samples: [Cloud Tasks] Add HTTP push queue sample (#1355)

* Add HTTP sample

* Fix linting

* remove CLI

* Move http sample

* Fix pom.xml

* Update pom and linting

* Update tasks version

tasks/snippets/src/main/java/com/example/task/CreateHttpTask.java

@@ -0,0 +1,64 @@
+/*
+ * Copyright 2018 Google LLC
+ *
+ * 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.example.task;
+
+// [START cloud_tasks_create_http_task]
+import com.google.cloud.tasks.v2beta3.CloudTasksClient;
+import com.google.cloud.tasks.v2beta3.HttpMethod;
+import com.google.cloud.tasks.v2beta3.HttpRequest;
+import com.google.cloud.tasks.v2beta3.QueueName;
+import com.google.cloud.tasks.v2beta3.Task;
+import com.google.protobuf.ByteString;
+import java.nio.charset.Charset;
+
+public class CreateHttpTask {
+
+  public static void main(String[] args) throws Exception {
+    String projectId = System.getenv("PROJECT_ID");
+    String queueName = System.getenv("QUEUE_ID");
+    String location = System.getenv("LOCATION_ID");
+    String url = System.getenv("URL");
+
+    // Instantiates a client.
+    try (CloudTasksClient client = CloudTasksClient.create()) {
+      // Variables provided by the system variables.
+      // projectId = "my-project-id";
+      // queueName = "my-appengine-queue";
+      // location = "us-central1";
+      // url = "https://<project-id>.appspot.com/tasks/create";
+      String payload = "hello";
+
+      // Construct the fully qualified queue name.
+      String queuePath = QueueName.of(projectId, location, queueName).toString();
+
+      // Construct the task body.
+      Task.Builder taskBuilder =
+          Task.newBuilder()
+              .setHttpRequest(
+                  HttpRequest.newBuilder()
+                      .setBody(ByteString.copyFrom(payload, Charset.defaultCharset()))
+                      .setUrl(url)
+                      .setHttpMethod(HttpMethod.POST)
+                      .build());
+
+      // Send create task request.
+      Task task = client.createTask(queuePath, taskBuilder.build());
+      System.out.println("Task created: " + task.getName());
+    }
+  }
+}
+// [END cloud_tasks_create_http_task]