Servlet与JSP实现用户注册

SaveServlet
注意:
response.setContentType("text/html");
request.setCharacterEncoding("UTF-8");
response.setCharacterEncoding("UTF-8");
必须位于数据库操作和PrintWriter out=response.getWriter()之前，否则会乱码

package com.baozi;

import java.io.IOException;
import java.io.PrintWriter;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;

import javax.servlet.ServletConfig;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
@WebServlet(name="saveServlet",urlPatterns="/SaveServlet") //必须支持servlet3.0注释
public class SaveServlet extends HttpServlet {
    private static final long serialVersionUID = 1L;
    private Connection con=null;
    public SaveServlet() {
        super();

    }
    public void init(ServletConfig config) throws ServletException{
        String driver="com.mysql.jdbc.Driver";
        String url="jdbc:mysql://localhost:3306/javaweb";
        String user="root";
        String password="root";
        try {
            Class.forName(driver);
            con=DriverManager.getConnection(url,user,password);
            if(con!=null)
                System.out.println("数据库连接成功!");
        }catch(Exception e) {
            e.printStackTrace();
        }
        
    }
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

    //  response.getWriter().append("Served at: ").append(request.getContextPath());
    }

    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        response.setContentType("text/html");
        request.setCharacterEncoding("UTF-8");
        response.setCharacterEncoding("UTF-8");
        String username=request.getParameter("username");
        String useremail=request.getParameter("useremail");
        if(con!=null) {
            try {
                String sql="insert into userreg(username,useremail) values"+"(?,?)";
                PreparedStatement ps=con.prepareStatement(sql);
                ps.setString(1,username);
                ps.setString(2, useremail);
                ps.executeUpdate();
                PrintWriter out=response.getWriter();
                out.print(username);
                out.flush();
                out.close();
            }catch(Exception e) {
                e.printStackTrace();
            }
        }else {
            response.sendError(500,"数据库连接错误!");
        }
    }

}