org.eclipse.jgit.lfs.server/src/org/eclipse/jgit/lfs/server/LfsProtocolServlet.java - sop/jgit - Git at Google

 /*
  * Copyright (C) 2015, Sasa Zivkov <sasa.zivkov@sap.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.server;

 import static java.nio.charset.StandardCharsets.UTF_8;
 import static org.apache.http.HttpStatus.SC_FORBIDDEN;
 import static org.apache.http.HttpStatus.SC_INSUFFICIENT_STORAGE;
 import static org.apache.http.HttpStatus.SC_INTERNAL_SERVER_ERROR;
 import static org.apache.http.HttpStatus.SC_NOT_FOUND;
 import static org.apache.http.HttpStatus.SC_OK;
 import static org.apache.http.HttpStatus.SC_SERVICE_UNAVAILABLE;
 import static org.apache.http.HttpStatus.SC_UNAUTHORIZED;
 import static org.apache.http.HttpStatus.SC_UNPROCESSABLE_ENTITY;
 import static org.eclipse.jgit.lfs.lib.Constants.DOWNLOAD;
 import static org.eclipse.jgit.lfs.lib.Constants.UPLOAD;
 import static org.eclipse.jgit.lfs.lib.Constants.VERIFY;
 import static org.eclipse.jgit.util.HttpSupport.HDR_AUTHORIZATION;

 import java.io.BufferedReader;
 import java.io.BufferedWriter;
 import java.io.IOException;
 import java.io.InputStreamReader;
 import java.io.OutputStreamWriter;
 import java.io.Reader;
 import java.io.Writer;
 import java.text.MessageFormat;
 import java.util.List;

 import javax.servlet.ServletException;
 import javax.servlet.http.HttpServlet;
 import javax.servlet.http.HttpServletRequest;
 import javax.servlet.http.HttpServletResponse;

 import org.eclipse.jgit.lfs.errors.LfsBandwidthLimitExceeded;
 import org.eclipse.jgit.lfs.errors.LfsException;
 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.LfsUnauthorized;
 import org.eclipse.jgit.lfs.errors.LfsUnavailable;
 import org.eclipse.jgit.lfs.errors.LfsValidationError;
 import org.eclipse.jgit.lfs.internal.LfsText;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;

 import com.google.gson.FieldNamingPolicy;
 import com.google.gson.Gson;
 import com.google.gson.GsonBuilder;

 /**
  * LFS protocol handler implementing the LFS batch API [1]
  *
  * [1] https://github.com/github/git-lfs/blob/master/docs/api/v1/http-v1-batch.md
  *
  * @since 4.3
  */
 public abstract class LfsProtocolServlet extends HttpServlet {
 	private static Logger LOG = LoggerFactory
 			.getLogger(LfsProtocolServlet.class);

 	private static final long serialVersionUID = 1L;

 	private static final String CONTENTTYPE_VND_GIT_LFS_JSON =
 			"application/vnd.git-lfs+json; charset=utf-8"; //$NON-NLS-1$

 	private static final int SC_RATE_LIMIT_EXCEEDED = 429;

 	private static final int SC_BANDWIDTH_LIMIT_EXCEEDED = 509;

 	private Gson gson = createGson();

