用Kotlin创建JPA规范对象

dependencies {
    implementation("org.jetbrains.kotlin:kotlin-stdlib-jdk8")
    implementation("org.springframework.boot:spring-boot-starter-data-jpa")
    implementation("com.h2database:h2")
}

import javax.persistence.*

@Entity
@Table(name = "users")
data class User(
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    val id: Long = 0,

    @Column(nullable = false)
    val name: String,

    @Column(nullable = false)
    val email: String
)

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

interface UserRepository : JpaRepository<User, Long>

spring.datasource.url=jdbc:h2:mem:testdb
spring.datasource.driverClassName=org.h2.Driver
spring.datasource.username=sa
spring.datasource.password=
spring.jpa.database-platform=org.hibernate.dialect.H2Dialect
spring.jpa.show-sql=true
spring.jpa.hibernate.ddl-auto=create

import org.springframework.stereotype.Service
import org.springframework.transaction.annotation.Transactional

@Service
@Transactional
class UserService(private val userRepository: UserRepository) {
    fun createUser(name: String, email: String): User {
        val user = User(name = name, email = email)
        return userRepository.save(user)
    }

    fun getUserById(id: Long): User? {
        return userRepository.findById(id).orElse(null)
    }

    // 其他操作方法...
}