mysql连接serlevt的eclipse用法

//设置类对象
 package code;public class use {
 private String id;
 private String name;
 private String pre_cno;
 private String grade;
 use a;public String getId() {
  return id;
}
public void setId(String id) {
  this.id = id;
}
public String getName() {
  return name;
}
public void setName(String name) {
  this.name = name;
}
public String getPre_cno() {
  return pre_cno;
}
public void setPre_cno(String pre_cno) {
  this.pre_cno = pre_cno;
}
public String getGrade() {
  return grade;
}
public void setGrade(String grade) {
  this.grade = grade;
}}
 //获取数据库连接
 package code;import java.sql.Connection;
 import java.sql.DriverManager;
 import java.sql.Statement;
 import java.sql.ResultSet;
 import java.sql.SQLException;public class test {
 public static Connection conn=null;
 // 加载数据库驱动 com.mysql.jdbc.Driver
 public static Connection getConn(){
 String driver = “com.mysql.jdbc.Driver”;
 // 获取mysql连接地址
 String url = “jdbc:mysql://localhost:3306/user?&useSSL=false&serverTimezone=UTC”;
 // 数据名称
 String username = “****”;//填自己的用户名
 // 数据库密码
 String password = “root”;
 // 获取一个数据的连接// 获取连接的一个状态
    try{
        Class.forName(driver);
        //getConnection()方法，连接MySQL数据库！
        conn=DriverManager.getConnection(url,username,password);
        
         
      
     }
     catch(ClassNotFoundException e){
         //数据库驱动类异常处理
    System.out.println("数据库驱动加载失败！");
    e.printStackTrace();
     }
    catch(SQLException e1){
    //数据库连接失败异常处理
     e1.printStackTrace();
    }
    catch(Exception e2){
    e2.printStackTrace();
    }
    return conn;}
 }

在这里插入代码片
package code;

import java.io.IOException;
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;

/**
 * Servlet implementation class test01
 */
@WebServlet("/test01")
public class test01 extends HttpServlet {
  private static final long serialVersionUID = 1L;
       
    /**
     * @see HttpServlet#HttpServlet()
     */
    public test01() {
        super();
        // TODO Auto-generated constructor stub
    }

  /**
   * @see Servlet#init(ServletConfig)
   */
  public void init(ServletConfig config) throws ServletException {
    // TODO Auto-generated method stub
  }

  /**
   * @see Servlet#destroy()
   */
  public void destroy() {
    // TODO Auto-generated method stub
  }

  /**
   * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
   */
  protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    // TODO Auto-generated method stub
  }

  /**
   * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
   */
  protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
  request.setCharacterEncoding("UTF-8");
  String name=request.getParameter("username");
  String password=request.getParameter("password");
  if(name.equals("mr")&&password.equals("12345")){
    System.out.println("登陆成功");
    use user=new use();
    user.setGrade("95");
    user.setId("20181181");
    user.setName("林非凡");
    user.setPre_cno("c语言");
    boolean res=login.get().save(user);
    if(res==true){
      System.out.println("插入数据成功");
    }
    
    
}
  else{
    System.out.println("登陆失败");
  }
  }
  

}
package code;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.Statement;
import java.sql.ResultSet;
import java.sql.SQLException;

import com.mysql.jdbc.PreparedStatement;
public class login {
  public  static login connect=null;
  public  static login get(){
    if(connect==null){
      connect=new login();
      
    }
    return connect;
  }
  public boolean save(use a){
    Connection conn=null;
     try{
       conn=test.getConn();
         String sql="INSERT INTO lokin(Cno,Cname,Pre_cno,Credits)VALUES(?,?,?,?)";//注意填写中英文格式
         PreparedStatement pstmt=(PreparedStatement) conn.prepareStatement(sql);
       pstmt.setString(1,a.getGrade());
       pstmt.setString(2,a.getId());
       pstmt.setString(3,a.getName());
       pstmt.setString(4,a.getPre_cno());
       pstmt.executeUpdate();
       return true;
    }
      catch(SQLException e1){
          //数据库连接失败异常处理
           e1.printStackTrace();
           
          }
          catch(Exception e2){
          e2.printStackTrace();
          }
     finally{
       try{
         conn.close();
       }
       catch(SQLException e1){
              //数据库连接失败异常处理
               e1.printStackTrace();
              }
     }
      
     return false; 
          
  }
  

}
`
<%@ page language="java" contentType="text/html; charset=utf-8"
    pageEncoding="utf-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<title>我的</title>
</head>
<body>
<body>
  <h1>用户登录</h1> <hr>
        <form action="test01" method="post">
            <table>
                <tr>
                    <td>用户名：</td>
                    <td><input type="text" name="username" /></td>
                </tr>
                <tr>
                    <td>密码：</td>
                    <td><input type="password" name="password" /></td>
                </tr>
                <tr>
                    <td colspan="2"><input type="submit" name="login" value="登录"/></td>
                </tr>
            </table>    
        </form>
  </body>
</body>
</html>