import com.xer.aisell.query.BaseQuery;
import org.springframework.data.domain.Page;
import org.springframework.data.jpa.repository.JpaRepository;
import org.springframework.data.jpa.repository.JpaSpecificationExecutor;
import org.springframework.data.repository.NoRepositoryBean;
import java.io.Serializable;
import java.util.List;
/**
 * 雖然jpadata提供的功能已經(jīng)足夠強(qiáng)大了，但是依然還是不能滿足實(shí)際開發(fā)中的所有需求
 * 所以希望在具有它功能的前提下再拓展一些功能
 * 之前是通過每個(gè)實(shí)體類的repository接口來(lái)直接繼承JpaRepository接口，現(xiàn)在我們可以在中間添加一個(gè)父類接口BaseRepository
 * BaseRepository繼承JpaRepository，再由實(shí)體類repository來(lái)繼承BaseRepository
 * 這樣就能夠?qū)崿F(xiàn)既實(shí)現(xiàn)了功能，又能隨時(shí)擴(kuò)展功能
 * @param <T>
 * @param <ID>
 */
@NoRepositoryBean
public interface BaseRepository<T,ID extends Serializable> extends JpaRepository<T,ID>,JpaSpecificationExecutor<T>{
    //根據(jù)Query拿到分頁(yè)對(duì)象(分頁(yè))
    Page findPageByQuery(BaseQuery baseQuery);
    //根據(jù)Query拿到對(duì)應(yīng)的所有數(shù)據(jù)(不分頁(yè))
    List<T> findByQuery(BaseQuery baseQuery);
    //根據(jù)jpql與對(duì)應(yīng)的參數(shù)拿到數(shù)據(jù)
    List findByJpql(String jpql,Object... values);
}

import com.xer.aisell.query.BaseQuery;
import org.springframework.data.domain.Page;
import org.springframework.data.domain.PageRequest;
import org.springframework.data.domain.Pageable;
import org.springframework.data.domain.Sort;
import org.springframework.data.jpa.domain.Specification;
import org.springframework.data.jpa.repository.support.SimpleJpaRepository;
import javax.persistence.EntityManager;
import javax.persistence.Query;
import java.io.Serializable;
import java.util.List;
public class BaseRepositoryImpl<T,ID extends Serializable> extends SimpleJpaRepository<T,ID> implements BaseRepository<T,ID> {
    private final EntityManager entityManager;
    public BaseRepositoryImpl(Class<T> domainClass, EntityManager em) {
        super(domainClass, em);
        this.entityManager = em;
    }
    @Override
    /**
     * 分頁(yè)
     */
    public Page findPageByQuery(BaseQuery baseQuery) {
        //拿到條件
        Specification spec = baseQuery.createSpec();
        //創(chuàng)建排序
        Sort sort = baseQuery.getSort();
        //分頁(yè)
        Pageable page = new PageRequest(baseQuery.getJPACurrentPage(), baseQuery.getPageSize(), sort);
        return super.findAll(spec,page);
    }
    /**
     * 不分頁(yè)查詢
     * @param baseQuery
     * @return
     */
    @Override
    public List findByQuery(BaseQuery baseQuery) {
        //獲取到條件
        Specification spec = baseQuery.createSpec();
        //排序
        Sort sort = baseQuery.getSort();
        return super.findAll(spec,sort);
    }
    /**
     *
     * 根據(jù)傳入JPQL查詢
     * @param jpql
     * @param values
     * @return
     */
    @Override
    public List findByJpql(String jpql, Object... values) {
        Query query = entityManager.createQuery(jpql);
        //為傳入JPQL填充條件值
        if (values != null) {
            for (int i = 0;i < values.length;i++) {
                query.setParameter(i+1,values[i]);
            }
        }
        return query.getResultList();
    }
}

import com.xer.aisell.domain.Employee;
import org.springframework.data.jpa.repository.JpaRepository;
import org.springframework.data.jpa.repository.JpaSpecificationExecutor;
import org.springframework.data.jpa.repository.Query;
import java.util.List;
/***
 *用于數(shù)據(jù)庫(kù)操作
 */
public interface EmployeeRepository extends BaseRepository<Employee,Long> {
    /**
     * 可以自己擴(kuò)展
     */
    List<Employee> findByUsernameLike(String username);
    /**
     * 使用@Query
     *  實(shí)現(xiàn)自己寫JPQL查詢
     */
    @Query("select o from Employee o where username like ?1")
    List<Employee> findByUsername(String username);
    /**
     * 當(dāng)然也可以實(shí)現(xiàn)自己寫SQL
     */
    @Query(nativeQuery = true,value = "SELECT COUNT(*) FROM employee")
    Long getCount();
}

import org.springframework.data.jpa.repository.support.JpaRepositoryFactory;
import org.springframework.data.jpa.repository.support.JpaRepositoryFactoryBean;
import org.springframework.data.repository.Repository;
import org.springframework.data.repository.core.RepositoryInformation;
import org.springframework.data.repository.core.RepositoryMetadata;
import org.springframework.data.repository.core.support.RepositoryFactorySupport;
import javax.persistence.EntityManager;
import java.io.Serializable;
public class BaseRepositoryFactoryBean<T extends Repository<S, ID>, S, ID extends Serializable> extends JpaRepositoryFactoryBean<T,S,ID> {
    @Override
    protected RepositoryFactorySupport createRepositoryFactory(EntityManager entityManager) {
        return new MyRepositoryFactory<T,ID>(entityManager); //注：這里創(chuàng)建是我們的自定義類
    }
    //繼承JpaRepositoryFactory后，把返回的對(duì)象修改成我們自己的實(shí)現(xiàn)
    private static  class MyRepositoryFactory<T,ID extends Serializable>   extends JpaRepositoryFactory {
        private final EntityManager entityManager;
        /**
         * Creates a new {@link JpaRepositoryFactory}.
         *
         * @param entityManager must not be {@literal null}
         */
        public MyRepositoryFactory(EntityManager entityManager) {
            super(entityManager);
            this.entityManager = entityManager;
        }
        //這里返回最后的功能對(duì)象
        @Override
        protected Object getTargetRepository(RepositoryInformation information) {
            return new BaseRepositoryImpl<T,ID>((Class<T>)information.getDomainType(),entityManager);
        }
        //確定功能對(duì)象的類型
        @Override
        protected Class<?> getRepositoryBaseClass(RepositoryMetadata metadata) {
            return BaseRepositoryImpl.class;
        }
    }
}

 <jpa:repositories base-package="com.xer.aisell.dao" entity-manager-factory-ref="entityManagerFactory"
                      transaction-manager-ref="transactionManager"
                        factory-class="com.xer.aisell.dao.BaseRepositoryFactoryBean"/>