java 代码

import java.io.IOException;
import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
public class FilterDemo1 implements Filter {
    @Override
    public void init(FilterConfig filterConfig) throws ServletException {
        // TODO Auto-generated method stub
        System.out.println("FilterDemo1的init方法被调用");
    }
    @Override
    public void doFilter(ServletRequest request, ServletResponse response,
            FilterChain chain) throws IOException, ServletException {
        // TODO Auto-generated method stub
        System.out.println("我是FilterDemo1，客户端向Servlet发送的请求被我拦截到了");
        chain.doFilter(request, response);
        System.out.println("我是FilterDemo1，Servlet向客户端发送的响应被我拦截到了");
    }
    @Override
    public void destroy() {
        System.out.println("FilterDemo1的destroy方法被调用");
    }
}

web.xml

<filter>
      <filter-name>filterDemo1</filter-name>
      <filter-class>com.filter.FilterDemo1</filter-class>
  </filter>
  <filter-mapping>
      <filter-name>filterDemo1</filter-name>
      <url-pattern>/*</url-pattern>
      <!-- /*是对所有的文件进行拦截 -->
  </filter-mapping>