Java SDK Access Example

This topic describes how to connect an AMQP-compliant JMS client to the IoT platform and receive subscribed messages from the platform.

Development Environment Requirements

JDK 1.8 or later has been installed.

Obtaining the Java SDK

The AMQP SDK is an open-source SDK. If you use Java, you are advised to use the Apache Qpid JMS client. Visit Qpid JMS to download the client and view the instructions for use.

Adding a Maven Dependency

<!-- amqp 1.0 qpid client -->
 <dependency>
   <groupId>org.apache.qpid</groupId>
   <artifactId>qpid-jms-client</artifactId>
   <version>0.61.0</version>
 </dependency>

Sample Code

You can click here to obtain the Java SDK access example. For details on the parameters involved in the demo, see AMQP Client Access.

All sample code contains the logic of server reconnection upon disconnection.

You can obtain AmqpClient.java, AmqpClientOptions.java, and AmqpConstants.java used in the sample code from here.

1. Create AmqpClient.

// Change the values of the following parameters as required.
AmqpClientOptions options = AmqpClientOptions.builder()
                .host(AmqpConstants.HOST)
                .port(AmqpConstants.PORT)
                .accessKey(AmqpConstants.ACCESS_KEY)
                .accessCode(AmqpConstants.ACCESS_CODE)
                .queuePrefetch(1000) // The SDK allocates the queue with the memory size set in this parameter to receive messages. If the client memory size is small, set this parameter to a smaller value.
                .build();
        AmqpClient amqpClient = new AmqpClient(options);
        amqpClient.initialize();

2. Configure a listener to consume AMQP messages.

 try {
     MessageConsumer consumer = amqpClient.newConsumer(AmqpConstants.DEFAULT_QUEUE);
     consumer.setMessageListener(message -> {
         try {
             // Process messages. If the processing is time-consuming, you are advised to start a new thread. Otherwise, the connection may be cut off due to heartbeat timeout.
             processMessage(message.getBody(String.class));
             // If options.isAutoAcknowledge==false is configured, call message.acknowledge();
         } catch (Exception e) {
             log.warn("message.getBody error,exception is ", e);
         }
     });
 } catch (Exception e) {
     log.warn("Consumer initialize error,", e);
 }

3. Pull AMQP messages.

  // Create a thread pool to pull messages.
  ExecutorService executorService = new ThreadPoolExecutor(1, 1, 60, TimeUnit.SECONDS,new LinkedBlockingQueue<>(1));

      try {
            MessageConsumer consumer = amqpClient.newConsumer(AmqpConstants.DEFAULT_QUEUE);
            executorService.execute(() -> {
                while (!isClose.get()) {
                    try {
                        Message message = consumer.receive();
                        // Process messages. If the processing is time-consuming, you are advised to start a new thread. Otherwise, the connection may be cut off due to heartbeat timeout.
                        processMessage(message.getBody(String.class));
                        // If options.isAutoAcknowledge==false is configured, call message.acknowledge();
                    } catch (JMSException e) {
                        log.warn("receive message error,", e);
                    }
                }
            });
        } catch (Exception e) {
            log.warn("Consumer initialize error,", e);
        }

4. For more demos about AMQP message consumption, see the access demo project that uses the java SDK.

Resources

AmqpClient.java

package com.iot.amqp;

import lombok.extern.slf4j.Slf4j;
import org.apache.commons.lang3.StringUtils;
import org.apache.qpid.jms.JmsConnection;
import org.apache.qpid.jms.JmsConnectionExtensions;
import org.apache.qpid.jms.JmsConnectionFactory;
import org.apache.qpid.jms.JmsQueue;
import org.apache.qpid.jms.transports.TransportOptions;
import org.apache.qpid.jms.transports.TransportSupport;

import javax.jms.Connection;
import javax.jms.JMSException;
import javax.jms.MessageConsumer;
import javax.jms.Session;
import java.util.Collections;
import java.util.HashSet;
import java.util.Set;

