Useful Filter Examples

Some Useful Examples of Filter are Given Below.

Example of Sending Response By Filter only:

MyFilter.java

import java.io.*;  
import javax.servlet.*;    

public class MyFilter implements Filter{  
    public void init(FilterConfig arg0) throws ServletException {}    

    public void doFilter(ServletRequest req, ServletResponse res,  
            FilterChain chain) throws IOException, ServletException {        

        PrintWriter out=res.getWriter();  
          
        out.print("<br/>this site is underconstruction..");  
        out.close();            

    }  
    public void destroy() {}  
}  

Counting number of visitors for a single Page in filter- Example

MyFilter.java

import java.io.*;  
import javax.servlet.*;    

public class MyFilter implements Filter{  
    static int count=0;  
    public void init(FilterConfig arg0) throws ServletException {}   

    public void doFilter(ServletRequest req, ServletResponse res,  
            FilterChain chain) throws IOException, ServletException {       

        PrintWriter out=res.getWriter();  
        chain.doFilter(request,response);           

        out.print("<br/>Total visitors "+(++count));  
        out.close();     

    }  
   public void destroy() {}  
}  

Checking Total Response Time in Filter- Example

MyFilter.java

import java.io.*;  
import javax.servlet.*;   

public class MyFilter implements Filter{  
    static int count=0;  
    public void init(FilterConfig arg0) throws ServletException {}   

    public void doFilter(ServletRequest req, ServletResponse res,  
            FilterChain chain) throws IOException, ServletException {       

        PrintWriter out=res.getWriter();  
        long before=System.currentTimeMillis();    

        chain.doFilter(request,response);            

        long after=System.currentTimeMillis();  
        out.print("<br/>Total response time "+(after-before)+" miliseconds");  
        out.close();           

    }  
    public void destroy() {}  
}