Spring Data 01 ：JDBC 访问 MySQL

目录

Spring Data 01 ：JDBC 访问 MySQL

Spring Data 02 ：Spring JdbcTemplate 访问 MySQL

Spring Data 03 ：JPA入门

Spring Data 04：Spring Data JPA入门

Spring Data 05 ： Spring Data JPA + SpringBoot2 集成多数据源

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一、添加依赖：jdbc的mysql连接驱动

    
      mysql
      mysql-connector-java
      8.0.15
    

    
      junit
      junit
      4.11
      test
    
  

二、添加JDBCUtil工具类：获取Connection，关闭Connection、Statement、ResultSet

package com.springboot.utils;
/**
 * author: x
 * Date:6/21/2019 11:03 AM
 */

import java.io.IOException;
import java.sql.*;


public class JDBCUtil {

    /**
     * @Description 获取Connection
     * @Return 所获得的JDBC的Connection
     * 工具类一般都是静态的，当其被使用时，直接通过类名.方法直接获取，不需要创建
     * */
    public static Connection getConnection() throws ClassNotFoundException, SQLException, IOException {
        String url = "jdbc:mysql://localhost:3306/student";
        String user = "root";
        String password = "root";
        String driverClass = "com.mysql.jdbc.Driver";

        Class.forName(driverClass);
        Connection connection = DriverManager.getConnection(url,user,password);
        return connection;
    }

    /**
     * 释放DB相关的资源
      */
    public static void release(ResultSet resultSet, Statement statement, Connection connection){
        if (resultSet != null){
            try {
                resultSet.clearWarnings();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
        if (statement != null){
            try {
                statement.clearWarnings();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
        if (connection != null){
            try {
                connection.clearWarnings();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
    }
}

三、建立student数据库和表

CREATE TABLE `student` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `name` varchar(255) DEFAULT NULL,
  `age` int(11) DEFAULT NULL,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=7 DEFAULT CHARSET=utf8;

四、创建Entity：Student

package com.springboot.domain;


public class Student {
    private int id;
    private String name;
    private int age;

    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

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

    public int getAge() {
        return age;
    }

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

五创建Student的dao接口和实现
接口：StudentDAO

package com.springboot.dao;

import com.springboot.domain.Student;
import java.util.List;

public interface StudentDAO {
    //查询所有学生
    public List query();

    //新增学生
    public void save(Student student);
}

实现：StudentDAOImpl

package com.springboot.dao;

import com.springboot.domain.Student;
import com.springboot.utils.JDBCUtil;

import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.util.ArrayList;
import java.util.List;

public class StudentDAOImpl implements StudentDAO {
    @Override
    public List query() {

        ArrayList students = new ArrayList<>();

        Connection connection = null;
        PreparedStatement preparedStatement = null;
        ResultSet resultSet = null;

        String sql = "select id, name, age from student";

        try {
                connection = JDBCUtil.getConnection();
                preparedStatement = connection.prepareStatement(sql);
                resultSet = preparedStatement.executeQuery();

                Student student = null;
                while (resultSet.next()){
                    int id = resultSet.getInt("id");
                    String name = resultSet.getString("name");
                    int age = resultSet.getInt("age");

                    student = new Student();
                    student.setId(id);
                    student.setName(name);
                    student.setAge(age);

                    students.add(student);
                }

        }catch (Exception e){
            e.printStackTrace();
        }finally {
            JDBCUtil.release(resultSet, preparedStatement, connection);
        }
        return students;
    }

    @Override
    public void save(Student student) {

        Connection connection = null;
        PreparedStatement preparedStatement = null;
        ResultSet resultSet = null;

        String sql = "insert into student(name ,age) values (?,?)";
        try {
            connection = JDBCUtil.getConnection();
            preparedStatement = connection.prepareStatement(sql);
            preparedStatement.setString(1,student.getName());
            preparedStatement.setInt(2,student.getAge());
            preparedStatement.executeUpdate();

        }catch (Exception e){
            e.printStackTrace();
        }finally {
            JDBCUtil.release(resultSet, preparedStatement, connection);
        }
    }
}

六、创建StudentDAOImpl的单元测试：StudentDAOImplTest

package com.springboot.utils.dao;

import com.springboot.dao.StudentDAOImpl;
import com.springboot.domain.Student;
import org.junit.Test;

import java.util.List;

public class StudentDAOImplTest {

    // 查询所有记录
    @Test
    public void testQuery(){
        StudentDAOImpl studentDAO = new StudentDAOImpl();
        List students = studentDAO.query();
        for (Student student:students){
            System.out.println("id"+student.getId()
                    +"name"+student.getName()
                    +"age"+student.getAge()
            );
        }

    }

    // 新增一个记录
    @Test
    public void testSave(){
        Student student = new Student();
        student.setName("小七");
        student.setAge(25);
        StudentDAOImpl studentDAO = new StudentDAOImpl();
        studentDAO.save(student);
    }
}

---

附：将数据库连接信息放到配置文件里的写法

• 修改代码成如下内容

        InputStream inputStream = JDBCUtil.class.getClassLoader().getResourceAsStream("db.properties");
        Properties properties = new Properties();
        properties.load(inputStream);

        String url = properties.getProperty("jdbc.url");
        String user = ("jdbc.user");
        String password = ("jdbc.password");
        String driverClass = ("jdbc.driverClass");

• 在resources目录新建db.properties 数据库连接配置文件

jdbc.url = jdbc:mysql:///student;
jdbc.user = root;
jdbc.password = root;
jdbc.driverClass = com.mysql.jdbc.Driver;