SpringBoot整合JPA

1.创建SpringBoot工程，引入依赖如下：

<dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-data-jpa</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-jdbc</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
            <version>1.18.8</version>
            <scope>provided</scope>
        </dependency>

        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <scope>runtime</scope>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
            <exclusions>
                <exclusion>
                    <groupId>org.junit.vintage</groupId>
                    <artifactId>junit-vintage-engine</artifactId>
                </exclusion>
            </exclusions>
        </dependency>
</dependencies>

2.创建application.yml，配置相关属性：

spring:
  datasource:
    url: jdbc:mysql://localhost:3306/jpa?useUnicode=true&characterEncoding=utf-8&useSSL=false
    username: root
    password: ******
    driver-class-name: com.mysql.jdbc.Driver
  jpa:
    hibernate:
      ddl-auto: update #更新或者创建数据表
    show-sql: true #控制体显示sql语句

3.创建实体类User

package com.chenpeng.springboot.entity;

import lombok.Data;

import javax.persistence.*;

@Data//生成get和set方法
@Entity//告诉JPA这是一个实体类（和数据报映射的类）
@Table(name = "t_user")//@Table来指定和哪个数据表对应，如果省略默认表名就是类名小写
public class User {
    @Id//这是一个主键
    @GeneratedValue(strategy = GenerationType.IDENTITY)//自增主键
    private Integer id;

    @Column(name = "name", length = 10)
    private String name;

    @Column//省略默认类名就是属性名
    private String age;
}

4.创建UserRepository接口

package com.chenpeng.springboot.repository;

import com.chenpeng.springboot.entity.User;
import org.springframework.data.jpa.repository.JpaRepository;

//继承JpaRepository来完成对数据库的操作
public interface UserRepository extends JpaRepository<User, Integer> {

}

5.创建UserController

package com.chenpeng.springboot.controller;

import com.chenpeng.springboot.entity.User;
import com.chenpeng.springboot.repository.UserRepository;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RestController;

@RestController
public class UserController {

    @Autowired
    UserRepository userRepository;

    @GetMapping("/user/{id}")
    public User getUserById(@PathVariable("id") Integer id){
        //springboot版本2.0以后，废除了原来的findOne(id)方法，查询对象使用findById(id).get()
        User user = userRepository.findById(id).get();
        return user;
    }

    @GetMapping("/user")
    public User insertUser(User user){
        User save = userRepository.save(user);
        return save;
    }
}