Ray Milkey | 27bd335 | 2014-05-14 16:59:25 -0700 | [diff] [blame] | 1 | package net.onrc.onos.core.util; |
| 2 | |
| 3 | import org.hamcrest.Description; |
| 4 | import org.hamcrest.StringDescription; |
| 5 | |
| 6 | import java.lang.reflect.Field; |
| 7 | import java.lang.reflect.Method; |
| 8 | import java.lang.reflect.Modifier; |
| 9 | |
| 10 | /** |
| 11 | * Hamcrest style class for verifying that a class follows the |
| 12 | * accepted rules for immutable classes. |
| 13 | * |
| 14 | * The rules that are enforced for immutable classes: |
| 15 | * - the class must be declared final |
| 16 | * - all data members of the class must be declared private and final |
| 17 | * - the class must not define any setter methods |
| 18 | */ |
| 19 | |
| 20 | public class ImmutableClassChecker { |
| 21 | |
| 22 | private String failureReason = ""; |
| 23 | |
| 24 | /** |
| 25 | * Method to determine if a given class is a properly specified |
| 26 | * immutable class. |
| 27 | * |
| 28 | * @param clazz the class to check |
| 29 | * @return true if the given class is a properly specified immutable class. |
| 30 | */ |
Ray Milkey | e3dadc3 | 2014-05-19 15:27:42 -0700 | [diff] [blame] | 31 | private boolean isImmutableClass(Class<?> clazz) { |
Ray Milkey | 27bd335 | 2014-05-14 16:59:25 -0700 | [diff] [blame] | 32 | // class must be declared final |
| 33 | if (!Modifier.isFinal(clazz.getModifiers())) { |
| 34 | failureReason = "a class that is not final"; |
| 35 | return false; |
| 36 | } |
| 37 | |
| 38 | // class must have only final and private data members |
| 39 | for (final Field field : clazz.getDeclaredFields()) { |
Ray Milkey | 4567e4c | 2014-05-15 19:28:24 -0700 | [diff] [blame] | 40 | if (field.getName().startsWith("__cobertura")) { |
| 41 | // cobertura sticks these fields into classes - ignore them |
| 42 | continue; |
| 43 | } |
Ray Milkey | 27bd335 | 2014-05-14 16:59:25 -0700 | [diff] [blame] | 44 | if (!Modifier.isFinal(field.getModifiers())) { |
| 45 | failureReason = "a field named '" + field.getName() + |
| 46 | "' that is not final"; |
| 47 | return false; |
| 48 | } |
| 49 | if (!Modifier.isPrivate(field.getModifiers())) { |
| 50 | failureReason = "a field named '" + field.getName() + |
| 51 | "' that is not private"; |
| 52 | return false; |
| 53 | } |
| 54 | } |
| 55 | |
| 56 | // class must not define any setters |
| 57 | for (final Method method : clazz.getMethods()) { |
| 58 | if (method.getDeclaringClass().equals(clazz)) { |
| 59 | if (method.getName().startsWith("set")) { |
| 60 | failureReason = "a class with a setter named '" + method.getName() + "'"; |
| 61 | return false; |
| 62 | } |
| 63 | } |
| 64 | } |
| 65 | |
| 66 | return true; |
| 67 | } |
| 68 | |
| 69 | /** |
| 70 | * Describe why an error was reported. Uses Hamcrest style Description |
| 71 | * interfaces. |
| 72 | * |
| 73 | * @param description the Description object to use for reporting the |
| 74 | * mismatch |
| 75 | */ |
| 76 | public void describeMismatch(Description description) { |
| 77 | description.appendText(failureReason); |
| 78 | } |
| 79 | |
| 80 | /** |
| 81 | * Describe the source object that caused an error, using a Hamcrest |
| 82 | * Matcher style interface. In this case, it always returns |
| 83 | * that we are looking for a properly defined utility class. |
| 84 | * |
| 85 | * @param description the Description object to use to report the "to" |
| 86 | * object |
| 87 | */ |
| 88 | public void describeTo(Description description) { |
| 89 | description.appendText("a properly defined immutable class"); |
| 90 | } |
| 91 | |
| 92 | /** |
| 93 | * Assert that the given class adheres to the utility class rules. |
| 94 | * |
| 95 | * @param clazz the class to check |
| 96 | * |
| 97 | * @throws java.lang.AssertionError if the class is not a valid |
| 98 | * utility class |
| 99 | */ |
Ray Milkey | e3dadc3 | 2014-05-19 15:27:42 -0700 | [diff] [blame] | 100 | public static void assertThatClassIsImmutable(Class<?> clazz) { |
Ray Milkey | 27bd335 | 2014-05-14 16:59:25 -0700 | [diff] [blame] | 101 | final ImmutableClassChecker checker = new ImmutableClassChecker(); |
| 102 | if (!checker.isImmutableClass(clazz)) { |
| 103 | final Description toDescription = new StringDescription(); |
| 104 | final Description mismatchDescription = new StringDescription(); |
| 105 | |
| 106 | checker.describeTo(toDescription); |
| 107 | checker.describeMismatch(mismatchDescription); |
| 108 | final String reason = |
| 109 | "\n" + |
| 110 | "Expected: is \"" + toDescription.toString() + "\"\n" + |
| 111 | " but : was \"" + mismatchDescription.toString() + "\""; |
| 112 | |
| 113 | throw new AssertionError(reason); |
| 114 | } |
| 115 | } |
| 116 | } |