LMS-641 Move method Util.assertInterfaceWithOnlyVoidMethods from project...

LMS-641 Move method Util.assertInterfaceWithOnlyVoidMethods from project 'server-common' to ClassUtils. Also tests added.

SVN: 8956

common/source/java/ch/systemsx/cisd/common/utilities/ClassUtils.java

@@ -84,6 +84,27 @@ public final class ClassUtils
         return org.apache.commons.lang.ClassUtils.getAllSuperclasses(object.getClass());
     }
 
+    /**
+     * Asserts that the specified class is an interface which has only methods with no return value.
+     * 
+     * @throws AssertionError if it isn't an interface or at least one method has a return value.
+     */
+    public static void assertInterfaceWithOnlyVoidMethods(Class<?> clazz)
+    {
+        assert clazz != null : "Unspecified class.";
+        assert clazz.isInterface() : "Is not an interface: " + clazz.getName();
+        Method[] methods = clazz.getMethods();
+        for (Method method : methods)
+        {
+            Class<?> returnType = method.getReturnType();
+            if (Void.TYPE.equals(returnType) == false)
+            {
+                throw new AssertionError("Method " + clazz.getName() + "." + method.getName()
+                        + " has non-void return type: " + returnType.getName());
+            }
+        }
+    }
+    
     /**
      * Creates a new instance of a class specified by its fully-qualified name.
      * 
@@ -479,4 +500,5 @@ public final class ClassUtils
             throw new CheckedExceptionTunnel(ex);
         }
     }
+
 }
\ No newline at end of file

common/sourceTest/java/ch/systemsx/cisd/common/utilities/ClassUtilsTest.java

@@ -123,7 +123,52 @@ public final class ClassUtilsTest
                 ClassUtils.create(Appendable.class, MyClass.class.getName(), list);
         assertSame(list, ((MyClass) appendable).iterable);
     }
+    
+    private static interface AnInterfaceWithOnlyVoidMethods
+    {
+        public void exec();
+        public void print(String message);
+    }
+    
+    private static interface AnInterfaceWithNotOnlyVoidMethods
+    {
+        public int exec();
+        public void print(String message);
+    }
+    
+    @Test
+    public void testAssertInterfaceWithOnlyVoidMethodsWithAnInterfaceWithOnlyVoidMethods()
+    {
+        ClassUtils.assertInterfaceWithOnlyVoidMethods(AnInterfaceWithOnlyVoidMethods.class);
+    }
 
+    @Test
+    public void testAssertInterfaceWithOnlyVoidMethodsWithAnInterfaceWithNotOnlyVoidMethods()
+    {
+        try
+        {
+            ClassUtils.assertInterfaceWithOnlyVoidMethods(AnInterfaceWithNotOnlyVoidMethods.class);
+            fail("AssertionError expected");
+        } catch (AssertionError e)
+        {
+            assertEquals("Method " + AnInterfaceWithNotOnlyVoidMethods.class.getName()
+                    + ".exec has non-void return type: int", e.getMessage());
+        }
+    }
+    
+    @Test
+    public void testAssertInterfaceWithOnlyVoidMethodsWithAClass()
+    {
+        try
+        {
+            ClassUtils.assertInterfaceWithOnlyVoidMethods(String.class);
+            fail("AssertionError expected");
+        } catch (AssertionError e)
+        {
+            assertEquals("Is not an interface: java.lang.String", e.getMessage());
+        }
+    }
+    
     @Test
     public final void testSetFieldValueWithExpectedThrowable()
     {