Minor refactoring in listeners; create listener consistency test

- Export duplicated code into a service
- Remove canConnect attribute from AuthMe class - was unused and doesn't seem sensible
- Add consistency test for listener classes

src/test/java/fr/xephi/authme/listener/ListenerConsistencyTest.java

@@ -0,0 +1,76 @@
+package fr.xephi.authme.listener;
+
+import com.google.common.collect.Sets;
+import org.bukkit.event.EventHandler;
+import org.junit.Test;
+
+import java.lang.reflect.Method;
+import java.lang.reflect.Modifier;
+import java.util.Set;
+
+import static org.hamcrest.Matchers.equalTo;
+import static org.junit.Assert.assertThat;
+import static org.junit.Assert.fail;
+
+/**
+ * Test for verifying that AuthMe listener methods are well-formed.
+ */
+public final class ListenerConsistencyTest {
+
+    private static final Class<?>[] LISTENERS = { AuthMeBlockListener.class, AuthMeEntityListener.class,
+        AuthMePlayerListener.class, AuthMePlayerListener16.class, AuthMePlayerListener18.class,
+        AuthMeServerListener.class };
+
+    // TODO #368: Ensure that these exceptions are really intentional, if not fix them and remove them here
+    private static final Set<String> CANCELED_EXCEPTIONS = Sets.newHashSet("AuthMePlayerListener#onPlayerJoin",
+        "AuthMePlayerListener#onPreLogin", "AuthMePlayerListener#onPlayerLogin",
+        "AuthMePlayerListener#onPlayerQuit", "AuthMeServerListener#onPluginDisable",
+        "AuthMeServerListener#onServerPing", "AuthMeServerListener#onPluginEnable");
+
+    @Test
+    public void shouldSetIgnoreCancelledToTrue() {
+        for (Class<?> listener : LISTENERS) {
+            checkCanceledAttribute(listener);
+        }
+    }
+
+    @Test
+    public void shouldHaveOnlyEventListenersAsPublicMembers() {
+        for (Class<?> listener : LISTENERS) {
+            checkPublicMethodsAreListeners(listener);
+        }
+    }
+
+    private static void checkCanceledAttribute(Class<?> listenerClass) {
+        final String clazz = listenerClass.getSimpleName();
+        Method[] methods = listenerClass.getDeclaredMethods();
+        for (Method method : methods) {
+            if (isTestableMethod(method) && method.isAnnotationPresent(EventHandler.class)) {
+                if (CANCELED_EXCEPTIONS.contains(clazz + "#" + method.getName())) {
+                    continue;
+                }
+
+                EventHandler eventHandlerAnnotation = method.getAnnotation(EventHandler.class);
+                assertThat("Method " + clazz + "#" + method.getName() + " should have ignoreCancelled = true",
+                    eventHandlerAnnotation.ignoreCancelled(), equalTo(true));
+            }
+        }
+    }
+
+    private static void checkPublicMethodsAreListeners(Class<?> listenerClass) {
+        final String clazz = listenerClass.getSimpleName();
+        Method[] methods = listenerClass.getDeclaredMethods();
+        for (Method method : methods) {
+            if (isTestableMethod(method) && !method.isAnnotationPresent(EventHandler.class)) {
+                fail("Expected @EventHandler annotation on non-private method " + clazz + "#" + method.getName());
+            }
+        }
+    }
+
+    private static boolean isTestableMethod(Method method) {
+        // A method like "access$000" is created by the compiler when a private member is being accessed by an inner
+        // class, so we need to ignore such methods
+        return !Modifier.isPrivate(method.getModifiers()) && !method.getName().startsWith("access$");
+    }
+
+}