samples: add quickstart publish and comments (#243)

Author: anguillanneuf

samples/snippets/src/main/java/pubsub/PublishWithBatchSettingsExample.java

@@ -55,7 +55,7 @@ public static void publishWithBatchSettingsExample(String projectId, String topi
       Duration publishDelayThreshold = Duration.ofMillis(100); // default : 1 ms
 
       // Publish request get triggered based on request size, messages count & time since last
-      // publish
+      // publish, whichever condition is met first.
       BatchingSettings batchingSettings =
           BatchingSettings.newBuilder()
               .setElementCountThreshold(messageCountBatchSize)

samples/snippets/src/main/java/pubsub/PublisherExample.java

@@ -0,0 +1,65 @@
+/*
+ * Copyright 2020 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 pubsub;
+
+// [START pubsub_quickstart_publisher]
+
+import com.google.api.core.ApiFuture;
+import com.google.cloud.pubsub.v1.Publisher;
+import com.google.protobuf.ByteString;
+import com.google.pubsub.v1.PubsubMessage;
+import com.google.pubsub.v1.TopicName;
+import java.io.IOException;
+import java.util.concurrent.ExecutionException;
+import java.util.concurrent.TimeUnit;
+
+public class PublisherExample {
+  public static void main(String... args) throws Exception {
+    // TODO(developer): Replace these variables before running the sample.
+    String projectId = "your-project-id";
+    String topicId = "your-topic-id";
+
+    publisherExample(projectId, topicId);
+  }
+
+  public static void publisherExample(String projectId, String topicId)
+      throws IOException, ExecutionException, InterruptedException {
+    TopicName topicName = TopicName.of(projectId, topicId);
+
+    Publisher publisher = null;
+    try {
+      // Create a publisher instance with default settings bound to the topic
+      publisher = Publisher.newBuilder(topicName).build();
+
+      String message = "Hello World!";
+      ByteString data = ByteString.copyFromUtf8(message);
+      PubsubMessage pubsubMessage = PubsubMessage.newBuilder().setData(data).build();
+
+      // Once published, returns a server-assigned message id (unique within the topic)
+      ApiFuture<String> messageIdFuture = publisher.publish(pubsubMessage);
+      String messageId = messageIdFuture.get();
+      System.out.println("Published message ID: " + messageId);
+    } finally {
+      if (publisher != null) {
+        // When finished with the publisher, shutdown to free up resources.
+        publisher.shutdown();
+        publisher.awaitTermination(1, TimeUnit.MINUTES);
+      }
+    }
+  }
+}
+// [END pubsub_quickstart_publisher]

samples/snippets/src/test/java/pubsub/PublisherIT.java

@@ -77,6 +77,11 @@ public void tearDown() throws Exception {
 
   @Test
   public void testPublisher() throws Exception {
+    // Test quickstart publish
+    PublisherExample.publisherExample(projectId, topicId);
+    assertThat(bout.toString()).contains("Published message ID: ");
+
+    bout.reset();
     // Test publish with error handling
     PublishWithErrorHandlerExample.publishWithErrorHandlerExample(projectId, topicId);
     assertThat(bout.toString()).contains("Published message ID: ");