 	/**
 	 * Get the large file repository for the given request and path.
 	 *
 	 * @param request
 	 *            the request
 	 * @param path
 	 *            the path
 	 *
 	 * @return the large file repository storing large files.
 	 * @throws LfsException
 	 *             implementations should throw more specific exceptions to
 	 *             signal which type of error occurred:
 	 *             <dl>
 	 *             <dt>{@link LfsValidationError}</dt>
 	 *             <dd>when there is a validation error with one or more of the
 	 *             objects in the request</dd>
 	 *             <dt>{@link LfsRepositoryNotFound}</dt>
 	 *             <dd>when the repository does not exist for the user</dd>
 	 *             <dt>{@link LfsRepositoryReadOnly}</dt>
 	 *             <dd>when the user has read, but not write access. Only
 	 *             applicable when the operation in the request is "upload"</dd>
 	 *             <dt>{@link LfsRateLimitExceeded}</dt>
 	 *             <dd>when the user has hit a rate limit with the server</dd>
 	 *             <dt>{@link LfsBandwidthLimitExceeded}</dt>
 	 *             <dd>when the bandwidth limit for the user or repository has
 	 *             been exceeded</dd>
 	 *             <dt>{@link LfsInsufficientStorage}</dt>
 	 *             <dd>when there is insufficient storage on the server</dd>
 	 *             <dt>{@link LfsUnavailable}</dt>
 	 *             <dd>when LFS is not available</dd>
 	 *             <dt>{@link LfsException}</dt>
 	 *             <dd>when an unexpected internal server error occurred</dd>
 	 *             </dl>
 	 * @since 4.5
 	 * @deprecated use
 	 *             {@link #getLargeFileRepository(LfsRequest, String, String)}
 	 */
 	@Deprecated
 	protected LargeFileRepository getLargeFileRepository(LfsRequest request,
 			String path) throws LfsException {
 		return getLargeFileRepository(request, path, null);
 	}

 	/**
 	 * Get the large file repository for the given request and path.
 	 *
 	 * @param request
 	 *            the request
 	 * @param path
 	 *            the path
 	 * @param auth
 	 *            the Authorization HTTP header
 	 *
 	 * @return the large file repository storing large files.
 	 * @throws LfsException
 	 *             implementations should throw more specific exceptions to
 	 *             signal which type of error occurred:
 	 *             <dl>
 	 *             <dt>{@link LfsValidationError}</dt>
 	 *             <dd>when there is a validation error with one or more of the
 	 *             objects in the request</dd>
 	 *             <dt>{@link LfsRepositoryNotFound}</dt>
 	 *             <dd>when the repository does not exist for the user</dd>
 	 *             <dt>{@link LfsRepositoryReadOnly}</dt>
 	 *             <dd>when the user has read, but not write access. Only
 	 *             applicable when the operation in the request is "upload"</dd>
 	 *             <dt>{@link LfsRateLimitExceeded}</dt>
 	 *             <dd>when the user has hit a rate limit with the server</dd>
 	 *             <dt>{@link LfsBandwidthLimitExceeded}</dt>
 	 *             <dd>when the bandwidth limit for the user or repository has
 	 *             been exceeded</dd>
 	 *             <dt>{@link LfsInsufficientStorage}</dt>
 	 *             <dd>when there is insufficient storage on the server</dd>
 	 *             <dt>{@link LfsUnavailable}</dt>
 	 *             <dd>when LFS is not available</dd>
 	 *             <dt>{@link LfsException}</dt>
 	 *             <dd>when an unexpected internal server error occurred</dd>
 	 *             </dl>
 	 * @since 4.7
 	 */
 	protected abstract LargeFileRepository getLargeFileRepository(
 			LfsRequest request, String path, String auth) throws LfsException;

 	/**
 	 * LFS request.
 	 *
 	 * @since 4.5
 	 */
 	protected static class LfsRequest {
 		private String operation;

 		private List<LfsObject> objects;

 		/**
 		 * Get the LFS operation.
 		 *
 		 * @return the operation
 		 */
 		public String getOperation() {
 			return operation;
 		}

 		/**
 		 * Get the LFS objects.
 		 *
 		 * @return the objects
 		 */
 		public List<LfsObject> getObjects() {
 			return objects;
 		}

 		/**
 		 * @return true if the operation is upload.
 		 * @since 4.7
 		 */
 		public boolean isUpload() {
 			return operation.equals(UPLOAD);
 		}

 		/**
 		 * @return true if the operation is download.
 		 * @since 4.7
 		 */
 		public boolean isDownload() {
 			return operation.equals(DOWNLOAD);
 		}

 		/**
 		 * @return true if the operation is verify.
 		 * @since 4.7
 		 */
 		public boolean isVerify() {
 			return operation.equals(VERIFY);
 		}
 	}

 	@Override
 	protected void doPost(HttpServletRequest req, HttpServletResponse res)
 			throws ServletException, IOException {
 		Writer w = new BufferedWriter(
 				new OutputStreamWriter(res.getOutputStream(), UTF_8));

