如何解决如何访问通过JPA中的join创建的表
我正在创建一个有两个实体的应用程序
-
用户
-
聊天室
用户和聊天室之间存在多对多关系。 我使用名为users_chatrooms的联接表创建了多对多关系。当我为用户加入聊天室编写代码时,这些值已正确填充到联接表中。
我的问题是,我需要一个可以获取给定聊天室所有用户的终结点。为此,我需要将联接创建的表(users_chatrooms)作为Jpa的一部分。如何在JPA中完成此任务?
用户类别
package com.example.chat.models;
import javax.persistence.*;
import java.util.List;
@Entity
@Table(name="USERS")
public class User {
@Id
@Column(name="userid")
private String username;
@Column(name="pass")
private String password;
@ManyToMany(mappedBy = "users",fetch=FetchType.EAGER,cascade = CascadeType.ALL)
List<Chatroom>rooms;
public List<Chatroom> getRooms() {
return rooms;
}
public void setRooms(List<Chatroom> rooms) {
this.rooms = rooms;
}
public void setUsername(String username) {
this.username = username;
}
public String getUsername() {
return username;
}
public String getPassword() {
return password;
}
public void setPassword(String password) {
this.password = password;
}
}
聊天室
package com.example.chat.models;
import javax.persistence.*;
import java.util.List;
@Entity
@Table(name="Chatrooms")
public class Chatroom {
@Id
@Column(name="chatroomId")
private String id;
@Column(name="chatRoomName")
private String name;
@Column(name="chatroomDesc")
private String description;
@ManyToMany(fetch=FetchType.EAGER,cascade = CascadeType.ALL)
@JoinTable(
name = "users_chatrooms",joinColumns = @JoinColumn(name = "chatroomId"),inverseJoinColumns = @JoinColumn(name = "userid"))
private List<User>users;
public List<User> getUsers() {
return users;
}
public void setUsers(List<User> users) {
this.users = users;
}
public String getId() {
return id;
}
public void setId(String id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public String getDescription() {
return description;
}
public void setDescription(String description) {
this.description = description;
}
}
解决方法
您可以简单地使用@JoinColumn
@Entity
@Table(name="Chatrooms")
public class Chatroom {
@Id
@Column(name="chatroomId")
private String id;
@Column(name="chatRoomName")
private String name;
@Column(name="chatroomDesc")
private String description;
@ManyToMany(fetch=FetchType.EAGER,cascade = CascadeType.ALL)
@JoinColumn(name = "userid",referencedColumnName = "chatroomId")
private List<User>users;
// getters and setters
}
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