@Slf4j
public class AmqpClient {
    private final AmqpClientOptions options;
    private Connection connection;
    private Session session;
    private final Set<MessageConsumer> consumerSet = Collections.synchronizedSet(new HashSet<>());

    public AmqpClient(AmqpClientOptions options) {
        this.options = options;
    }

    public String getId() {
        return options.getClientId();
    }

    public void initialize() throws Exception {
        String connectionUrl = options.generateConnectUrl();
        log.info("connectionUrl={}", connectionUrl);
        JmsConnectionFactory cf = new JmsConnectionFactory(connectionUrl);
        // Trust the server.
        TransportOptions to = new TransportOptions();
        to.setTrustAll(true);
        cf.setSslContext(TransportSupport.createJdkSslContext(to));
        String userName = "accessKey=" + options.getAccessKey();
        cf.setExtension(JmsConnectionExtensions.USERNAME_OVERRIDE.toString(), (connection, uri) -> {
            String newUserName = userName;
            if (connection instanceof JmsConnection) {
                newUserName = ((JmsConnection) connection).getUsername();
            }
            if (StringUtils.isEmpty(options.getInstanceId())) {
            // userName of IoTDA is in the following format: accessKey=${accessKey}|timestamp=${timestamp}.
                return newUserName + "|timestamp=" + System.currentTimeMillis();
            } else {
            //If multiple Standard Editions are purchased in the same region, the format of userName is accessKey=${accessKey}|timestamp=${timestamp}|instanceId=${instanceId}.
                return newUserName + "|timestamp=" + System.currentTimeMillis() + "|instanceId=" + options.getInstanceId();
            }
        });
        // Create a connection.
        connection = cf.createConnection(userName, options.getAccessCode());
        // Create sessions Session.CLIENT_ACKNOWLEDGE and Session.AUTO_ACKNOWLEDGE. For Session.CLIENT_ACKNOWLEDGE, manually call message.acknowledge() after receiving a message. For Session.AUTO_ACKNOWLEDGE, the SDK automatically responds with an ACK message (recommended).
        session = connection.createSession(false, options.isAutoAcknowledge() ? Session.AUTO_ACKNOWLEDGE : Session.CLIENT_ACKNOWLEDGE);
        connection.start();
    }

    public MessageConsumer newConsumer(String queueName) throws Exception {
        if (connection == null || !(connection instanceof JmsConnection) || ((JmsConnection) connection).isClosed()) {
            throw new Exception("create consumer failed,the connection is disconnected.");
        }
        MessageConsumer consumer;

        consumer = session.createConsumer(new JmsQueue(queueName));
        if (consumer != null) {
            consumerSet.add(consumer);
        }
        return consumer;
    }

    public void close() {
        consumerSet.forEach(consumer -> {
            try {
                consumer.close();
            } catch (JMSException e) {
                log.warn("consumer close error,exception is ", e);
            }
        });

        if (session != null) {
            try {
                session.close();
            } catch (JMSException e) {
                log.warn("session close error,exception is ", e);
            }
        }

        if (connection != null) {
            try {
                connection.close();
            } catch (JMSException e) {
                log.warn("connection close error,exception is", e);
            }
        }
    }
}

AmqpClientOptions.java

package com.iot.amqp;

import lombok.Builder;
import lombok.Data;
import org.apache.commons.lang3.StringUtils;

import java.text.MessageFormat;
import java.util.HashMap;
import java.util.Map;
import java.util.UUID;
import java.util.stream.Collectors;

@Data
@Builder
public class AmqpClientOptions {
    private String host;
    @Builder.Default
    private int port = 5671;
    private String accessKey;
    private String accessCode;
    private String clientId;

    /**
     * Specifies the instance ID. This parameter is required when multiple instances of the Standard Edition are purchased in the same region.
     */
    private String instanceId;

    /**
     * Only true is supported.
     */
    @Builder.Default
    private boolean useSsl = true;

    /**
     * IoTDA supports default only.
     */
    @Builder.Default
    private String vhost = "default";

    /**
     * IoTDA supports PLAIN only.
     */
    @Builder.Default
    private String saslMechanisms = "PLAIN";

