【SpringDataJPA】——SpringDataJPA入门实例

布满荆棘的人生 2022-06-18 08:38 358阅读 0赞

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》][Spring Data JPA]、[《SpringDataJPA方法命名与操作对照》][SpringDataJPA]。

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>
                    
                    <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

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

[Spring Data JPA]: http://blog.csdn.net/linxingliang/article/details/52566963
[SpringDataJPA]: https://my.oschina.net/u/1778309/blog/783983
[SpringDataJPA_SpringDataJPA]: http://blog.csdn.net/huyuyang6688/article/details/68948126