">The <code>doFilter</code> method of the Filter is called by the container each time a request/response pair is |
| passed through the chain due to a client request for a resource at the end of the chain. The FilterChain passed |
| in to this method allows the Filter to pass on the request and response to the next entity in the chain. |
| |
| <p> |
| A typical implementation of this method would follow the following pattern: |
| <ol> |
| <li>Examine the request |
| <li>Optionally wrap the request object with a custom implementation to filter content or headers for input |
| filtering |
| <li>Optionally wrap the response object with a custom implementation to filter content or headers for output |
| filtering |
| <li> |
| <ul> |
| <li><strong>Either</strong> invoke the next entity in the chain using the FilterChain object |
| (<code>chain.doFilter()</code>), |
| <li><strong>or</strong> not pass on the request/response pair to the next entity in the filter chain to block the |
| request processing |
| </ul> |
| <li>Directly set headers on the response after invocation of the next entity in the filter chain. |
| </ol></div> |
| <dl> |
| <dt><span class="paramLabel">Parameters:</span></dt> |
| <dd><code>request</code> - the <code>ServletRequest</code> object contains the client's request</dd> |
| <dd><code>response</code> - the <code>ServletResponse</code> object contains the filter's response</dd> |
| <dd><code>chain</code> - the <code>FilterChain</code> for invoking the next filter or the resource</dd> |
| <dt><span class="throwsLabel">Throws:</span></dt> |
| <dd><code>java.io.IOException</code> - if an I/O related error has occurred during the processing</dd> |
| <dd><code><a href="../../javax/servlet/ServletException.html" title="class in javax.servlet">ServletException</a></code> - if an exception occurs that interferes with the filter's normal operation</dd> |
| <dt><span class="seeLabel">See Also:</span></dt> |
| <dd><a href="../../javax/servlet/UnavailableException.html" title="class in javax.servlet"><code>UnavailableException</code></a></dd> |
| </dl> |
| </li> |
| </ul> |
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| <h4>destroy</h4> |
| <pre>default void destroy()</pre> |
| <div class="block"><p> |
| Called by the web container to indicate to a filter that it is being taken out of service. |
| </p> |
| |
| <p> |
| This method is only called once all threads within the filter's doFilter method have exited or after a timeout |
| period has passed. After the web container calls this method, it will not call the doFilter method again on this |
| instance of the filter. |
| </p> |
| |
| <p> |
| This method gives the filter an opportunity to clean up any resources that are being held (for example, memory, |
| file handles, threads) and make sure that any persistent state is synchronized with the filter's current state in |
| memory. |
| </p></div> |
| </li> |
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