Spring Data JPA,基础学习笔记.

http://static.springsource.org/spring-data/data-jpa/docs/current/reference/html/

1. Spring 配置简述.

	<jpa:repositories base-package="org.e.test.**.dao" entity-manager-factory-ref="entityManagerFactory" transaction-manager-ref="transactionManager"  />

        <tx:annotation-driven transaction-manager="transactionManager"  />
	
        <bean id="entityManagerFactory" class="org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean">
		<property name="dataSource" ref="dataSource" />
		<property name="jpaVendorAdapter" ref="hibernateJpaVendorAdapter" />
		<property name="packagesToScan">
			<list>
				<value>org.e.test.**.model</value>
			</list>
		</property>
		<property name="jpaProperties">
			<props>
				<prop key="hibernate.dialect">${hibernate.dialect}</prop>
				<prop key="hibernate.show_sql">${hibernate.show_sql}</prop>
				<prop key="hibernate.format_sql">true</prop>
......etc
			</props>
		</property>
	</bean>

	<bean id="hibernateJpaVendorAdapter" class="org.springframework.orm.jpa.vendor.HibernateJpaVendorAdapter">
		<property name="databasePlatform" value="${hibernate.dialect}" />
	</bean>
	
	<bean id="transactionManager" class="org.springframework.orm.jpa.JpaTransactionManager">
		<property name="entityManagerFactory" ref="entityManagerFactory" />
	</bean>

2.DAO


@Transactional 方面基本不变,该怎么用怎么用..

假设已有 Entity 类 User

@Entity
@Table(name = "t_user")
public class User
{
	@Id
	@Column(name = "user_id")
	@GeneratedValue(strategy = GenerationType.AUTO)
	private long userId;
	private String username;
	private String password;

2.1. DAO 类.
可以继承的接口有:

CRUD 功能的接口:
CrudRepository : org.springframework.data.repository.CrudRepository<T, ID>
CRUD + 分页的接口:
PagingAndSortingRepository : org.springframework.data.repository.PagingAndSortingRepository<T, ID>

例如:

public interface UserDao extends PagingAndSortingRepository<User, Long>

2.2 DAO 方法

已经定义了 UserDao 接口.不用实现里面的任何方法,spring 会帮你生成对应的代理类.也不用加 @Repository annotation,因为已经继承了 Repository 接口.

对于已有的方法就不做多的说明了,看了方法名就会用的.使用的时候在 Service 层注入对应的 UserDao 代理对象即可.


自定义方法.

例1.
根据命名规则写对应的抽象方法即可.根据 username 查找 user.只需在 UserDao 中 填写如下方法.

public List<User> findByUsername(String username);

例2.
根据两个属性查询.

public List<User> findByUsernameAndPassword(String username,String password);

附方法定义规则表:
http://static.springsource.org/spring-data/data-jpa/docs/current/reference/html/
Table 2.2. Supported keywords inside method names 部分.

例3.
锁:
可以使用 @Lock , 里面填入的是 JPA 的 LockModeType
*

	@Lock(LockModeType.PESSIMISTIC_READ)
	public List<User> findByUsername(String username);

对应的 sql 就是:

select * from t_user where username=? lock in share mode

*

	@Lock(LockModeType.PESSIMISTIC_WRITE)
	public List<User> findByUsername(String username);

对应的 sql 就是:

select * from t_user where username=? for update

例4.
分页

public List<User> findByUsername(String username, Pageable pageable);

Pageable 是一个定义分页属性的类.可以创建 Pageable 的实现类 PageRequest对象使用.

PageRequest pr = new PageRequest(int page, int size);
PageRequest pr = new PageRequest(int page, int size, Sort sort);

etc...

例5.
自己定义 query 语句.
@Query

 @Query("select u from User u where u.username= ?1")
  User findByUsername(String username);