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http://www.stripesframework.org/jira/browse/STS-884?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]
Martin Cortez updated STS-884:
------------------------------
Attachment: STS-884.patch
I think I fixed the problem (although someone could review my code to make sure
I didn't introduce any new bugs.) I've attached my changes to the
{{NodeEvaluation}} and {{PropertyExpressionEvaluation}}.
The problem seemed to be that the
{{PropertyExpressionEvaluation.getTypeVariableValue()}} method couldn't figure
out the type for generic types that were subtyped. The {{TypeVariable
typeVar}} parameter represented the correct method return type, however it
couldn't be resolved without the subtype {{Class<?>}}.
To fix it, I added a variable called {{declaringType}} to {{NodeEvaluation}}
which contains the class that is having the method invoked on it. (Now that I
think about it... maybe invokingType would have been a better name.)
The logic in {{PropertyExpressionEvaluation.getTypeVariableValue()}} new uses
the {{declaringType}} to scan the superclasses for generic declarations. (Using
some existing code that I pulled into a new method.)
> PropertyExpressionEvaluation returns null for certain generics
> --------------------------------------------------------------
>
> Key: STS-884
> URL: http://www.stripesframework.org/jira/browse/STS-884
> Project: Stripes
> Issue Type: Bug
> Components: ActionBean Dispatching
> Affects Versions: Release 1.5.7
> Reporter: Martin Cortez
> Labels: binding
> Attachments: STS-884.patch
>
>
> I have a Stripes project where my domain objects have several layers of
> generics. It seems that in a certain combination, calling
> {{PropertyExpressionEvaluation.getType()}} returns {{null}}. This seems to
> be the simplest scenario where it fails:
> {code:title=Main.java|borderStyle=solid}
> import net.sourceforge.stripes.util.bean.PropertyExpression;
> import net.sourceforge.stripes.util.bean.PropertyExpressionEvaluation;
> public final class Main {
> public static void main(final String... args) throws Throwable {
> printType(new Bean(), "listValues");
> printType(new Bean(), "listValues.values");
> printType(new Bean(), "listValues.values[0]");
> printType(new Bean(), "listValues.values[0].alpha");
> printType(new Bean(), "listValues.values[0].beta");
> }
> private static void printType(Object bean, String expression) {
> PropertyExpression exp =
> PropertyExpression.getExpression(expression);
> PropertyExpressionEvaluation eval = new
> PropertyExpressionEvaluation(
> exp, bean);
> Class<?> clazz = eval.getType();
> System.out.println("Expression: " + expression);
> System.out.println("Object: " + bean);
> System.out.println("Type: " + clazz);
> System.out.println();
> }
> }
> {code}
> {code:title=Bean.java|borderStyle=solid}
> public class Bean {
> public ListValues<Child> getListValues() { return null; }
> }
> {code}
> {code:title=ListValues.java|borderStyle=solid}
> public class ListValues<V> {
> public java.util.List<V> getValues() { return null; }
> }
> {code}
> {code:title=Parent.java|borderStyle=solid}
> public class Parent<A> {
> public A getAlpha() { return null; }
> public Beta getBeta() { return null; }
> }
> {code}
> {code:title=Child.java|borderStyle=solid}
> public class Child extends Parent<Alpha> {}
> {code}
> {code:title=Alpha.java|borderStyle=solid}
> public class Alpha {}
> {code}
> {code:title=Beta.java|borderStyle=solid}
> public class Beta {}
> {code}
> Running Main prints the following output:
> {noformat}
> Expression: listValues
> Object: Bean@4d20a47e
> Type: class ListValues
> Expression: listValues.values
> Object: Bean@2b86c6b2
> Type: interface java.util.List
> Expression: listValues.values[0]
> Object: Bean@593d93f4
> Type: class Child
> Expression: listValues.values[0].alpha
> Object: Bean@635b9e68
> Type: null
> Expression: listValues.values[0].beta
> Object: Bean@13fcf0ce
> Type: class Beta
> {noformat}
> Without understanding the {{PropertyExpressionEvaluation}} code too much, I
> think the problem is at the following line:
> {code:title=PropertyExpressionEvaluation.java|borderStyle=solid}
> type = getBeanPropertyType(clazz, property);
>
> // XXX What do we do if type is a generic type?
> {code}
> The type returned by {{getBeanPropertyType()}} is a {{TypeVariable}} and,
> according to the comment, it seems like this scenario isn't handled yet. For
> now, I guess I can just create a few concrete classes without using so many
> generics... but it would be nice if this worked. Maybe my test classes will
> help someone figure out the correct logic?
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