Java Database Connectivity

网页后端基础：连接数据库

调用mysql-connector-java包(包装了方法)，实现数据库的连接。

MySQL数据库结构

运行结果

源码

package com.company;

import java.sql.*;

public class JDBC {

    String getInfo() {
        String url = "jdbc:mysql://localhost:3306/test?useTimezone=true&serverTimezone=GMT%2B8&useSSL=false&allowPublicKeyRetrieval=true";
        String username = "root";
        String password = "root";
        Connection conn = null;
        PreparedStatement pst = null;
        String sql = "select age,name from user";
        ResultSet rs = null;
        User user = new User();
        String result = "";

        try {
            Class.forName("com.mysql.cj.jdbc.Driver");

            conn = DriverManager.getConnection(url, username, password);
            //3.获取用于向数据库发送sql语句的

            pst =conn.prepareStatement(sql);//在此次传入，进行预编译

            pst.executeQuery();//在这里不需要传入sql


            sql = "select age,name from user";

            rs = pst.executeQuery(sql);

            while(rs.next()) {

                user.setAge(rs.getInt("age"));
                user.setName(rs.getString("name"));
                result += user.toString();
            }


        }catch (Exception e){
            e.printStackTrace();
        }


        if(rs!=null || pst!=null || conn!=null){
            try{
                assert rs != null;
                rs.close();
                pst.close();
                conn.close();
            }catch (Exception e) {
                e.printStackTrace();
            }
        }
        return result;
    }



    Result login(int username, int password){
        Result result = new Result();

        String url = "jdbc:mysql://localhost:3306/test?useTimezone=true&serverTimezone=GMT%2B8&useSSL=false&allowPublicKeyRetrieval=true";
        String user = "root";
        String pswd = "root";
        Connection conn = null;
        PreparedStatement pst = null;
        String sql = "select username,password from user";
        ResultSet rs = null;

        try {
            Class.forName("com.mysql.cj.jdbc.Driver");
            conn = DriverManager.getConnection(url, user, pswd);
            pst =conn.prepareStatement(sql);
            pst.executeQuery();
            sql = "select username,password from user";
            rs = pst.executeQuery(sql);

            while(rs.next()) {
                if(username == rs.getInt("username") &&
                        password == rs.getInt("password")){

                    rs.close();
                    pst.close();
                    conn.close();

                    result.setCode(10000);
                    result.setMsg("登陆成功");
                    return result;
                }
            }
        }catch (Exception e){
            e.printStackTrace();
        }

        try{
            assert rs != null;
            rs.close();
            pst.close();
            conn.close();
        }catch (Exception e) {
            e.printStackTrace();
        }

        result.setCode(10001);
        result.setMsg("登陆失败");
        return result;
    }
}
package com.company;

public class Result {
    private int code;
    private String msg;

    public String toString(){
        String str;
        str = "{  'code': " + code + ", " +
                "'msg': '" + msg + "' " +
                "}";
        return str;
    }

    public int getCode() {
        return code;
    }

    public void setCode(int code) {
        this.code = code;
    }

    public String getMsg() {
        return msg;
    }

    public void setMsg(String msg) {
        this.msg = msg;
    }
}
package com.company;


public class User {
    private int age;
    private String name;

    public String toString(){
        String str;
        str = "{  'age': " + age + ", " +
                "'name': '" + name + "' " +
                "}";
        return str;
    }

    String getName() {
        return name;
    }

    void setName(String name) {
        this.name = name;
    }

    int getAge() {
        return age;
    }

    void setAge(int age) {
        this.age = age;
    }
}

最后：主函数调用

package com.company;

import java.util.Scanner;

public class Main {

    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        JDBC jdbc = new JDBC();

        String str = jdbc.getInfo();
        System.out.println(str);

        int username = in.nextInt(), password = in.nextInt();
        Result result = jdbc.login(username, password);
        System.out.println(result.toString());
    }
}