Hello, i'm using hibernate 5.2.

Given an arbitrary HQL query like this:



does it exist a way (before loading the data) to ask to the Query object (q) for the list of returned fields names in form of entity+attribute name?

For the given example I would like to obtain something like:

"Person.id"
"Person.name"
"Person.age"
"Address.city"
"Address.street"

I need a way to dynamically analyze a hql query and determine the "source" of each returned value.

Thank you.

I don't think there's anything you could to get the list of fields to be returned.



What is it that you are trying to achieve with this feature?

We are developing a complex product.

Our persistent domain entities are "annotated" with a lot of extra information (metadata),
such as labels to display on UI, weak references, and so on.

This metadata is needed to dynamically build the UI, and to implement some automatic UI behaviors.

I need to extract such metadata also on HQL queries written by the end user, which are used to display data on the UI.

I hope I explained myself.

You can extract the metadata using Java reflection and then match it against what the User sends to the DAO layer. That's not Hibernate related in any way, it's just a custom query building alternative.

And while at it, make sure you use the Criteria API since you don't want to end up concatenating String and exposing your app to SQL Injection attacks.

Yes, the problem is how to match it! I need the entities/properties names of returned values of HQL query.

Just use Java Reflection for that. You can then match the annotated property and build a Map of properties to their UI labels.

I don't understand. I have a query string like SELECT P.name FROM Person P
I (already) have all the metadata available for the entity attribute Person.name
Now I have to match P.name with Person.name, how is it possible?

Unless you write a JPQL parser, you won't be able to know it. And what about custom SQL queries. However, you can solve this with DTO projections and the mapping between a given property/column to a DTO property is done through the query. You just have to associate the DTO projection to the entity metadata, and you are done. Easy peasy!

Thank you.

Yes, unfortunately I think I need to parse the HQL/JPQL query, if the Query object does not offer me such information.

Yes, currently we already use DTO classes, but they are to much inflexible (hard coded).

No, you don't. That will not solve the case when you have native SQL queries, which you need for any non-trivial project.



They are not inflexible and they will work for any type of query you have. Every DTO will be responsible for the associated entity property. It's easier to do it this way and effective too.

Would it be possible to add this feature to the Query class? I think hibernate already does parsing and already has this information.

I found the (deprecated) methods:
query.getReturnAliases()
query.getReturnTypes()

It would be useful for me something like:
query.getReturnAttributes()

Thank you!

This method will be removed in 6.0. As for getReturnAttributes, I don't see any reason why we should expose Hibernate internals. As I already pointed out, there are better ways to deal with this issue.

Thank you again for your time and your answers.

My requirement is:

Give to the "end user" the ability to query (select only) data from a "query model" (which is not the real entities model, but a query model like in CQRS).
The "end user" is a person who uses HQL (no java, no compiler) to configure some applications at installation time.
These "configured" applications are able to automatically build the UI and load/display the data, but they need some "metadata" to do this.
Metadata is already available, and is bound to query model entities/attributes.
So, again, I need a way to analyze the returned fields in HQL queries and match them with entities/attributes, so I can get the metadata.

Thanks again.