Spring经常喜欢做的事情就是封装，经过spring的封装结出的一大果实——SpringDataJPA可以很大程度上提高我们持久层的开发效率。
在SpringDataJPA下，只需要关注业务实现，无需关注持久层的逻辑，需要做的工作只是声明持久层的接口，并不需要亲自实现，实现接口这些工作SpringDataJPA都会帮你做好。它有个比较智能的特点，可以根据接口名称来判断你想进行的操作。比如针对UserDO定义如下一个Dao层接口：
public class UserDO{ private Long id; private String name; } public interface UserDAO extends PagingAndSortingRepository<UserDO,Long>{ public UserDO findUserById(Long id); public UserDO findUserByIdAndName(Long id,String name) }
仅仅需要定义上面的接口，不需要任何实现，调用的时候SpringDataJPA会自动根据findUserById方法的名字判断出来是根据id查询用户，根据findUserByIdAndName判断出是根据id和name查询用户，前提是接口名称需要遵守规范，SpringDataJPA就规定了方法命名的规范，规定方法前缀(find、read、get)、字段命名格式(字段首字母大写)、关键字(And、Or……)，详细规范可参考《Spring Data JPA方法定义规范》、《SpringDataJPA方法命名与操作对照》。
下面主要分享个入门时的小例子：
实体类UserDO.java
@Entity @Table(name="t_user") public class UserDO extends BaseEntity{ @Id @GeneratedValue(strategy= GenerationType.AUTO) private Long id; @Column(name = "name") private String name; public Long getId() { return id; } public UserDO setId(Long id) { this.id = id; return this; } public String getName() { return name; } public UserDO setName(String name) { this.name = name; return this; } }
对应接口UserDAO.java
public interface UserDAO extends PagingAndSortingRepository<UserDO,Long> { public UserDO findById(Long id); public UserDO findByIdAndName(Long id,String name); }
SpringDataJPA配置文件applicationContext-persistence.xml、
<?xml version="1.0" encoding="UTF-8"?> <beans xmlns="http://www.springframework.org/schema/beans" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:tx="http://www.springframework.org/schema/tx" xmlns:context="http://www.springframework.org/schema/context" xmlns:jpa="http://www.springframework.org/schema/data/jpa" xsi:schemaLocation=" http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-3.2.xsd http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx-3.2.xsd http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-3.2.xsd http://www.springframework.org/schema/data/jpa http://www.springframework.org/schema/data/jpa/spring-jpa-1.0.xsd"> <context:component-scan base-package="com.danny.springdata.dao"/> <bean id="myEmf" class="org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean"> <property name="dataSource" ref="dataSource"/> <property name="packagesToScan" value="com.danny.springdata.entities"/> <property name="jpaVendorAdapter"> <bean class="org.springframework.orm.jpa.vendor.HibernateJpaVendorAdapter"/> </property> <property name="jpaProperties"> <props> <prop key="hibernate.hbm2ddl.auto">update</prop> <prop key="hibernate.dialect">org.hibernate.dialect.MySQL5Dialect</prop> <!-- 自动建表 --> <prop key="hibernate.ddl-auto">update</prop> </props> </property> </bean> <bean id="dataSource" class="org.springframework.jdbc.datasource.DriverManagerDataSource"> <property name="driverClassName" value="com.mysql.jdbc.Driver"/> <property name="url" value="jdbc:mysql://localhost:3306/springdatajpa"/> <property name="username" value="root"/> <property name="password" value="123456"/> </bean> <bean id="transactionManager" class="org.springframework.orm.jpa.JpaTransactionManager"> <property name="entityManagerFactory" ref="myEmf"/> </bean> <tx:annotation-driven/> <bean id="persistenceExceptionTranslationPostProcessor" class="org.springframework.dao.annotation.PersistenceExceptionTranslationPostProcessor"/> <jpa:repositories base-package="com.danny.springdata.dao" entity-manager-factory-ref="myEmf" transaction-manager-ref="transactionManager"/> </beans>
测试UserDAOTest.java
@RunWith(SpringJUnit4ClassRunner.class) @ContextConfiguration(locations = {"classpath*:applicationContext-*.xml"}) public class UserDAOTest{ @Autowired private UserDAO userDAO; @Test public void findByIdTest() { UserDO userDO=userDAO.findById(1L); Assert.assertNotNull(userDO); } @Test public void findByIdAndNameTest() { UserDO userDO=userDAO.findByIdAndName(1L,"danny"); Assert.assertNotNull(userDO); } }
仅仅如此，so easy！
源码地址：git@github.com:DannyHoo/SpringDataJPADemo.git
