IDEA 中创建Spring Data Jpa 项目的示例代码

<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>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>
 </dependency>
</dependencies>

spring:
 datasource:
 url: jdbc:mysql://dbserver.com:3306/user?useUnicode=true&characterEncoding=utf-8
 username: username
 password: password
 driver-class-name: com.mysql.cj.jdbc.Driver

server:
 port: 8080
 compression:
 enabled: true
 servlet:
 context-path: /

/**
 * 使用JPA注解配置映射关系
 */
@Entity //告诉JPA这是一个实体类（和数据表映射的类）
@Table(name = "tbl_user") //@Table来指定和哪个数据表对应；如果省略，默认表名就是该类名的小写：user
public class User {
 @Id //表示这个属性是数据表中的主键
 @GeneratedValue(strategy = GenerationType.IDENTITY) //还是一个自增的主键
 private Integer id;
 @Column(name = "last_name",length = 50) //这是和数据表对应的一个列,可以定义其在数据表中的名字及长度
 private String lastName;
 @Column //省略的情况，默认列名就是属性名
 private String email;
}

jpa:
 hibernate:
 ddl-auto: update #定义数据表的生成策略。update：更新或者创建数据表结构
 show-sql: true #控制台显示sql语句

/**
 * Dao/UserRepository.java
 * 继承JpaRepository来完成对数据库的操作
 * JpaRepository<T,id>,T表示要进行操作的实体类，id表示类的主键的类型
 */
public interface UserRepository extends JpaRepository<User,Integer> {
}

@RestController
@EnableAutoConfiguration
public class UserController {
 @Autowired
 UserRepository userRepository;

 @GetMapping("/user/{id}")
 public User getUser(@PathVariable("id") Integer id) {
 Optional<User> optional = userRepository.findById(id);
 if (optional.isPresent()) {
 User user = optional.get();
 return user;
 } else {
 return new User();
 }
 }

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