烦恼岁月

Based on the popular and very useful mod_rewrite for apache, UrlRewriteFilter is a Java Web Filter for any J2EE compliant web application server (such as Resin, Orion or Tomcat), which allows you to rewrite URLs before they get to your code. It is a very powerful tool just like Apache's mod_rewrite.

URL rewriting is very common with Apache Web Server (see mod_rewrite's rewriting guide) but has not been possible in most java web application servers. The main things it is used for are:

• URL Tidyness / URL Abstraction - keep URLs tidy irrespective of the underlying technology or framework (JSP, Servlet, Struts etc).
• Browser Detection - Allows you to rewrite URLs based on request HTTP headers (such as user-agent or charset).
• Date based rewriting - Allows you to forward or redirect to other URL's based on the date/time (good for planned outages).
• Moved content - enable a graceful move of content or even a change in CMS.
• Tiny/Friendly URL's (i.e. blah.com/latest can be redirected to blah.com/download/ver1.2.46.2/setup.exe)
• A Servlet mapping engine (see Method Invocation)

UrlRewriteFilter uses an xml file, called urlrewrite.xml (it goes into the WEB-INF directory), for configuration. Most parameters can be Perl5 style Regular Expressions or Wildcard Expressions. This makes it very powerful indeed.

example:

web.xml

  <filter>
        <filter-name>UrlRewriteFilter</filter-name>
        <filter-class>org.tuckey.web.filters.urlrewrite.UrlRewriteFilter</filter-class>
    </filter>
    <filter-mapping>
        <filter-name>UrlRewriteFilter</filter-name>
        <url-pattern>/*</url-pattern>
        <dispatcher>REQUEST</dispatcher>
        <dispatcher>FORWARD</dispatcher>
    </filter-mapping>

urlrewrite.xml

<?xml version="1.0" encoding="utf-8"?>

    <!DOCTYPE urlrewrite
        PUBLIC "-//tuckey.org//DTD UrlRewrite 3.0//EN"
        "http://tuckey.org/res/dtds/urlrewrite3.0.dtd">

    <urlrewrite>
        <rule>
           <from>^/some/olddir/(.*)$</from>
           <to type="redirect">/very/newdir/$1</to>
        </rule>

        <rule match-type="wildcard">
           <from>/blog/archive/**</from>
           <to type="redirect">/roller/history/$1</to>
        </rule>
    </urlrewrite>