[英]How to manage several entities with JPA?
Context语境
I'm trying to create a simple API to learn Spring Boot and JPA.我正在尝试创建一个简单的 API 来学习 Spring Boot 和 JPA。 Informations are stored into H2 database.
信息存储在H2数据库中。
I have 2 entities : mission
and user
.我有 2 个实体:
mission
和user
。
Several users are assigned to a mission.多个用户被分配到一个任务。 And users can be assigned to different missions.
并且用户可以被分配到不同的任务。
So, my class Mission
has an attribute private ArrayList<User> users;
所以,我的类
Mission
有一个属性private ArrayList<User> users;
. .
Objective客观的
My goal is to create some requests as :我的目标是创建一些请求:
IP/missions/123456/users
: Get all users assigned to mission 123456
IP/missions/123456/users
: 获取分配给任务123456
所有用户IP/missions/456789
: Assigned users to mission 456789
IP/missions/456789
: 分配给任务456789
用户So, tied both entities.所以,绑定两个实体。
Problematic有问题
But I don't know how to store/tie informations relative to mission
and user
.但我不知道如何存储/绑定与
mission
和user
。 The good way is to create an "associative table" with the scheme Assignements(id_user, id_mission)
?好的方法是使用方案
Assignements(id_user, id_mission)
创建一个“关联表”?
Thanks for help!感谢帮助!
Edit 1 : Code编辑1:代码
Entity Mission实体使命
@Entity
public class Mission{
@Id
private String id;
private String name;
private Date start;
private Date end;
private ArrayList<User> users;
private int status;
public Mission() {
}
public Mission(String name, Date start, Date end) {
this.name = name;
this.start = start;
this.end = end;
this.status = 0;
}
// getters and setters
}
Entity User实体用户
@Entity
public class User {
@Id
private String id;
private String name;
public User() {
}
public User(String name) {
this.name = name;
}
// getters and setters
}
SQL SQL
I use a SQL script.我使用 SQL 脚本。 Currently, script looks like :
目前,脚本看起来像:
INSERT INTO mission (id, name, start, end, status) VALUES ('de7d9052-4961-4b4f-938a-3cd12cbe1f82', 'mission 1', '2019-02-11', '2019-02-13', 0)
INSERT INTO mission (id, name, start, end, status) VALUES ('425e7701-02c6-4de3-9333-a2459eece1c8', 'mission 2', '2019-02-10', '2019-02-15', 0)
Edit 2 : New code (with @ManyToMany)编辑 2:新代码(使用@ManyToMany)
Entities实体
@Entity
public class Mission {
@Id
private String missionid;
private String namemission;
private Date start;
private Date end;
@ManyToMany
@JoinTable(name = "mission_user",
joinColumns = @JoinColumn(name = "missionid"),
inverseJoinColumns = @JoinColumn(name = "userid")
)
private Set<User> users = new HashSet<>();
private int status;
public Mission() {}
public Mission(String name, Date start, Date end) {
this.namemission = name;
this.start = start;
this.end = end;
this.status = 0;
}
}
@Entity
public class User {
@Id
private String iduser;
private String nomuser;
@ManyToMany(mappedBy = "users")
private Set<Mission> missions = new HashSet<>();
public User() {}
public User(String nom) {
this.nomuser = nom;
}
}
Repositories存储库
@RepositoryRestResource(collectionResourceRel = "mission")
public interface MissionResource extends JpaRepository<Mission, String> {
...
}
@RepositoryRestResource(collectionResourceRel = "user")
public interface UserResource extends JpaRepository<User, String> {
...
}
Rest Controller休息控制器
@RestController
@RequestMapping(value = "/missions", produces = MediaType.APPLICATION_JSON_VALUE)
@ExposesResourceFor(Mission.class)
public class MissionRepresentation {
private final MissionResource missionResource;
private final UserResource userResource;
public MissionRepresentation(MissionResource missionResource, UserResource userResource) {
this.missionResource = missionResource;
this.userResource = userResource;
}
// mapping
}
The best would be to implement a joining table, just as you said.最好的办法是实现一个连接表,就像你说的那样。 That would be something like:
那将是这样的:
create table mission_user (
mission_id int,
user_id int,
primary key (mission_id, user_id)
)
Then a @ManyToMany
using this table as mapping or entity like MissionUser
and map both User
and Mission
as @OneToMany
to it.然后
@ManyToMany
使用此表作为映射或实体(如MissionUser
并将User
和Mission
作为@OneToMany
到它。
The mission class will have:任务类将有:
@Entity
public class Mission {
...
@ManyToMany(mappedBy = "missions")
private List<User> users;
...
}
and User class will have:和用户类将有:
@Entity
public class User {
...
@ManyToMany(mappedBy = "users")
private List<Mission> missions;
...
}
this will create a table in your database with name something like: missions_uesrs and it will have missionId and userId as only columns.这将在您的数据库中创建一个名称类似于:missions_uesrs 的表,并且它只会将 MissionId 和 userId 作为列。
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