数据库

表company

id, name

表employee

employee_id,employee_name,company_id,price,monthtime,amount

实体类

Company

import lombok.Data;

import javax.persistence.*;

import java.util.ArrayList;

import java.util.List;

/**

* 测试一对多的查询 跟数据拼装差不多

*/

@Entity

@Table(name = "company")

@Data

public class Company {

@Id

@GeneratedValue(strategy = GenerationType.AUTO)

private int id;

private String name;

//最重要的地方 1

@OneToMany(cascade = CascadeType.ALL,fetch = FetchType.EAGER)

@JoinColumn(name = "companyId")//指2表连接的关键字

//or 2

@oneToMany(mappedBy="companyId",cascade=CascadeType.All,fetch=FetchType.EAGER)

private List employees=new ArrayList<>();

}

注解属性 mappedBy,是指关联关系可以从company类中的employees属性上获取；cascade属性设置成CascadeType.ALL,是说主从表全面建立级联关系；fetch属性设置成FetchType.EAGER，是指加载规则是即时加载。查看源码会发现默认情况下，OneToMany注解的fetch属性设置的是FetchType.LAZY。

Employee

import com.fasterxml.jackson.annotation.JsonProperty;

import lombok.Data;

import javax.persistence.*;

import java.math.BigDecimal;

@Entity

@Table(name = "employee")

@Data

public class Employee {

@Id

@GeneratedValue(strategy = GenerationType.AUTO)

private int employeeId;

private String employeeName;

private int companyId;

private BigDecimal price;

private int monthtime;

private BigDecimal amount;

}

Repository类

import com.xb.selltest.model.Company;

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

import org.springframework.stereotype.Repository;

import javax.swing.text.html.Option;

import java.util.List;

import java.util.Optional;

public interface CompanyRepository extends JpaRepository {

List findById(int id);

}

后面的方法大家都该知道，写service,impl,controller.或者直接去test也行