git clone https://github.com/spring-guides/gs-accessing-data-jpa.git

└── src
  └── main
    └── java
      └── hello

buildscript {
  repositories {
    mavenCentral()
  }
  dependencies {
    classpath("org.springframework.boot:spring-boot-gradle-plugin:1.3.3.RELEASE")
  }
}

apply plugin: 'java'
apply plugin: 'eclipse'
apply plugin: 'idea'
apply plugin: 'spring-boot'

jar {
  baseName = 'gs-spring-boot'
  version = '0.1.0'
}

repositories {
  mavenCentral()
}

sourceCompatibility = 1.8
targetCompatibility = 1.8

dependencies {
  // tag::jetty[]
  compile("org.springframework.boot:spring-boot-starter-web") {
    exclude module: "spring-boot-starter-tomcat"
  }
  compile("org.springframework.boot:spring-boot-starter-jetty")
  // end::jetty[]
  // tag::actuator[]
  compile("org.springframework.boot:spring-boot-starter-actuator")
  // end::actuator[]
  compile('org.springframework.boot:spring-boot-starter-data-jpa:1.3.3.RELEASE')

  compile('mysql:mysql-connector-java:5.1.13')

  testCompile("junit:junit")
}

task wrapper(type: Wrapper) {
  gradleVersion = '2.3'
}

spring.datasource.url = jdbc:mysql://localhost:3306/test
spring.datasource.username = root
spring.datasource.password = root
#spring.datasource.driverClassName = com.mysql.jdbc.Driver

# Specify the DBMS
spring.jpa.database = MYSQL

# Keep the connection alive if idle for a long time (needed in production)
spring.datasource.testWhileIdle = true
spring.datasource.validationQuery = SELECT 1

# Show or not log for each sql query
spring.jpa.show-sql = true

# Hibernate ddl auto (create, create-drop, update)
spring.jpa.hibernate.ddl-auto = update

# Naming strategy
spring.jpa.hibernate.naming-strategy = org.hibernate.cfg.ImprovedNamingStrategy

# Use spring.jpa.properties.* for Hibernate native properties (the prefix is
# stripped before adding them to the entity manager)

# The SQL dialect makes Hibernate generate better SQL for the chosen database
spring.jpa.properties.hibernate.dialect = org.hibernate.dialect.MySQL5Dialect

package hello.Entities

import javax.validation.constraints.NotNull
import java.io.Serializable;
import javax.persistence.*;

/**
 * Created by Bruce on 2016/3/9.
 */
@Entity
@Table(name = "user")
data class User(@Id @GeneratedValue(strategy = GenerationType.AUTO) var id: Long? = 0,
        @Column(nullable = false) var name: String? = null,
        @Column(nullable = false) var email: String? = null) : Serializable {

  protected constructor() : this(id = null, name = null, email = null) {
  }
}

package hello.Entities

import org.springframework.data.repository.CrudRepository
import org.springframework.transaction.annotation.Transactional

@Transactional
interface UserDao : CrudRepository<User, Long> {
  fun findByEmail(email: String): User?
}

package hello.Controllers

import hello.Entities.User
import hello.Entities.UserDao
import org.springframework.beans.factory.annotation.Autowired
import org.springframework.web.bind.annotation.RestController
import org.springframework.web.bind.annotation.RequestMapping
import org.springframework.web.bind.annotation.ResponseBody

/**
 * Created by Bruce on 2016/3/9.
 */

@RestController
class UserController {
  @Autowired
  private var userDao: UserDao? = null

  @RequestMapping("/create")
  @ResponseBody
  public fun create(name: String, email: String): User? {
    try {
      var newUser = User(name = name, email = email)
      userDao?.save(newUser)

      return newUser
    } catch(e: Exception) {
      return null
    }
  }

  @RequestMapping("/delete")
  @ResponseBody
  public fun delete(id: Long): String {
    try {
      var user = User(id)
      userDao?.delete(user)

      return id.toString() + "deleted"
    } catch(e: Exception) {
      return "delete error " + e.message.toString()
    }
  }

  @RequestMapping("/get-by-email")
  @ResponseBody
  public fun getByEmail(email: String): User? {
    try {
      var user = userDao?.findByEmail(email)
      if (user != null) {
        return user
      } else {
        return null
      }
    } catch(e: Exception) {
      return null
    }
  }

  @RequestMapping("/update")
  @ResponseBody
  public fun updateUser(id: Long, name: String, email: String): User? {
    try {
      var user: User? = userDao?.findOne(id) ?: return null

      user?.name = name
      user?.email = email
      userDao?.save(user)

      return user
    } catch(e: Exception) {
      return null
    }
  }
}