通过自定义特性进行发布

使用自定义特性发布消息。

深入探索

如需查看包含此代码示例的详细文档，请参阅以下内容：

代码示例

C++

试用此示例之前，请按照 Pub/Sub 快速入门：使用客户端库中的 C++ 设置说明进行操作。 如需了解详情，请参阅 Pub/Sub C++ API 参考文档。

如需向 Pub/Sub 进行身份验证，请设置应用默认凭据。如需了解详情，请参阅为本地开发环境设置身份验证。 

namespace pubsub = ::google::cloud::pubsub;
using ::google::cloud::future;
using ::google::cloud::StatusOr;
[](pubsub::Publisher publisher) {
  std::vector<future<void>> done;
  for (int i = 0; i != 10; ++i) {
    auto message_id = publisher.Publish(
        pubsub::MessageBuilder{}
            .SetData("Hello World! [" + std::to_string(i) + "]")
            .SetAttribute("origin", "cpp-sample")
            .SetAttribute("username", "gcp")
            .Build());
    done.push_back(message_id.then([i](future<StatusOr<std::string>> f) {
      auto id = f.get();
      if (!id) throw std::move(id).status();
      std::cout << "Message " << i << " published with id=" << *id << "\n";
    }));
  }
  publisher.Flush();
  // Block until all the messages are published (optional)
  for (auto& f : done) f.get();
}

C#

试用此示例之前，请按照 Pub/Sub 快速入门：使用客户端库中的 C# 设置说明进行操作。 如需了解详情，请参阅 Pub/Sub C# API 参考文档。

如需向 Pub/Sub 进行身份验证，请设置应用默认凭据。如需了解详情，请参阅为本地开发环境设置身份验证。 


using Google.Cloud.PubSub.V1;
using Google.Protobuf;
using System;
using System.Threading.Tasks;

public class PublishMessageWithCustomAttributesAsyncSample
{
    public async Task PublishMessageWithCustomAttributesAsync(string projectId, string topicId, string messageText)
    {
        TopicName topicName = TopicName.FromProjectTopic(projectId, topicId);
        PublisherClient publisher = await PublisherClient.CreateAsync(topicName);

        var pubsubMessage = new PubsubMessage
        {
            // The data is any arbitrary ByteString. Here, we're using text.
            Data = ByteString.CopyFromUtf8(messageText),
            // The attributes provide metadata in a string-to-string dictionary.
            Attributes =
            {
                { "year", "2020" },
                { "author", "unknown" }
            }
        };
        string message = await publisher.PublishAsync(pubsubMessage);
        Console.WriteLine($"Published message {message}");
        // PublisherClient instance should be shutdown after use.
        // The TimeSpan specifies for how long to attempt to publish locally queued messages.
        await publisher.ShutdownAsync(TimeSpan.FromSeconds(15));
    }
}

Go

试用此示例之前，请按照 Pub/Sub 快速入门：使用客户端库中的 Go 设置说明进行操作。 如需了解详情，请参阅 Pub/Sub Go API 参考文档。

如需向 Pub/Sub 进行身份验证，请设置应用默认凭据。如需了解详情，请参阅为本地开发环境设置身份验证。 

import (
	"context"
	"fmt"
	"io"

	"cloud.google.com/go/pubsub/v2"
)

func publishCustomAttributes(w io.Writer, projectID, topicID string) error {
	// projectID := "my-project-id"
	// topicID := "my-topic"
	ctx := context.Background()
	client, err := pubsub.NewClient(ctx, projectID)
	if err != nil {
		return fmt.Errorf("pubsub.NewClient: %w", err)
	}
	defer client.Close()

	// client.Publisher can be passed a topic ID (e.g. "my-topic") or
	// a fully qualified name (e.g. "projects/my-project/topics/my-topic").
	// If a topic ID is provided, the project ID from the client is used.
	// Reuse this publisher for all publish calls to send messages in batches.
	publisher := client.Publisher(topicID)
	result := publisher.Publish(ctx, &pubsub.Message{
		Data: []byte("Hello world!"),
		Attributes: map[string]string{
			"origin":   "golang",
			"username": "gcp",
		},
	})
	// Block until the result is returned and a server-generated
	// ID is returned for the published message.
	id, err := result.Get(ctx)
	if err != nil {
		return fmt.Errorf("Get: %w", err)
	}
	fmt.Fprintf(w, "Published message with custom attributes; msg ID: %v\n", id)
	return nil
}

Java

试用此示例之前，请按照 Pub/Sub 快速入门：使用客户端库中的 Java 设置说明进行操作。 如需了解详情，请参阅 Pub/Sub Java API 参考文档。

