在本节中，给出了一个有用的过滤器示例。
这是一个仅通过过滤器发送响应的示例 -
文件：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() {}
}
计算单页访问次数的示例
文件：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
文件：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() {}
}
