SpringData:关联查询

一、查询方式

1、导航式查询

　　使用“对象.属性” 进行查询；对于多的查询，默认就是延迟加载，添加注解@Transactional

　　在OneToMany 注解中需要添加属性 fetch：值：FetchType.LAZY 延迟加载　　FetchType.ENAGER 及时加载

通过联系人查询客户；一的查询默认是及时加载，可以配置成延时加载

2、Specification查询

　　需求查询客户信息根据联系人的手机号查

　　需要查询 CustomerDao2需要继承JpaSpecificationExecutor接口

二、编写实体类

1、主表实体类关联从表添加属性所需添加的注解　　@OneToMany(mappedBy = "customer",cascade = CascadeType.ALL,fetch = FetchType.LAZY)

2、从表实体类关联主表添加属性所需添加的注解　　@ManyToOne(fetch = FetchType.LAZY)　　@JoinColumn(name="custid",referencedColumnName = "cust_id")

三、编写dao；主表da需要继承JpaRepository和JpaSpecificationExecutor从表dao需要继承JpaRepository

四、测试

package cn.zrf.jpa;

import cn.zrf.jpa.dao.Customer2Dao;

import cn.zrf.jpa.dao.LinkManDao;

import cn.zrf.jpa.entity.Customer2;

import cn.zrf.jpa.entity.LinkMan;

import org.junit.Test;

import org.junit.runner.RunWith;

import org.springframework.beans.factory.annotation.Autowired;

import org.springframework.data.jpa.domain.Specification;

import org.springframework.test.context.ContextConfiguration;

import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;

import org.springframework.transaction.annotation.Transactional;

import javax.persistence.criteria.*;

import java.util.Set;

@RunWith(SpringJUnit4ClassRunner.class)

@ContextConfiguration("classpath:applicationContext.xml")

public class QueryTest {

    @Autowired

    Customer2Dao customer2Dao;

    @Autowired

    LinkManDao linkManDao;

    @Test

    @Transactional

    public void queryCustomer(){

        Customer2 one = customer2Dao.findOne(1l);

//        System.out.println(one);

        //根据客户查询联系人信息

        Set<LinkMan> set = one.getLinkMans();

        for(LinkMan linkMan:set){

            System.out.println(linkMan);

        }

    }

    //根据联系人查询客户

    @Test

    @Transactional

    public void queryLinkMan(){

        LinkMan one = linkManDao.findOne(3l);

        System.out.println(one);

        Customer2 customer2 = one.getCustomer2();

        System.out.println(customer2);

    }

    //根据手机号查询

    @Test

    @Transactional

    public void questPhone(){

        Customer2 customer2 = customer2Dao.findOne(new Specification<Customer2>() {

            @Override

            public Predicate toPredicate(Root<Customer2> root, CriteriaQuery<?> criteriaQuery, CriteriaBuilder criteriaBuilder) {

                //root:关联联系人表

                //参数1、Customer2实体类中关联的属性的名称 参数2、连接方式

                Join<Object, Object> join = root.join("linkMans", JoinType.LEFT);

                //创建查询条件

                Predicate predicate = criteriaBuilder.equal(join.get("lkmPhone"), "1234");

                return predicate;

            }

        });

//        System.out.println(customer2);

        //获得客户信息查询联系人

        Set<LinkMan> linkMans = customer2.getLinkMans();

        for (LinkMan linkMan:linkMans){

            System.out.println(linkMan);

        }

    }

}

巴特西

SpringData:关联查询

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