一、SpringData JPA是什麼

而SpringDataJPA是什麼樣子的呢？相信學過hibernate的同學一定也學過hibernate template，甚至自己實現過hibernate template。沒錯，SpringData JPA就很像這樣一款template，把該有的東西都給你封裝好，當然，其強大不止這一點點。相信學過mybatis的同學也知道，我們只需要一個mapper介面與一些mapper.xml，就可以讓其代理實現的持久層。SpringDataJPA在使用的時候，也只需要宣告一個介面，讓其Spring以代理的形式生成Dao。對於SpringDataJPA與hibernate等ORM框架、JPA的關係是這樣子的：

SpringDataJPA對類似hibernate這樣的框架又做了一層封裝，以便於我們程式設計的時候使用更方便。好了，說了那麼多理論，下面就開始實踐吧。

二、開始實踐

1.建立maven web專案，名稱為springboot-jpa，在pom.xml中匯入以下依賴：

	<parent>
		<groupId>org.springframework.boot</groupId>
		<artifactId>spring-boot-starter-parent</artifactId>
		<version>1.4.1.RELEASE</version>
	</parent>

	<properties>
		<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
		<java.version>1.8</java.version>
		<springBoot.groupId>org.springframework.boot</springBoot.groupId>
	</properties>

	<dependencies>
		<!-- SpringBoot Start -->
		<dependency>
			<groupId>${springBoot.groupId}</groupId>
			<artifactId>spring-boot-starter-web</artifactId>
		</dependency>
		<!-- jpa -->
		<dependency>
			<groupId>${springBoot.groupId}</groupId>
			<artifactId>spring-boot-starter-data-jpa</artifactId>
		</dependency>
		<dependency>
			<groupId>${springBoot.groupId}</groupId>
			<artifactId>spring-boot-starter-test</artifactId>
		</dependency>
		<!-- mysql -->
		<dependency>
			<groupId>mysql</groupId>
			<artifactId>mysql-connector-java</artifactId>
		</dependency>
		<dependency>
			<groupId>junit</groupId>
			<artifactId>junit</artifactId>
			<version>4.12</version>
		</dependency>
	</dependencies>
 

2.編輯配置

server:
  port: 8080
  tomcat:
    uri-encoding: UTF-8
spring:
  datasource:
    url: jdbc:mysql://127.0.0.1:3306/springboot_test?characterEncoding=utf8
    username: root
    password: root
  jpa:
    database: MYSQL
    show-sql: true
    #hibernate ddl auto(validate,create,update,create-drop)
    hibernate:
      ddl-auto: update
      naming:
        strategy: org.hibernate.cfg.ImprovedNamingStrategy
    properties:
      hibernate:
        dialect: org.hibernate.dialect.MySQL5Dialect

package org.fage;

import org.springframework.boot.autoconfigure.domain.EntityScan;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.core.Ordered;
import org.springframework.core.annotation.Order;
import org.springframework.dao.annotation.PersistenceExceptionTranslationPostProcessor;
import org.springframework.data.jpa.repository.config.EnableJpaRepositories;
import org.springframework.transaction.annotation.EnableTransactionManagement;

/**
 * 
 * @author Caizhfy
 * @email [email protected]
 * @createTime 2017年10月30日
 * @description JPA基礎配置類
 *
 */
@Order(Ordered.HIGHEST_PRECEDENCE)
@Configuration
@EnableTransactionManagement(proxyTargetClass=true)
@EnableJpaRepositories(basePackages={"org.fage.**.repository"})
@EntityScan(basePackages={"org.fage.**.domain"})
public class JpaConfiguration {
	@Bean
	PersistenceExceptionTranslationPostProcessor persistenceExceptionTranslationPostProcessor(){
		return new  PersistenceExceptionTranslationPostProcessor();
	}
}

package org.fage;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.ImportAutoConfiguration;
import org.springframework.boot.autoconfigure.SpringBootApplication;
/**
 * 
 * @author Caizhfy
 * @email [email protected]
 * @createTime 2017年10月30日
 * @description Springboot-jpa學習建立步驟：
 * 						1.建立專案 
 *						2.新增依賴，填寫配置類
 *						3.配置application.yml
 *						4.配置實體jpa關係
 *						5.繼承jpaRepository
 *						6.編寫測試用例
 */

@SpringBootApplication
@ImportAutoConfiguration(value=JpaConfiguration.class)
public class App {
	public static void main(String[] args) {
		SpringApplication.run(App.class, args);
	}
}

