Re: [eclipselink-users] Search using Expression API - Is there an easier

[James Sutherland <jamesssss@xxxxxxxxx>]

Not certain what you mean, but this may be simpler,

private Expression getSearchExpression(MyFruit fruit)
        {
                Expression eb = new ExpressionBuilder();
                Expression expression;
                if(!example.getColor().isEmpty())
                        expression =
eb.get("color").equal(example.getColor()).and(expression);
               
                if(!example.getTaste().isEmpty())
                        expression =
eb.get("taste").equal(example.getTaste()).and(expression);
               
                if(!example.getSmell().isEmpty())
                        expression =
eb.get("smell").equal(example.getSmell()).and(expression);

                return expression;
        } 

You may also wish to investigate EclipseLink's Query By Example
(ReadAllQuery.setExampleObject()).


tch wrote:
> 
> I am starting to play with the expression API more, and it seems a bit
> clunky to me. Perhaps I'm just dense, but the issue seems to be the
> need to logically join each condition.
> 
> This gets really messy when you're trying to do a generic search in a
> web app - there are 20 fields, each field they enter a value on should
> be anded with any other fields present. This is a pretty common
> pattern.
> 
> I was hoping I would be able to have the expression built
> automatically perhaps with a default logical condition somehow. I
> could probably build something in a half hour that did that, but it
> seems like this functionality should exist somewhere already. How are
> other people dealing with this common pattern?
> 
> Here's what I came up with, as the simplest solution, am I missing
> something? It's tedious with all the null checking, etc.
> 
> 	private Expression getSearchExpression(MyFruit fruit)
> 	{
> 		Expression eb = new ExpressionBuilder();
> 		Expression color = null,taste = null,smell = null;
> 		if(!example.getColor().isEmpty())
> 			color = eb.get("color").equal(example.getColor());
> 		
> 		if(!example.getTaste().isEmpty())
> 			taste  = eb.get("taste").equal(example.getTaste());
> 		
> 		if(!example.getSmell().isEmpty())
> 			smell = eb.get("smell").equal(example.getSmell());
> 
> 		return andConditions(color,taste,smell);
> 	}
> 
> 
> 	private Expression andConditions(Expression...exps)
> 	{
> 		if(exps ==  null)
> 			return null;
> 		
> 		if(exps.length == 1)
> 			return exps[0];
> 		
> 		Expression e = null;
> 		boolean initExp = false;
> 		for (Expression tmpE : exps) {
> 			if(tmpE != null)
> 			{
> 				if(!initExp)
> 				{
> 					e = tmpE;
> 					initExp = true;
> 				}
> 				else
> 				{
> 					e = e.and(tmpE);
> 				}
> 			}
> 		}
> 		return e;
> 	}
> 
> 
> ./tch
> 
> 


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