| package net.onrc.onos.core.util; |
| |
| import org.hamcrest.Description; |
| import org.hamcrest.StringDescription; |
| |
| import java.lang.reflect.Constructor; |
| import java.lang.reflect.Method; |
| import java.lang.reflect.Modifier; |
| |
| |
| /** |
| * Hamcrest style class for verifying that a class follows the |
| * accepted rules for utility classes. |
| * |
| * The rules that are enforced for utility classes: |
| * - the class must be declared final |
| * - the class must have only one constructor |
| * - the constructor must be private and inaccessible to callers |
| * - the class must have only static methods |
| */ |
| |
| public class UtilityClassChecker { |
| |
| private String failureReason = ""; |
| |
| /** |
| * Method to determine if a given class is a properly specified |
| * utility class. In addition to checking that the class meets the criteria |
| * for utility classes, an object of the class type is allocated to force |
| * test code coverage onto the class constructor. |
| * |
| * @param clazz the class to check |
| * @return true if the given class is a properly specified utility class. |
| */ |
| private boolean isProperlyDefinedUtilityClass(Class<?> clazz) { |
| // class must be declared final |
| if (!Modifier.isFinal(clazz.getModifiers())) { |
| failureReason = "a class that is not final"; |
| return false; |
| } |
| |
| // class must have only one constructor |
| final Constructor<?>[] constructors = clazz.getDeclaredConstructors(); |
| if (constructors.length != 1) { |
| failureReason = "a class with more than one constructor"; |
| return false; |
| } |
| |
| // constructor must not be accessible outside of the class |
| final Constructor<?> constructor = constructors[0]; |
| if (constructor.isAccessible()) { |
| failureReason = "a class with an accessible default constructor"; |
| return false; |
| } |
| |
| // constructor must be private |
| if (!Modifier.isPrivate(constructor.getModifiers())) { |
| failureReason = "a class with a default constructor that is not private"; |
| return false; |
| } |
| |
| // class must have only static methods |
| for (final Method method : clazz.getMethods()) { |
| if (method.getDeclaringClass().equals(clazz)) { |
| if (!Modifier.isStatic(method.getModifiers())) { |
| failureReason = "a class with one or more non-static methods"; |
| return false; |
| } |
| } |
| |
| } |
| |
| final Object newObject = TestUtils.callConstructor(constructor); |
| if (newObject == null) { |
| failureReason = "could not instantiate a new object"; |
| return false; |
| } |
| return true; |
| } |
| |
| /** |
| * Describe why an error was reported. Uses Hamcrest style Description |
| * interfaces. |
| * |
| * @param description the Description object to use for reporting the |
| * mismatch |
| */ |
| public void describeMismatch(Description description) { |
| description.appendText(failureReason); |
| } |
| |
| /** |
| * Describe the source object that caused an error, using a Hamcrest |
| * Matcher style interface. In this case, it always returns |
| * that we are looking for a properly defined utility class. |
| * |
| * @param description the Description object to use to report the "to" |
| * object |
| */ |
| public void describeTo(Description description) { |
| description.appendText("a properly defined utility class"); |
| } |
| |
| /** |
| * Assert that the given class adheres to the utility class rules. |
| * |
| * @param clazz the class to check |
| * |
| * @throws java.lang.AssertionError if the class is not a valid |
| * utility class |
| */ |
| public static void assertThatClassIsUtility(Class<?> clazz) { |
| final UtilityClassChecker checker = new UtilityClassChecker(); |
| if (!checker.isProperlyDefinedUtilityClass(clazz)) { |
| final Description toDescription = new StringDescription(); |
| final Description mismatchDescription = new StringDescription(); |
| |
| checker.describeTo(toDescription); |
| checker.describeMismatch(mismatchDescription); |
| final String reason = |
| "\n" + |
| "Expected: is \"" + toDescription.toString() + "\"\n" + |
| " but : was \"" + mismatchDescription.toString() + "\""; |
| |
| throw new AssertionError(reason); |
| } |
| } |
| } |