org.mortbay.servlet.UserAgentFilter Maven / Gradle / Ivy
// ========================================================================
// 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.HashMap;
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.
*
* This filter allows efficient matching of user agent strings for
* downstream or extended filters to use for browser specific logic.
*
*
* The filter is configured with the following init parameters:
*
* - attribute
- If set, then the request attribute of this name is set with the matched user agent string
* - 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
* - 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
*
* An example value for pattern is (?: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;
}
}