Hql加入并按问题分组

本文介绍了Hql加入并按问题分组的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！ 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.