Test that LaunchedURLClassLoader works when thread is interrupted

Previously, RandomAccessDataFile used a semaphore and acquired it
interruptibly. This meant that an interrupted thread was unable to
access the file. Notably, this would prevent LaunchedURLClassLoader from
loading classes or resources on an interrupted thread.

The previous commit (937f8576) updates RandomAccessDataFile to acquire
the semaphore uninterruptibly. This commit adds a test to
LaunchedURLClassLoader to verify that it can now load a resource from
an interrupted thread.

Closes gh-6683

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

 /*
- * Copyright 2012-2014 the original author or authors.
+ * Copyright 2012-2016 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -36,6 +36,7 @@ import static org.junit.Assert.assertTrue;
  *
  * @author Dave Syer
  * @author Phillip Webb
+ * @author Andy Wilkinson
  */
 @SuppressWarnings("resource")
 public class LaunchedURLClassLoaderTests {
@@ -101,4 +102,23 @@ public class LaunchedURLClassLoaderTests {
 		assertThat(resource.openConnection().getInputStream().read(), equalTo(3));
 	}
 
+	@Test
+	public void resolveFromNestedWhileThreadIsInterrupted() throws Exception {
+		File file = this.temporaryFolder.newFile();
+		TestJarCreator.createTestJar(file);
+		JarFile jarFile = new JarFile(file);
+		URL url = jarFile.getUrl();
+		LaunchedURLClassLoader loader = new LaunchedURLClassLoader(new URL[] { url },
+				null);
+		try {
+			Thread.currentThread().interrupt();
+			URL resource = loader.getResource("nested.jar!/3.dat");
+			assertThat(resource.toString(), equalTo(url + "nested.jar!/3.dat"));
+			assertThat(resource.openConnection().getInputStream().read(), equalTo(3));
+		}
+		finally {
+			Thread.interrupted();
+		}
+	}
+
 }