Add escape hatch for ClassLoader.findResource() for invalid path

The source of the exception is in sun.misc (so hard to track down precisely)
but it's clear that the LaunchedJarURLClassLoader needs to be more
defensive and return null from findResource() if it can't find it.

Fixes gh-486

spring-boot-tools/spring-boot-loader/src/main/java/org/springframework/boot/loader/LaunchedURLClassLoader.java

@@ -73,8 +73,13 @@ public class LaunchedURLClassLoader extends URLClassLoader {
 				return urls[0];
 			}
 		}
+		try {
 			return super.findResource(name);
 		}
+		catch (IllegalArgumentException e) {
+			return null;
+		}
+	}
 
 	@Override
 	public Enumeration<URL> findResources(String name) throws IOException {

spring-boot-tools/spring-boot-loader/src/test/java/org/springframework/boot/loader/LaunchedURLClassLoaderTests.java

@@ -21,6 +21,7 @@ import java.net.URL;
 import org.junit.Test;
 
 import static org.junit.Assert.assertNotNull;
+import static org.junit.Assert.assertNull;
 import static org.junit.Assert.assertTrue;
 
 /**
@@ -28,6 +29,19 @@ import static org.junit.Assert.assertTrue;
  */
 public class LaunchedURLClassLoaderTests {
 
+	@Test
+	public void resolveResourceFromWindowsFilesystem() throws Exception {
+		// This path is invalid - it should return null even on Windows.
+		// A regular URLClassLoader will deal with it gracefully.
+		assertNull(getClass().getClassLoader().getResource(
+				"c:\\Users\\user\\bar.properties"));
+		LaunchedURLClassLoader loader = new LaunchedURLClassLoader(new URL[] { new URL(
+				"jar:file:src/test/resources/jars/app.jar!/") }, getClass()
+				.getClassLoader());
+		// So we should too...
+		assertNull(loader.getResource("c:\\Users\\user\\bar.properties"));
+	}
+
 	@Test
 	public void resolveResourceFromArchive() throws Exception {
 		LaunchedURLClassLoader loader = new LaunchedURLClassLoader(new URL[] { new URL(