Verify return type matches the declared query

[spring-projects-issues]

Jacopo Carravieri opened DATAJPA-824 and commented

When using a wrong query, that extracts only a portion of particular object

// Home contains other fields
@Query("SELECT home.id, home.address FROM Home")
List<Home> findAll();

The framework silently casts the result to List<Home>, but actually it turns out to be a List<Object[]>. As soon as a call to get() is made an exception is raised.

I would expect a ClassCastException or something similar thrown by the framework itself. I made some tests, it is possible to make such kind of casts only when the List is first instantiated without the template argument.

// No complain
List list = new ArrayList();
list.add(new Object());
return (List<Home>) list;

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Affects: 1.9.1 (Gosling SR1)

[spring-projects-issues]

Oliver Drotbohm commented

Well, how does it make sense to declare a return type of List<Home> in the first place? Or are you asking for us to rather detect the failure scenario?

[spring-projects-issues]

Jacopo Carravieri commented

That query was of course an oversight, but yes I think the error should be detected. It can happen easily