Display proper error if file diff fails because content is too large

File diffs can only be displayed for files that do not exceed a threshold
for big files. If a file is larger, building the patch script fails with
org.eclipse.jgit.errors.LargeObjectException. Since
org.eclipse.jgit.errors.LargeObjectException is a RuntimeException the
GerritJsonServlet treats it as internal failure and as result the web ui
just shows 'Internal Server Error'.

This change ensures that a proper error message is displayed in this case.
This is done by wrapping the org.eclipse.jgit.errors.LargeObjectException
into a normal Exception.

Change-Id: I708957a2fadfce88f3c0c6a433343274ae169b6f
Signed-off-by: Edwin Kempin <edwin.kempin@sap.com>

gerrit-httpd/src/main/java/com/google/gerrit/httpd/rpc/patch/PatchScriptFactory.java

@@ -31,6 +31,7 @@ import com.google.gerrit.server.CurrentUser;
 import com.google.gerrit.server.IdentifiedUser;
 import com.google.gerrit.server.account.AccountInfoCacheFactory;
 import com.google.gerrit.server.git.GitRepositoryManager;
+import com.google.gerrit.server.git.LargeObjectException;
 import com.google.gerrit.server.patch.PatchList;
 import com.google.gerrit.server.patch.PatchListCache;
 import com.google.gerrit.server.patch.PatchListEntry;
@@ -120,7 +121,8 @@ class PatchScriptFactory extends Handler<PatchScript> {
   }
 
   @Override
-  public PatchScript call() throws OrmException, NoSuchChangeException {
+  public PatchScript call() throws OrmException, NoSuchChangeException,
+      LargeObjectException {
     validatePatchSetId(psa);
     validatePatchSetId(psb);
 
@@ -156,6 +158,8 @@ class PatchScriptFactory extends Handler<PatchScript> {
       } catch (IOException e) {
         log.error("File content unavailable", e);
         throw new NoSuchChangeException(changeId, e);
+      } catch (org.eclipse.jgit.errors.LargeObjectException err) {
+        throw new LargeObjectException("File content is too large", err);
       }
     } finally {
       git.close();

gerrit-server/src/main/java/com/google/gerrit/server/git/LargeObjectException.java

@@ -0,0 +1,33 @@
+// Copyright (C) 2012 The Android Open Source Project
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package com.google.gerrit.server.git;
+
+/**
+ * Wrapper for {@link org.eclipse.jgit.errors.LargeObjectException}. Since
+ * org.eclipse.jgit.errors.LargeObjectException is a {@link RuntimeException}
+ * the GerritJsonServlet would treat it as internal failure and as result the
+ * web ui would just show 'Internal Server Error'. Wrapping
+ * org.eclipse.jgit.errors.LargeObjectException into a normal {@link Exception}
+ * allows to display a proper error message.
+ */
+public class LargeObjectException extends Exception {
+
+  private static final long serialVersionUID = 1L;
+
+  public LargeObjectException(final String message,
+      final org.eclipse.jgit.errors.LargeObjectException cause) {
+    super(message, cause);
+  }
+}