Use fast exceptions in findResource(s)

Some libraries like aspectj are using findResource to see the raw
bytecode of a class. It will even call findResource for every method of
every class of beans that are post processed. This can be significant
performance hit on startup when LaunchedURLClassLoader and there are a
lot of nested jars.

See gh-3640
Fixes gh-4557

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

@@ -82,8 +82,14 @@ public class LaunchedURLClassLoader extends URLClassLoader {
 			if (name.equals("") && hasURLs()) {
 				return getURLs()[0];
 			}
+			Handler.setUseFastConnectionExceptions(true);
+			try {
 				return super.findResource(name);
 			}
+			finally {
+				Handler.setUseFastConnectionExceptions(false);
+			}
+		}
 		catch (IllegalArgumentException ex) {
 			return null;
 		}
@@ -94,8 +100,14 @@ public class LaunchedURLClassLoader extends URLClassLoader {
 		if (name.equals("") && hasURLs()) {
 			return Collections.enumeration(Arrays.asList(getURLs()));
 		}
+		Handler.setUseFastConnectionExceptions(true);
+		try {
 			return super.findResources(name);
 		}
+		finally {
+			Handler.setUseFastConnectionExceptions(false);
+		}
+	}
 
 	private boolean hasURLs() {
 		return getURLs().length > 0;
@@ -291,6 +303,6 @@ public class LaunchedURLClassLoader extends URLClassLoader {
 			return this.localResources.nextElement();
 		}
 
-	};
+	}
 
 }