Example: com.ibm.websphere.LoggingFilter.java

The following example shows how to implement a filter:

package com.ibm.websphere;

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

public class LoggingFilter implements Filter 
{
    File _loggingFile = null;

    // implement the required init method     public void init(FilterConfig fc)
    {
        // create the logging file         xxx;
    }

    // implement the required doFilter method...this is where most of 
   the work is done     public void doFilter(ServletRequest request, 
     ServletResponse response, FilterChain chain)
    {
        try         {
            // add request info to the log file             synchronized(_loggingFile)
            {
                xxx;
            }
 
            // pass the request on to the next resource in the chain             chain.doFilter(request, response);
        }
        catch (Throwable t)
        {
            // handle problem...
        }
    }

    // implement the required destroy method     public void destroy()
    {
        // make sure logging file is closed         _loggingFile.close();
    }
}

Related concepts
Servlet filtering

Related reference
Filter, FilterChain, FilterConfig classes for servlet filtering
Web applications: Resources for learning