Spring Data JPA 全局DAO的擴展(第一次用JPA時總是提示 另人抓狂的錯誤： No property find for type class )

前幾天看了springside4的mini-web代碼發現確實有不少新的東東，咱這次單說說Spring Data JPA吧。 

引用springside4的 wiki關於對Spring Data JPA的簡介 

Spring Data JPA在JPA上又做了一層封裝，只要編寫接口就夠了，不用寫一行實現代碼，CRUD方法啦，分頁啦，自動將findByLoginName()的方法定義翻譯成適當的QL啦都由它包了：

public interface UserDao extends PagingAndSortingRepository<User, Long> { 
User findByLoginName(String loginName); 
} 
使用上很簡單，快速瀏覽一下下面的資料就夠了。 

只有一個坑爹的地方，如果要爲UserDao擴展方法(而不是接口)，要新增一個UserDaoCustom接口，這時候，實現類的名字必須是UserDaoImpl，而不是UserDaoCustomImpl。

另外，除了智能地翻譯連Less,Not,And,Or都支持的方法名，它當然也可以直接用@Query在方法上標註複雜的查詢語句。 

資料 
•官方文檔

•使用 Spring Data JPA 簡化 JPA 開發 IBM DW上的中文版教程.

 如果看完上面的資料 也許你對Spring Data JPA有了初步的認識，動動手你就知道他的強大，但是對DAO的擴展上有點麻煩，上面紅字部分是對單個dao進行擴展的方法。下面我們來說一下對全局DAO的擴展，創建你自己的CustomRepository。

 

首先咱們要建一個自己的擴展接口類MyRepository

 

import java.io.Serializable;

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

public interface MyRepository<T, ID extends Serializable>
extends JpaRepository<T, ID> {

String  sharedCustomMethod();
}

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是全局的共享自定義方法。

 

然後在建一個實現類MyCustomRepository

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
}
}

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，還有全局的擴展實現類不要用Imp作爲後綴名，不然會報異常的（目前還沒搞清楚報異常的具體原因，個人猜測可能是和局部的擴展有衝突吧）。

 

然後在定義MyRepositoryFactory

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;
    }
}

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;
    }
}

 

接着在建一個MyRepositoryFactoryBean

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);
    }
}

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);
    }
}

 
最後在配置文件裏需要定義

<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"/>

 其實這裏還有個repository-impl-postfix=" "個人理解他是來定義局部擴展庫的實現類的後綴的默認是Imp。

 

 呵呵 這樣你就可以使用全局的自定義擴展庫了。

 

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

}

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