| package org.onlab.junit; |
| |
| import org.hamcrest.Description; |
| import org.hamcrest.StringDescription; |
| |
| import java.lang.reflect.Field; |
| import java.lang.reflect.Method; |
| import java.lang.reflect.Modifier; |
| |
| /** |
| * Hamcrest style class for verifying that a class follows the |
| * accepted rules for immutable classes. |
| * |
| * The rules that are enforced for immutable classes: |
| * - the class must be declared final |
| * - all data members of the class must be declared private and final |
| * - the class must not define any setter methods |
| */ |
| |
| public class ImmutableClassChecker { |
| |
| private String failureReason = ""; |
| |
| /** |
| * Method to determine if a given class is a properly specified |
| * immutable class. |
| * |
| * @param clazz the class to check |
| * @return true if the given class is a properly specified immutable class. |
| */ |
| private boolean isImmutableClass(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 final and private data members |
| for (final Field field : clazz.getDeclaredFields()) { |
| if (field.getName().startsWith("__cobertura")) { |
| // cobertura sticks these fields into classes - ignore them |
| continue; |
| } |
| if (!Modifier.isFinal(field.getModifiers())) { |
| failureReason = "a field named '" + field.getName() + |
| "' that is not final"; |
| return false; |
| } |
| if (!Modifier.isPrivate(field.getModifiers())) { |
| // |
| // NOTE: We relax the recommended rules for defining immutable |
| // objects and allow "static final" fields that are not |
| // private. The "final" check was already done above so we |
| // don't repeat it here. |
| // |
| if (!Modifier.isStatic(field.getModifiers())) { |
| failureReason = "a field named '" + field.getName() + |
| "' that is not private and is not static"; |
| return false; |
| } |
| } |
| } |
| |
| // class must not define any setters |
| for (final Method method : clazz.getMethods()) { |
| if (method.getDeclaringClass().equals(clazz)) { |
| if (method.getName().startsWith("set")) { |
| failureReason = "a class with a setter named '" + method.getName() + "'"; |
| 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 immutable 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 assertThatClassIsImmutable(Class<?> clazz) { |
| final ImmutableClassChecker checker = new ImmutableClassChecker(); |
| if (!checker.isImmutableClass(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); |
| } |
| } |
| } |