如何在 Spring 数据 Jpa 中使用 object null 对元素进行排序

Question

I have two entity below:

@Entity
public class Task {
...
@ManyToOne
private User user;
...
}

@Entity
public class User {
private String firstName;
private String lastName;
@OneToMany(mappedBy = "task")
private Set<Task> task;
...
}

How can I using Sort to Sort Task by firstName of User with User is null on top?

I have try Sort.by(Sort.Order.asc("user.firstName").nullsFirst()); But I got the error: NullpointerException

Answer 1

You can create something like this.

Criteria criteria = ...;
criteria.addOrder( Order.asc( "firstName" ).nulls(NullPrecedence.FIRST) );

for more information you can check this documentation.

NullPrecedence