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Publish events to namespace topics using Java

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This article provides a quick, step-by-step guide to publish CloudEvents using Java. The sample code in this article uses the CloudEvents JSON format when sending events.

Prerequisites

The prerequisites you need to have in place before proceeding are:

  • A namespace, topic, and event subscription.

  • The latest beta SDK package. If you're using maven, you can consult the maven central repository.

    Important

    Pull delivery data plane SDK support is available in beta packages. You should use the latest beta package in your project.

  • An IDE that support Java like IntelliJ IDEA, Eclipse IDE, or Visual Studio Code.

  • Java JRE running Java 8 language level.

Publish events to a namespace topic

Use the following class to understand the basic steps to publish events.

package com.azure.messaging.eventgrid.samples;

import com.azure.core.credential.AzureKeyCredential;
import com.azure.core.http.HttpClient;
import com.azure.core.models.CloudEvent;
import com.azure.core.models.CloudEventDataFormat;
import com.azure.core.util.BinaryData;
import com.azure.messaging.eventgrid.EventGridClient;
import com.azure.messaging.eventgrid.EventGridClientBuilder;
import com.azure.messaging.eventgrid.EventGridMessagingServiceVersion;

import java.time.OffsetDateTime;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Random;

/**
 * <p>Simple demo publisher of CloudEvents to Event Grid namespace topics.
 *
 * This code samples should use Java 1.8 level or above to avoid compilation errors.
 *
 * You should consult the resources below to use the client SDK and set up your project using maven.
 * @see <a href="https://github.com/Azure/azure-sdk-for-java/tree/main/sdk/eventgrid/azure-messaging-eventgrid">Event Grid data plane client SDK documentation</a>
 * @see <a href="https://github.com/Azure/azure-sdk-for-java/blob/main/sdk/boms/azure-sdk-bom/README.md">Azure BOM for client libraries</a>
 * @see <a href="https://aka.ms/spring/versions">Spring Version Mapping</a> if you are using Spring.
 * @see <a href="https://aka.ms/azsdk">Tool with links to control plane and data plane SDKs across all languages supported</a>.
 *</p>
 */
public class NamespaceTopicPublisher {
    private static final String TOPIC_NAME = "<yourNamespaceTopicName>";
    public static final String ENDPOINT =  "<yourFullHttpsUrlToTheNamespaceEndpoint>";
    public static final int NUMBER_OF_EVENTS_TO_BUILD_THAT_DOES_NOT_EXCEED_100 = 10;

    //TODO  Do NOT include keys in source code. This code's objective is to give you a succinct sample about using Event Grid, not to provide an authoritative example for handling secrets in applications.
    /**
    *  For security concerns, you should not have keys or any other secret in any part of the application code.
     *  You should use services like Azure Key Vault for managing your keys.
     */
    public static final AzureKeyCredential CREDENTIAL = new AzureKeyCredential("<namespace key>");

    public static void main(String[] args) {
        //TODO Update Event Grid version number to your desired version. You can find more information on data plane APIs here:
        //https://learn.microsoft.com/en-us/rest/api/eventgrid/.
        EventGridClient eventGridClient = new EventGridClientBuilder()
                .httpClient(HttpClient.createDefault())  // Requires Java 1.8 level
                .endpoint(ENDPOINT)
                .serviceVersion(EventGridMessagingServiceVersion.V2023_06_01_PREVIEW)
                .credential(CREDENTIAL).buildClient();   // you may want to use .buildAsyncClient() for an asynchronous (project reactor) client.

        List<CloudEvent> cloudEvents = buildCloudEvents(NUMBER_OF_EVENTS_TO_BUILD_THAT_DOES_NOT_EXCEED_100);

        eventGridClient.publishCloudEvents(TOPIC_NAME, cloudEvents);

        System.out.println("--> Number of events published: " + NUMBER_OF_EVENTS_TO_BUILD_THAT_DOES_NOT_EXCEED_100); // There is no partial publish. Either all succeed or none.
    }

    /**
     * <p>Builds a list of valid CloudEvents for testing purposes</p>
     * @param numberOfEventsToBuild this should not exceed 100, which is the maximum number of events allowed in a single HTTP request or 1MB in size, whichever is met first.
     * @return the list of CloudEvents
     */
    private static List<CloudEvent> buildCloudEvents(int numberOfEventsToBuild) {
        List<CloudEvent> cloudEvents = new ArrayList<>(numberOfEventsToBuild);
        while (numberOfEventsToBuild >= 1) {
            cloudEvents.add(buildCloudEvent());
            numberOfEventsToBuild--;
        }
        return cloudEvents;
    }

    /**
     * <p>Builds a valid CloudEvent for testing purposes.</p>
     * @return a CloudEvent
     */
    private static CloudEvent buildCloudEvent() {
        String orderId = Integer.toString(new Random().nextInt(1000-10+1) + 10);  // Generates a random integer between 1000 and 1 (exclusive)

        return new CloudEvent("/account/a-4305/orders", "com.MyCompanyName.OrderCreated",
                BinaryData.fromObject(new HashMap<String, String>() {
                    {
                        put("orderId", orderId);
                        put("orderResourceURL", "https://www.MyCompanyName.com/orders/" + orderId);
                        put("isRushOrder", "true");
                        put("customerType", "Institutional");
                    }
                }), CloudEventDataFormat.JSON, "application/json")
                .setTime(OffsetDateTime.now());
    }
}

Next steps