SpringBoot2.3.0配置JPA的实现示例

JPA顾名思义就是Java Persistence API的意思，是JDK 5.0注解或XML描述对象－关系表的映射关系，并将运行期的实体对象持久化到数据库中。

依赖

spring-boot-starter-data-jdbc
spring-boot-starter-data-jpa
mysql-connector-java

									<dependency>

									  <groupId>org.springframework.boot</groupId>

									  <artifactId>spring-boot-starter-data-jdbc</artifactId>

									</dependency>

									<dependency>

									  <groupId>org.springframework.boot</groupId>

									  <artifactId>spring-boot-starter-data-jpa</artifactId>

									</dependency>

									<dependency>

									  <groupId>mysql</groupId>

									  <artifactId>mysql-connector-java</artifactId>

									  <scope>runtime</scope>

									</dependency>

application.yml

spring.jpa.hibernate.ddl-auto=update

如果数据库内没有表或表结构改变时根据Entity创建/更新

spring.jpa.show-sql=true

控制台打印sql

spring.jpa.database

指定数据库类型，可写可不写

									spring:

									 datasource:

									  driver-class-name: com.mysql.cj.jdbc.Driver

									  url: jdbc:mysql://localhost:3306/spring_boot?serverTimezone=GMT%2B8

									  username: root

									  password: root

									 jpa:

									  hibernate:

									   ddl-auto: update

									  show-sql: true

									  database: mysql

POJO

@Data是Lombok
@Entity告诉JPA这是一个实体类（和数据表映射的类）
@Table(name = “jpa_user”) 给表起名，不写默认为类名小写（user）
@Id设置主键
@GeneratedValue(strategy = GenerationType.IDENTITY) 使用自增
@Column(name = “jpa_username”,length = 40) 给列起名，不写默认为属性名（username）

									import lombok.Data;

									import javax.persistence.*;

									@Entity

									@Table(name = "jpa_user")

									@Data

									public class User {

									  @Id

									  @GeneratedValue(strategy = GenerationType.IDENTITY)

									  private Integer id;

									  @Column(name = "jpa_username",length = 40)

									  private String username;

									  @Column(name = "jpa_password")

									  private String password;

									}

Repository

JpaRepository的继承关系

SpringBoot2.3.0配置JPA的实现示例

所以继承JpaRepository

JpaRepository<T, ID>
第一个泛型就是要操作的Entity
第二个泛型就是Entity的Id主键类型
JpaRepository<User, Integer>

									package com.live.repository;

									import com.live.model.User;

									import org.springframework.data.jpa.repository.JpaRepository;

									public interface UserRepository extends JpaRepository<User,Integer> {

									}

Controller（测试）

1 2	`@Autowired` `@Autowired` `UserRepository userRepository;`

									package com.live.controller;

									import com.live.model.User;

									import com.live.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;

									import java.util.List;

									import java.util.Optional;

									@RestController

									public class UserJPAController {

									  @Autowired

									  UserRepository userRepository;

									  @GetMapping("/findAll")

									  public List<User> findAll() {

									    return userRepository.findAll();

									  }

									  @GetMapping("/findOne/{id}")

									  public Optional<User> findOne(@PathVariable(value = "id") Integer id) {

									    return userRepository.findById(id);

									  }

									  @GetMapping("/insert")

									  public User insertOne(User user) {

									    return userRepository.save(user);

									  }

									}