Add Types.location which throws an exception

Like Types.load, this provides another signature with a
"quietly" flag for toggling the exception throwing behavior.

To test it, we load a class from a byte array,
to ensure there is no discernable location.

Author: ctrueden

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

@@ -58,6 +58,7 @@
 import java.lang.reflect.WildcardType;
 import java.net.MalformedURLException;
 import java.net.URL;
+import java.security.CodeSource;
 import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.Collections;
@@ -218,6 +219,18 @@ public static Class<?> load(final String name, final ClassLoader classLoader,
 		}
 	}
 
+	/**
+	 * Gets the base location of the given class.
+	 *
+	 * @param c The class whose location is desired.
+	 * @return URL pointing to the class, or null if the location could not be
+	 *         determined.
+	 * @see #location(Class, boolean)
+	 */
+	public static URL location(final Class<?> c) {
+		return location(c, true);
+	}
+
 	/**
 	 * Gets the base location of the given class.
 	 * <p>
@@ -232,22 +245,33 @@ public static Class<?> load(final String name, final ClassLoader classLoader,
 	 * </p>
 	 *
 	 * @param c The class whose location is desired.
+	 * @param quietly Whether to return {@code null} (rather than throwing
+	 *          {@link IllegalArgumentException}) if something goes wrong
+	 *          determining the location.
 	 * @return URL pointing to the class, or null if the location could not be
-	 *         determined.
+	 *         determined and the {@code quietly} flag is set.
+	 * @throws IllegalArgumentException If the location cannot be determined and
+	 *           the {@code quietly} flag is not set.
 	 * @see FileUtils#urlToFile(URL) to convert the result to a {@link File}.
 	 */
-	public static URL location(final Class<?> c) {
+	public static URL location(final Class<?> c, final boolean quietly) {
+		Exception cause = null;
+		String why = null;
+
 		// try the easy way first
 		try {
-			final URL codeSourceLocation =
-				c.getProtectionDomain().getCodeSource().getLocation();
-			if (codeSourceLocation != null) return codeSourceLocation;
+			final CodeSource codeSource = c.getProtectionDomain().getCodeSource();
+			if (codeSource != null) {
+				final URL location = codeSource.getLocation();
+				if (location != null) return location;
+				why = "null code source location";
+			}
+			else why = "null code source";
 		}
 		catch (final SecurityException exc) {
 			// NB: Cannot access protection domain.
-		}
-		catch (final NullPointerException exc) {
-			// NB: Protection domain or code source is null.
+			cause = exc;
+			why = "cannot access protection domain";
 		}
 
 		// NB: The easy way failed, so we try the hard way. We ask for the class
@@ -256,11 +280,19 @@ public static URL location(final Class<?> c) {
 
 		// get the class's raw resource path
 		final URL classResource = c.getResource(c.getSimpleName() + ".class");
-		if (classResource == null) return null; // cannot find class resource
+		if (classResource == null) {
+			// cannot find class resource
+			if (quietly) return null;
+			throw iae(cause, "No class resource for class: " + name(c), why);
+		}
 
 		final String url = classResource.toString();
 		final String suffix = c.getCanonicalName().replace('.', '/') + ".class";
-		if (!url.endsWith(suffix)) return null; // weird URL
+		if (!url.endsWith(suffix)) {
+			// weird URL
+			if (quietly) return null;
+			throw iae(cause, "Unsupported URL format: " + url, why);
+		}
 
 		// strip the class's path from the URL string
 		final String base = url.substring(0, url.length() - suffix.length());
@@ -274,7 +306,8 @@ public static URL location(final Class<?> c) {
 			return new URL(path);
 		}
 		catch (final MalformedURLException e) {
-			return null;
+			if (quietly) return null;
+			throw iae(e, "Malformed URL", why);
 		}
 	}
 

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

@@ -185,6 +185,22 @@ public void testLocationClassInJar() throws IOException {
 		jar.deleteOnExit();
 	}
 
+	/** Tests quiet behavior of {@link Types#location(Class, boolean)}. */
+	@Test
+	public void testLocationFailureQuiet() {
+		final Class<?> weirdClass = loadCustomClass();
+		assertEquals("Hello", weirdClass.getName());
+		assertNull(Types.location(weirdClass));
+	}
+
+	/** Tests exceptions from {@link Types#location(Class, boolean)}. */
+	@Test(expected = IllegalArgumentException.class)
+	public void testLocationFailureLoud() {
+		final Class<?> weirdClass = loadCustomClass();
+		assertEquals("Hello", weirdClass.getName());
+		Types.location(weirdClass, false);
+	}
+
 	/** Tests {@link Types#name}. */
 	public void testName() {
 		@SuppressWarnings("unused")
@@ -582,6 +598,30 @@ private void copy(final InputStream in, final OutputStream out,
 		if (closeOut) out.close();
 	}
 
+	private Class<?> loadCustomClass() {
+		// NB: The bytecode below was compiled from the following source:
+		//
+		//     public class Hello {}
+		//
+		final byte[] bytecode = { -54, -2, -70, -66, 0, 0, 0, 52, 0, 13, 10, 0, 3,
+			0, 10, 7, 0, 11, 7, 0, 12, 1, 0, 6, 60, 105, 110, 105, 116, 62, 1, 0, 3,
+			40, 41, 86, 1, 0, 4, 67, 111, 100, 101, 1, 0, 15, 76, 105, 110, 101, 78,
+			117, 109, 98, 101, 114, 84, 97, 98, 108, 101, 1, 0, 10, 83, 111, 117, 114,
+			99, 101, 70, 105, 108, 101, 1, 0, 10, 72, 101, 108, 108, 111, 46, 106, 97,
+			118, 97, 12, 0, 4, 0, 5, 1, 0, 5, 72, 101, 108, 108, 111, 1, 0, 16, 106,
+			97, 118, 97, 47, 108, 97, 110, 103, 47, 79, 98, 106, 101, 99, 116, 0, 33,
+			0, 2, 0, 3, 0, 0, 0, 0, 0, 1, 0, 1, 0, 4, 0, 5, 0, 1, 0, 6, 0, 0, 0, 29,
+			0, 1, 0, 1, 0, 0, 0, 5, 42, -73, 0, 1, -79, 0, 0, 0, 1, 0, 7, 0, 0, 0, 6,
+			0, 1, 0, 0, 0, 1, 0, 1, 0, 8, 0, 0, 0, 2, 0, 9 };
+
+		class BytesClassLoader extends ClassLoader {
+			public Class<?> load(final String name, final byte[] b) {
+				return defineClass(name, b, 0, b.length);
+			}
+		}
+		return new BytesClassLoader().load("Hello", bytecode);
+	}
+
 	/** Convenience method to get the {@link Type} of a field. */
 	private Type type(final Class<?> c, final String fieldName) {
 		return Types.field(c, fieldName).getGenericType();