Merge pull request #230 from scijava/load-class-loudly

Do proper exception handling when loading classes

Author: ctrueden

src/main/java/org/scijava/Context.java

@@ -320,10 +320,7 @@ public <S extends Service> S service(final Class<S> c) {
 	 *           service.
 	 */
 	public Service service(final String className) {
-		final Class<?> c = ClassUtils.loadClass(className);
-		if (c == null) {
-			throw new IllegalArgumentException("No such class: " + className);
-		}
+		final Class<?> c = ClassUtils.loadClass(className, false);
 		if (!Service.class.isAssignableFrom(c)) {
 			throw new IllegalArgumentException("Not a service class: " + c.getName());
 		}

src/main/java/org/scijava/main/DefaultMainService.java

@@ -101,10 +101,13 @@ public String[] args() {
 		@Override
 		public void exec() {
 			try {
-				final Class<?> mainClass = ClassUtils.loadClass(className);
+				final Class<?> mainClass = ClassUtils.loadClass(className, false);
 				final Method main = mainClass.getMethod("main", String[].class);
 				main.invoke(null, new Object[] { args });
 			}
+			catch (final IllegalArgumentException exc) {
+				if (log != null) log.error(exc);
+			}
 			catch (final NoSuchMethodException exc) {
 				if (log != null) {
 					log.error("No main method for class: " + className, exc);

src/main/java/org/scijava/menu/ShadowMenu.java

@@ -231,13 +231,20 @@ public URL getIconURL() {
 			else return null;
 		}
 		final String className = moduleInfo.getDelegateClassName();
-		final Class<?> c = ClassUtils.loadClass(className);
-		if (c == null) return null;
-		final URL iconURL = c.getResource(iconPath);
-		if (iconURL == null) {
-			if (log != null) log.error("Could not load icon: " + iconPath);
+		try {
+			final Class<?> c = ClassUtils.loadClass(className, false);
+			final URL iconURL = c.getResource(iconPath);
+			if (iconURL == null) {
+				if (log != null) log.error("Could not load icon: " + iconPath);
+			}
+			return iconURL;
+		}
+		catch (final IllegalArgumentException exc) {
+			final String message = "Could not load icon for class: " + className;
+			if (log.isDebug()) log.debug(message, exc);
+			else log.error(message);
+			return null;
 		}
-		return iconURL;
 	}
 
 	/**

src/main/java/org/scijava/plugin/PluginInfo.java

@@ -280,13 +280,15 @@ public String getClassName() {
 	@Override
 	public Class<? extends PT> loadClass() throws InstantiableException {
 		if (pluginClass == null) {
-			final Class<?> c = ClassUtils.loadClass(className, classLoader);
-			if (c == null) {
-				throw new InstantiableException("Class not found: " + className);
+			try {
+				final Class<?> c = ClassUtils.loadClass(className, classLoader, false);
+				@SuppressWarnings("unchecked")
+				final Class<? extends PT> typedClass = (Class<? extends PT>) c;
+				pluginClass = typedClass;
+			}
+			catch (final IllegalArgumentException exc) {
+				throw new InstantiableException("Class not found: " + className, exc);
 			}
-			@SuppressWarnings("unchecked")
-			final Class<? extends PT> typedClass = (Class<? extends PT>) c;
-			pluginClass = typedClass;
 		}
 
 		return pluginClass;

src/main/java/org/scijava/script/DefaultScriptService.java

@@ -255,13 +255,16 @@ public synchronized Class<?> lookupClass(final String alias)
 		final Class<?> type = aliasMap().get(alias);
 		if (type != null) return type;
 
-		final Class<?> c = ClassUtils.loadClass(alias);
-		if (c != null) {
+		try {
+			final Class<?> c = ClassUtils.loadClass(alias, false);
 			aliasMap().put(alias, c);
 			return c;
 		}
-
-		throw new ScriptException("Unknown type: " + alias);
+		catch (final IllegalArgumentException exc) {
+			final ScriptException se = new ScriptException("Unknown type: " + alias);
+			se.initCause(exc);
+			throw se;
+		}
 	}
 
