Expressions in 1-M relationships

Question

Let's say I have a USERS table with a 1-M relationship with a PARAMETERS table. PARAMETERS hold things like custom-defined fields for a USER.
USERS has 2 fields of interest:
ID
NAME
PARAMETERS has 3 fields of interest:
USERID
PARAMETERNAME
VALUE
The objects are mapped properly and the User object has a 1-M relationship with Parameter.
Now, Let's say I have 2 USERS:
1 Bob
2 Tom
And they have the following PARAMETERS set:
1 RANK A
1 GRADE 4
2 RANK A
2 GRADE 3
As you can see, Bob has Rank=A and Grade=4. Tom has Rank=A also, and Grade=3.
I want to build an expression that will return all the Users that have Rank=A AND Grade=4. (This should return Bob).
This is the Java code I have created (I've tried lots of variations on this as well):
ExpressionBuilder user = new ExpressionBuilder();
Expression exp = user.anyOf("_parameters").get("_parameterName").equal("Rank");
exp = exp.and(user.get("_parameters").get("_value").equal("A"));
ExpressionBuilder user2= new ExpressionBuilder();
Expression exp2 = user2.anyOf("_parameters").get("_parameterName").equal("Title");     
exp2 = exp2.and(user2.get("_parameters").get("_value").equal(4));
exp = exp.and(exp2);
ReadAllQuery query = new ReadAllQuery(RKUser.class, exp);
This produces NO RESULTS because the query joins on the wrong tables. It produces this:
SELECT u.name, u.id FROM users u, parameters p0, parameters p1 WHERE (p0.parametername = 'Rank' AND p0.value = 'A') AND (p1.parametername = 'Grade' AND p0.value = '4')......
Notice the 2nd set of params with p1.parametername = 'Grade' AND p0.value = '4'? "p0" is incorrect. It should be p1.value = '4'!
How can I build the expression properly? I've read through the docs, but nothing is very clear on how to enforce this.
Any help would be appreciated.

Answer 1

OK. Solved it. Found the best explanation I've seen so far in 10g FAQ's: http://otn.oracle.com/products/ias/toplink/technical/tl10g_faq.htm
I keep getting multiple joins when I use multiple anyOf( ) functions in my expression, which is returning too many results. How do I get it down to one join instead?
Each time you use anyOf() in your expression, you get another join in your database. For example, the OracleAS TopLink expression:
emp.anyOf("managedEmployees").get("lastName").equal("Smith").and(emp.anyOf("managedEmployees").get("firstName").equal("John"));
will return any Employee who manages a John or a Smith, not just John Smith. This is because a separate join is performed for each anyOf() . To force a single join, the same anyOf node must be used for each query:
Expression managedEmployees = emp.anyOf("managedEmployees");
managedEmployees.get("lastName").equal("Smith").and(managedEmployees.get("firstName").equal("John"));
So the answer is, I need only 1 ExpressionBuilder and 2 Expressions returned from the "anyOf()" method. The Expressions returned from "anyOf()" are my joins.
The following works:
ExpressionBuilder eb = new ExpressionBuilder();
Expression p0 = eb.anyOf("_parameters");
Expression p1 = eb.anyOf("_parameters");
Expression exp = p0.get("_parameterName").equal("Rank");
exp = exp.and(p0.get("_value").equal("A"));
exp = exp.and(p1.get("_parameterName").equal("Grade"));
exp = exp.and(p1.get("_value).equal(4));
This works fine.