【SpringDataJPA】——SpringDataJPA入门实例

　　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：[e-mail]:DannyHoo/SpringDataJPADemo.git

【 转载请注明出处——胡玉洋《【SpringDataJPA】——SpringDataJPA入门实例》】