在servlet中設置的字符編碼集爲什麼還會出現亂碼(親測)

首先我們拿個簡單的登錄看一下

代碼實例如下:
我們先看一下錯誤的代碼
1.LoginServlet.java

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

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

import org.apache.logging.log4j.LogManager;
import org.apache.logging.log4j.Logger;
/**
 * 登錄驗證控制模塊
 * @author 演示
 *
 */

public class LoginServlet extends BaseServlet {

	private static final Logger logger = LogManager.getLogger(LoginServlet.class);
	public void doGet(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		this.doPost(request, response);
	}

	public void doPost(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		
		login(request, response);
		
	}
	private void login(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		PrintWriter out = response.getWriter();
		response.setCharacterEncoding("utf-8");
		response.setContentType("text/html;charset=utf-8");
		
		String username = request.getParameter("userid");
		String pwd = request.getParameter("pwd");
		String path="welcome.jsp";
		try{
			if(username.equals("niuniu") && pwd.equals("0516")) {
				 process(request, response, path);
			}else {
				out.println("用戶名或者密碼錯誤！");
			}
		}catch(Exception e){
			e.printStackTrace();
			path="error/500.jsp";
		}
	}


}

頁面顯示亂碼

當我們改變代碼的順序再看

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

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

import org.apache.logging.log4j.LogManager;
import org.apache.logging.log4j.Logger;
/**
 * 登錄驗證控制模塊
 * @author 演示
 *
 */

public class LoginServlet extends BaseServlet {

	private static final Logger logger = LogManager.getLogger(LoginServlet.class);
	public void doGet(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		this.doPost(request, response);
	}

	public void doPost(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		
		login(request, response);
		
	}
	private void login(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		//設置編碼集，防止亂碼，這兩行必須放在最前面，即放在輸出流的前面
		response.setCharacterEncoding("utf-8");
		response.setContentType("text/html;charset=utf-8");
		PrintWriter out = response.getWriter();
		
		String username = request.getParameter("userid");
		String pwd = request.getParameter("pwd");
		String path="welcome.jsp";
		try{
			if(username.equals("niuniu") && pwd.equals("0516")) {
				 process(request, response, path);
			}else {
				out.println("用戶名或者密碼錯誤！");
			}
		}catch(Exception e){
			e.printStackTrace();
			path="error/500.jsp";
		}
	}


}

問題解決了