## org.mortbay.servlet
Class UserAgentFilter

    java.lang.Object
      org.mortbay.servlet.UserAgentFilter

All Implemented Interfaces:
  Filter

Direct Known Subclasses:
  GzipFilter

    public class UserAgentFilter

extends Object
implements Filter

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 `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

Constructor Summary
`UserAgentFilter()`

Method Summary
`void` `destroy()`
`void` `doFilter(ServletRequest request, ServletResponse response, FilterChain chain)`
`String` `getUserAgent(ServletRequest request)`
`String` `getUserAgent(String ua)` Get UserAgent.
`void` `init(FilterConfig filterConfig)`

Methods inherited from class java.lang.Object
`clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

Constructor Detail

### UserAgentFilter

    public UserAgentFilter()

Method Detail

### destroy

    public void destroy()

  Specified by:
    `destroy` in interface `Filter`

### doFilter

    public void doFilter(ServletRequest request,
                         ServletResponse response,
                         FilterChain chain)
                  throws IOException,
                         ServletException

  Specified by:
    `doFilter` in interface `Filter`
  Throws:
    `IOException`
    `ServletException`

### init

    public void init(FilterConfig filterConfig)
              throws ServletException

  Specified by:
    `init` in interface `Filter`
  Throws:
    `ServletException`

### getUserAgent

    public String getUserAgent(ServletRequest request)

### getUserAgent

    public String getUserAgent(String 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.

  Parameters:
    `ua` - A user agent string
  Returns:
    The matched pattern groups or the original user agent string

Copyright © 1995-2008 Mort Bay Consulting. All Rights Reserved.