Best way to implement dynamic search criteria

Question

I was recently showing a group of developers some of the Toplink basics. As an example I showed a way to build a Toplink expression for an object search where the search criteria are determined at runtime. Doing this in raw SQL is a bit tricky because you need to place the 'AND' statements between the criteria, but I found a simple method to do this with an expression (or at least I think I did). I simply used and() to add each criteria expression, including the first one. Toplink seemed smart enough to derive the SQL without the additional AND statement.
My question to the Forum is, is this the best way to build the expression and is it flawed? Here is my code snippet and the generated SQL.
public Expression createExpression(ExpressionBuilder builder, Object[] parameters) {
// Build expression for a Dealer Search
String name = (String)parameters[0];
String location = (String)parameters[1];
String email = (String)parameters[2];
Expression searchExpression = builder;
// NAME = 'name'
if (name != null) {
searchExpression =
searchExpression.and(builder.get("name").equal(name));
// LOCATION = 'location'
if (location != null) {
searchExpression =
searchExpression.and(builder.get("location").equal(location));
// EMAIL = 'email
if (email != null) {
searchExpression =
searchExpression.and(builder.get("contactInfo").get("email").equal(email));
return searchExpression;
Toplink generated SQL with location="Mt. Prospect, IL", email=null, and name=null:
SELECT VERSION, LOCATION, ID, NAME FROM DEALER WHERE (LOCATION = 'Mt. Prospect, IL')
Thanks.

Answer 1

All JPA strategies require something (like a table or sequence object) be in the database, with table sequencing being the most portable, though EclipseLink does allow custom sequence stratgies where you could use something else, such as the UUID. Sequencing is described here described here http://wiki.eclipse.org/EclipseLink/Examples/JPA/PrimaryKey with a custom UUID example shown here http://wiki.eclipse.org/EclipseLink/Examples/JPA/CustomSequencing .