Spring Data JPA 全局DAO的扩展

前几天看了springside4的mini-web代码发现确实有不少新的东东，咱这次单说说Spring Data JPA吧。

引用springside4的 wiki关于对Spring Data JPA的简介

Spring Data JPA在JPA上又做了一层封装，只要编写接口就够了，不用写一行实现代码，CRUD方法啦，分页啦，自动将findByLoginName()的方法定义翻译成适当的QL啦都由它包了：

public interface UserDao extends PagingAndSortingRepository<User, Long> {
User findByLoginName(String loginName);
}
使用上很简单，快速浏览一下下面的资料就够了。

只有一个坑爹的地方，如果要为UserDao扩展方法(而不是接口)，要新增一个UserDaoCustom接口，这时候，实现类的名字必须是UserDaoImpl，而不是UserDaoCustomImpl。

另外，除了智能地翻译连Less,Not,And,Or都支持的方法名，它当然也可以直接用@Query在方法上标注复杂的查询语句。

资料
•官方文档

•使用 Spring Data JPA 简化 JPA 开发 IBM DW上的中文版教程.

如果看完上面的资料 也许你对Spring Data JPA有了初步的认识，动动手你就知道他的强大，但是对DAO的扩展上有点麻烦，上面红字部分是对单个dao进行扩展的方法。下面我们来说一下对全局DAO的扩展，创建你自己的CustomRepository。

首先咱们要建一个自己的扩展接口类MyRepository

 importjava.io.Serializable;

 importorg.springframework.data.jpa.repository.JpaRepository;

 publicinterfaceMyRepository<T,IDextendsSerializable>
 extendsJpaRepository<T,ID>{

 StringsharedCustomMethod();
 }

 importjava.io.Serializable;

 importorg.springframework.data.jpa.repository.JpaRepository;

 publicinterfaceMyRepository<T,IDextendsSerializable>
 extendsJpaRepository<T,ID>{

 StringsharedCustomMethod();
 }

其中sharedCustomMethod是全局的共享自定义方法。

然后在建一个实现类MyCustomRepository

 importjava.io.Serializable;

 importjavax.persistence.EntityManager;

 importorg.springframework.data.jpa.repository.support.JpaEntityInformation;
 importorg.springframework.data.jpa.repository.support.SimpleJpaRepository;
 importorg.springframework.data.repository.NoRepositoryBean;

 @NoRepositoryBean
 publicclassMyCustomRepository<T,IDextendsSerializable>
 extendsSimpleJpaRepository<T,ID>implementsMyRepository<T,ID>{


 privatefinalEntityManagerentityManager;

 publicMyCustomRepository(Class<T>domainClass,EntityManagerem){
 super(domainClass,em);
 //TODOAuto-generatedconstructorstub

 entityManager=em;
 }

 publicMyCustomRepository(finalJpaEntityInformation<T,?>entityInformation,finalEntityManagerentityManager){
 super(entityInformation,entityManager);
 this.entityManager=entityManager;
 }


 publicStringsharedCustomMethod(){
 return"hellosharedCustomMethod";
 //implementationgoeshere
 }
 }

 importjava.io.Serializable;

 importjavax.persistence.EntityManager;

 importorg.springframework.data.jpa.repository.support.JpaEntityInformation;
 importorg.springframework.data.jpa.repository.support.SimpleJpaRepository;
 importorg.springframework.data.repository.NoRepositoryBean;

 @NoRepositoryBean
 publicclassMyCustomRepository<T,IDextendsSerializable>
 extendsSimpleJpaRepository<T,ID>implementsMyRepository<T,ID>{


 privatefinalEntityManagerentityManager;

 publicMyCustomRepository(Class<T>domainClass,EntityManagerem){
 super(domainClass,em);
 //TODOAuto-generatedconstructorstub

 entityManager=em;
 }

 publicMyCustomRepository(finalJpaEntityInformation<T,?>entityInformation,finalEntityManagerentityManager){
 super(entityInformation,entityManager);
 this.entityManager=entityManager;
 }


 publicStringsharedCustomMethod(){
 return"hellosharedCustomMethod";
 //implementationgoeshere
 }
 }

注意 @NoRepositoryBean一定要有的，还有全局的扩展实现类不要用Imp作为后缀名，不然会报异常的（目前还没搞清楚报异常的具体原因，个人猜测可能是和局部的扩展有冲突吧）。

