2个有用的过滤器示例

给出了一些有用的过滤器示例。

仅通过过滤器发送响应的示例

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() {}
}

单页访问者计数示例

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() {}
}

在过滤器中检查总响应时间的示例

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() {}
}