Passing empty list as parameter to JPA query throws error

Question

If I pass an empty list into a JPA query, I get an error. For example:

List municipalities = myDao.findAll();  // returns empty list
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Answer 1

If you are using spring/hibernate annotations then one of the easiest ways of working around this is having two parameters. First lets define our JPA annotation:

        + "AND (p.myVarin :state OR :nullCheckMyVar is null) "

Then pass those parameters in as normal:

    @Param("myVarin") List myVarin,
    @Param("nullCheckMyVar") Integer nullCheckMyVar,

Finally in what ever service call you can do the following:

    Integer nullCheckInteger = null;
    if (myVarIn != null && !myVarIn.isEmpty()) {
        // we can use any integer
        nullCheckInteger = 1;
    }
    repo.callService(myVarIn, nullCheckInteger);

And then pass those two parms into the call.

What does this do? If myVarIn is not null and filled then we can specify "all" as 1 != null. Otherwise we pass in our list and null is null and therefore ignored. This either selects "all" when empty or something when not empty.