/*
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* Licensed to the Apache Software Foundation (ASF) under one or more
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* contributor license agreements. See the NOTICE file distributed with
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* this work for additional information regarding copyright ownership.
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* The ASF licenses this file to You under the Apache License, Version 2.0
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* (the "License"); you may not use this file except in compliance with
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* the License. You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package filters;
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import java.io.IOException;
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import javax.servlet.Filter;
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import javax.servlet.FilterChain;
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import javax.servlet.FilterConfig;
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import javax.servlet.ServletException;
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import javax.servlet.ServletRequest;
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import javax.servlet.ServletResponse;
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/**
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* Example filter that can be attached to either an individual servlet
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* or to a URL pattern. This filter performs the following functions:
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* <ul>
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* <li>Attaches itself as a request attribute, under the attribute name
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* defined by the value of the <code>attribute</code> initialization
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* parameter.</li>
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* <li>Calculates the number of milliseconds required to perform the
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* servlet processing required by this request, including any
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* subsequently defined filters, and logs the result to the servlet
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* context log for this application.
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* </ul>
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*
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* @author Craig McClanahan
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*/
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public final class ExampleFilter implements Filter {
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// ----------------------------------------------------- Instance Variables
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/**
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* The request attribute name under which we store a reference to ourself.
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*/
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private String attribute = null;
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/**
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* The filter configuration object we are associated with. If this value
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* is null, this filter instance is not currently configured.
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*/
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private FilterConfig filterConfig = null;
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// --------------------------------------------------------- Public Methods
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/**
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* Take this filter out of service.
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*/
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@Override
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public void destroy() {
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this.attribute = null;
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this.filterConfig = null;
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}
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/**
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* Time the processing that is performed by all subsequent filters in the
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* current filter stack, including the ultimately invoked servlet.
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*
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* @param request The servlet request we are processing
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* @param response The servlet response we are creating
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* @param chain The filter chain we are processing
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*
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* @exception IOException if an input/output error occurs
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* @exception ServletException if a servlet error occurs
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*/
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@Override
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public void doFilter(ServletRequest request, ServletResponse response,
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FilterChain chain)
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throws IOException, ServletException {
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// Store ourselves as a request attribute (if requested)
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if (attribute != null) {
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request.setAttribute(attribute, this);
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}
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// Time and log the subsequent processing
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long startTime = System.currentTimeMillis();
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chain.doFilter(request, response);
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long stopTime = System.currentTimeMillis();
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filterConfig.getServletContext().log
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(this.toString() + ": " + (stopTime - startTime) +
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" milliseconds");
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}
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/**
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* Place this filter into service.
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*
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* @param fConfig The filter configuration object
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*/
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@Override
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public void init(FilterConfig fConfig) throws ServletException {
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this.filterConfig = fConfig;
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this.attribute = fConfig.getInitParameter("attribute");
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}
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/**
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* Return a String representation of this object.
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*/
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@Override
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public String toString() {
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if (filterConfig == null) {
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return ("ExampleFilter()");
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}
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return "ExampleFilter(" + filterConfig + ")";
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}
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}
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