如何检索特定关系中存在的所有记录？ [英] How to retrieve all records that exists in a specific relationship?

问题描述

我有一类电脑，每一个都可以组装。我需要检索那些有Assembler的Computer类的记录。

  @Entity 
公共类计算机{
 ... 
 @OneToMany 
 private Set< Assembler>装配; 
 .... 
} 
 
 @实体
公共类汇编程序{
 ... 
 @OneToOne 
私有用户用户; 
 
 @OneToMany 
 @LazyCollection（LazyCollectionOption.FALSE）
 private Set< Tools>工具; 
 .... 
} 
 
 @实体
公共类工具{
 .... 
 @OneToOne 
私有电子电子; 
 
 @OneToOne 
 private手动手动; 
 
 $ b  

代码

  Criteria cre = session.createCriteria（Computer.class，computer）
 .createAlias（computer.assembler，assem）
 cre 。新增（Restrictions.not（Restrictions.eq（ assem.id，NULL）））; 
 List computer =（List< Computer>）cre.list（）; 
 System.out.println（computer.size（））：<<返回0，但应返回1 
  

解决方案

/ p>

  cre.add（Restrictions.not（Restrictions.eq（assem.id，null）））; 
  

试试：

  cre.add（Restrictions.isNotEmpty（assemblers））; 
  

（删除别名）

I have a class of computer and each of it can be assembled. I need to retrieve those records of Computer class that has Assembler. I've tried to use criteria but could not retrieve them.

@Entity
public class Computer{
  ....
  @OneToMany
  private Set <Assembler> assemblers;
  ....
}

@Entity    
public class Assembler{
  ...
  @OneToOne
  private User user;

  @OneToMany
  @LazyCollection(LazyCollectionOption.FALSE)
  private Set<Tools> tools;
  ....
}

@Entity
public class Tools{
   ....
   @OneToOne
   private Electronic electronic;

   @OneToOne
   private Manual manual;

}

Code

 Criteria cre = session.createCriteria(Computer.class, "computer")
                       .createAlias("computer.assembler", "assem")
 cre.add(Restrictions.not(Restrictions.eq("assem.id",null)));
 List computer = (List<Computer>) cre.list();
 System.out.println(computer.size()): << returns zero but should return 1

解决方案

Instead of using:

 cre.add(Restrictions.not(Restrictions.eq("assem.id",null)));

Try:

 cre.add(Restrictions.isNotEmpty("assemblers"));

(remove the alias)

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