SFW-8224: distance can be used when computing method matches in ReflectiveMethodResolver

org.springframework.expression/src/main/java/org/springframework/expression/spel/support/ReflectionHelper.java

@@ -102,6 +102,49 @@ public class ReflectionHelper {
 			}
 		}
 	}
+	
+	/**
+	 * Based on {@link MethodInvoker.getTypeDifferenceWeight} but operates on TypeDescriptors.
+	 */
+	public static int getTypeDifferenceWeight(List<TypeDescriptor> paramTypes, List<TypeDescriptor> argTypes) {
+		int result = 0;
+		for (int i = 0,max=paramTypes.size(); i < max; i++) {
+			TypeDescriptor argType = argTypes.get(i);
+			TypeDescriptor paramType = paramTypes.get(i);
+			if (argType==TypeDescriptor.NULL) {
+				if (paramType.isPrimitive()) {
+					return Integer.MAX_VALUE;
+				}
+			}
+			if (!ClassUtils.isAssignable(paramType.getClass(), argType.getClass())) {
+				return Integer.MAX_VALUE;
+			}
+			if (argType != TypeDescriptor.NULL) {
+				Class paramTypeClazz = paramType.getType();
+				if (paramTypeClazz.isPrimitive()) {
+					paramTypeClazz = Object.class;
+			    }
+				Class superClass = argType.getClass().getSuperclass();
+				while (superClass != null) {
+					if (paramType.equals(superClass)) {
+						result = result + 2;
+						superClass = null;
+					}
+					else if (ClassUtils.isAssignable(paramTypeClazz, superClass)) {
+						result = result + 2;
+						superClass = superClass.getSuperclass();
+					}
+					else {
+						superClass = null;
+					}
+				}
+				if (paramTypeClazz.isInterface()) {
+					result = result + 1;
+				}
+			}
+		}
+		return result;
+	}
 
 	/**
 	 * Compare argument arrays and return information about whether they match. A supplied type converter and

org.springframework.expression/src/main/java/org/springframework/expression/spel/support/ReflectiveMethodResolver.java

@@ -49,8 +49,29 @@ public class ReflectiveMethodResolver implements MethodResolver {
 	private static Method[] NO_METHODS = new Method[0];
 
 	private Map<Class<?>, MethodFilter> filters = null;
+	
+	// Using distance will ensure a more accurate match is discovered, 
+	// more closely following the Java rules.
+	private boolean useDistance = false;
 
 	
+	public ReflectiveMethodResolver() {
+		
+	}
+	
+	/**
+	 * This constructors allows the ReflectiveMethodResolver to be configured such that it will
+	 * use a distance computation to check which is the better of two close matches (when there
+	 * are multiple matches).  Using the distance computation is intended to ensure matches
+	 * are more closely representative of what a Java compiler would do when taking into 
+	 * account boxing/unboxing and whether the method candidates are declared to handle a
+	 * supertype of the type (of the argument) being passed in.
+	 * @param useDistance true if distance computation should be used when calculating matches
+	 */
+	public ReflectiveMethodResolver(boolean useDistance) {
+		this.useDistance = useDistance;
+	}
+	
 	/**
 	 * Locate a method on a type. There are three kinds of match that might occur:
 	 * <ol>
@@ -93,6 +114,7 @@ public class ReflectiveMethodResolver implements MethodResolver {
 			});
 
 			Method closeMatch = null;
+			int closeMatchDistance = Integer.MAX_VALUE;
 			int[] argsToConvert = null;
 			Method matchRequiringConversion = null;
 			boolean multipleOptions = false;
@@ -121,7 +143,16 @@ public class ReflectiveMethodResolver implements MethodResolver {
 							return new ReflectiveMethodExecutor(method, null);
 						}
 						else if (matchInfo.kind == ReflectionHelper.ArgsMatchKind.CLOSE) {
-							closeMatch = method;
+							if (!useDistance) {
+								closeMatch = method;
+							} else {
+								int matchDistance = ReflectionHelper.getTypeDifferenceWeight(paramDescriptors, argumentTypes);
+								if (matchDistance<closeMatchDistance) {
+									// this is a better match
+									closeMatchDistance = matchDistance;
+									closeMatch = method;
+								}
+							}
 						}
 						else if (matchInfo.kind == ReflectionHelper.ArgsMatchKind.REQUIRES_CONVERSION) {
 							if (matchRequiringConversion != null) {

org.springframework.expression/src/test/java/org/springframework/expression/spel/SpringEL300Tests.java

