Add test for Storage.signUrl with object names starting with /

Author: mziccard

gcloud-java-storage/src/test/java/com/google/cloud/storage/StorageImplTest.java

@@ -1155,6 +1155,36 @@ public void testSignUrl() throws NoSuchAlgorithmException, InvalidKeyException,
         URLDecoder.decode(signature, UTF_8.name()))));
   }
 
+  @Test
+  public void testSignUrlLeadingSlash() throws NoSuchAlgorithmException, InvalidKeyException,
+      SignatureException, UnsupportedEncodingException {
+    String blobName = "/b1";
+    EasyMock.replay(storageRpcMock);
+    ServiceAccountAuthCredentials authCredentials =
+        ServiceAccountAuthCredentials.createFor(ACCOUNT, privateKey);
+    storage = options.toBuilder().authCredentials(authCredentials).build().service();
+    URL url = storage.signUrl(BlobInfo.builder(BUCKET_NAME1, blobName).build(), 14, TimeUnit.DAYS);
+    String stringUrl = url.toString();
+    String expectedUrl =
+        new StringBuilder("https://storage.googleapis.com/").append(BUCKET_NAME1).append(blobName)
+            .append("?GoogleAccessId=").append(ACCOUNT).append("&Expires=").append(42L + 1209600)
+            .append("&Signature=").toString();
+    System.out.println(stringUrl);
+    System.out.println(expectedUrl);
+    assertTrue(stringUrl.startsWith(expectedUrl));
+    String signature = stringUrl.substring(expectedUrl.length());
+
+    StringBuilder signedMessageBuilder = new StringBuilder();
+    signedMessageBuilder.append(HttpMethod.GET).append('\n').append('\n').append('\n')
+        .append(42L + 1209600).append('\n').append("/").append(BUCKET_NAME1).append(blobName);
+
+    Signature signer = Signature.getInstance("SHA256withRSA");
+    signer.initVerify(publicKey);
+    signer.update(signedMessageBuilder.toString().getBytes(UTF_8));
+    assertTrue(signer.verify(BaseEncoding.base64().decode(
+        URLDecoder.decode(signature, UTF_8.name()))));
+  }
+
   @Test
   public void testSignUrlWithOptions() throws NoSuchAlgorithmException, InvalidKeyException,
       SignatureException, UnsupportedEncodingException {