Spring Data JPA 全局DAO的扩展(第一次用JPA时总是提示 另人抓狂的错误： No property find for type class )

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

Java代码







import java.io.Serializable;

import org.springframework.data.jpa.repository.JpaRepository;

public interface MyRepository<T, ID extends Serializable>

extends JpaRepository<T, ID> {

String sharedCustomMethod();

}

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import java.io.Serializable;

import org.springframework.data.jpa.repository.JpaRepository;

public interface MyRepository<T, ID extends Serializable>

extends JpaRepository<T, ID> {

String sharedCustomMethod();

}

其中sharedCustomMethod是全局的共享自定义方法。

然后在建一个实现类MyCustomRepository

Java代码







import java.io.Serializable;

import javax.persistence.EntityManager;

import org.springframework.data.jpa.repository.support.JpaEntityInformation;

import org.springframework.data.jpa.repository.support.SimpleJpaRepository;

import org.springframework.data.repository.NoRepositoryBean;

@NoRepositoryBean

public class MyCustomRepository<T, ID extends Serializable>

extends SimpleJpaRepository<T, ID> implements MyRepository<T, ID> {

private final EntityManager entityManager;

public MyCustomRepository(Class<T> domainClass, EntityManager em) {

super(domainClass, em);

// TODO Auto-generated constructor stub

entityManager=em;

}

public MyCustomRepository(final JpaEntityInformation<T, ?> entityInformation, final EntityManager entityManager) {

super(entityInformation, entityManager);

this.entityManager = entityManager;

}

public String sharedCustomMethod() {

return "hello sharedCustomMethod";

// implementation goes here

}

}

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import java.io.Serializable;

import javax.persistence.EntityManager;

import org.springframework.data.jpa.repository.support.JpaEntityInformation;

import org.springframework.data.jpa.repository.support.SimpleJpaRepository;

import org.springframework.data.repository.NoRepositoryBean;

@NoRepositoryBean

public class MyCustomRepository<T, ID extends Serializable>

extends SimpleJpaRepository<T, ID> implements MyRepository<T, ID> {

private final EntityManager entityManager;

public MyCustomRepository(Class<T> domainClass, EntityManager em) {

super(domainClass, em);

// TODO Auto-generated constructor stub

entityManager=em;

}

public MyCustomRepository(final JpaEntityInformation<T, ?> entityInformation, final EntityManager entityManager) {

super(entityInformation, entityManager);

this.entityManager = entityManager;

}

public String sharedCustomMethod() {

return "hello sharedCustomMethod";

// implementation goes here

}

}

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

Java代码







import java.io.Serializable;

import static org.mockito.Mockito.*;

import javax.persistence.EntityManager;

import org.springframework.data.jpa.repository.JpaRepository;

import org.springframework.data.jpa.repository.support.JpaEntityInformation;

import org.springframework.data.jpa.repository.support.JpaRepositoryFactory;

import org.springframework.data.repository.core.RepositoryMetadata;

public class MyRepositoryFactory extends JpaRepositoryFactory {

public MyRepositoryFactory(EntityManager entityManager) {

super(entityManager);

// TODO Auto-generated constructor stub

}

@Override

@SuppressWarnings("unchecked")

protected JpaRepository<?, ?> getTargetRepository(RepositoryMetadata metadata, EntityManager em) {

JpaEntityInformation<Object, Serializable> entityMetadata = mock(JpaEntityInformation.class);

when(entityMetadata.getJavaType()).thenReturn((Class<Object>) metadata.getDomainType());

return new MyCustomRepository<Object, Serializable>(entityMetadata, em);

}

/*

* (non-Javadoc)

*

* @see

* org.springframework.data.repository.support.RepositoryFactorySupport#

* getRepositoryBaseClass()

*/

@Override

protected Class<?> getRepositoryBaseClass(RepositoryMetadata metadata) {

return MyCustomRepository.class;

}

}

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import java.io.Serializable;

import static org.mockito.Mockito.*;

import javax.persistence.EntityManager;

import org.springframework.data.jpa.repository.JpaRepository;

import org.springframework.data.jpa.repository.support.JpaEntityInformation;

import org.springframework.data.jpa.repository.support.JpaRepositoryFactory;

import org.springframework.data.repository.core.RepositoryMetadata;

public class MyRepositoryFactory extends JpaRepositoryFactory {

public MyRepositoryFactory(EntityManager entityManager) {

super(entityManager);

// TODO Auto-generated constructor stub

}

@Override

@SuppressWarnings("unchecked")

protected JpaRepository<?, ?> getTargetRepository(RepositoryMetadata metadata, EntityManager em) {

JpaEntityInformation<Object, Serializable> entityMetadata = mock(JpaEntityInformation.class);

when(entityMetadata.getJavaType()).thenReturn((Class<Object>) metadata.getDomainType());

return new MyCustomRepository<Object, Serializable>(entityMetadata, em);

}

/*

* (non-Javadoc)

*

* @see

* org.springframework.data.repository.support.RepositoryFactorySupport#

* getRepositoryBaseClass()

*/

@Override

protected Class<?> getRepositoryBaseClass(RepositoryMetadata metadata) {

return MyCustomRepository.class;

}

}

接着在建一个MyRepositoryFactoryBean

Java代码







import java.io.Serializable;

import javax.persistence.EntityManager;

import org.springframework.data.jpa.repository.JpaRepository;

import org.springframework.data.jpa.repository.support.JpaRepositoryFactoryBean;

import org.springframework.data.repository.core.support.RepositoryFactorySupport;

public class MyRepositoryFactoryBean<T extends JpaRepository<Object, Serializable>> extends JpaRepositoryFactoryBean<T, Object, Serializable> {

@Override

protected RepositoryFactorySupport createRepositoryFactory(EntityManager em) {

return new MyRepositoryFactory(em);

}

}

[java] view
plaincopy

import java.io.Serializable;

import javax.persistence.EntityManager;

import org.springframework.data.jpa.repository.JpaRepository;

import org.springframework.data.jpa.repository.support.JpaRepositoryFactoryBean;

import org.springframework.data.repository.core.support.RepositoryFactorySupport;

public class MyRepositoryFactoryBean<T extends JpaRepository<Object, Serializable>> extends JpaRepositoryFactoryBean<T, Object, Serializable> {

@Override

protected RepositoryFactorySupport createRepositoryFactory(EntityManager em) {

return new MyRepositoryFactory(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。

Java代码







public interface UserDao extends MyRepository<User, Long> ,JpaSpecificationExecutor<User>{

}

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public interface UserDao extends MyRepository<User, Long> ,JpaSpecificationExecutor<User>{