@@ -813,6 +813,96 @@ public class SpringEL300Tests extends ExpressionTestCase {
         assertEquals("[D(aaa), D(bbb), D(ccc)]",value3.toString());
 	}
 
+	/**
+	 * Test whether {@link ReflectiveMethodResolver} follows Java Method Invocation Conversion order. And more precisely
+	 * that widening reference conversion is 'higher' than a unboxing conversion.
+	 */
+	@Test
+	public void testConversionPriority_8224() throws Exception {
+
+		@SuppressWarnings("unused")
+		class ConversionPriority1 {
+			public int getX(Number i) {
+				return 20;
+			}
+
+			public int getX(int i) {
+				return 10;
+			}
+		}
+
+		@SuppressWarnings("unused")
+		class ConversionPriority2 {
+			public int getX(int i) {
+				return 10;
+			}
+
+			public int getX(Number i) {
+				return 20;
+			}
+		}
+
+		final Integer INTEGER = Integer.valueOf(7);
+
+		EvaluationContext emptyEvalContext = new StandardEvaluationContext();
+
+		List<TypeDescriptor> args = new ArrayList<TypeDescriptor>();
+		args.add(TypeDescriptor.forObject(new Integer(42)));
+
+		ConversionPriority1 target = new ConversionPriority1();
+		MethodExecutor me = new ReflectiveMethodResolver(true).resolve(emptyEvalContext, target, "getX", args);
+		// MethodInvoker chooses getX(int i) when passing Integer
+		final int actual = (Integer) me.execute(emptyEvalContext, target, new Integer(42)).getValue();
+		// Compiler chooses getX(Number i) when passing Integer
+		final int compiler = target.getX(INTEGER);
+		// Fails!
+		assertEquals(compiler, actual);
+
+		ConversionPriority2 target2 = new ConversionPriority2();
+		MethodExecutor me2 = new ReflectiveMethodResolver(true).resolve(emptyEvalContext, target2, "getX", args);
+		// MethodInvoker chooses getX(int i) when passing Integer
+		int actual2 = (Integer) me2.execute(emptyEvalContext, target2, new Integer(42)).getValue();
+		// Compiler chooses getX(Number i) when passing Integer
+		int compiler2 = target2.getX(INTEGER);
+		// Fails!
+		assertEquals(compiler2, actual2);
+
+	}
+
+	/**
+	 * Test whether {@link ReflectiveMethodResolver} handles Widening Primitive Conversion. That's passing an 'int' to a
+	 * method accepting 'long' is ok.
+	 */
+	@Test
+	public void testWideningPrimitiveConversion_8224() throws Exception {
+
+		class WideningPrimitiveConversion {
+
+			public int getX(long i) {
+				return 10;
+			}
+		}
+
+		final Integer INTEGER_VALUE = Integer.valueOf(7);
+
+		WideningPrimitiveConversion target = new WideningPrimitiveConversion();
+
+		EvaluationContext emptyEvalContext = new StandardEvaluationContext();
+
+		List<TypeDescriptor> args = new ArrayList<TypeDescriptor>();
+		args.add(TypeDescriptor.forObject(INTEGER_VALUE));
+
+		MethodExecutor me = new ReflectiveMethodResolver(true).resolve(emptyEvalContext, target, "getX", args);
+
+		final int actual = (Integer) me.execute(emptyEvalContext, target, INTEGER_VALUE).getValue();
+
+		final int compiler = target.getX(INTEGER_VALUE);
+
+		assertEquals(compiler, actual);
+	}
+
+
+	
 	@Test
 	public void varargsAndPrimitives_SPR8174() throws Exception  {
 		EvaluationContext emptyEvalContext = new StandardEvaluationContext();