JSP过滤器的应用 编码过滤器

过滤器是向 Web 应用程序的请求和响应处理添加功能的Web 服务组件。
过滤器生命周期的各个阶段：
实例化->初始化--->过滤--->销毁
•过滤器必须实现javax.servlet.Filter接口,该接口中有
–init(…)
•参数类型：FilterConfig（初始化参数对象）
–doFilter(…)
•参数有三个类型分别是：ServletRequest，ServletResponse，FilterChain
–destroy()
在SRC下创建一个filter包创建一个filterEncoding类继承filter接口
 
[html]  package filter; 
 
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; 
 
/** 
 * @author Administrator 
 *字符编码的过滤器 
 */ 
public class filterEncoding implements Filter { 
    private String requestEncoding=""; 
    private String responseEncoding=""; 
   
    public void destroy() { 
        // TODO Auto-generated method stub 
        System.out.println("字符编码过滤器销毁！"); 
    } 
 
    public void doFilter(ServletRequest request, ServletResponse response, 
            FilterChain chain) throws IOException, ServletException { 
        // TODO Auto-generated method stub 
//      System.out.println("编码过滤器运行中。。。"); 
        //获取过滤链 
        request.setCharacterEncoding(requestEncoding); 
        response.setContentType(responseEncoding); 
        //执行过滤链 
        chain.doFilter(request, response); 
 
    } 
 
    public void init(FilterConfig conif) throws ServletException { 
        // TODO Auto-generated method stub 
        System.out.println("字符编码过滤器初始化！"); 
        //初始化时获取web.xml中的数据 
        requestEncoding=conif.getInitParameter("requestEncoding"); 
        responseEncoding=conif.getInitParameter("responseEncoding"); 
      
    } 
 
} 

package filter;

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;

/**
 * @author Administrator
 *字符编码的过滤器
 */
public class filterEncoding implements Filter {
 private String requestEncoding="";
 private String responseEncoding="";
 
 public void destroy() {
  // TODO Auto-generated method stub
  System.out.println("字符编码过滤器销毁！");
 }

 public void doFilter(ServletRequest request, ServletResponse response,
   FilterChain chain) throws IOException, ServletException {
  // TODO Auto-generated method stub
//  System.out.println("编码过滤器运行中。。。");
  //获取过滤链
  request.setCharacterEncoding(requestEncoding);
  response.setContentType(responseEncoding);
  //执行过滤链
  chain.doFilter(request, response);

 }

 public void init(FilterConfig conif) throws ServletException {
  // TODO Auto-generated method stub
  System.out.println("字符编码过滤器初始化！");
  //初始化时获取web.xml中的数据
  requestEncoding=conif.getInitParameter("requestEncoding");
  responseEncoding=conif.getInitParameter("responseEncoding");
    
 }

}
接着在web.xml中配置
[plain] <!-- 编码过滤器开始 -->  
 <filter> 
  <filter-name>filterEncoding</filter-name> 
  <filter-class>filter.filterEncoding</filter-class> 
  <init-param> 
   <param-name>requestEncoding</param-name> 
   <param-value>utf-8</param-value> 
  </init-param> 
  <init-param> 
   <param-name>responseEncoding</param-name> 
   <param-value>text/html;charset=utf-8</param-value> 
  </init-param> 
 </filter> 
  
 <filter-mapping> 
  <filter-name>filterEncoding</filter-name> 
  <url-pattern>/*</url-pattern> 
 </filter-mapping> 
<!-- 编码过滤器结束 --