Servlet Filters Filter

The filter is a Java class that implements the Javax.servlet.Filter interface. The Javax.servlet.Filter interface defines three methods:

Here is the code filter for all

 Packagefilter;Importjava.io.IOException;ImportJavax.servlet.Filter;ImportJavax.servlet.FilterChain;ImportJavax.servlet.FilterConfig;Importjavax.servlet.ServletException;Importjavax.servlet.ServletRequest;ImportJavax.servlet.ServletResponse; Public classCharacterencodingfilterImplementsFilter {filterconfig config;  Public voiddestroy () {//TODO auto-generated Method Stub            }     Public voidDoFilter (ServletRequest arg0, Servletresponse arg1, Filterchain arg2)throwsIOException, servletexception {String characterencoding=config.getinitparameter ("Characterencoding");        Arg0.setcharacterencoding (characterencoding);        Arg1.setcharacterencoding (characterencoding); Arg1.setcontenttype ("Text/html;charset=" +characterencoding);    Arg2.dofilter (arg0, arg1); }     Public voidInit (Filterconfig arg0)throwsservletexception {//TODO auto-generated Method Stub         This. config=arg0; }}

Web. XML configuration

  <Filter>      <Filter-name>Characterencodingfilter</Filter-name>      <Filter-class>Filter. Characterencodingfilter</Filter-class>      <Init-param>          <Param-name>Characterencoding</Param-name>          <Param-value>UTF-8</Param-value>      </Init-param>  </Filter>  <filter-mapping>      <Filter-name>Characterencodingfilter</Filter-name>      <Url-pattern>/*</Url-pattern>  </filter-mapping>

Using multiple filters

A WEB application can define several different filters based on specific purposes. Assume that you have defined two filters authenfilter and logfilter. You need to create a different mapping as described below, with the rest being roughly the same as explained above:

<Filter>   <Filter-name>Logfilter</Filter-name>   <Filter-class>Logfilter</Filter-class>   <Init-param>      <Param-name>Test-param</Param-name>      <Param-value>Initialization paramter</Param-value>   </Init-param></Filter><Filter>   <Filter-name>Authenfilter</Filter-name>   <Filter-class>Authenfilter</Filter-class>   <Init-param>      <Param-name>Test-param</Param-name>      <Param-value>Initialization paramter</Param-value>   </Init-param></Filter><filter-mapping>   <Filter-name>Logfilter</Filter-name>   <Url-pattern>/*</Url-pattern></filter-mapping><filter-mapping>   <Filter-name>Authenfilter</Filter-name>   <Url-pattern>/*</Url-pattern></filter-mapping>

Application Order of filters

The order of the filter-mapping elements in Web. XML determines the order in which the filter is applied to the Servlet by the website container. To reverse the order of the filters, you only need to invert the filter-mapping element in the Web. xml file.

For example, the above instance will first apply Logfilter and then apply Authenfilter, but the following instance will reverse the order:

<filter-mapping>   <Filter-name>Authenfilter</Filter-name>   <Url-pattern>/*</Url-pattern></filter-mapping><filter-mapping>   <Filter-name>Logfilter</Filter-name>   <Url-pattern>/*</Url-pattern></filter-mapping>

Servlet Filters Filter