Rest API: Add HEAD support for /{index}/{type}/{id} to quickly ch…

…eck if doc exists or not, closes #2047.

src/main/java/org/elasticsearch/rest/action/RestActionModule.java

@@ -64,6 +64,7 @@
 import org.elasticsearch.rest.action.delete.RestDeleteAction;
 import org.elasticsearch.rest.action.deletebyquery.RestDeleteByQueryAction;
 import org.elasticsearch.rest.action.get.RestGetAction;
+import org.elasticsearch.rest.action.get.RestHeadAction;
 import org.elasticsearch.rest.action.get.RestMultiGetAction;
 import org.elasticsearch.rest.action.index.RestIndexAction;
 import org.elasticsearch.rest.action.main.RestMainAction;
@@ -140,6 +141,7 @@ protected void configure() {
 
         bind(RestIndexAction.class).asEagerSingleton();
         bind(RestGetAction.class).asEagerSingleton();
+        bind(RestHeadAction.class).asEagerSingleton();
         bind(RestMultiGetAction.class).asEagerSingleton();
         bind(RestDeleteAction.class).asEagerSingleton();
         bind(RestDeleteByQueryAction.class).asEagerSingleton();

src/main/java/org/elasticsearch/rest/action/get/RestHeadAction.java

@@ -0,0 +1,86 @@
+/*
+ * Licensed to ElasticSearch and Shay Banon under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership. ElasticSearch licenses this
+ * file to you 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 org.elasticsearch.rest.action.get;
+
+import org.elasticsearch.action.ActionListener;
+import org.elasticsearch.action.get.GetRequest;
+import org.elasticsearch.action.get.GetResponse;
+import org.elasticsearch.client.Client;
+import org.elasticsearch.common.Strings;
+import org.elasticsearch.common.inject.Inject;
+import org.elasticsearch.common.settings.Settings;
+import org.elasticsearch.rest.*;
+
+import java.io.IOException;
+
+import static org.elasticsearch.rest.RestRequest.Method.HEAD;
+import static org.elasticsearch.rest.RestStatus.NOT_FOUND;
+import static org.elasticsearch.rest.RestStatus.OK;
+
+/**
+ *
+ */
+public class RestHeadAction extends BaseRestHandler {
+
+    @Inject
+    public RestHeadAction(Settings settings, Client client, RestController controller) {
+        super(settings, client);
+        controller.registerHandler(HEAD, "/{index}/{type}/{id}", this);
+    }
+
+    @Override
+    public void handleRequest(final RestRequest request, final RestChannel channel) {
+        final GetRequest getRequest = new GetRequest(request.param("index"), request.param("type"), request.param("id"));
+        getRequest.listenerThreaded(false);
+        getRequest.operationThreaded(true);
+        getRequest.refresh(request.paramAsBoolean("refresh", getRequest.refresh()));
+        getRequest.parent(request.param("parent"));
+        getRequest.routing(request.param("routing"));
+        getRequest.preference(request.param("preference"));
+        getRequest.realtime(request.paramAsBooleanOptional("realtime", null));
+        // don't get any fields back...
+        getRequest.fields(Strings.EMPTY_ARRAY);
+        // TODO we can also just return the document size as Content-Length
+
+        client.get(getRequest, new ActionListener<GetResponse>() {
+            @Override
+            public void onResponse(GetResponse response) {
+                try {
+                    if (!response.exists()) {
+                        channel.sendResponse(new StringRestResponse(NOT_FOUND));
+                    } else {
+                        channel.sendResponse(new StringRestResponse(OK));
+                    }
+                } catch (Exception e) {
+                    onFailure(e);
+                }
+            }
+
+            @Override
+            public void onFailure(Throwable e) {
+                try {
+                    channel.sendResponse(new XContentThrowableRestResponse(request, e));
+                } catch (IOException e1) {
+                    logger.error("Failed to send failure response", e1);
+                }
+            }
+        });
+    }
+}