springBoot jpa 表单关联查询

1、创建两个实体类

import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;

import javax.persistence.*;

@Entity
@Table(name = "link")
public class Link {
    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    private Integer id;
    private String name;
    private String link;
    private String img;
    private Integer code;
    private String shijian;

    public Link(){

    }

    public Integer getId() {
        return id;
    }

    public void setId(Integer id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getLink() {
        return link;
    }

    public void setLink(String link) {
        this.link = link;
    }

    public String getImg() {
        return img;
    }

    public void setImg(String img) {
        this.img = img;
    }

    public Integer getCode() {
        return code;
    }

    public void setCode(Integer code) {
        this.code = code;
    }

    public String getShijian() {
        return shijian;
    }

    public void setShijian(String shijian) {
        this.shijian = shijian;
    }
}

　　

import javax.persistence.*;

@Entity
@Table(name = "Link_url")
public class LinkUrl{
    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    private Integer id;
    @ManyToOne
    private Link link;

    public LinkUrl(){

    }
    public Integer getId() {
        return id;
    }

    public void setId(Integer id) {
        this.id = id;
    }

    public Link getLink() {
        return link;
    }

    public void setLink(Link link) {
        this.link = link;
    }
}

　　其中在第二个实体类中

@ManyToOne
    private Link link;

　　是其关联字段

2、controller 查询

Link <LinkUrl> datas = linkUrlRepository.findAll();

查询结果中  link中的对象就是关联的Link对象

查询 数据中 link对象里面的id为6的数据

Link <LinkUrl> datas = linkUrlRepository.findByLinkId(6);