 		Reader r = new BufferedReader(
 				new InputStreamReader(req.getInputStream(), UTF_8));
 		LfsRequest request = gson.fromJson(r, LfsRequest.class);
 		String path = req.getPathInfo();

 		res.setContentType(CONTENTTYPE_VND_GIT_LFS_JSON);
 		LargeFileRepository repo = null;
 		try {
 			repo = getLargeFileRepository(request, path,
 					req.getHeader(HDR_AUTHORIZATION));
 			if (repo == null) {
 				String error = MessageFormat
 						.format(LfsText.get().lfsFailedToGetRepository, path);
 				LOG.error(error);
 				throw new LfsException(error);
 			}
 			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) {
 			sendError(res, w, SC_NOT_FOUND, e.getMessage());
 		} catch (LfsRepositoryReadOnly e) {
 			sendError(res, w, SC_FORBIDDEN, e.getMessage());
 		} catch (LfsRateLimitExceeded e) {
 			sendError(res, w, SC_RATE_LIMIT_EXCEEDED, e.getMessage());
 		} catch (LfsBandwidthLimitExceeded e) {
 			sendError(res, w, SC_BANDWIDTH_LIMIT_EXCEEDED, e.getMessage());
 		} catch (LfsInsufficientStorage e) {
 			sendError(res, w, SC_INSUFFICIENT_STORAGE, e.getMessage());
 		} catch (LfsUnavailable e) {
 			sendError(res, w, SC_SERVICE_UNAVAILABLE, e.getMessage());
 		} catch (LfsUnauthorized e) {
 			sendError(res, w, SC_UNAUTHORIZED, e.getMessage());
 		} catch (LfsException e) {
 			sendError(res, w, SC_INTERNAL_SERVER_ERROR, e.getMessage());
 		} finally {
 			w.flush();
 		}
 	}

 	static class Error {
 		String message;

 		Error(String m) {
 			this.message = m;
 		}
 	}

 	private void sendError(HttpServletResponse rsp, Writer writer, int status,
 			String message) {
 		rsp.setStatus(status);
 		gson.toJson(new Error(message), writer);
 	}

 	private Gson createGson() {
 		return new GsonBuilder()
 				.setFieldNamingPolicy(FieldNamingPolicy.LOWER_CASE_WITH_UNDERSCORES)
 				.disableHtmlEscaping()
 				.create();
 	}
 }
	/*
	* Copyright (C) 2015, Sasa Zivkov <sasa.zivkov@sap.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.server;

	import static java.nio.charset.StandardCharsets.UTF_8;
	import static org.apache.http.HttpStatus.SC_FORBIDDEN;
	import static org.apache.http.HttpStatus.SC_INSUFFICIENT_STORAGE;
	import static org.apache.http.HttpStatus.SC_INTERNAL_SERVER_ERROR;
	import static org.apache.http.HttpStatus.SC_NOT_FOUND;
	import static org.apache.http.HttpStatus.SC_OK;
	import static org.apache.http.HttpStatus.SC_SERVICE_UNAVAILABLE;
	import static org.apache.http.HttpStatus.SC_UNAUTHORIZED;
	import static org.apache.http.HttpStatus.SC_UNPROCESSABLE_ENTITY;
	import static org.eclipse.jgit.lfs.lib.Constants.DOWNLOAD;
	import static org.eclipse.jgit.lfs.lib.Constants.UPLOAD;
	import static org.eclipse.jgit.lfs.lib.Constants.VERIFY;
	import static org.eclipse.jgit.util.HttpSupport.HDR_AUTHORIZATION;

	import java.io.BufferedReader;
	import java.io.BufferedWriter;
	import java.io.IOException;
	import java.io.InputStreamReader;
	import java.io.OutputStreamWriter;
	import java.io.Reader;
	import java.io.Writer;
	import java.text.MessageFormat;
	import java.util.List;

