Java JPA多对多查询

我有以下课程：

聊天室课程：

@Entity
public class ChatRoom {

    @Column(name="chatroom_id")
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private long chatroomId;

    @ManyToMany(fetch=FetchType.EAGER)
    @JoinTable(
        name="CHATROOM_USER",
        joinColumns = {@JoinColumn(name="chatroom_id",referencedColumnName="chatroom_id")},
        inverseJoinColumns={@JoinColumn(name="user_id",referencedColumnName="user_id")}
    )
    private Set<User> users;

    @OneToMany(mappedBy="chatroom", cascade=CascadeType.PERSIST, orphanRemoval=true)
    private Set<ChatRoomMessage> messages;
}

@Entity
public class User {
    @Id
    @Column(name="user_id", length=40, unique=true, updatable=false)
    private String  userId;
}

@Entity
public class ChatRoomMessage {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private long messageId;

    @ManyToOne(optional=false)
    @JoinColumn(name="session_id", nullable=false)
    private User sender;

    @ManyToOne(optional=false)
    @JoinColumn(name="chatroom_id", nullable=true)
    private ChatRoom chatroom;
}

@Repository
public class MessageDaoImpl implements MessageDaoI {
    @Override
    public List<ChatRoomMessage> getMessages(User u){
        Criteria c = sessionFactory.getCurrentSession().createCriteria(ChatRoomMessage.class, "cmessage");
        c.createAlias("cmessage.sender", "sender");
        c.add(Restrictions.eq("sender", u));
        return c.list();
    }
}

聊天室消息类：

@Entity
public class ChatRoom {

    @Column(name="chatroom_id")
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private long chatroomId;

    @ManyToMany(fetch=FetchType.EAGER)
    @JoinTable(
        name="CHATROOM_USER",
        joinColumns = {@JoinColumn(name="chatroom_id",referencedColumnName="chatroom_id")},
        inverseJoinColumns={@JoinColumn(name="user_id",referencedColumnName="user_id")}
    )
    private Set<User> users;

    @OneToMany(mappedBy="chatroom", cascade=CascadeType.PERSIST, orphanRemoval=true)
    private Set<ChatRoomMessage> messages;
}

@Entity
public class User {
    @Id
    @Column(name="user_id", length=40, unique=true, updatable=false)
    private String  userId;
}

@Entity
public class ChatRoomMessage {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private long messageId;

    @ManyToOne(optional=false)
    @JoinColumn(name="session_id", nullable=false)
    private User sender;

    @ManyToOne(optional=false)
    @JoinColumn(name="chatroom_id", nullable=true)
    private ChatRoom chatroom;
}

@Repository
public class MessageDaoImpl implements MessageDaoI {
    @Override
    public List<ChatRoomMessage> getMessages(User u){
        Criteria c = sessionFactory.getCurrentSession().createCriteria(ChatRoomMessage.class, "cmessage");
        c.createAlias("cmessage.sender", "sender");
        c.add(Restrictions.eq("sender", u));
        return c.list();
    }
}

如果我想要用户发送的所有消息，我在DAO上做了如下操作：

MessagesDAO类：

@Entity
public class ChatRoom {

    @Column(name="chatroom_id")
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private long chatroomId;

    @ManyToMany(fetch=FetchType.EAGER)
    @JoinTable(
        name="CHATROOM_USER",
        joinColumns = {@JoinColumn(name="chatroom_id",referencedColumnName="chatroom_id")},
        inverseJoinColumns={@JoinColumn(name="user_id",referencedColumnName="user_id")}
    )
    private Set<User> users;

    @OneToMany(mappedBy="chatroom", cascade=CascadeType.PERSIST, orphanRemoval=true)
    private Set<ChatRoomMessage> messages;
}

@Entity
public class User {
    @Id
    @Column(name="user_id", length=40, unique=true, updatable=false)
    private String  userId;
}

@Entity
public class ChatRoomMessage {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private long messageId;

    @ManyToOne(optional=false)
    @JoinColumn(name="session_id", nullable=false)
    private User sender;

    @ManyToOne(optional=false)
    @JoinColumn(name="chatroom_id", nullable=true)
    private ChatRoom chatroom;
}

@Repository
public class MessageDaoImpl implements MessageDaoI {
    @Override
    public List<ChatRoomMessage> getMessages(User u){
        Criteria c = sessionFactory.getCurrentSession().createCriteria(ChatRoomMessage.class, "cmessage");
        c.createAlias("cmessage.sender", "sender");
        c.add(Restrictions.eq("sender", u));
        return c.list();
    }
}

@存储库
公共类MessageDaoImpl实现MessageDaoI{
@凌驾
公共列表获取消息（用户u）{
条件c=sessionFactory.getCurrentSession（）.createCriteria（ChatRoomMessage.class，“cmessage”）；
c、 createAlias（“cmessage.sender”、“sender”）；
c、 添加（限制条件，等式（“发送方”，u））；
返回c.list（）；
}
}

当我尝试编写下一个查询代码时，问题就开始了：

获取用户发送或接收的所有聊天室消息

获取用户在聊天室上发送或接收的所有聊天室消息

---

你能谈谈如何解决这些问题吗

您可以按如下方式编写查询：

第一个问题：

Query query = session.createQuery("from ChatRoomMessage as c JOIN c.sender where c.sender.userId = :senderUserId");
query.setString("senderUserId", "SENDER_USER_ID_TO_BE_SEARCHED");
List list = query.list();

第二个问题：

Query query = session.createQuery("from ChatRoomMessage as c JOIN fetch c.chatroom where c.chatroom.users.userId = :senderUserId");
query.setString("senderUserId", "SENDER_USER_ID_TO_BE_SEARCHED");
List list = query.list();

---

希望这能解决您的问题。

您可以编写以下查询：

第一个问题：

Query query = session.createQuery("from ChatRoomMessage as c JOIN c.sender where c.sender.userId = :senderUserId");
query.setString("senderUserId", "SENDER_USER_ID_TO_BE_SEARCHED");
List list = query.list();

第二个问题：

Query query = session.createQuery("from ChatRoomMessage as c JOIN fetch c.chatroom where c.chatroom.users.userId = :senderUserId");
query.setString("senderUserId", "SENDER_USER_ID_TO_BE_SEARCHED");
List list = query.list();

---

希望解决了你的问题。

“问题开始……”哪个问题？我的意思是构造查询的标准。“问题开始了……”哪个问题？我的意思是构造查询的标准。你好，如果他们只考虑发送者，这些查询会起作用，但是；它们都需要考虑用户是否发送或接收聊天消息。如果消息被接收或发送，哪个属性保持？一个聊天信息由用户发送（CHATROOMMeX类上的属性“发送器”），并发送到聊天室（ChaloRoM消息类上的“聊天室”），聊天室类包含用户集。聊天室中的所有用户必须接收消息（ChaloMoMead）Hello，如果只考虑发送者，这些查询将工作，但是，它们都需要考虑用户是否发送或接收聊天信息。如果接收或发送消息，哪个属性维护？用户是否发送聊天信息。（chatroommessage类上的属性“sender”）并发送到聊天室（chatroommessage类上的属性“chatroom”），聊天室类包含用户集（多对多关系）。聊天室中的所有用户都必须接收该消息（chatroommessage）