servlet学习笔记二

配置过滤器

web.xml文件配置

一个过滤

<filter>   <filter-name>LogFilter</filter-name>   <filter-class>LogFilter</filter-class>   <init-param>  <param-name>test-param</param-name>  <param-value>Initialization Paramter</param-value>   </init-param></filter><filter-mapping>   <filter-name>LogFilter</filter-name>   <url-pattern>/*</url-pattern></filter-mapping>

多个过滤

<filter>   <filter-name>LogFilter</filter-name>   <filter-class>LogFilter</filter-class>   <init-param>  <param-name>test-param</param-name>  <param-value>Initialization Paramter</param-value>   </init-param></filter><filter>   <filter-name>AuthenFilter</filter-name>   <filter-class>AuthenFilter</filter-class>   <init-param>  <param-name>test-param</param-name>  <param-value>Initialization Paramter</param-value>   </init-param></filter><filter-mapping>   <filter-name>LogFilter</filter-name>   <url-pattern>/*</url-pattern></filter-mapping><filter-mapping>   <filter-name>AuthenFilter</filter-name>   <url-pattern>/*</url-pattern></filter-mapping>

需要注意的是：这些都是按顺序来执行的（关于执行和加载顺序以及web.xml的文件配置和详解可以看另一篇文章）

所以最好把filter放前边

然后是过滤器的文件代码

package com.bestnet.servlet;


import java.io.IOException;
import java.util.Date;


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 LogFilter implements Filter{


public void init(FilterConfig filterConfig) throws ServletException {
// TODO Auto-generated method stub
   // 获取初始化参数
     String testParam = filterConfig.getInitParameter("test-param"); 


     // 输出初始化参数
     System.out.println("Test Param: " + testParam); 
}





public void doFilter(ServletRequest request, ServletResponse response,
FilterChain chain) throws IOException, ServletException {
// TODO Auto-generated method stub
// 获取客户机的 IP 地址   
     String ipAddress = request.getRemoteAddr();


     // 记录 IP 地址和当前时间戳
     System.out.println("IP "+ ipAddress + ", Time "
                                      + new Date().toString());


     // 把请求传回过滤链
     chain.doFilter(request,response);
}


public void destroy() {
// TODO Auto-generated method stub

}
}