搜索多個標籤的文章 - 休眠許多一對多

Question

我存儲與多個標籤的文章如下：

import java.util.ArrayList; 
import java.util.Arrays; 
import java.util.List; 

import javax.persistence.Entity; 
import javax.persistence.GeneratedValue; 
import javax.persistence.Id; 
import javax.persistence.ManyToMany; 

@Entity 
public class Article { 

    @Id 
    @GeneratedValue 
    private Integer id; 

    @ManyToMany 
    private List<Tag> tags; 

    private String subject; 

} 

和

import javax.persistence.Entity; 
import javax.persistence.Id; 

@Entity 
public class Tag { 

    @Id 
    private String name; 

    private String description; 

} 

我想搜索的文章裏面包含了一些標記，爲例如，像這個問題hibernate和many-to-many。所以，我想爲：

import static org.hibernate.criterion.Restrictions.*; 

// ... 

Criteria criteria = session.createCriteria(Article.class); 
Criteria tagCriteria = criteria.createCriteria("tags"); 
tagCriteria.add(and(eq("name", "hibernate"), eq("name", "many-to-many"))); 

@SuppressWarnings("unchecked") 
List<Article> list = criteria.list(); 

但是，沒有工作和返回的列表是空的，因爲登錄SQL顯示爲：

select 
    this_.id as id1_1_, 
    this_.subject as subject1_1_, 
    tags3_.Article_id as Article1_, 
    tag1_.name as tags2_, 
    tag1_.name as name0_0_, 
    tag1_.description as descript2_0_0_ 
from 
    Article this_ 
    inner join Article_Tag tags3_ on this_.id=tags3_.Article_id 
    inner join Tag tag1_ on tags3_.tags_name=tag1_.name 
where 
    tag1_.name=? // assign 'hibernate' 
    and 
    tag1_.name=? // assign 'many-to-many' 

當更換and到or返回太多的文章，因爲生成的SQL是... where (tag1_.name=? or tag1_.name=?)。

我想究竟可能看起來像：

select 
    this_.id as id1_1_, 
    this_.subject as subject1_1_, 
    tags3_.Article_id as Article1_, 
    tag1_.name as tags4_, 
    tag1_.name as name0_0_, 
    tag1_.description as descript2_0_0_ 
from 
    Article this_ 
    inner join Article_Tag tags3_ on this_.id=tags3_.Article_id 
    inner join Tag   tag1_ on tags3_.tags_name=tag1_.name 
    // following 2 lines are added 
    inner join Article_Tag tags4_ on this_.id=tags4_.Article_id 
    inner join Tag   tag5_ on tags4_.tags_name=tag5_.name 
where 
    tag1_.name=? // assign 'hibernate' 
    and 
    tag5_.name=? // assign 'many-to-many' 

是否有可能時，我只用HQL？

Answer 1

你應該嘗試類似的東西：

Criteria criteria = getSession().createCriteria(Article.class); 
    int i=0; 
    for (String tagName : tagNames) { 
     String aliasName = "alias_" + i; 
     criteria.createAlias("tags", aliasName, Criteria.INNER_JOIN); 
     criteria.add(Restrictions.eq(aliasName+".name",tagName)); 
     i++; 
    } 

其實這個問題是，當你做一個簡單的內連接，OK，你已經加入你的結果與標籤，但問題是，該數據實際上是在2行...所以如果你加入2次，你將能夠獲得一行數據。

，我認爲它不是真正的優雅，但它應該工作...