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Jetty example source code file (UserAgentFilter.java)

This example Jetty source code file (UserAgentFilter.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Java - Jetty tags/keywords

filter, filterchain, hashmap, http, ioexception, map, matcher, pattern, regex, request, response, servlet, servletexception, servletexception, servletresponse, string, string, user-agent, useragentfilter, util

The Jetty UserAgentFilter.java source code

// ========================================================================
// Copyright 2006 Mort Bay Consulting Pty. Ltd.
// ------------------------------------------------------------------------
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at 
// http://www.apache.org/licenses/LICENSE-2.0
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
// ========================================================================

package org.mortbay.servlet;

import java.io.IOException;
import java.util.ArrayList;
import java.util.Enumeration;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.http.HttpServletRequest;

/* ------------------------------------------------------------ */
/** User Agent Filter.
 * <p>
 * This filter allows efficient matching of user agent strings for
 * downstream or extended filters to use for browser specific logic.
 * </p>
 * <p>
 * The filter is configured with the following init parameters:
 * <dl>
 * <dt>attribute
If set, then the request attribute of this name is set with the matched user agent string
* <dt>cacheSize
The size of the user-agent cache, used to avoid reparsing of user agent strings. The entire cache is flushed * when this size is reached</dd> * <dt>userAgent
A regex {@link Pattern} to extract the essential elements of the user agent. * The concatenation of matched pattern groups is used as the user agent name</dd> * <dl> * An example value for pattern is <code>(?:Mozilla[^\(]*\(compatible;\s*+([^;]*);.*)|(?:.*?([^\s]+/[^\s]+).*). These two * pattern match the common compatibility user-agent strings and extract the real user agent, failing that, the first * element of the agent string is returned. * @author gregw * */ public class UserAgentFilter implements Filter { private Pattern _pattern; private Map _agentCache = new HashMap(); private int _agentCacheSize=1024; private String _attribute; /* ------------------------------------------------------------ */ /* (non-Javadoc) * @see javax.servlet.Filter#destroy() */ public void destroy() { } /* ------------------------------------------------------------ */ /* (non-Javadoc) * @see javax.servlet.Filter#doFilter(javax.servlet.ServletRequest, javax.servlet.ServletResponse, javax.servlet.FilterChain) */ public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException { if (_attribute!=null && _pattern!=null) { String ua=getUserAgent(request); request.setAttribute(_attribute,ua); } chain.doFilter(request,response); } /* ------------------------------------------------------------ */ /* (non-Javadoc) * @see javax.servlet.Filter#init(javax.servlet.FilterConfig) */ public void init(FilterConfig filterConfig) throws ServletException { _attribute=filterConfig.getInitParameter("attribute"); String p=filterConfig.getInitParameter("userAgent"); if (p!=null) _pattern=Pattern.compile(p); String size=filterConfig.getInitParameter("cacheSize"); if (size!=null) _agentCacheSize=Integer.parseInt(size); } /* ------------------------------------------------------------ */ public String getUserAgent(ServletRequest request) { String ua=((HttpServletRequest)request).getHeader("User-Agent"); return getUserAgent(ua); } /* ------------------------------------------------------------ */ /** Get UserAgent. * The configured agent patterns are used to match against the passed user agent string. * If any patterns match, the concatenation of pattern groups is returned as the user agent * string. Match results are cached. * @param ua A user agent string * @return The matched pattern groups or the original user agent string */ public String getUserAgent(String ua) { if (ua==null) return null; String tag; synchronized(_agentCache) { tag = (String)_agentCache.get(ua); } if (tag==null) { Matcher matcher=_pattern.matcher(ua); if (matcher.matches()) { if(matcher.groupCount()>0) { for (int g=1;g<=matcher.groupCount();g++) { String group=matcher.group(g); if (group!=null) tag=tag==null?group:(tag+group); } } else tag=matcher.group(); } else tag=ua; synchronized(_agentCache) { if (_agentCache.size()>=_agentCacheSize) _agentCache.clear(); _agentCache.put(ua,tag); } } return tag; } }

Other Jetty examples (source code examples)

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