javaweb中的乱码问题大集合

package com.itheima.response;

import java.io.IOException;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
//使用字节流输出中文内容
public class ResponseDemo1 extends HttpServlet {

	public void doGet(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		test2(response);
	}
	//服务器端 UTF-8
	private void test2(HttpServletResponse response) throws IOException {
		String data = "您吃了吗";
		byte [] b = data.getBytes("UTF-8");
//服务器端 UTF-8		
		//通知浏览器，查UTF-8码表
，下面 三句话等效，写任意一句都对。		
		//response.getOutputStream().write("<meta http-equiv=‘Content-Type‘ content=‘text/html;charset=UTF-8‘>".getBytes());
		//response.setHeader("Content-Type", "text/html;charset=UTF-8");
		response.setContentType("text/html;charset=UTF-8");
		response.getOutputStream().write(b);
	}
	//服务器端和客户端都使用本地默认的编码GBK：没有乱码
	private void test1(HttpServletResponse response) throws IOException {
		String data = "您吃了吗";
		byte [] b = data.getBytes();//查GBK（本地默认的）
		response.getOutputStream().write(b);
	}

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

		doGet(request, response);
	}

}

2.用字符流输出中文，1是字节流输出中文

package com.itheima.response;

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;
//用字符流输出中文
public class ResponseDemo2 extends HttpServlet {

	public void doGet(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		String data = "还没有吃吃吃吃吃吃";
//		response.setCharacterEncoding("UTF-8");//该字符流默认的编码为UTF-8
//		response.setContentType("text/html;charset=UTF-8");//通知浏览器使用UTF-8
		//下面一句相当于上面的两句
		response.setContentType("text/html;charset=UTF-8");//不仅能通知浏览器使用UTF-8，而且还会改字符流的编码为UTF-8
		
		PrintWriter pw = response.getWriter();//在Servlet中，协议规定使用ISO-8859-1
		pw.write(data);
		
	}

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

		doGet(request, response);
	}

}

上面两个程序都是输出数据，以下是从表单(区别get和post两种方式，post方式处理起来比较简单)中获取中文数据，如何防止乱码呢？请看下面。。。

3.常用表单输入域的值获取

package com.itheima.request;

import java.io.IOException;
import java.lang.reflect.InvocationTargetException;

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

import org.apache.commons.beanutils.BeanUtils;

import com.itheima.domain.Student;
//常用表单输入域的值获取
public class RequestDemo5 extends HttpServlet {
	//GET请求方式的参数编码
	public void doGet(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		String name = request.getParameter("name");//码编错了
		//取到你传给我的字节序列
		byte b[] = name.getBytes("ISO-8859-1");
		//重新编码
		System.out.println(new String(b,"UTF-8"));
	}
	//POST请求方式的数据编码：建议使用
	public void doPost(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		
		request.setCharacterEncoding("UTF-8");//只对POST请求方式有效
		
		Student s = new Student();
		try {
			BeanUtils.populate(s, request.getParameterMap());//发生类型的自动转换，但仅限基本数据类型
		} catch (Exception e) {
			e.printStackTrace();
		}
		System.out.println(s);
	}

}

private void testDemo1(HttpServletRequest request)
			throws UnsupportedEncodingException {
		request.setCharacterEncoding("UTF-8");
		//response.setContentType("text/html;charset=UTF-8");//把得到的数据给浏览器的话，就要加上这句。如果是在控制台输出，就不需要加这句。
		String username = request.getParameter("username");
		System.out.println(username);
//		response.getWriter().write(username);
	}

4,分清请求编码和响应输出的编码，两者并没有关系

package com.itheima.request;

import java.io.IOException;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
//分清请求编码和响应输出的编码，两者并没有关系
public class RequestDemo6 extends HttpServlet {

	public void doGet(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		//接收数据：请求
		request.setCharacterEncoding("UTF-8");
		String name = request.getParameter("name");
		//----------------------------------------------------
		//响应数据：响应
		response.setContentType("text/html;charset=GBK");
		response.getWriter().write(name);
	}

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

		doGet(request, response);
	}

}

5.把表单中的数据封装到JavaBean，输入中文，也不报错。请看下面。。。

package com.itheima.request;

import java.io.IOException;
import java.lang.reflect.InvocationTargetException;
import java.util.Map;

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

import org.apache.commons.beanutils.BeanUtils;

import com.itheima.domain.User2;

public class RequestDemo0 extends HttpServlet {

	public void doGet(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		User2 user = new User2();
		
		request.setCharacterEncoding("UTF-8");
		
		System.out.println("封装前"+user.toString());
		Map<String, String[]> map = request.getParameterMap();
		response.setContentType("text/html;charset=UTF-8");
		try {
			BeanUtils.populate(user, map);
		} catch (IllegalAccessException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} catch (InvocationTargetException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
		
		System.out.println("封装后"+user.toString());
		response.getWriter().write(user.toString());
			
	}

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

		doGet(request, response);
	}

}

JavaBean：

package com.itheima.domain;

import java.util.Arrays;

public class User2 {
		private String username;
		private String[] password;
		private String code;
		@Override
		public String toString() {
			return "User2 [username=" + username + ", password="
					+ Arrays.toString(password) + ", code=" + code + "]";
		}
		public String getUsername() {
			return username;
		}
		public void setUsername(String username) {
			this.username = username;
		}
		public String[] getPassword() {
			return password;
		}
		public void setPassword(String[] password) {
			this.password = password;
		}
		public String getCode() {
			return code;
		}
		public void setCode(String code) {
			this.code = code;
		}
		
}

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