Fix handling of jar files with + chars in their path

Closes gh-17208

Author: wilkinsona

spring-boot-project/spring-boot-tools/spring-boot-loader/src/main/java/org/springframework/boot/loader/jar/Handler.java

@@ -20,9 +20,9 @@
 import java.io.IOException;
 import java.lang.ref.SoftReference;
 import java.net.MalformedURLException;
+import java.net.URI;
 import java.net.URL;
 import java.net.URLConnection;
-import java.net.URLDecoder;
 import java.net.URLStreamHandler;
 import java.util.Map;
 import java.util.concurrent.ConcurrentHashMap;
@@ -302,8 +302,7 @@ private JarFile getRootJarFile(String name) throws IOException {
 			if (!name.startsWith(FILE_PROTOCOL)) {
 				throw new IllegalStateException("Not a file URL");
 			}
-			String path = name.substring(FILE_PROTOCOL.length());
-			File file = new File(URLDecoder.decode(path, "UTF-8"));
+			File file = new File(URI.create(name));
 			Map<File, JarFile> cache = rootFileCache.get();
 			JarFile result = (cache != null) ? cache.get(file) : null;
 			if (result == null) {

spring-boot-project/spring-boot-tools/spring-boot-loader/src/test/java/org/springframework/boot/loader/jar/HandlerTests.java

@@ -167,6 +167,34 @@ public void fallbackToJdksJarUrlStreamHandler() throws Exception {
 		assertThat(jdkConnection).isNotInstanceOf(JarURLConnection.class);
 	}
 
+	@Test
+	public void whenJarHasAPlusInItsPathConnectionJarFileMatchesOriginalJarFile() throws Exception {
+		File testJar = this.temporaryFolder.newFile("t+e+s+t.jar");
+		TestJarCreator.createTestJar(testJar);
+		URL url = new URL(null, "jar:" + testJar.toURI().toURL() + "!/nested.jar!/3.dat", this.handler);
+		JarURLConnection connection = (JarURLConnection) url.openConnection();
+		try {
+			assertThat(connection.getJarFile().getRootJarFile().getFile()).isEqualTo(testJar);
+		}
+		finally {
+			connection.getJarFile().close();
+		}
+	}
+
+	@Test
+	public void whenJarHasASpaceInItsPathConnectionJarFileMatchesOriginalJarFile() throws Exception {
+		File testJar = this.temporaryFolder.newFile("t e s t.jar");
+		TestJarCreator.createTestJar(testJar);
+		URL url = new URL(null, "jar:" + testJar.toURI().toURL() + "!/nested.jar!/3.dat", this.handler);
+		JarURLConnection connection = (JarURLConnection) url.openConnection();
+		try {
+			assertThat(connection.getJarFile().getRootJarFile().getFile()).isEqualTo(testJar);
+		}
+		finally {
+			connection.getJarFile().close();
+		}
+	}
+
 	private void assertStandardAndCustomHandlerUrlsAreEqual(String context, String spec) throws MalformedURLException {
 		URL standardUrl = new URL(new URL("jar:" + context), spec);
 		URL customHandlerUrl = new URL(new URL("jar", null, -1, context, this.handler), spec);