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POHibernate HQL m:n join problem
 

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  1. POHibernate HQL m:n join problem
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    <p>I am very unfamiliar with SQL/HQL , and am currently stuck with this 'maybe' simple problem :</p> <p>I have two many-to-many Entities , with a relation table :</p> <p>Car , CarProblem , and Problem .</p> <p>One Car may have many Problems , </p> <p>One Problem may appear in many Cars,</p> <p>CarProblem is the association table with other properties .</p> <p>Now , I want to find Car(s) with specified Problem , how do I write such HQL ? All ids are Long type .</p> <p>I've tried a lot of join / inner-join combinations , but all in vain..</p> <p>-- updated :</p> <p>Sorry , forget to mention :</p> <p>Car has many CarProblem</p> <p>Problem has many CarProblem</p> <p>Car and Problem are not directly connected in Java Object.</p> <p>-- update , java code below --</p> <pre><code>@Entity public class Car extends Model{ @OneToMany(mappedBy="car" , cascade=CascadeType.ALL) public Set&lt;CarProblem&gt; carProblems; } @Entity public class CarProblem extends Model{ @ManyToOne public Car car; @ManyToOne public Problem problem; ... other properties } @Entity public class Problem extends Model { other properties ... // not link to CarProblem , It seems not related to this problem // **This is a very stupid query , I want to get rid of it ...** public List&lt;Car&gt; findCars() { List&lt;CarProblem&gt; list = CarProblem.find("from CarProblem as cp where cp.problem.id = ? ", id).fetch(); Set&lt;Car&gt; result = new HashSet&lt;Car&gt;(); for(CarProblem cp : list) result.add(cp.car); return new ArrayList&lt;Car&gt;(result); } } </code></pre> <p>The Model is from Play! framework , so these properties are all public .</p>
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    1. USdigitaljoel
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      1. USPascal Thivent
 

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