DATACMNS-533 - Added test cases for root object integration in SpEL extension API.

Changed SPI to expose a Function type rather than plain methods as well as an arbitrary root object.

Related pull request: spring-projects/spring-data-jpa#101
Related ticket: DATAJPA-564

src/main/java/org/springframework/data/repository/query/spi/EvaluationContextExtension.java

@@ -15,7 +15,6 @@
  */
 package org.springframework.data.repository.query.spi;
 
-import java.lang.reflect.Method;
 import java.util.Map;
 
 import org.springframework.data.repository.query.ExtensionAwareEvaluationContextProvider;
@@ -51,5 +50,14 @@ public interface EvaluationContextExtension {
 	 * 
 	 * @return the functions
 	 */
-	Map<String, Method> getFunctions();
+	Map<String, Function> getFunctions();
+
+	/**
+	 * Returns the root object to be exposed by the extension. It's strongly recommended to declare the most concrete type
+	 * possible as return type of the implementation method. This will allow us to obtain the necessary metadata once and
+	 * not for every evaluation.
+	 * 
+	 * @return
+	 */
+	Object getRootObject();
 }

src/main/java/org/springframework/data/repository/query/spi/Function.java

@@ -0,0 +1,118 @@
+/*
+ * Copyright 2014 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.data.repository.query.spi;
+
+import java.lang.reflect.Method;
+import java.lang.reflect.Modifier;
+import java.util.List;
+
+import org.springframework.core.convert.TypeDescriptor;
+import org.springframework.util.Assert;
+import org.springframework.util.TypeUtils;
+
+/**
+ * Value object to represent a function. Can either be backed by a static {@link Method} invocation (see
+ * {@link #Function(Method)}) or a method invocation on an instance (see {@link #Function(Method, Object)}.
+ * 
+ * @author Thomas Darimont
+ * @author Oliver Gierke
+ * @since 1.9
+ */
+public class Function {
+
+	private final Method method;
+	private final Object target;
+
+	/**
+	 * Creates a new {@link Function} to statically invoke the given {@link Method}.
+	 * 
+	 * @param method
+	 */
+	public Function(Method method) {
+
+		this(method, null);
+
+		Assert.isTrue(Modifier.isStatic(method.getModifiers()), "Method must be static!");
+	}
+
+	/**
+	 * Creates a new {@link Function} for the given method on the given target instance.
+	 * 
+	 * @param method must not be {@literal null}.
+	 * @param target can be {@literal null}, if so, the method
+	 */
+	public Function(Method method, Object target) {
+
+		Assert.notNull(method, "Method must not be null!");
+		Assert.isTrue(target != null || Modifier.isStatic(method.getModifiers()),
+				"Method must either be static or a non-static one with a target object!");
+
+		this.method = method;
+		this.target = target;
+	}
+
+	/**
+	 * Invokes the function with the given arguments.
+	 * 
+	 * @param arguments must not be {@literal null}.
+	 * @return
+	 * @throws Exception
+	 */
+	public Object invoke(Object[] arguments) throws Exception {
+		return method.invoke(target, arguments);
+	}
+
+	/**
+	 * Returns the name of the function.
+	 * 
+	 * @return
+	 */
+	public String getName() {
+		return method.getName();
+	}
+
+	/**
+	 * Returns the type declaring the {@link Function}.
+	 * 
+	 * @return
+	 */
+	public Class<?> getDeclaringClass() {
+		return method.getDeclaringClass();
+	}
+
+	/**
+	 * Returns {@literal true} if the function can be called with the given {@code argumentTypes}.
+	 * 
+	 * @param argumentTypes
+	 * @return
+	 */
+	public boolean supports(List<TypeDescriptor> argumentTypes) {
+
+		Class<?>[] parameterTypes = method.getParameterTypes();
+
+		if (parameterTypes.length != argumentTypes.size()) {
+			return false;
+		}
+
+		for (int i = 0; i < parameterTypes.length; i++) {
+			if (!TypeUtils.isAssignable(parameterTypes[i], argumentTypes.get(i).getType())) {
+				return false;
+			}
+		}
+
+		return true;
+	}
+}