How to dynamically build JDO Queries on multiple parameters

Question

One can easily use JDO syntax to query on multiple parameters as follows:

//specify the persistent entity you're querying and you filter usign params
query = pm.newQuery(MyClass.class, " customer == paramCustomer && date >= paramStartDate && date <=paramEndDate ");

// declare params used above
query.declareParameters("com.google.appengine.api.users.User paramCustomer, java.util.Date paramStartDate, java.util.Date paramEndDate"); 

//pass the object declared as params
MyClassList = (List<MyClass>) query.execute(user, startDate, endDate);

It's straightforward to programmatically build a string with the filter:

"customer == paramCustomer && date >= paramStartDate && date <=paramEndDate"

and another strign with the params declaration:

"com.google.appengine.api.users.User paramCustomer, java.util.Date paramStartDate, java.util.Date paramEndDate"

What's not immediate is to come up with a strategy for executing the query depending on which params are in the filter (and have been declared), so you end up with a number of really ugly and ad-hoc cascading if-else statements with all the possible permutations of the query execution (all the params, only the first, only the second, first and second etc...):

MyClassList = (List<MyClass>) query.execute(user, startDate, endDate);

I am sure this is a common task and someone else is doing it in a more general and efficient way.

Any suggestion?

Answer 1

I found a solution in the method query.executeWithArray.

This way I can build filters and param declaration dynamically an load up the actual objects into an array of object which is then passed to the method mentioned above.