SpEL evaluator cannot convert method parameters even if the TypeConverter can [SPR-7410]

[spring-projects-issues]

Dave Syer opened SPR-7410 and commented

Example:

@Test
public void testCoercionToCollectionOfPrimitive() throws Exception {

	class TestTarget {
		@SuppressWarnings("unused")
		public int sum(Collection<Integer> numbers) {
			int total = 0;
			for (int i : numbers) {
				total += i;
			}
			return total;
		}
	}

	StandardEvaluationContext evaluationContext = new StandardEvaluationContext();

	TypeDescriptor collectionType = new TypeDescriptor(new MethodParameter(TestTarget.class.getDeclaredMethod(
			"sum", Collection.class), 0));
	// The type conversion is possible
	assertTrue(evaluationContext.getTypeConverter()
			.canConvert(TypeDescriptor.valueOf(String.class), collectionType));
	// ... and it can be done successfully
	assertEquals("[1, 2, 3, 4]", evaluationContext.getTypeConverter().convertValue("1,2,3,4",
			TypeDescriptor.valueOf(String.class), collectionType).toString());


	evaluationContext.setVariable("target", new TestTarget());

	// OK up to here, so the evaluation should be fine...
	// ... but this fails
	int result = (Integer) parser.parseExpression("#target.sum(#root)").getValue(evaluationContext, "1,2,3,4");
	assertEquals("Wrong result: " + result, 10, result);

}

Here's the stack trace:

java.lang.ClassCastException: java.lang.String cannot be cast to java.lang.Integer
	at org.springframework.sample.ExpressionTests$2TestTarget.sum(ExpressionTests.java:127)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
	at java.lang.reflect.Method.invoke(Method.java:597)
	at org.springframework.expression.spel.support.ReflectiveMethodExecutor.execute(ReflectiveMethodExecutor.java:58)
	at org.springframework.expression.spel.ast.MethodReference.getValueInternal(MethodReference.java:104)
	at org.springframework.expression.spel.ast.CompoundExpression.getValueInternal(CompoundExpression.java:57)
	at org.springframework.expression.spel.ast.SpelNodeImpl.getValue(SpelNodeImpl.java:93)
	at org.springframework.expression.spel.standard.SpelExpression.getValue(SpelExpression.java:93)
	at org.springframework.sample.ExpressionTests.testCoercionToCollectionOfPrimitive(ExpressionTests.java:144)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
	at java.lang.reflect.Method.invoke(Method.java:597)
	at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:44)
	at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:15)
	at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:41)
	at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:20)
	at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:76)
	at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:50)
	at org.junit.runners.ParentRunner$3.run(ParentRunner.java:193)
	at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:52)
	at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:191)
	at org.junit.runners.ParentRunner.access$000(ParentRunner.java:42)
	at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:184)
	at org.junit.runners.ParentRunner.run(ParentRunner.java:236)
	at org.eclipse.jdt.internal.junit4.runner.JUnit4TestReference.run(JUnit4TestReference.java:46)
	at org.eclipse.jdt.internal.junit.runner.TestExecution.run(TestExecution.java:38)
	at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:467)
	at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:683)
	at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:390)
	at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:197)

---

Affects: 3.0.3

Referenced from: commits 58b07f5

[spring-projects-issues]

Juergen Hoeller commented

Good catch! SpEL passes the full collection type context (generics, annotations) to the ConversionService now, not just the base type.

Juergen