如需向 Pub/Sub 进行身份验证，请设置应用默认凭据。如需了解详情，请参阅为本地开发环境设置身份验证。 


import com.google.api.core.ApiFuture;
import com.google.cloud.pubsub.v1.Publisher;
import com.google.common.collect.ImmutableMap;
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 PublishWithCustomAttributesExample {
  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";

    publishWithCustomAttributesExample(projectId, topicId);
  }

  public static void publishWithCustomAttributesExample(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 = "first message";
      ByteString data = ByteString.copyFromUtf8(message);
      PubsubMessage pubsubMessage =
          PubsubMessage.newBuilder()
              .setData(data)
              .putAllAttributes(ImmutableMap.of("year", "2020", "author", "unknown"))
              .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 a message with custom attributes: " + messageId);

    } finally {
      if (publisher != null) {
        // When finished with the publisher, shutdown to free up resources.
        publisher.shutdown();
        publisher.awaitTermination(1, TimeUnit.MINUTES);
      }
    }
  }
}

Kotlin

import com.google.api.gax.rpc.ApiException
import com.google.api.gax.rpc.NotFoundException
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

/**
 * Publishes a UTF-8 message payload with custom attributes to a Pub/Sub topic.
 *
 * @param projectId Google Cloud project identifier (for example, "example-project-id").
 * @param topicId Target Pub/Sub topic identifier (for example, "example-topic-id").
 */
fun publishMessage(projectId: String, topicId: String) {
  val topicName = TopicName.of(projectId, topicId)
  val payloadText = "Example Pub/Sub message payload"
  val messageData = ByteString.copyFromUtf8(payloadText)
  val messageAttributes =
    mapOf("environment" to "production", "origin" to "example-kotlin-publisher")
  val pubsubMessage =
    PubsubMessage.newBuilder()
      .setData(messageData)
      .putAllAttributes(messageAttributes)
      .build()

  var publisher: Publisher? = null
  try {
    publisher = Publisher.newBuilder(topicName).build()
    println("Publishing message to topic '${topicName}'...")
    val messageIdFuture = publisher.publish(pubsubMessage)
    val messageId = messageIdFuture.get()

    println("Resource ID: $messageId")
    println("Attributes: $messageAttributes")
    println("Topic: $topicName")
  } catch (err: ExecutionException) {
    val message =
      when (val cause = err.cause) {
        is NotFoundException ->
          "error: topic '$topicId' not found in project '$projectId': ${cause.message}"
        is ApiException ->
          "error: failed to publish message to topic '$topicId' in project '$projectId': ${cause.message}"
        else ->
          "error: execution failed while publishing to topic '$topicId' in project '$projectId': ${err.message}"
      }
    System.err.println(message)
  } catch (err: InterruptedException) {
    Thread.currentThread().interrupt()
    System.err.println(
      "error: interrupted while publishing to topic '$topicId' in project '$projectId': ${err.message}"
    )
  } catch (err: IOException) {
    System.err.println(
      "error: failed to initialize Publisher for topic '$topicId' in project '$projectId': ${err.message}"
    )
  } finally {
    if (publisher != null) {
      publisher.shutdown()
      try {
        publisher.awaitTermination(1, TimeUnit.MINUTES)
      } catch (err: InterruptedException) {
        Thread.currentThread().interrupt()
      }
    }
  }
}

Ruby

试用此示例之前，请按照 Pub/Sub 快速入门：使用客户端库中的 Ruby 设置说明进行操作。 如需了解详情，请参阅 Pub/Sub Ruby API 参考文档。

如需向 Pub/Sub 进行身份验证，请设置应用默认凭据。如需了解详情，请参阅为本地开发环境设置身份验证。 

# topic_id = "your-topic-id"

pubsub = Google::Cloud::PubSub.new
publisher = pubsub.publisher topic_id

# Add two attributes, origin and username, to the message
publisher.publish_async "This is a test message.",
                        origin:   "ruby-sample",
                        username: "gcp" do |result|
  raise "Failed to publish the message." unless result.succeeded?
  puts "Message with custom attributes published asynchronously."
end

# Stop the async_publisher to send all queued messages immediately.
publisher.async_publisher.stop.wait!

Rust

use google_cloud_pubsub::client::Publisher;
use google_cloud_pubsub::model::Message;

pub async fn sample(project_id: &str, topic_id: &str) -> anyhow::Result<()> {
    let topic_name = format!("projects/{project_id}/topics/{topic_id}");
    let publisher = Publisher::builder(topic_name).build().await?;

    let message = Message::new()
        .set_data("Hello, World!")
        .set_attributes([("origin", "rust-sample"), ("username", "gcp")]);
    let message_id = publisher.publish(message).await?;

    println!("published message with custom attributes; message ID: {message_id}");
    Ok(())
}

后续步骤

如需搜索和过滤其他 Google Cloud 产品的代码示例，请参阅Google Cloud 示例浏览器。