Added HandlerMethodUtils.

org.springframework.integration/src/main/java/org/springframework/integration/handler/HandlerMethodUtils.java

@@ -0,0 +1,80 @@
+/*
+ * Copyright 2002-2008 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.integration.handler;
+
+import java.lang.annotation.Annotation;
+import java.lang.reflect.Method;
+import java.lang.reflect.Modifier;
+
+import org.springframework.integration.annotation.Header;
+import org.springframework.integration.annotation.Headers;
+
+/**
+ * Utility methods for common behavior related to Message-handling methods.
+ * 
+ * @author Mark Fisher
+ */
+public abstract class HandlerMethodUtils {
+
+	/**
+	 * Verifies that the provided Method is capable of handling Messages.
+	 * It must accept at least one parameter, and if it expects more than one
+	 * parameter, at most one of them may expect the payload object. Others
+	 * must be annotated for accepting Message header values.
+	 */
+	public static boolean isValidHandlerMethod(Method method) {
+		if (method.getDeclaringClass().equals(Object.class)) {
+			return false;
+		}
+		if (!Modifier.isPublic(method.getModifiers())) {
+			return false;
+		}
+		Class<?>[] parameterTypes = method.getParameterTypes();
+		if (parameterTypes.length == 0) {
+			return false;
+		}
+		if (parameterTypes.length > 1) {
+			// at most one parameter can be lacking @Header or @Headers
+			boolean foundPayloadParam = false;
+			Annotation[][] allParamAnnotations = method.getParameterAnnotations();
+			for (Annotation[] paramAnnotations : allParamAnnotations) {
+				if (!containsHeaderAnnotation(paramAnnotations)) {
+					if (foundPayloadParam) {
+						return false;
+					}
+					foundPayloadParam = true;
+				}
+			}
+		}
+		return true;
+	}
+
+	/**
+	 * Checks the array of Annotations for a method parameter to see if either
+	 * the @Header or @Headers annotation is present.
+	 */
+	public static boolean containsHeaderAnnotation(Annotation[] parameterAnnotations) {
+		for (Annotation annotation : parameterAnnotations) {
+			if (annotation.annotationType().equals(Header.class)
+					|| annotation.annotationType().equals(Headers.class)) {
+				return true;
+			}
+		}
+		return false;
+	}
+
+}