CODEWITHSUNDEEP
javahibernatejpaorm
user5620472
user5620472

Reputation: 2882

How can I join 2 entity tables if I not have relation between this tables?

I have 2 entities

@Entity
@Table(name = "USER")
public class User implements Serializable {
    private Long id;
    private String username;
}

And 

@Entity
@Table(name = "LOGS")
public class Logs implements Serializable {
        private Long id;
        private Long userId;
        private String message;
}

This entity does not have relations. When LOGS fill I do not have User entity(but I have userId) and I set userId in LOGS (not User entity/ Only Long userId).

When I show logs for user on web page I need to show all fields of LOGS:

id userId message
1  1       message1
2  1       message2
3  2       message3
4  2       message4

But I need replase userId to UserName:

id user message
1  Bill       message1
2  Bill       message2
3  John       message3
4  John       message4

How can I join 2 tables if I there is no relation between then? I can use native query but maybe it is not necessary?

Upvotes: 2

Views: 102

Answers (2)

Maciej Kowalski
Maciej Kowalski

Reputation: 26522

Updated

In your query you should use the 'old' style on joining when you match the columns in the where clause:

1) Create the class for projected fields:

package org.myapp;

public class UserLogs{

   private Long id;
   private String username;
   private String message;

   public UserLogs(Long id, String username, String message){
       this.id = id;
       this.username = username;
       this.message = message;
   }

}

2) Perform the query

String query =
   " select new org.myapp.UserLogs"+
   "(l.id, u.username, l.message) "+
   " from Logs l, User u"+
   " where l.userId = u.id";

List<UserLogs> userLogs = session.createQuery(query)
                      .list();

// process list

Upvotes: 2

cralfaro
cralfaro

Reputation: 5948

You can add a relationship ManyToOne 

@Entity
@Table(name = "LOGS")
public class Logs implements Serializable {
    private Long id;
    private Long userId;
    private String message;

    @Getter
    @Setter
    @ManyToOne(fetch = FetchType.LAZY, cascade = CascadeType.DETACH)
    @JoinColumn(name = "USER_ID")
    private User user;

}

Upvotes: 0

Related Questions