Allow a REST view to decide how long its response should be cached

Change-Id: I1bb924cbe341d577656df8099214433c734a1563
Signed-off-by: Edwin Kempin <edwin.kempin@sap.com>

gerrit-extension-api/src/main/java/com/google/gerrit/extensions/restapi/CacheControl.java

@@ -0,0 +1,56 @@
+// Copyright (C) 2013 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;
+
+import java.util.concurrent.TimeUnit;
+
+public class CacheControl {
+
+  public enum Type {
+    NONE, PUBLIC, PRIVATE;
+  }
+
+  public final static CacheControl NONE = new CacheControl(Type.NONE, 0, null);
+
+  public static CacheControl PUBLIC(long age, TimeUnit unit) {
+    return new CacheControl(Type.PUBLIC, age, unit);
+  }
+
+  public static CacheControl PRIVATE(long age, TimeUnit unit) {
+    return new CacheControl(Type.PRIVATE, age, unit);
+  }
+
+  private final Type type;
+  private final long age;
+  private final TimeUnit unit;
+
+  private CacheControl(Type type, long age, TimeUnit unit) {
+    this.type = type;
+    this.age = age;
+    this.unit = unit;
+  }
+
+  public Type getType() {
+    return type;
+  }
+
+  public long getAge() {
+    return age;
+  }
+
+  public TimeUnit getUnit() {
+    return unit;
+  }
+}

gerrit-extension-api/src/main/java/com/google/gerrit/extensions/restapi/Response.java

@@ -19,10 +19,6 @@ public abstract class Response<T> {
   @SuppressWarnings({"rawtypes"})
   private static final Response NONE = new None();
 
-  public enum CacheControl {
-    NONE, PUBLIC, PRIVATE;
-  }
-
   /** HTTP 200 OK: pointless wrapper for type safety. */
   public static <T> Response<T> ok(T value) {
     return new Impl<T>(200, value);

gerrit-httpd/src/main/java/com/google/gerrit/httpd/restapi/RestApiServlet.java

@@ -52,6 +52,7 @@ import com.google.gerrit.extensions.restapi.AcceptsPost;
 import com.google.gerrit.extensions.restapi.AuthException;
 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.IdString;
 import com.google.gerrit.extensions.restapi.MethodNotAllowedException;
@@ -112,7 +113,6 @@ import java.util.Collections;
 import java.util.List;
 import java.util.Map;
 import java.util.Set;
-import java.util.concurrent.TimeUnit;
 import java.util.regex.Pattern;
 import java.util.zip.GZIPOutputStream;
 
@@ -302,7 +302,7 @@ public class RestApiServlet extends HttpServlet {
         @SuppressWarnings("rawtypes")
         Response r = (Response) result;
         status = r.statusCode();
-        configureCaching(req, res, r);
+        configureCaching(req, res, r.caching());
       } else if (result instanceof Response.Redirect) {
         CacheHeaders.setNotCacheable(res);
         res.sendRedirect(((Response.Redirect) result).location());
@@ -354,18 +354,18 @@ public class RestApiServlet extends HttpServlet {
   }
 
   private static <T> void configureCaching(HttpServletRequest req,
-      HttpServletResponse res, Response<T> r) {
+      HttpServletResponse res, CacheControl c) {
     if ("GET".equals(req.getMethod())) {
-      switch (r.caching()) {
+      switch (c.getType()) {
         case NONE:
         default:
           CacheHeaders.setNotCacheable(res);
           break;
         case PRIVATE:
-          CacheHeaders.setCacheablePrivate(res, 7, TimeUnit.DAYS);
+          CacheHeaders.setCacheablePrivate(res, c.getAge(), c.getUnit());
           break;
         case PUBLIC:
-          CacheHeaders.setCacheable(req, res, 7, TimeUnit.DAYS);
+          CacheHeaders.setCacheable(req, res, c.getAge(), c.getUnit());
           break;
       }
     } else {

gerrit-server/src/main/java/com/google/gerrit/server/change/GetDiff.java

@@ -22,6 +22,7 @@ import com.google.common.collect.Lists;
 import com.google.gerrit.common.data.PatchScript;
 import com.google.gerrit.common.data.PatchScript.DisplayMethod;
 import com.google.gerrit.common.data.PatchScript.FileMode;
+import com.google.gerrit.extensions.restapi.CacheControl;
 import com.google.gerrit.extensions.restapi.IdString;
 import com.google.gerrit.extensions.restapi.ResourceNotFoundException;
 import com.google.gerrit.extensions.restapi.Response;
@@ -49,6 +50,7 @@ import org.kohsuke.args4j.spi.Parameters;
 import org.kohsuke.args4j.spi.Setter;
 
 import java.util.List;
+import java.util.concurrent.TimeUnit;
 
 public class GetDiff implements RestReadView<FileResource> {
   private final PatchScriptFactory.Factory patchScriptFactoryFactory;
@@ -150,7 +152,7 @@ public class GetDiff implements RestReadView<FileResource> {
       result.diffHeader = ps.getPatchHeader();
     }
     result.content = content.lines;
-    return Response.ok(result).caching(Response.CacheControl.PRIVATE);
+    return Response.ok(result).caching(CacheControl.PRIVATE(7, TimeUnit.DAYS));
   }
 
   static class Result {