Wiring ComputedAttribute/ComputedRelationship with transactions

[xiaoyao1991]

Problem Description

I have a use case where I have a @ComputedAttribute getter in the model, and it return a private transient field which should be set by something from the transaction. To make it clear:

@Setter private String url;  // not a column in the database

@Transient
@ComputedAttribute
public String getUrl() {
  return url;
}

In my transaction impl, I have a DAO that will load url from another service based on some other attributes of the model, and set the url to the model. And I call the DAO methods in the load functions inherited from DataStoreTransaction, so GET requests work perfectly(the computed fields are showing correctly).

However, when making a POST/PUT/PATCH requests to create this resource, the url field in the JSON response shows null, I see that the Persistence.toResource method simply calls the getters of the attributes, and thus the url field is not properly set by the DAO.

Ask

I wonder if returning null for computed things on creation is a good experience or not. If I want the computed fields to show up correctly, we may want to wire the computed methods somehow with the transaction, or provide some injection point in the PersistenceResource.

I know that we have plan to delegate setAttribute/getAttribute/updateAttribute from PersistenceResource to DataStoreTransaction in Elide 3.0, I wonder would this issue be resolved when that's finally in place.

Any thoughts?

[clayreimann]

I think this is strongly related to #234 and merits investigation. It could be the case that mapping DAOs to web services (at least in some corner cases) is necessary and would require custom object instantiation.

[aklish]

setAttribute is now invoked in DataStoreTransaction (since Elide 6)