Useful Filter Examples

There is given some useful examples of filter.

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() {}
}

Example of counting number of visitors for a single page

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() {}
}

Example of checking total response time in filter

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() {}
}

Next TopicServletInputStream Class

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