Hibernate throws NullPointerException from HqlSqlWalker

Question

I have a web application, which has a search form and HQL is generated on the fly. Also, user can click on the column headers to sort items as needed. Some columns get ther data from very deep down the structure. I have this HQL, for example, which works flawlessly: ``` SELECT s FROM Application s LEFT JOIN s.product AS product LEFT JOIN product.originCountry AS origin WHERE s.nr = ? ORDER BY origin.name ASC ``` But this one fails miserably: ``` SELECT s FROM Application s LEFT JOIN s.product AS product LEFT JOIN product.producer AS producer LEFT JOIN producer.address AS address LEFT JOIN address.country AS country WHERE s.nr = ? ORDER BY country.name ASC ``` Can someone point out, where am I going wrong. Isn't such deep syntax supported or something? Hibernate version is 3.2.1. Sorry, forgot the stacktrace: ``` 2012-04-04 18:59:42,198 ERROR [foo.impl.ServiceImpl] java.lang.NullPointerException java.lang.NullPointerException at org.hibernate.hql.ast.HqlSqlWalker.createFromJoinElement(…

Accepted Answer

As @JBNizet correctly pointed out, the problem was that one of the classes (named `address` to be exact) on the path was not an entity, it was an embeddable object and thus it doesn't need to be joined.

So the second query written correctly in my case would be:

```
SELECT s FROM Application s
    LEFT JOIN s.product AS product
    LEFT JOIN product.producer AS producer
    LEFT JOIN producer.address.country AS country
WHERE s.nr = ? ORDER BY country.name ASC
```

Hibernate throws NullPointerException from HqlSqlWalker

Solution

Problem