查询与Hibernate标准的ManyToMany关系 [英] Querying ManyToMany relationship with Hibernate Criteria

问题描述

我不确定如何描述这个问题，所以我认为一个例子是问我问题的最好方法：

我有两张表，其中包含manyToMany关系：

DriversLicence< - > LicenceClass

LicenceClass是类似于Car，Motorbike，和Medium Rigid。

使用Hibernate Criteria，我怎么能找到所有拥有Car和MotorbikeLicenceClass的许可证？

UPDATE 12/11/2008
我发现使用自定义ResultTransformer可以轻松实现。然而，问题是只有在查询返回结果后才会应用结果转换器，结果转换器实际上不会成为SQL的一部分。所以我想现在我的问题是：你能做我最初在SQL中描述过的东西 - 是否有Hibernate Criteria模拟？ 解决方案

以下是我最终如何使用HQL实现它：

  public List< DriversLicence> findDriversLicencesWith（List< LicenceClass> licenceClasses）{
 String hqlString =从DriversLicenceImpl dl中选择dl，其中1 = 1; 
 for（int i = 0; i< licenceClasses.size（）; i ++）{
 hqlString + =and：licenceClass+ i += some elements（dl.licenceClasses）; 
} 
 
 Query query = getSession（）。createQuery（hqlString）; 
 for（int i = 0; i< licenceClasses.size（）; i ++）{
 query.setParameter（licenceClass+ i，licenceClasses.get（i））; 
} 
返回query.list（）; 
} 
  

或者使用Hibernate Criteria和sqlRestriction：

（LicenceClass licenceClass：licenceClasses）{
criteria.add（Restrictions.sqlRestriction（？= some（选择+ LicenceClass.PRIMARY_KEY +）的

  + 
 LICENCE_CLASS_JOIN_TABLE +where {alias}。+ 
 DriversLicence.PRIMARY_KEY +=+ DriversLicence.PRIMARY_KEY +），
 licenceClass.getId（），Hibernate.LONG） ）; 
 
 $ / code> 

LICENCE_CLASS_JOIN_TABLE是hibernate为支持many-to driverLicence和LicenceClass之间的许多关系。

I'm not sure how to describe this problem, so I think an example is the best way to ask my question:

I have two tables with a manyToMany relationship:

DriversLicence <-> LicenceClass

LicenceClass is things like "Car", "Motorbike", and "Medium Rigid".

Using Hibernate Criteria, how can I find all licences that have both "Car" and "Motorbike" LicenceClasses?

UPDATE 12/11/2008 I have discovered that this can easily be achieved by using a custom ResultTransformer. However the problem is that a result transformer only gets applied AFTER the query returns its results, it does not actually become part of the SQL. So I guess my question is now "Can you do what I initially described in SQL - and is there a Hibernate Criteria analog?"

解决方案

Here's how I finally achieved it using HQL:

public List<DriversLicence> findDriversLicencesWith(List<LicenceClass> licenceClasses) {
    String hqlString = "select dl from DriversLicenceImpl dl where 1=1 ";
    for (int i = 0; i < licenceClasses.size(); i++) {
        hqlString += " and :licenceClass" + i + " = some elements(dl.licenceClasses)";
    }

    Query query = getSession().createQuery(hqlString);
    for (int i = 0; i < licenceClasses.size(); i++) {
        query.setParameter("licenceClass" + i, licenceClasses.get(i));
    }
    return query.list();
}

Or using Hibernate Criteria with an sqlRestriction:

for (LicenceClass licenceClass : licenceClasses) {               
    criteria.add(Restrictions.sqlRestriction("? = some(select " + LicenceClass.PRIMARY_KEY + " from " +
                    LICENCE_CLASS_JOIN_TABLE + "  where {alias}." +
                    DriversLicence.PRIMARY_KEY + " = " + DriversLicence.PRIMARY_KEY + ")",
                    licenceClass.getId(), Hibernate.LONG));
}

LICENCE_CLASS_JOIN_TABLE is the name of the table that hibernate generates to support the many-to-many relationship between driversLicence and LicenceClass.

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