Add specific exception for LFS unavailable

Instead of returning null, LfsProtocolServlet#getLargeFileRepository
should throw LfsUnavailable.

If null is returned, throw a generic LfsException.

Handle LfsException as an internal server error and return HTTP 500.

Change-Id: I33e2a19fcc0fde8aaf0f703860c8fa8ce2de2db5
Signed-off-by: David Pursehouse <david.pursehouse@gmail.com>

org.eclipse.jgit.lfs.server/src/org/eclipse/jgit/lfs/server/LfsProtocolServlet.java

@@ -44,6 +44,7 @@ package org.eclipse.jgit.lfs.server;
 
 import static java.nio.charset.StandardCharsets.UTF_8;
 import static org.apache.http.HttpStatus.SC_FORBIDDEN;
+import static org.apache.http.HttpStatus.SC_INTERNAL_SERVER_ERROR;
 import static org.apache.http.HttpStatus.SC_INSUFFICIENT_STORAGE;
 import static org.apache.http.HttpStatus.SC_NOT_FOUND;
 import static org.apache.http.HttpStatus.SC_OK;
@@ -70,6 +71,7 @@ import org.eclipse.jgit.lfs.errors.LfsInsufficientStorage;
 import org.eclipse.jgit.lfs.errors.LfsRateLimitExceeded;
 import org.eclipse.jgit.lfs.errors.LfsRepositoryNotFound;
 import org.eclipse.jgit.lfs.errors.LfsRepositoryReadOnly;
+import org.eclipse.jgit.lfs.errors.LfsUnavailable;
 import org.eclipse.jgit.lfs.errors.LfsValidationError;
 
 import com.google.gson.FieldNamingPolicy;
@@ -104,8 +106,7 @@ public abstract class LfsProtocolServlet extends HttpServlet {
 	 * @param path
 	 *            the path
 	 *
-	 * @return the large file repository storing large files or null if the
+	 * @return the large file repository storing large files.
-	 *         request is not supported.
 	 * @throws LfsException
 	 * @since 4.5
 	 */
@@ -157,14 +158,12 @@ public abstract class LfsProtocolServlet extends HttpServlet {
 		try {
 			repo = getLargeFileRepository(request, path);
 			if (repo == null) {
-				sendError(res, w, SC_SERVICE_UNAVAILABLE,
+				throw new LfsException("unexpected error"); //$NON-NLS-1$
-						"LFS is not available"); //$NON-NLS-1$
+			}
-			} else {
 			res.setStatus(SC_OK);
 			TransferHandler handler = TransferHandler
 					.forOperation(request.operation, repo, request.objects);
 			gson.toJson(handler.process(), w);
-			}
 		} catch (LfsValidationError e) {
 			sendError(res, w, SC_UNPROCESSABLE_ENTITY, e.getMessage());
 		} catch (LfsRepositoryNotFound e) {
@@ -177,8 +176,10 @@ public abstract class LfsProtocolServlet extends HttpServlet {
 			sendError(res, w, SC_BANDWIDTH_LIMIT_EXCEEDED, e.getMessage());
 		} catch (LfsInsufficientStorage e) {
 			sendError(res, w, SC_INSUFFICIENT_STORAGE, e.getMessage());
-		} catch (LfsException e) {
+		} catch (LfsUnavailable e) {
 			sendError(res, w, SC_SERVICE_UNAVAILABLE, e.getMessage());
+		} catch (LfsException e) {
+			sendError(res, w, SC_INTERNAL_SERVER_ERROR, e.getMessage());
 		} finally {
 			w.flush();
 		}

org.eclipse.jgit.lfs/resources/org/eclipse/jgit/lfs/internal/LfsText.properties

@@ -4,3 +4,4 @@ invalidLongIdLength=Invalid id length {0}; should be {1}
 requiredHashFunctionNotAvailable=Required hash function {0} not available.
 repositoryNotFound=Repository {0} not found
 repositoryReadOnly=Repository {0} is read-only
+lfsUnavailable=LFS is not available for repository {0}

org.eclipse.jgit.lfs/src/org/eclipse/jgit/lfs/errors/LfsUnavailable.java

@@ -0,0 +1,65 @@
+/*
+ * Copyright (C) 2016, David Pursehouse <david.pursehouse@gmail.com>
+ * and other copyright owners as documented in the project's IP log.
+ *
+ * This program and the accompanying materials are made available
+ * under the terms of the Eclipse Distribution License v1.0 which
+ * accompanies this distribution, is reproduced below, and is
+ * available at http://www.eclipse.org/org/documents/edl-v10.php
+ *
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or
+ * without modification, are permitted provided that the following
+ * conditions are met:
+ *
+ * - Redistributions of source code must retain the above copyright
+ *   notice, this list of conditions and the following disclaimer.
+ *
+ * - Redistributions in binary form must reproduce the above
+ *   copyright notice, this list of conditions and the following
+ *   disclaimer in the documentation and/or other materials provided
+ *   with the distribution.
+ *
+ * - Neither the name of the Eclipse Foundation, Inc. nor the
+ *   names of its contributors may be used to endorse or promote
+ *   products derived from this software without specific prior
+ *   written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND
+ * CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES,
+ * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
+ * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
+ * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
+ * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+ * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
+ * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
+ * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+package org.eclipse.jgit.lfs.errors;
+
+import java.text.MessageFormat;
+
+import org.eclipse.jgit.lfs.internal.LfsText;
+
+/**
+ * Thrown when LFS is not available.
+ *
+ * @since 4.5
+ */
+public class LfsUnavailable extends LfsException {
+	private static final long serialVersionUID = 1L;
+
+	/**
+	 * @param name
+	 *            the repository name.
+	 */
+	public LfsUnavailable(String name) {
+		super(MessageFormat.format(LfsText.get().lfsUnavailable, name));
+	}
+}

org.eclipse.jgit.lfs/src/org/eclipse/jgit/lfs/internal/LfsText.java

@@ -64,4 +64,5 @@ public class LfsText extends TranslationBundle {
 	/***/ public String requiredHashFunctionNotAvailable;
 	/***/ public String repositoryNotFound;
 	/***/ public String repositoryReadOnly;
+	/***/ public String lfsUnavailable;
 }