utility for determining if a method has an optional returntype

core/src/main/java/org/jclouds/util/Optionals2.java

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+/**
+ * Licensed to jclouds, Inc. (jclouds) under one or more
+ * contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  jclouds licenses this file
+ * to you 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.jclouds.util;
+
+import java.lang.reflect.Method;
+import java.lang.reflect.ParameterizedType;
+
+import com.google.common.base.Optional;
+
+/**
+ * 
+ * @author Adrian Cole
+ */
+public class Optionals2 {
+
+   public static Class<?> returnTypeOrTypeOfOptional(Method method) {
+      boolean optional = isReturnTypeOptional(method);
+      Class<?> syncClass;
+      if (optional) {
+         ParameterizedType futureType = ParameterizedType.class.cast(method.getGenericReturnType());
+         // TODO: error checking in case this is a type, not a class.
+         syncClass = Class.class.cast(futureType.getActualTypeArguments()[0]);
+      } else {
+         syncClass = method.getReturnType();
+      }
+      return syncClass;
+   }
+
+   public static boolean isReturnTypeOptional(Method method) {
+      boolean optional = method.getReturnType().isAssignableFrom(Optional.class);
+      return optional;
+   }
+
+}

core/src/test/java/org/jclouds/util/Optionals2Test.java

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+/**
+ * Licensed to jclouds, Inc. (jclouds) under one or more
+ * contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  jclouds licenses this file
+ * to you 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.jclouds.util;
+
+import static org.testng.Assert.assertEquals;
+import static org.testng.Assert.assertFalse;
+import static org.testng.Assert.assertTrue;
+
+import java.lang.reflect.Method;
+
+import org.testng.annotations.Test;
+
+import com.google.common.base.Optional;
+
+/**
+ * @author Adrian Cole
+ */
+@Test
+public class Optionals2Test {
+
+   public static interface Test {
+      Optional<String> getOptional();
+
+      String getNotOptional();
+   }
+
+   public void testReturnTypeOrTypeOfOptionalWhenOptional() throws SecurityException, NoSuchMethodException {
+      Method method = Test.class.getMethod("getOptional");
+
+      assertEquals(Optionals2.returnTypeOrTypeOfOptional(method), String.class);
+   }
+
+   public void testReturnTypeOrTypeOfOptionalWhenNotOptional() throws SecurityException, NoSuchMethodException {
+      Method method = Test.class.getMethod("getNotOptional");
+
+      assertEquals(Optionals2.returnTypeOrTypeOfOptional(method), String.class);
+   }
+
+   public void testIsReturnTypeOptionalWhenOptional() throws SecurityException, NoSuchMethodException {
+      Method method = Test.class.getMethod("getOptional");
+
+      assertTrue(Optionals2.isReturnTypeOptional(method));
+   }
+
+   public void testIsReturnTypeOptionalWhenNotOptional() throws SecurityException, NoSuchMethodException {
+      Method method = Test.class.getMethod("getNotOptional");
+
+      assertFalse(Optionals2.isReturnTypeOptional(method));
+   }
+}