Question

I have a many-to-many relationship between 2 tables that I define with a join table.

//MyClassA
@ManyToMany
@JoinTable(name="A_TO_B", 
           joinColumns=@JoinColumn(name="A_UUID"), 
           inverseJoinColumns=@JoinColumn(name="B_UUID")
)
private List<MyClassB> classBs = new ArrayList<MyClassB>();

//MyClassB
@ManyToMany(mappedBy="classBs")
private List<MyClassA> classAs = new ArrayList<MyClassA>();

Due to company architecture restrictions, the join table must have a UUID column.

I have a DAO method called associateItems which should insert a row into the join column. In order to test everything, I do the following in a jUnit test.

myDao.associateItems(classAItem, classBItem);

classAItem = myDao.get(classAItem.getUuid());
classBItem = myDao.get(classBItem.getUuid());

assertEquals(1, classAItem.getClassBs().size());
assertEquals(1, classBItem.getClassAs().size());

This test fails on the last 2 lines.

In my DAO, I have tried a number of things. I tried adding the classAItem and classBItem to each others lists and merging them. But this causes an error because the join table object doesn’t have a UUID. And I tried creating the join table object and persisting that. But then the last 2 lines of the test fail because it thinks the size of the lists are 0.

I have been sticking with the second solution (fail is better than error).

public void associateItems(MyClassA classAItem, MyClassB classBItem) {
    //UUID populated in constructor
    AToB association = new AToB(classAItem, classBItem); 
    entityManager.persist(association);
}

I know that the join table item is getting inserted into the database. I also manually entered a join table item and made sure the lists are populated when an association is found. So the test just has an issue with making the join table item and then associating the relevant lists.

I have tried messing with cascades, fetch types, and flushes. But I can’t seem to find a way to make the tests pass.

Anyone know what I need to do to fix this?

Answer 1

This was actually a problem with the get method in the DAO. I added the following hint and test run without failure.

query.setHint(QueryHints.REFRESH, HintValues.TRUE);