英文:
How to access table created by join in JPA
问题
我正在创建一个应用程序，其中有两个实体：
-
用户
-
聊天室
用户和聊天室之间存在多对多的关系。
我使用一个名为"users_chatrooms"的连接表创建了一个多对多的关系。当我为用户编写代码加入聊天室时，连接表中的值被正确地填充。
我的问题是，我需要一个能够获取给定聊天室中所有用户的端点。为此，我需要将连接创建的表（users_chatrooms）作为 JPA 的一部分。如何在 JPA 中实现这一点？
用户类
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;}}
聊天室类
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;}}
请注意，以上内容仅为翻译结果，可能需要根据你的实际需求进行调整。
英文:
I am creating an app where there are two entities
-
users
-
chatrooms
There is a many to many relationship between users and chatrooms.
I created a many to many relationship with a join table named users_chatrooms. The values are getting populated in the join table correctly when I wrote code for a user to join a chatroom.
My issue is that, I need an endpoint that can fetch all the users of a given chatroom. For this, I need the table created by the join (users_chatrooms) as part of Jpa. How to accomplish this in JPA ?
User class
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;}}
Chatroom class
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;}}
答案1
得分: 1
你可以简单地使用 @JoinColumn 来连接这两个实体。
@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}
英文:
You can simply join the two entities using @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}
通过集体智慧和协作来改善编程学习和解决问题的方式。致力于成为全球开发者共同参与的知识库，让每个人都能够通过互相帮助和分享经验来进步。
评论