From ea34214362fe9b70e9d5af85c5a21f6fffef87c7 Mon Sep 17 00:00:00 2001
From: Stefan Beller <sbeller@google.com>
Date: Thu, 5 Feb 2015 10:57:11 -0800
Subject: [PATCH] Add new ETagView interface

This allows views to have an ETag.

Change-Id: I6cb4cfe9ad2a4386f38cd662cda6ce260964f687
---
 .../gerrit/extensions/restapi/ETagView.java   | 22 +++++++++++++++++++
 .../gerrit/httpd/restapi/RestApiServlet.java  | 14 ++++++++++--
 2 files changed, 34 insertions(+), 2 deletions(-)
 create mode 100644 gerrit-extension-api/src/main/java/com/google/gerrit/extensions/restapi/ETagView.java

diff --git a/gerrit-extension-api/src/main/java/com/google/gerrit/extensions/restapi/ETagView.java b/gerrit-extension-api/src/main/java/com/google/gerrit/extensions/restapi/ETagView.java
new file mode 100644
index 0000000000..f95161d00e
--- /dev/null
+++ b/gerrit-extension-api/src/main/java/com/google/gerrit/extensions/restapi/ETagView.java
@@ -0,0 +1,22 @@
+// Copyright (C) 2015 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.extensions.restapi;
+
+/**
+ * A view which may change, although the underlying resource did not change
+ */
+public interface ETagView<R extends RestResource> extends RestReadView<R> {
+  public String getETag(R rsrc);
+}
diff --git a/gerrit-httpd/src/main/java/com/google/gerrit/httpd/restapi/RestApiServlet.java b/gerrit-httpd/src/main/java/com/google/gerrit/httpd/restapi/RestApiServlet.java
index dd36495671..8f34d391f1 100644
--- a/gerrit-httpd/src/main/java/com/google/gerrit/httpd/restapi/RestApiServlet.java
+++ b/gerrit-httpd/src/main/java/com/google/gerrit/httpd/restapi/RestApiServlet.java
@@ -58,6 +58,7 @@ import com.google.gerrit.extensions.restapi.BadRequestException;
 import com.google.gerrit.extensions.restapi.BinaryResult;
 import com.google.gerrit.extensions.restapi.CacheControl;
 import com.google.gerrit.extensions.restapi.DefaultInput;
+import com.google.gerrit.extensions.restapi.ETagView;
 import com.google.gerrit.extensions.restapi.IdString;
 import com.google.gerrit.extensions.restapi.MethodNotAllowedException;
 import com.google.gerrit.extensions.restapi.PreconditionFailedException;
@@ -299,7 +300,7 @@ public class RestApiServlet extends HttpServlet {
         checkRequiresCapability(viewData);
       }
 
-      if (notModified(req, rsrc)) {
+      if (notModified(req, rsrc, viewData.view)) {
         res.sendError(SC_NOT_MODIFIED);
         return;
       }
@@ -392,11 +393,20 @@ public class RestApiServlet extends HttpServlet {
     return defaultMessage;
   }
 
-  private static boolean notModified(HttpServletRequest req, RestResource rsrc) {
+  @SuppressWarnings({"unchecked", "rawtypes"})
+  private static boolean notModified(HttpServletRequest req, RestResource rsrc,
+      RestView<RestResource> view) {
     if (!isGetOrHead(req)) {
       return false;
     }
 
+    if (view instanceof ETagView) {
+      String have = req.getHeader(HttpHeaders.IF_NONE_MATCH);
+      if (have != null) {
+        return have.equals(((ETagView) view).getETag(rsrc));
+      }
+    }
+
     if (rsrc instanceof RestResource.HasETag) {
       String have = req.getHeader(HttpHeaders.IF_NONE_MATCH);
       if (have != null) {