Question

I would like to filter return values of methods which have a @Filter annotation and return a Collection, an Array or a Map by a certain predicate.

I tried something like:

    @Pointcut("execution(@example.annotations.Filter * *(..)) "
            + "&& @annotation(filter) ")
    public void filterOperation(final Filter filter) {
        /* ... */
    }

But I get syntax errors if I add execution((java.util.Collection+ || java.util.Map+) * * (..)) to the PointCut above.

How would a solution look like, preferable one where I could error out if some method was annotated with @Filter but would not return a collection?

Answer 1

Did you tried to use execution((java.util.Collection+ || java.util.Map+) *.* (..))?

Or you can use:

@Pointcut("execution(@example.annotations.Filter java.util.Collection+ || java.util.Map+ *(..)) "
        + "&& @annotation(filter) ")
public void filterOperation(final Filter filter) {
    /* ... */
}

You can handle return value the following way:

@AfterReturning(value="filterOperation(filter)", returning="collection")
public void handlingReturnValue(final Filter filter, Object collection) {
    System.out.println(collection);
}

But I suppose it will be better to use separate advices for Maps and Collections:

@Pointcut("execution(@Filter java.util.Collection+ *(..)) "
        + "&& @annotation(filter) ")
public void filterCollection(final Filter filter) {
    /* ... */
}

@Pointcut("execution(@Filter java.util.Map+ *(..)) "
        + "&& @annotation(filter) ")
public void filterMap(final Filter filter) {
    /* ... */
}

@AfterReturning(value="filterCollection(filter)", returning="collection")
public void handlingReturnCollection(final Filter filter, Collection collection) {
    System.out.println(collection);
}

@AfterReturning(value="filterMap(filter)", returning="map")
public void handlingReturnMap(final Filter filter, Map map) {
    System.out.println(map);
}