ConstantExpression returns null when evaluated with a context
-------------------------------------------------------------
Key: GEOT-2875
URL: http://jira.codehaus.org/browse/GEOT-2875
Project: GeoTools
Issue Type: Bug
Components: core main
Affects Versions: 2.6.0
Reporter: Andrea Aime
Assignee: Jody Garnett
Priority: Critical
Fix For: 2.6.1
ConstantExpression is used in a number of places as a replacement for Literal.
However ConstantExpression breaks the contract of evaluate(object, context) in
that it can only return its value if the context is of the same type as the
value, otherwise it returns null:
{code}
public <T> T evaluate(Object object, Class<T> context) {
if(value == null || value.getClass().equals(context))
return context.cast( value );
else
return null;
}
{code}
Compare this with LiteralImpl, that uses Converters:
{code}
public Object evaluate(Object feature, Class context) {
return Converters.convert(literal, context);
}
{code}
At first reaction I'd say that ConstantExpression should use Converters, but
unfortunately it lives in api, where Converters is not available.
It cannot be moved to main either, since ConstantExperssion is used in a number
of places in api itself.
Very bad situation I'd say, not sure how to get out of it. Certainly we cannot
recode all the code that relies on evaluate(xxx, context) to make a special
case for ConstantExpression.
Maybe we can move Converters back to gt-api? The api module would starting
looking less like an api thought...
Suggestion? Bright ideas?
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