然后在定义MyRepositoryFactory

 importjava.io.Serializable;

 importstaticorg.mockito.Mockito.*;

 importjavax.persistence.EntityManager;

 importorg.springframework.data.jpa.repository.JpaRepository;
 importorg.springframework.data.jpa.repository.support.JpaEntityInformation;
 importorg.springframework.data.jpa.repository.support.JpaRepositoryFactory;
 importorg.springframework.data.repository.core.RepositoryMetadata;


 publicclassMyRepositoryFactoryextendsJpaRepositoryFactory{

 publicMyRepositoryFactory(EntityManagerentityManager){
 super(entityManager);
 //TODOAuto-generatedconstructorstub
 }
 @Override
 @SuppressWarnings("unchecked")
 protectedJpaRepository<?,?>getTargetRepository(RepositoryMetadatametadata,EntityManagerem){

 JpaEntityInformation<Object,Serializable>entityMetadata=mock(JpaEntityInformation.class);
 when(entityMetadata.getJavaType()).thenReturn((Class<Object>)metadata.getDomainType());
 returnnewMyCustomRepository<Object,Serializable>(entityMetadata,em);
 }

 /*
 *(non-Javadoc)
 *
 *@see
 *org.springframework.data.repository.support.RepositoryFactorySupport#
 *getRepositoryBaseClass()
 */
 @Override
 protectedClass<?>getRepositoryBaseClass(RepositoryMetadatametadata){

 returnMyCustomRepository.class;
 }
 }

 importjava.io.Serializable;

 importstaticorg.mockito.Mockito.*;

 importjavax.persistence.EntityManager;

 importorg.springframework.data.jpa.repository.JpaRepository;
 importorg.springframework.data.jpa.repository.support.JpaEntityInformation;
 importorg.springframework.data.jpa.repository.support.JpaRepositoryFactory;
 importorg.springframework.data.repository.core.RepositoryMetadata;


 publicclassMyRepositoryFactoryextendsJpaRepositoryFactory{

 publicMyRepositoryFactory(EntityManagerentityManager){
 super(entityManager);
 //TODOAuto-generatedconstructorstub
 }
 @Override
 @SuppressWarnings("unchecked")
 protectedJpaRepository<?,?>getTargetRepository(RepositoryMetadatametadata,EntityManagerem){

 JpaEntityInformation<Object,Serializable>entityMetadata=mock(JpaEntityInformation.class);
 when(entityMetadata.getJavaType()).thenReturn((Class<Object>)metadata.getDomainType());
 returnnewMyCustomRepository<Object,Serializable>(entityMetadata,em);
 }

 /*
 *(non-Javadoc)
 *
 *@see
 *org.springframework.data.repository.support.RepositoryFactorySupport#
 *getRepositoryBaseClass()
 */
 @Override
 protectedClass<?>getRepositoryBaseClass(RepositoryMetadatametadata){

 returnMyCustomRepository.class;
 }
 }

接着在建一个MyRepositoryFactoryBean

 importjava.io.Serializable;

 importjavax.persistence.EntityManager;

 importorg.springframework.data.jpa.repository.JpaRepository;
 importorg.springframework.data.jpa.repository.support.JpaRepositoryFactoryBean;
 importorg.springframework.data.repository.core.support.RepositoryFactorySupport;

 publicclassMyRepositoryFactoryBean<TextendsJpaRepository<Object,Serializable>>extendsJpaRepositoryFactoryBean<T,Object,Serializable>{


 @Override
 protectedRepositoryFactorySupportcreateRepositoryFactory(EntityManagerem){

 returnnewMyRepositoryFactory(em);
 }
 }

 importjava.io.Serializable;

 importjavax.persistence.EntityManager;

 importorg.springframework.data.jpa.repository.JpaRepository;
 importorg.springframework.data.jpa.repository.support.JpaRepositoryFactoryBean;
 importorg.springframework.data.repository.core.support.RepositoryFactorySupport;

 publicclassMyRepositoryFactoryBean<TextendsJpaRepository<Object,Serializable>>extendsJpaRepositoryFactoryBean<T,Object,Serializable>{


 @Override
 protectedRepositoryFactorySupportcreateRepositoryFactory(EntityManagerem){

 returnnewMyRepositoryFactory(em);
 }
 }

最后在配置文件里需要定义

<jpa:repositories base-package="org.springside.examples.miniweb" transaction-manager-ref="transactionManager"

factory-class="org.springside.examples.miniweb.dao.account.MyRepositoryFactoryBean"

entity-manager-factory-ref="entityManagerFactory"/>

其实这里还有个repository-impl-postfix=" "个人理解他是来定义局部扩展库的实现类的后缀的默认是Imp。

呵呵 这样你就可以使用全局的自定义扩展库了。