The purpose of dispatcher in filter-mapping in web.xml

 I used urlrewriter, but found some problems, the configuration is as follows:

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-->    < filter > <filter-name>UrlRewriteFilter</filter-name><filter-class>          org.tuckey.web.filters.urlrewrite.UrlRewriteFilter</filter-class><init-param><param-name>logLevel</param-name><param-value>TRACE</param-value></
    
    

    
            
            
         init-param >
     </ filter >
     < filter-mapping >
         < filter-name > UrlRewriteFilter </ filter-name >
         < url-pattern > *.do </ url-pattern >
     </ filter-mapping >

The 2.4 version of the servlet specification adds a new <dispatcher> element to the deployment descriptor. This element has four possible values: REQUEST, FORWARD, INCLUDE and ERROR. Any number can be added to a <filter-mapping> element The <dispatcher> makes the filter act on requests directly from the client, requests from forward, requests from include, and requests from <error-page>. If no <dispatcher> element is specified, the default value is REQUEST.
The following examples illustrate its usage:
Example 1:

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--> < filter-mapping >      //Filter mapping
< filter-name > Logging Filter </ filter-name >     //The name of the filter
< url-pattern > /person/* </ url-pattern >      // Intercept the url starting with person
</ filter-mapping >

In this case, the filter will be applied to requests that start with /person/... sent directly from the client. Because there is no <dispatcher> element specified here, the default value is REQUEST.

Example 2:

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--> < filter-mapping >
< filter-name > Logging Filter </ filter-name >      //过滤器的名字
< servlet-name > LogServlet </ servlet-name >  //截获名字为LogServlet的servletl
< dispatcher > INCLUDE </ dispatcher >   
</filter-mapping>

 
Intercepting a request for transmitting over ProductServlet to request dispatcher include a method of

Example 3:

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--> < filter-mapping >
< filter-name > Logging Filter </ filter-name >
< url-pattern > /person/* </ url-pattern >
< dispatcher > FORWARD </ dispatcher >
< dispatcher > REQUEST </ dispatcher >
</ filter-mapping >

In this case, if the request starts with /person/... and is passed through the forward method of the request dispatcher or directly from the client, it must pass through this filter.