Hql加入并按问题分组 [英] Hql join and group by problem

问题描述

我试图在hql中进行查询。我有这些bean：

Bean1

  @Entity 
 @Table（name =bean1）
 public class Bean1 {
 
 ... 
 private List< Bean2> bean2; 
 ... 
 @ManyToMany（
 cascade = {CascadeType.ALL}，
 fetch = FetchType.LAZY）
 @JoinTable（
 name = bean1_bean2，
 joinColumns = @ JoinColumn（name =bean1_id），
 inverseJoinColumns = @ JoinColumn（name =bean2_id）
）
 public List< Bean2> getBean2（）{
 return bean2; 
 
 
 public void setTags（List< Bean2> bean2）{
 this.bean2 = bean2; 
} 
 
 
 ... 
} 
  

Bean2

  @Entity 
 @Table（name =bean2）
 public class Bean2 {
 
 private String bean2_id; 
私人列表< Bean1> bean1; 
 
 @Id 
 @Column（name =bean2_id，length = 100，unique = true，nullable = false）
 public String getBean2_id（）{
 return bean2_id; 
} 
 public void setBean2_id（String bean2_id）{
 this.bean2_id = bean2_id; 
 
 
 @ManyToMany（
 cascade = {CascadeType.PERSIST，CascadeType.MERGE}，
 fetch = FetchType.LAZY，
 mappedBy =bean2 
）
 public List< Bean1> getBean1（）{
 return bean1; 
} 
 public void setBean1（List< Bean1> bean1）{
 this.bean1 = bean1; 
} 
 
} 
  

然后查询：

 查询查询= session.createQuery（SELECT bean1 FROM+ 
（（Class）Bean1.class.getName（）+ bean1+ 
WHERE+bean1.bean1_id =？+ 
JOIN bean1.bean2.bean2_id =？+ 
GROUP BY bean1.bean2
 ）; 
  

但是我得到这个异常：

org.springframework.orm.hibernate3.HibernateQueryException：
非法尝试解引用
集合

$
$ b

  Query query = session.createQuery（SELECT beab1.bean2 FROM+ b $ b 
 （（Class）Bean1.class.getName（）+bean1+JOIN bean1.bean2+bean2+WHERE+bean1.bean1_id =？+AND bean2.bean2_id =？ +group by bean1.bean2.bean2_id =？）; 
  

另一个例外：

org.springframework.orm.hibernate3.HibernateQueryException：
非法尝试解引用
集合[bean10_.bean1_id.bean2]
带有元素属性引用
[bean2_id]

我真正想得到的是有多少bean2_id被重复同一个bean1与给定的bean1_id。

我以正确的方式?? Hibernate 3.6.0
预先感谢

解决方案

如果我正确理解了你的问题，你应该这样做：

  select b1 from Bean1作为b1将b1.bean2作为b2加入其中b1.id =？1和b2.id =？2 b2.id组中的b 
 
 
 
 
 
然而，这可能不会起作用，因为您必须通过select中的某些东西进行组合。
 
 
 
但以下内容应该可以工作：  
 
 
  se从Bean1获取b2.id作为b1加入b1.bean2作为b2其中b1.id =？1和b2.id =？2 group by b2.id 
  
如果您想要获取b1，但要通过b2.id进行分组，您可以尝试如下所示： 
 
 
 从Bean1中选择b1，b2.id作为b1将b1.bean2作为b2其中b1.id =？1和b2.id =？2 b2 .id组中的b2。b 
  
请注意，您将在Bean1的索引0处得到结果数组。
 
I am trying to make a query in hql. I have these beans:  

Bean1  
@Entity
@Table(name = "bean1")
public class Bean1 {

        ...
        private List<Bean2> bean2;
...
@ManyToMany(
            cascade={CascadeType.ALL},  
            fetch=FetchType.LAZY)
@JoinTable( 
            name="bean1_bean2", 
            joinColumns=@JoinColumn(name="bean1_id"),   
            inverseJoinColumns=@JoinColumn(name="bean2_id") 
    )   
    public List<Bean2> getBean2() {
        return bean2;
    }

    public void setTags(List<Bean2> bean2) {
        this.bean2 = bean2;
    }


    ...
    }
Bean2
@Entity
@Table(name = "bean2")
public class Bean2 {

    private String bean2_id;    
    private List<Bean1> bean1;

    @Id
    @Column(name = "bean2_id", length = 100, unique = true, nullable = false)   
    public String getBean2_id() {
        return bean2_id;
    }
    public void setBean2_id(String bean2_id) {
        this.bean2_id = bean2_id;
    }

    @ManyToMany(
            cascade = {CascadeType.PERSIST, CascadeType.MERGE},
            fetch=FetchType.LAZY,
            mappedBy = "bean2"            
    )
    public List<Bean1> getBean1() {
        return bean1;
    }
    public void setBean1(List<Bean1> bean1) {
        this.bean1 = bean1;
    }

} 
And the query:  
Query query = session.createQuery("SELECT bean1 FROM " +
                             ((Class) Bean1.class.getName() + " bean1 " +                           
                            " WHERE " + "bean1.bean1_id=? " + 
                            " JOIN bean1.bean2.bean2_id=?" + 
                            " GROUP BY bean1.bean2"
                            );
But I am getting this exception:  

  
org.springframework.orm.hibernate3.HibernateQueryException:
  illegal attempt to dereference
  collection
I tried anothe query:  
Query query = session.createQuery("SELECT beab1.bean2 FROM " + ((Class) Bean1.class.getName() + " bean1 " + " JOIN bean1.bean2 " + "bean2" + " WHERE " + "bean1.bean1_id=? " + " AND bean2.bean2_id=? " + " group by bean1.bean2.bean2_id=?");
Another exception:

  
org.springframework.orm.hibernate3.HibernateQueryException:
  illegal attempt to dereference
  collection [bean10_.bean1_id.bean2]
  with element property reference
  [bean2_id]
What I really want to get is how many bean2_id are repeated in the same bean1 with a bean1_id given.

Am I in the right way?? Hibernate 3.6.0
Thanks in advance
解决方案
If I understand correctly your question, you should do something like this:
select b1 from Bean1 as b1 join b1.bean2 as b2 where b1.id = ?1 and b2.id= ?2 group by b2.id
However, this will probably won't work, since you must put in group by something from the select.

But the following should work:
select b2.id from Bean1 as b1 join b1.bean2 as b2 where b1.id = ?1 and b2.id= ?2 group by b2.id
If you want to fetch b1, but to group by b2.id, you can try something like this:
select b1, b2.id from Bean1 as b1 join b1.bean2 as b2 where b1.id = ?1 and b2.id= ?2 group by b2.id
Pay attention that you'll get array in the result with Bean1 at index 0.

                        
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