过滤器案例----解决全站中文乱码问题

全站乱码案例:

     * 利用Servlet的doGet()和doPost()方法中,可以解决中文乱码:

       * doGet()
         String value = request.getParameter("");
	 value = new String(value.getBytes("ISO8859-1"),"utf-8");

	 response.setContentType("text/html;charset=utf-8");
       * doPost()
         request.setCharacterEncoding("utf-8");
	 response.setContentType("text/html;charset=utf-8");

     * 以上问题:
       * 实际开发时,Web应用程序的逻辑比较复杂(多个Servlet).
       * 上述的解决方案,仅能解决当前Servlet的中文乱码问题.

       * 如果使用上述方案,解决中文乱码问题:代码重复性太多.

EncodingFilter：

package app.java.filter.demo1;

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;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

/**
 * 当前Filter用于解决全站中文乱码问题.
 * @author JYL
 */
public class EncodingFilter implements Filter {

	public void destroy() {
		
	}

	public void doFilter(ServletRequest req, ServletResponse resp,
			FilterChain chain) throws IOException, ServletException {
		
		//1 进行Request与Response对象的类型强转
		HttpServletRequest request = (HttpServletRequest)req;
		HttpServletResponse response = (HttpServletResponse)resp;
		
		//2 解决中文乱码问题:1)请求的中文乱码(GET\POST);2)响应的中文乱码.
		request.setCharacterEncoding("utf-8");
		response.setContentType("text/html;charset=utf-8");
		
		//3 创建自定义的Request对象
		MyRequest myRequest = new MyRequest(request);
		
		//3 放行
		chain.doFilter(myRequest, response);
	}

	public void init(FilterConfig arg0) throws ServletException {
	}

}

MyRequest:

package app.java.filter.demo1;

import java.io.UnsupportedEncodingException;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletRequestWrapper;
/**
 * 自定义的Request对象
 * @author JYL
 */
public class MyRequest extends HttpServletRequestWrapper {

	public MyRequest(HttpServletRequest request) {
		super(request);
	}
	
	@Override
	public String getParameter(String name) {
		String value = super.getParameter(name);
		if(super.getMethod().equalsIgnoreCase("GET")){
			try {
				value = new String(value.getBytes("ISO-8859-1"),"utf-8");
			} catch (UnsupportedEncodingException e) {
				e.printStackTrace();
			}
		}
		return value;
	}

}

TestServlet:

package app.java.filter.demo1;

import java.io.IOException;
import java.io.PrintWriter;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class TestServlet extends HttpServlet {

	public void doGet(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {

		String username = request.getParameter("username");
		String password = request.getParameter("password");
		
		System.out.println(username+" : "+password);
		
		response.getWriter().println("中文解决了,真好!!!!");
	}

	public void doPost(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {

		String username = request.getParameter("username");
		String password = request.getParameter("password");
		
		System.out.println(username+" : "+password);
		
		response.getWriter().println("中文解决了,真好!!!!");
	}

}

xml:

  	EncodingFilter
  	demo1.EncodingFilter
  
  
  	EncodingFilter
  	/*
  

jsp:

    	用户名:

    	密码:

    	
    
    GET方式发送的请求

另一种：

package com.itheima.filter;

import java.io.IOException;
import java.io.UnsupportedEncodingException;
import java.util.Map;

import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletRequestWrapper;

public class MyFilter implements Filter {

	public void init(FilterConfig filterConfig) throws ServletException {

	}

	public void doFilter(ServletRequest request, ServletResponse response,
			FilterChain chain) throws IOException, ServletException {
		HttpServletRequest req = (HttpServletRequest) request;
		// 解决post方式
		// req.setCharacterEncoding("UTF-8");
		req = new MyRequest(req);

		chain.doFilter(req, response);
	}

	public void destroy() {
	}
}

// 实现与被包装对象相同的接口
// 定义一个与被包装类相对象的引用
// 定义一个构造方法，把被包装对象传过来
// 对于不需要改写方法，直接调用
// 对于无需要改写方法，写自己的方法体
class MyRequest extends HttpServletRequestWrapper {
	HttpServletRequest request;

	public MyRequest(HttpServletRequest request) {
		super(request);
		this.request = request;
	}

	/*
	 * @Override public String getParameter(String name) { name =
	 * request.getParameter(name);//乱码 try { return new
	 * String(name.getBytes("iso-8859-1"),"UTF-8"); } catch
	 * (UnsupportedEncodingException e) { e.printStackTrace(); } return null; }
	 */

	@Override
	public String getParameter(String name) {
		Map map = getParameterMap();
		return map.get(name)[0];
	}

	@Override
	public String[] getParameterValues(String name) {
		Map map = getParameterMap();
		return map.get(name);
	}

	private boolean flag = true;

	@Override
	public Map getParameterMap() {
		Map map = request.getParameterMap();// 乱码
		if (flag) {
			for (Map.Entry m : map.entrySet()) {
				String[] values = m.getValue();
				for (int i = 0; i < values.length; i++) {
					try {
						values[i] = new String(
								values[i].getBytes("iso-8859-1"), "UTF-8");
					} catch (UnsupportedEncodingException e) {
						e.printStackTrace();
					}
				}

			}
			flag = false;
		}
		return map;

	}

}