springdatajpa多表一对多单向关联

7.多表关系—>一对多查询

7.1实体类配置–>一的一方:需要配置从表的外键

package com.xcl.domain;
import javax.persistence.*;
import java.util.HashSet;
import java.util.Set;
@Entity
@Table(name = "com_company")
public class Company {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Column(name = "com_id")
    private  Long comId;
    @Column(name = "com_name")
    private  String comName;
    @OneToMany(targetEntity = Employee.class,cascade = {CascadeType.PERSIST})//CascadeType.PERSIST级联新增
    @JoinColumn(name = "com_emp_id",referencedColumnName = "com_id")
    private Set<Employee> employees = new HashSet<Employee>(0);
    //TODO...
    //gettee()...
    //setter()...
    //toString()...
}

7.2实体类配置:多的一方–>正常配置,无需加入多余的信息

package com.xcl.domain;
import javax.persistence.*;
@Entity
@Table(name = "emp_employee")
public class Employee {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Column(name = "emp_id")
    private Long empId;
    @Column(name = "emp_name")
    private String empName;
}

7.3符合规范的Dao接口

package com.xcl.dao;
import com.xcl.domain.Company;
import org.springframework.data.jpa.repository.JpaRepository;
import org.springframework.data.jpa.repository.JpaSpecificationExecutor;
public interface CompanyDao extends JpaRepository<Company,Long>,JpaSpecificationExecutor<Company> {
}

package com.xcl.dao;
import com.xcl.domain.Employee;
import org.springframework.data.jpa.repository.JpaRepository;
import org.springframework.data.jpa.repository.JpaSpecificationExecutor;
public interface EmployeeDao extends JpaRepository<Employee,Long>,JpaSpecificationExecutor<Employee> {
}

7.4测试:多表关联一对多单向绑定操作

package com.xcl;
import com.xcl.dao.CompanyDao;
import com.xcl.dao.EmployeeDao;
import com.xcl.domain.Company;
import com.xcl.domain.Employee;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.test.annotation.Rollback;
import org.springframework.test.context.ContextConfiguration;
import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;
import org.springframework.transaction.annotation.Transactional;
import javax.persistence.Table;
import java.util.HashSet;
@RunWith(SpringJUnit4ClassRunner.class)
@ContextConfiguration(locations = "classpath:beans.xml")
public class OneToManyTest {
    @Autowired
    private CompanyDao companyDao;
    @Autowired
    private EmployeeDao employeeDao;
    /**
     * 一对多关系新增
     */
    @Test
    @Transactional  //配置事务
    @Rollback(false)    //不回滚
    public void test01() {
        //创建公司
        Company company = new Company();
        company.setComName("千度");
        //创建员工
        Employee employee01 = new Employee();
        employee01.setEmpName("小李");
        Employee employee02 = new Employee();
        employee02.setEmpName("老李");
        //添加员工到公司集合
        HashSet<Employee> empList = new HashSet<Employee>();
        empList.add(employee01);
        empList.add(employee02);
        company.setEmployees(empList);
        //执行保存操作
        companyDao.save(company);
        //执行结果-->保存 com_company 表一条信息-->保存emp_employee表两条信息,并增加外键字段com_emp_id,关联com_company表
    }
    /**
    *删除
    */
    @Test
    @Transactional
    @Rollback(false)
    public void test02() {
        //删除操作
        companyDao.delete(1L);
        //执行结果-->com_company表该条数据清除,与com_company表该条数据相关联的emp_employee表数据com_emp_id字段值变为null
    }
}