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;

/*
 * 字元編碼過濾器
*/
public class Encodingfilter implements
 
 Filter {
    //定義屬性儲存字元編碼集
        String encoding;
        
    //建構函式
    public Encodingfilter() {
        System.out.println("過濾器建構函式！");
    }
    //銷燬的方法
    public void destroy() {
        System.out.println("過濾器銷燬！");
    }
    //過濾的方法
    public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws
 
 IOException, ServletException {
        System.out.println("過濾器開始過濾！");
        
        //中文亂碼處理
        response.setContentType("text/html;charset="+encoding);
        response.setCharacterEncoding(encoding);
        request.setCharacterEncoding(encoding);
        
        //chain物件就是過濾器鏈物件
        //chain物件的doFilter方法令請求往下一個過濾器傳遞
 

        chain.doFilter(request, response);
    }

    //初始化的方法
    public void init(FilterConfig fConfig) throws ServletException {
        System.out.println("過濾器初始化！");
        
        //從配置檔案中讀取字元編碼集
        encoding = fConfig.getInitParameter("encoding");
    }

}

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;

/*
 * 字元編碼過濾器
*/
public class Encodingfilter implements Filter {
    //定義屬性儲存字元編碼集
        String encoding;
        
    //建構函式
    public Encodingfilter() {
        System.out.println("過濾器建構函式！");
    }
    //銷燬的方法
    public void destroy() {
        System.out.println("過濾器銷燬！");
    }
    //過濾的方法
    public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {
        System.out.println("過濾器開始過濾！");
        
        //中文亂碼處理
        response.setContentType("text/html;charset="+encoding);
        response.setCharacterEncoding(encoding);
        request.setCharacterEncoding(encoding);
        
        //chain物件就是過濾器鏈物件
        //chain物件的doFilter方法令請求往下一個過濾器傳遞
        chain.doFilter(request, response);
    }

    //初始化的方法
    public void init(FilterConfig fConfig) throws ServletException {
        System.out.println("過濾器初始化！");
        
        //從配置檔案中讀取字元編碼集
        encoding = fConfig.getInitParameter("encoding");
    }

}

xml配置：

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" id="WebApp_ID" version="2.5">
  <display-name>ch03</display-name>
  <welcome-file-list>
    <welcome-file>index.html</welcome-file>
    <welcome-file>index.htm</welcome-file>
    <welcome-file>index.jsp</welcome-file>
    <welcome-file>default.html</welcome-file>
    <welcome-file>default.htm</welcome-file>
    <welcome-file>default.jsp</welcome-file>
  </welcome-file-list>


  <context-param>
    <param-name>userName</param-name>
    <param-value>sa</param-value>
  </context-param>
  <context-param>
    <param-name>pwd</param-name>
    <param-value>888</param-value>
  </context-param>
  
  <!--過濾器-->
  <filter>
    <display-name>Encodingfilter</display-name>
    <filter-name>Encodingfilter</filter-name>
    <filter-class>filter.Encodingfilter</filter-class>
    <!--初始化-->
    <init-param>
      <param-name>encoding</param-name>
      <param-value>UTF-8</param-value>
    </init-param>
  </filter>
  <filter-mapping>
    <filter-name>Encodingfilter</filter-name>
    <url-pattern>/*</url-pattern>  <!--/*代表所有-->
  </filter-mapping>
  
</web-app>