 	// -- PTService methods --

src/main/java/org/scijava/util/ClassUtils.java

@@ -93,11 +93,48 @@ private ClassUtils() {
 	 * Loads the class with the given name, using the current thread's context
 	 * class loader, or null if it cannot be loaded.
 	 *
+	 * @param name The name of the class to load.
 	 * @return The loaded class, or null if the class could not be loaded.
-	 * @see #loadClass(String, ClassLoader)
+	 * @see #loadClass(String, ClassLoader, boolean)
 	 */
-	public static Class<?> loadClass(final String className) {
-		return loadClass(className, null);
+	public static Class<?> loadClass(final String name) {
+		return loadClass(name, null, true);
+	}
+
+	/**
+	 * Loads the class with the given name, using the specified
+	 * {@link ClassLoader}, or null if it cannot be loaded.
+	 *
+	 * @param name The name of the class to load.
+	 * @param classLoader The class loader with which to load the class; if null,
+	 *          the current thread's context class loader will be used.
+	 * @return The loaded class, or null if the class could not be loaded.
+	 * @see #loadClass(String, ClassLoader, boolean)
+	 */
+	public static Class<?> loadClass(final String name,
+		final ClassLoader classLoader)
+	{
+		return loadClass(name, classLoader, true);
+	}
+
+	/**
+	 * Loads the class with the given name, using the current thread's context
+	 * class loader.
+	 *
+	 * @param className the name of the class to load
+	 * @param quietly Whether to return {@code null} (rather than throwing
+	 *          {@link IllegalArgumentException}) if something goes wrong loading
+	 *          the class
+	 * @return The loaded class, or {@code null} if the class could not be loaded
+	 *         and the {@code quietly} flag is set.
+	 * @see #loadClass(String, ClassLoader, boolean)
+	 * @throws IllegalArgumentException If the class cannot be loaded and the
+	 *           {@code quietly} flag is not set.
+	 */
+	public static Class<?> loadClass(final String className,
+		final boolean quietly)
+	{
+		return loadClass(className, null, quietly);
 	}
 
 	/**
@@ -119,10 +156,16 @@ public static Class<?> loadClass(final String className) {
 	 * @param name The name of the class to load.
 	 * @param classLoader The class loader with which to load the class; if null,
 	 *          the current thread's context class loader will be used.
-	 * @return The loaded class, or null if the class could not be loaded.
+	 * @param quietly Whether to return {@code null} (rather than throwing
+	 *          {@link IllegalArgumentException}) if something goes wrong loading
+	 *          the class
+	 * @return The loaded class, or {@code null} if the class could not be loaded
+	 *         and the {@code quietly} flag is set.
+	 * @throws IllegalArgumentException If the class cannot be loaded and the
+	 *           {@code quietly} flag is not set.
 	 */
 	public static Class<?> loadClass(final String name,
-		final ClassLoader classLoader)
+		final ClassLoader classLoader, final boolean quietly)
 	{
 		// handle primitive types
 		if (name.equals("Z") || name.equals("boolean")) return boolean.class;
@@ -170,7 +213,8 @@ public static Class<?> loadClass(final String name,
 			// Not ClassNotFoundException.
 			// Not NoClassDefFoundError.
 			// Not UnsupportedClassVersionError!
-			return null;
+			if (quietly) return null;
+			throw new IllegalArgumentException("Cannot load class: " + className, t);
 		}
 	}
 

src/test/java/org/scijava/util/ClassUtilsTest.java

@@ -116,6 +116,16 @@ public void testLoadClass() {
 		assertLoaded(Number[][].class, "[[Ljava.lang.Number;");
 	}
 
+	@Test
+	public void testFailureQuiet() {
+		assertNull(ClassUtils.loadClass("a.non.existent.class"));
+	}
+
+	@Test(expected = IllegalArgumentException.class)
+	public void testFailureLoud() {
+		ClassUtils.loadClass("a.non.existent.class", false);
+	}
+
 	@Test
 	public void testGetArrayClass() {
 		assertSame(boolean[].class, ClassUtils.getArrayClass(boolean.class));