MySQL learning record 10getting started with JDBC

MySQL Learning record 10JDBC introduction

10.1 Database driven

The program transfers data through database driver and database

And suppose we have MySQL、Oracle、Sql Server Etc , Are we going to install multiple drivers ？ That's when JDBC.

10.2 What is? JDBC

JDBC（Java DataBase Connectivity） Namely Java Database connection , To put it bluntly, it is to use Java Language to operate the database . It turns out that we operate the database in the console SQL Statement to operate on the database ,JDBC Yes, it is Java Language sends to the database SQL sentence .

10.3 first JDBC Program

1、 Create a project , Create test database

CREATE DATABASE `jdbcStudy` CHARACTER SET utf8 COLLATE utf8_general_ci;

USE `jdbcStudy`;

CREATE TABLE `users`(
 `id` INT PRIMARY KEY,
 `NAME` VARCHAR(40),
 `PASSWORD` VARCHAR(40),
 `email` VARCHAR(60),
 birthday DATE
);

INSERT INTO `users`(`id`,`NAME`,`PASSWORD`,`email`,`birthday`)
VALUES(1,'zhangsan','123456','[email protected]','1980-12-04'),
(2,'lisi','123456','[email protected]','1981-12-04'),
(3,'wangwu','123456','[email protected]','1979-12-04')

2、 Import database driver

3、 Write test code

import java.sql.*;

// first jdbc Program 
public class JdbcFirstDemo {
    
    public static void main(String[] args) throws ClassNotFoundException, SQLException {
    
        //1. The load driver 
        Class.forName("com.mysql.jdbc.Driver");  // Fixed writing , The load driver 

        //2. User information and url
        String url = "jdbc:mysql://localhost:3306/jdbcstudy?useUnicode=true&characterEncoding=utf8&useSSL=false";
        String username = "root";
        String password = "123456";

        //3. Successful connection  Connection On behalf of the database 
        Connection connection = DriverManager.getConnection(url, username, password);

        //4. perform sql The object of 
        Statement statement = connection.createStatement();

        //5. perform sql
        String sql = "SELECT * FROM users";

        ResultSet resultSet = statement.executeQuery(sql);// Return result set   The result set encapsulates all the results of our query 

        while (resultSet.next()) {
    
            System.out.println("id=" + resultSet.getObject("id"));
            System.out.println("name=" + resultSet.getObject("NAME"));
            System.out.println("password=" + resultSet.getObject("PASSWORD"));
            System.out.println("email=" + resultSet.getObject("email"));
            System.out.println("birthday=" + resultSet.getObject("birthday"));
        }

        //6. Release the connection 
        resultSet.close();
        statement.close();
        connection.close();
    }
}

Step summary ：
1、 The load driver
2、 Connect to database DriverManager
3、 Get executed sql The object of Statement
4、 Get the returned result set
5、 Release the connection

DriverManager

Class.forName(“com.mysql.jdbc.Driver”); // Fixed writing , The load driver
Connection connection = DriverManager.getConnection(url, username, password);

connection On behalf of the database
Database settings auto commit

URL

String url = “jdbc:mysql:// The host address : Port number / Database name ? Parameters 1& Parameters 2&…”;
mysql The default port number is 3306

Statement

statement.executeQuery();// Query operation return Resultset
statement.execute();// Carry out any sql
statement.executeUpdate();// to update 、 Insert 、 Delete All use this Returns the number of rows affected

ResultSet： Query result set , Encapsulates all query results
Gets the specified data type

resultSet.getObject();// If you don't know the type of column, use this
resultSet.getString();// Know the type of column and use the corresponding
resultSet.getInt();
resultSet.getFloat();
resultSet.getDate();
...

Release resources

resultSet.close();
statement.close();
connection.close();