springboot-连接数据库的几种方式-JPA

前言

我们已经学习了如何通过IDEA创建一个简单的springboot helloworld了，那么springboot如何连接mysql呢？

几种方式

Spring为各种支持的持久化技术，都提供了简单操作的模板和回调，目前大概有如下几种

ORM持久化技术	模板类
JDBC	org.springframework.jdbc.core.JdbcTemplate
Hibernate	org.springframework.orm.hibernate.HibernateTemplate
IBatis	org.springframework.orm.ibatis.SqlMapClientTemplate
JPA	org.springfrmaework.orm.jpa.JpaTemplate

目前比较通用流行的做法是使用mybatis，这里我们简单的介绍下JPA的方式，因为它使用的也不少，后续的教程很多都是基于mybatis或mybatis-plus的，所以这边不多介绍。至于其它的方式，有时间我再补上。

创建空项目

首先我们使用IDEA创建一个基础的springboot2.0的项目（创建的过程略，可以参考前几章），无需加载任何依赖（依赖还是手动加载感悟更深）。

添加依赖

编辑pom.xml：

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <scope>runtime</scope>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-data-jpa</artifactId>
        </dependency>

如图

添加配置

更改application.properties为application.yml，添加内容：

spring:
  datasource:
    url: jdbc:mysql://192.168.145.131:3306/test?useUnicode=true&characterEncoding=UTF-8&useSSL=false&autoReconnect=true&failOverReadOnly=false&serverTimezone=GMT%2B8
    username: root
    password: 123456
    driver-class-name: com.mysql.cj.jdbc.Driver

建库

创建名为test的数据库，建表执行

CREATE TABLE `person` (
  `id` int(11) NOT NULL,
  `name` varchar(255) DEFAULT NULL,
  `age` int(11) DEFAULT NULL,
  PRIMARY KEY (`id`)
) ENGINE=MyISAM DEFAULT CHARSET=utf8;

INSERT INTO `person` VALUES ('1', '1', '1');
INSERT INTO `person` VALUES ('2', '2', '2');
INSERT INTO `person` VALUES ('3', '3', '3');
INSERT INTO `person` VALUES ('4', '4', '4');
INSERT INTO `person` VALUES ('5', '5', '5');
INSERT INTO `person` VALUES ('6', '6', '6');
INSERT INTO `person` VALUES ('7', '7', '7');
INSERT INTO `person` VALUES ('8', '8', '8');
INSERT INTO `person` VALUES ('9', '9', '9');
INSERT INTO `person` VALUES ('10', '10', '10');
INSERT INTO `person` VALUES ('11', '11', '11');

完善

创建controller、entity和service的package，并创建对应的类文件，目录如下

controller/PersonController:

package com.mrcoder.sbjpa.controller;

import com.mrcoder.sbjpa.entity.Person;
import com.mrcoder.sbjpa.service.PersonRepository;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.RestController;

import java.util.List;

@RestController
public class PersonController {
    @Autowired
    private PersonRepository personRepository;

    @RequestMapping(value = "/list", method = RequestMethod.GET)
    public List<Person> getPersonList(){
        return personRepository.findAll();
    }
}

entity/Person:

package com.mrcoder.sbjpa.entity;

import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;

@Entity
public class Person {
    @Id
    @GeneratedValue
    @Column(nullable = true)
    private String name;
    @Column(nullable = true)
    private int age;

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

    public int getAge() {
        return age;
    }

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

    @Override
    public String toString() {
        return "Student{" +
                "name='" + name + '\'' +
                ", age=" + age + '}';
    }

}

service/PersonRepository:

package com.mrcoder.sbjpa.service;
import com.mrcoder.sbjpa.entity.Person;
import org.springframework.data.jpa.repository.JpaRepository;

public interface PersonRepository extends JpaRepository<Person, Long> {

}

运行

项目地址

https://github.com/MrCoderStack/SpringBootDemo/tree/master/sb-jpa

https://gitee.com/MrCoderStack/MrCoderStackBlog/tree/master/sb-jpa