	import javax.servlet.ServletException;
	import javax.servlet.http.HttpServlet;
	import javax.servlet.http.HttpServletRequest;
	import javax.servlet.http.HttpServletResponse;

	import org.eclipse.jgit.lfs.errors.LfsBandwidthLimitExceeded;
	import org.eclipse.jgit.lfs.errors.LfsException;
	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.LfsUnauthorized;
	import org.eclipse.jgit.lfs.errors.LfsUnavailable;
	import org.eclipse.jgit.lfs.errors.LfsValidationError;
	import org.eclipse.jgit.lfs.internal.LfsText;
	import org.slf4j.Logger;
	import org.slf4j.LoggerFactory;

	import com.google.gson.FieldNamingPolicy;
	import com.google.gson.Gson;
	import com.google.gson.GsonBuilder;

	/**
	* LFS protocol handler implementing the LFS batch API [1]
	*
	* [1] https://github.com/github/git-lfs/blob/master/docs/api/v1/http-v1-batch.md
	*
	* @since 4.3
	*/
	public abstract class LfsProtocolServlet extends HttpServlet {
	private static Logger LOG = LoggerFactory
	.getLogger(LfsProtocolServlet.class);

	private static final long serialVersionUID = 1L;

	private static final String CONTENTTYPE_VND_GIT_LFS_JSON =
	"application/vnd.git-lfs+json; charset=utf-8"; //$NON-NLS-1$

	private static final int SC_RATE_LIMIT_EXCEEDED = 429;

	private static final int SC_BANDWIDTH_LIMIT_EXCEEDED = 509;

	private Gson gson = createGson();

	/**
	* Get the large file repository for the given request and path.
	*
	* @param request
	* the request
	* @param path
	* the path
	*
	* @return the large file repository storing large files.
	* @throws LfsException
	* implementations should throw more specific exceptions to
	* signal which type of error occurred:
	* <dl>
	* <dt>{@link LfsValidationError}</dt>
	* <dd>when there is a validation error with one or more of the
	* objects in the request</dd>
	* <dt>{@link LfsRepositoryNotFound}</dt>
	* <dd>when the repository does not exist for the user</dd>
	* <dt>{@link LfsRepositoryReadOnly}</dt>
	* <dd>when the user has read, but not write access. Only
	* applicable when the operation in the request is "upload"</dd>
	* <dt>{@link LfsRateLimitExceeded}</dt>
	* <dd>when the user has hit a rate limit with the server</dd>
	* <dt>{@link LfsBandwidthLimitExceeded}</dt>
	* <dd>when the bandwidth limit for the user or repository has
	* been exceeded</dd>
	* <dt>{@link LfsInsufficientStorage}</dt>
	* <dd>when there is insufficient storage on the server</dd>
	* <dt>{@link LfsUnavailable}</dt>
	* <dd>when LFS is not available</dd>
	* <dt>{@link LfsException}</dt>
	* <dd>when an unexpected internal server error occurred</dd>
	* </dl>
	* @since 4.5
	* @deprecated use
	* {@link #getLargeFileRepository(LfsRequest, String, String)}
	*/
	@Deprecated
	protected LargeFileRepository getLargeFileRepository(LfsRequest request,
	String path) throws LfsException {
	return getLargeFileRepository(request, path, null);
	}

	/**
	* Get the large file repository for the given request and path.
	*
	* @param request
	* the request
	* @param path
	* the path
	* @param auth
	* the Authorization HTTP header
	*
	* @return the large file repository storing large files.
	* @throws LfsException
	* implementations should throw more specific exceptions to
	* signal which type of error occurred:
	* <dl>
	* <dt>{@link LfsValidationError}</dt>
	* <dd>when there is a validation error with one or more of the
	* objects in the request</dd>
	* <dt>{@link LfsRepositoryNotFound}</dt>
	* <dd>when the repository does not exist for the user</dd>
	* <dt>{@link LfsRepositoryReadOnly}</dt>
	* <dd>when the user has read, but not write access. Only
	* applicable when the operation in the request is "upload"</dd>
	* <dt>{@link LfsRateLimitExceeded}</dt>
	* <dd>when the user has hit a rate limit with the server</dd>
	* <dt>{@link LfsBandwidthLimitExceeded}</dt>
	* <dd>when the bandwidth limit for the user or repository has
	* been exceeded</dd>
	* <dt>{@link LfsInsufficientStorage}</dt>
	* <dd>when there is insufficient storage on the server</dd>
	* <dt>{@link LfsUnavailable}</dt>
	* <dd>when LFS is not available</dd>
	* <dt>{@link LfsException}</dt>
	* <dd>when an unexpected internal server error occurred</dd>
	* </dl>
	* @since 4.7
	*/
	protected abstract LargeFileRepository getLargeFileRepository(
	LfsRequest request, String path, String auth) throws LfsException;