3.建立實體建模：

@Entity
@Table(name = "department")
public class Department implements Serializable {
	

	private static final long serialVersionUID = 159714803901985366L;
	@Id
	@GeneratedValue(strategy=GenerationType.IDENTITY)
	private Long id;
	private String name;
	@OneToMany(mappedBy="department",fetch=FetchType.LAZY)
	private List<User> users;
	
//getter and setter
...
}

@Entity
@Table(name = "user")
public class User implements Serializable{

	@Id
	@GeneratedValue(strategy = GenerationType.IDENTITY)
	private Long id;
	private String username;
	@Column(name = "create_date")
	@DateTimeFormat(pattern = "yyyy-MM-dd HH:mm:ss")
	@Temporal(TemporalType.TIMESTAMP)
	private Date createDate;
	//一對多對映
	@ManyToOne
	@JoinColumn(name = "department_id")
	@JsonBackReference // 防止物件的遞迴訪問
	private Department department;
	//多對多對映
	@ManyToMany(fetch=FetchType.EAGER)
	@JoinTable(name = "user_role",
			joinColumns = {@JoinColumn(name="user_id")},
			inverseJoinColumns = {@JoinColumn(name = "role_id")}
			)

//getter and setter
}

@Entity
@Table(name="role")
public class Role implements Serializable{
	
	@Id
	@GeneratedValue(strategy=GenerationType.IDENTITY)
	private Long id;
	private String name;
	
	
//getter and setter 
	
}

4.建立持久層Dao

package org.fage.repository;

import org.fage.domain.Department;
import org.springframework.data.jpa.repository.JpaRepository;
import org.springframework.stereotype.Repository;

@Repository
public interface DepartmentRepository extends JpaRepository<Department, Long>{}

@Repository
public interface UserRepository extends JpaRepository<User, Long>{
	//And用法
	User findById(long id);
	
	User findByIdAndUsername(long id, String username);
	
	//Or用法
	User findByIdOrUsername(long id, String name);
	
	//Between用法
	User findByCreateDateBetween(Date start, Date end);
	
	//LessThan用法
	List<User> findByCreateDateLessThan(Date start);
	
	//GreaterThan用法
	List<User> findByCreateDateGreaterThan(Date start);
	
	//IsNull/IsNutNull用法
	List<User> findByUsernameIsNull();
	
	//Like/NotLike用法
	List<User> findByUsernameLike(String username);
	
	//OrderBy用法
	List<User> findByUsernameOrderByIdAsc(String username);
	
	//Not用法
	List<User> findByUsernameNot(String username);
	
	//In/NotIn用法
	List<User> findByUsernameIn(Collection<String> nameList);
	
	
}

@Repository
public interface RoleRepository extends JpaRepository<Role, Long>{}

@RunWith(SpringRunner.class)
@SpringBootTest
public class RepositoryTest {
	private final Logger log = LoggerFactory.getLogger(RepositoryTest.class);
	
	
	@Autowired
	UserRepository userRepository;
	@Autowired
	RoleRepository roleRepository;
	@Autowired
	DepartmentRepository departmentRepository;

	@Before
	public void initData() {
		departmentRepository.deleteAll();
		roleRepository.deleteAll();
		userRepository.deleteAll();

		Department d = new Department();
		d.setName("開發部");
		departmentRepository.save(d);
		Assert.assertNotNull(d.getId());

		Role r = new Role();
		r.setName("部門經理");
		roleRepository.save(r);
		Assert.assertNotNull(r.getId());
		List<Role> roles = new ArrayList<Role>();
		roles.add(r);

		User u = new User();
		u.setUsername("蔡智法");
		u.setCreateDate(new Date());
		u.setDepartment(d);
		u.setRoles(roles);
		userRepository.save(u);
		Assert.assertNotNull(u.getId());
	}

	@Test
	public void testGeneralMethod(){
		System.out.println(userRepository.findByUsernameLike("蔡智法"));
	}
	
	
	@Test
	public void testFindPage() {
		//hibernate一對多分頁原理：先分頁，然後在將id作為引子查詢（效率低）
		Pageable pageable = new PageRequest(0, 5, new Sort(Sort.Direction.ASC, "id"));
		Page<Department> page = departmentRepository.findAll(pageable);
		System.out.println(page.getNumberOfElements());
	}

}