    /**
     * true: The SDK automatically responds with an ACK message (default).
     * false: After receiving a message, manually call message.acknowledge().
     */
    @Builder.Default
    private boolean isAutoAcknowledge = true;

    /**
     * Reconnection delay (ms)
     */
    @Builder.Default
    private long reconnectDelay = 3000L;

    /**
     * Maximum reconnection delay (ms). The reconnection delay increases with the number of reconnection times.
     */
    @Builder.Default
    private long maxReconnectDelay = 30 * 1000L;

    /**
     * Maximum number of reconnection times. The default value is –1, indicating that the number of reconnection times is not limited.
     */
    @Builder.Default
    private long maxReconnectAttempts = -1;

    /**
     * Idle timeout interval. If the peer end does not send an AMQP frame within the interval, the connection will be cut off. The default value is 30000, in milliseconds.
     */
    @Builder.Default
    private long idleTimeout = 30 * 1000L;

    /**
     * The values below control how many messages the remote peer can send to the client and be held in a pre-fetch buffer for each consumer instance.
     */
    @Builder.Default
    private int queuePrefetch = 1000;

    /**
     * Extended parameters
     */
    private Map<String, String> extendedOptions;

    public String generateConnectUrl() {
        String uri = MessageFormat.format("{0}://{1}:{2}", (useSsl ? "amqps" : "amqp"), host, String.valueOf(port));
        Map<String, String> uriOptions = new HashMap<>();
        uriOptions.put("amqp.vhost", vhost);
        uriOptions.put("amqp.idleTimeout", String.valueOf(idleTimeout));
        uriOptions.put("amqp.saslMechanisms", saslMechanisms);

        Map<String, String> jmsOptions = new HashMap<>();
        jmsOptions.put("jms.prefetchPolicy.queuePrefetch", String.valueOf(queuePrefetch));
        if (StringUtils.isNotEmpty(clientId)) {
            jmsOptions.put("jms.clientID", clientId);
        } else {
            jmsOptions.put("jms.clientID", UUID.randomUUID().toString());
        }
        jmsOptions.put("failover.reconnectDelay", String.valueOf(reconnectDelay));
        jmsOptions.put("failover.maxReconnectDelay", String.valueOf(maxReconnectDelay));
        if (maxReconnectAttempts > 0) {
            jmsOptions.put("failover.maxReconnectAttempts", String.valueOf(maxReconnectAttempts));
        }
        if (extendedOptions != null) {
            for (Map.Entry<String, String> option : extendedOptions.entrySet()) {
                if (option.getKey().startsWith("amqp.") || option.getKey().startsWith("transport.")) {
                    uriOptions.put(option.getKey(), option.getValue());
                } else {
                    jmsOptions.put(option.getKey(), option.getValue());
                }
            }
        }
        StringBuilder stringBuilder = new StringBuilder();
        stringBuilder.append(uriOptions.entrySet().stream()
                .map(option -> MessageFormat.format("{0}={1}", option.getKey(), option.getValue()))
                .collect(Collectors.joining("&", "failover:(" + uri + "?", ")")));
        stringBuilder.append(jmsOptions.entrySet().stream()
                .map(option -> MessageFormat.format("{0}={1}", option.getKey(), option.getValue()))
                .collect(Collectors.joining("&", "?", "")));
        return stringBuilder.toString();
    }
}

AmqpConstants.java

package com.iot.amqp;


public interface AmqpConstants {
    /**
     * AMQP access domain name
     * eg: "****.iot-amqps.cn-north-4.myhuaweicloud.com";
     */
    String HOST = "127.0.0.1";   

    /**
     * AMQP access port
     */
    int PORT = 5671;

    /**
     * Access key
     * A timestamp does not need to be combined.
     */
    String ACCESS_KEY = "accessKey";

    /**
     * Access code
     */
    String ACCESS_CODE = "accessCode";

    /**
     * Default queue
     */
    String DEFAULT_QUEUE = "DefaultQueue";
}

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