	/**
	* LFS request.
	*
	* @since 4.5
	*/
	protected static class LfsRequest {
	private String operation;

	private List<LfsObject> objects;

	/**
	* Get the LFS operation.
	*
	* @return the operation
	*/
	public String getOperation() {
	return operation;
	}

	/**
	* Get the LFS objects.
	*
	* @return the objects
	*/
	public List<LfsObject> getObjects() {
	return objects;
	}

	/**
	* @return true if the operation is upload.
	* @since 4.7
	*/
	public boolean isUpload() {
	return operation.equals(UPLOAD);
	}

	/**
	* @return true if the operation is download.
	* @since 4.7
	*/
	public boolean isDownload() {
	return operation.equals(DOWNLOAD);
	}

	/**
	* @return true if the operation is verify.
	* @since 4.7
	*/
	public boolean isVerify() {
	return operation.equals(VERIFY);
	}
	}

	@Override
	protected void doPost(HttpServletRequest req, HttpServletResponse res)
	throws ServletException, IOException {
	Writer w = new BufferedWriter(
	new OutputStreamWriter(res.getOutputStream(), UTF_8));

	Reader r = new BufferedReader(
	new InputStreamReader(req.getInputStream(), UTF_8));
	LfsRequest request = gson.fromJson(r, LfsRequest.class);
	String path = req.getPathInfo();

	res.setContentType(CONTENTTYPE_VND_GIT_LFS_JSON);
	LargeFileRepository repo = null;
	try {
	repo = getLargeFileRepository(request, path,
	req.getHeader(HDR_AUTHORIZATION));
	if (repo == null) {
	String error = MessageFormat
	.format(LfsText.get().lfsFailedToGetRepository, path);
	LOG.error(error);
	throw new LfsException(error);
	}
	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) {
	sendError(res, w, SC_NOT_FOUND, e.getMessage());
	} catch (LfsRepositoryReadOnly e) {
	sendError(res, w, SC_FORBIDDEN, e.getMessage());
	} catch (LfsRateLimitExceeded e) {
	sendError(res, w, SC_RATE_LIMIT_EXCEEDED, e.getMessage());
	} catch (LfsBandwidthLimitExceeded e) {
	sendError(res, w, SC_BANDWIDTH_LIMIT_EXCEEDED, e.getMessage());
	} catch (LfsInsufficientStorage e) {
	sendError(res, w, SC_INSUFFICIENT_STORAGE, e.getMessage());
	} catch (LfsUnavailable e) {
	sendError(res, w, SC_SERVICE_UNAVAILABLE, e.getMessage());
	} catch (LfsUnauthorized e) {
	sendError(res, w, SC_UNAUTHORIZED, e.getMessage());
	} catch (LfsException e) {
	sendError(res, w, SC_INTERNAL_SERVER_ERROR, e.getMessage());
	} finally {
	w.flush();
	}
	}

	static class Error {
	String message;

	Error(String m) {
	this.message = m;
	}
	}

	private void sendError(HttpServletResponse rsp, Writer writer, int status,
	String message) {
	rsp.setStatus(status);
	gson.toJson(new Error(message), writer);
	}

	private Gson createGson() {
	return new GsonBuilder()
	.setFieldNamingPolicy(FieldNamingPolicy.LOWER_CASE_WITH_UNDERSCORES)
	.disableHtmlEscaping()
	.create();
	}
	}