SpEL: Conversion of collection method parameters fails [SPR-7631]

[spring-projects-issues]

Oliver Becker opened SPR-7631 and commented

In the SpEL when a method is invoked that has a method parameter of a generic collection type (say Collection<T>), the elements of the passed collection (say Collection<S>) will not be converted. (Note: this works fine for setting properties.)

Here is a test case:

public class CollectionToCollectionConverterTest {

public static class Foo {

    private Collection<Foo> foos;

    public final String value;

    public Foo(String value) {
        this.value = value;
    }

    public void setFoos(Collection<Foo> foos) {
        this.foos = foos;
    }

    public Collection<Foo> getFoos() {
        return this.foos;
    }

}

@Test
public void testConvert() {
    ExpressionParser parser = new SpelExpressionParser();
    Foo root = new Foo("bar");
    EvaluationContext context = new StandardEvaluationContext(root);

    Collection<String> foos = Collections.singletonList("baz");

    // property access, works
    Expression expression = parser.parseExpression("foos");
    expression.setValue(context, foos);
    Foo baz = root.getFoos().iterator().next();
    Assert.assertEquals("baz", baz.value);

    // method call, fails (ClassCastException)
    expression = parser.parseExpression("setFoos(#foos)");
    context.setVariable("foos", foos);
    expression.getValue(context);
    baz = root.getFoos().iterator().next();
    Assert.assertEquals("baz", baz.value);
}

}

---

Affects: 3.0.4

[spring-projects-issues]

Oliver Becker commented

Hopefully better readable code:

public class CollectionToCollectionConverterTest {

   public static class Foo {

       private Collection<Foo> foos;

       public final String value;

       public Foo(String value) {
           this.value = value;
       }

       public void setFoos(Collection<Foo> foos) {
           this.foos = foos;
       }

       public Collection<Foo> getFoos() {
           return this.foos;
       }

   }

   @Test
   public void testConvert() {
       ExpressionParser parser = new SpelExpressionParser();
       Foo root = new Foo("bar");
       EvaluationContext context = new StandardEvaluationContext(root);

       Collection<String> foos = Collections.singletonList("baz");

       // property access, works
       Expression expression = parser.parseExpression("foos");
       expression.setValue(context, foos);
       Foo baz = root.getFoos().iterator().next();
       Assert.assertEquals("baz", baz.value);

       // method call, fails (ClassCastException)
       expression = parser.parseExpression("setFoos(#foos)");
       context.setVariable("foos", foos);
       expression.getValue(context);
       baz = root.getFoos().iterator().next();
       Assert.assertEquals("baz", baz.value);
   }
}

[spring-projects-issues]

Juergen Hoeller commented

This test actually passes against the latest 3.0.5 snapshot, probably due to a change related to TypeDescriptor handling in SpEL. Please give it a try and let us know whether it works for you as well...

Juergen