ebean | Multiple abstraction levels : Ebean provides multiple levels | Database library

The solution turns out to be adding insertable = false, updatable = false to @Column annotation on entryId. How can I retrieve the foreign key from a JPA ManyToOne mapping without hitting the target table?

Big entity graphs are in my experience (mostly worked on web apps where users can't digest big amounts of data) rather rare, but most of the time you can configure a proper batch size or use @Fetch(SUBSELECT) to improve performance when selecting multiple collections. The problem with List vs Set is specifically about the fact that a list could allow duplicates and is unordered i.e. you can't differentiate between the first and the second duplicate. When you join fetch a bag and then join fetch another bag, you get on the JDBC result set level a combination of rows from the two bags such that you can't differentiate objects anymore which could lead to wrong cardinalities. To solve that, you can either use a Set to ensure there can be no duplicates or define an index column @OrderColumn which allows to differentiate the duplicates.

Apart from all this, I think this is a perfect use case for Blaze-Persistence Entity Views and its MULTISET fetch strategy which is like a hybrid of join fetching and subselect fetching that is very efficient.

I created the library to allow easy mapping between JPA models and custom interface or abstract class defined models, something like Spring Data Projections on steroids. The idea is that you define your target structure(domain model) the way you like and map attributes(getters) via JPQL expressions to the entity model.

A DTO model for your use case could look like the following with Blaze-Persistence Entity-Views:

Okey so I was able to solve this issue. This pointed me to correct direction: Mockito - NullpointerException when stubbing Method

Here is the corrected Test class. I just had to mock and stubb bunch of classes and functions.

Now it works ;-)

conf.META-INF.persistence.xml

I have found a way to do it using a Converter:

Changing the name of the property from Symbol to symbol won't help since we still have the "Symbol" in the json file.

You can try to use the @JsonProperty annotation like in the example. For the "Symbol" json field it can look like this:

After formatting my hard drive thinking I was insane, it turns out that the newest version of SBT uses OpenJDK 14 (or the latest version) to do compilations or injections. I believe this is the case because Oracle JKD is no longer available in public facing repositories but requires one to create an Oracle account to download their JDK.

The BEST solution is to set a $JAVA_HOME on your terminal (i.e.: add it to .bashrc) to force SBT to use your preferred JDK. Any other way will result in SBT using the latest OpenJDK version.

Is it advisable to use JDBC batch using batch size attribute for transactional calls.

Assuming a transaction is inserting, updating or deleting more that 1 bean/row then in short yes.

The caveat is that in terms of application code the actual execution of DML can occur later with statement flush at batch size, at commit time etc. This means statements can execute later in application code (like at commit time).

This typically only really matters to application code when application code is looking to handle exceptions like db constraint violations, missing foreign keys, unique constraints etc and actually continue the transaction. In this case we might need to add explicit transaction.flush() into the application code to ensure the statements have been executed and hit the database.

You would use an orderBy expression: