FilterChain.doFilter(), what if I don't call this in Filter.doFilter()'s impl?

The FilterChain.doFilter() method is called somewhere in the Filter.doFilter() method's implementation. What if I don't call at all?

-- Srikanth

Hi,

The request processing will stop in the Filter.doFilter() method. It will not call next filter/resource in the chain.

Thanks

Thanks Narendra! But will the Servlet be called? (If there's a matching Servlet/JSP is found for that URL pattern) Sounds like a stupid question and I guess it will, am I right?

-- Srikanth

Try the following example. Run it first with no query string, then with the parameter interrupt=yes. (E.g, http://localhost/InterruptionFilterSample/index.jsp?interrupt=yes).

InterruptionFilter.java
-----------------------
package test;
 
import java.io.IOException;
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;
 
public class InterruptionFilter implements Filter{
    
    public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {
        HttpServletRequest req = (HttpServletRequest)request;
        
        if("yes".equalsIgnoreCase(req.getParameter("interrupt")))
            response.getWriter().write("Sorry, interrupted");
        else
            chain.doFilter(request, response);
        
        System.out.println("Returning from filter/servlet chain");
    }
    
    public void init(FilterConfig filterConfig) throws ServletException {
    }
    
    public void destroy() {
    }
}
 
index.jsp
---------
 
<%@page contentType="text/html"%>
<%@page pageEncoding="UTF-8"%>
<html>
    <head>
        <meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
        <title>Got there!</title>
    </head>
    <body>
 
    <h1>Got there!</h1>
    
    </body>
</html>
 
web.xml
-------
<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns="http://java.sun.com/xml/ns/j2ee"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee <a href="http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd"" target="_blank" rel="nofollow">http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd"</a>
         version="2.4">
    <welcome-file-list>
        <welcome-file>
            index.jsp
        </welcome-file>
    </welcome-file-list>
    
    <filter>
        <filter-name>InterruptionFilter</filter-name>
        <filter-class>test.InterruptionFilter</filter-class>
    </filter>
    
    <filter-mapping>
        <filter-name>InterruptionFilter</filter-name>
        <url-pattern>/index.jsp</url-pattern>
    </filter-mapping>
</web-app>

What do you see?
Why do you think it is called a FilterChain?
[ November 14, 2007: Message edited by: Jan van Mansum ]

Originally posted by Srikanth Raghavan:
Thanks Narendra! But will the Servlet be called? (If there's a matching Servlet/JSP is found for that URL pattern) Sounds like a stupid question and I guess it will, am I right?

-- Srikanth

Hi,

The FilterChain is built if the matching resource(Servlet/JSP) is found. If you do not call the doFilter method in the filter doFilter method, it means that you want to stop the processing and do not want to process the next filter or servlet or JSP. For example, you are writing the Security filter and do not want to process the Servlet/JSP if the user is not authenticated, then you can terminate the processing of request in the filter itself by not calling the FilterChain.doFilter method.

Hope this help

Thaks

Thanks Narendra and thank you Jan van Mansum for the wonderful example. Gonna take the exam on Saturday (tomorrow). I did the final Mock exam from HFSJ yesterday and I got 43 out of 69. I hope to get through the exam.

-- Srikanth