LfsProtocolServlet: Reuse existing Writer when sending error response

Trying to open a new writer on the response causes an illegal state
exception and the response is not sent.

Change-Id: Ic718d23cfb3e74f5691cc2aea7283003af7df207
Signed-off-by: David Pursehouse <david.pursehouse@gmail.com>

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

@@ -54,7 +54,6 @@ import java.io.BufferedWriter;
 import java.io.IOException;
 import java.io.InputStreamReader;
 import java.io.OutputStreamWriter;
-import java.io.PrintWriter;
 import java.io.Reader;
 import java.io.Writer;
 import java.util.List;
@@ -139,37 +138,34 @@ public abstract class LfsProtocolServlet extends HttpServlet {
 		Writer w = new BufferedWriter(
 				new OutputStreamWriter(res.getOutputStream(), UTF_8));
 
-		Reader r = new BufferedReader(new InputStreamReader(req.getInputStream(), UTF_8));
+		Reader r = new BufferedReader(
+				new InputStreamReader(req.getInputStream(), UTF_8));
 		LfsRequest request = gson.fromJson(r, LfsRequest.class);
 		String path = req.getPathInfo();
 
 		LargeFileRepository repo = null;
 		try {
 			repo = getLargeFileRepository(request, path);
+			if (repo == null) {
+				res.setStatus(SC_SERVICE_UNAVAILABLE);
+			} else {
+				res.setStatus(SC_OK);
+				res.setContentType(CONTENTTYPE_VND_GIT_LFS_JSON);
+				TransferHandler handler = TransferHandler
+						.forOperation(request.operation, repo, request.objects);
+				gson.toJson(handler.process(), w);
+			}
 		} catch (LfsValidationError e) {
-			sendError(res, SC_UNPROCESSABLE_ENTITY, e.getMessage());
-			return;
+			sendError(res, w, SC_UNPROCESSABLE_ENTITY, e.getMessage());
 		} catch (LfsRepositoryNotFound e) {
-			sendError(res, SC_NOT_FOUND, e.getMessage());
-			return;
+			sendError(res, w, SC_NOT_FOUND, e.getMessage());
 		} catch (LfsRepositoryReadOnly e) {
-			sendError(res, SC_FORBIDDEN, e.getMessage());
-			return;
+			sendError(res, w, SC_FORBIDDEN, e.getMessage());
 		} catch (LfsException e) {
-			sendError(res, SC_SERVICE_UNAVAILABLE, e.getMessage());
-			return;
+			sendError(res, w, SC_SERVICE_UNAVAILABLE, e.getMessage());
+		} finally {
+			w.flush();
 		}
-		if (repo == null) {
-			res.setStatus(SC_SERVICE_UNAVAILABLE);
-			return;
-		}
-
-		res.setStatus(SC_OK);
-		res.setContentType(CONTENTTYPE_VND_GIT_LFS_JSON);
-		TransferHandler handler = TransferHandler
-				.forOperation(request.operation, repo, request.objects);
-		gson.toJson(handler.process(), w);
-		w.flush();
 	}
 
 	static class Error {
@@ -180,14 +176,10 @@ public abstract class LfsProtocolServlet extends HttpServlet {
 		}
 	}
 
-	private void sendError(HttpServletResponse rsp, int status, String message)
-			throws IOException {
+	private void sendError(HttpServletResponse rsp, Writer writer, int status,
+			String message) {
 		rsp.setStatus(status);
-		PrintWriter writer = rsp.getWriter();
 		gson.toJson(new Error(message), writer);
-		writer.flush();
-		writer.close();
-		rsp.flushBuffer();
 	}
 
 	private Gson createGson() {