累积性中的 Java 客户端如何侦听事件

Question

目标是构建一个订阅和收听频道的java客户端。然后将从累积性服务器到Hadoop的到达事件进行处理。首先，使用 java 客户端很难连接（订阅）到累积性服务器。但是，现在我们有订阅者（因为我们能够获得一些价值，如代码注释中所述）。接下来，我们想要的是订阅者收听我们在 cumulocity 服务器中定义的频道。但是我们无法在 cumulocity java 文档中获得任何有助于实现这一步的方法或任何有用的东西。这是代码。我已经匿名化了凭据和服务器网址。

        package c8y.example.hello_agent;
    import c8y.IsDevice;
    import com.cumulocity.model.authentication.CumulocityCredentials;
    import com.cumulocity.rest.representation.inventory.ManagedObjectRepresentation;
    import com.cumulocity.sdk.client.Platform;
    import com.cumulocity.sdk.client.PlatformImpl;
    import com.cumulocity.sdk.client.inventory.InventoryApi;
    import com.cumulocity.sdk.client.PlatformParameters;
    import com.cumulocity.sdk.client.SDKException;
    import com.cumulocity.sdk.client.notification.*;
    import com.cumulocity.sdk.client.ClientConfiguration;
    import com.cumulocity.*;
    import c8y.example.hello_agent.cred;
    public class CepCustomNotificationsSubscriber implements Subscriber<String, Object> {
        public static final String CEP_CUSTOM_NOTIFICATIONS_URL = "test/sendTemperature";
        private final Subscriber<String, Object> subscriber;
        public CepCustomNotificationsSubscriber(PlatformParameters parameters) {
            subscriber = createSubscriber(parameters);
        }
        private Subscriber<String, Object> createSubscriber(PlatformParameters parameters) {
            // @formatter:off
            return SubscriberBuilder.<String, Object>anSubscriber()
                        .withParameters(parameters)
                        .withEndpoint(CEP_CUSTOM_NOTIFICATIONS_URL)
                        .withSubscriptionNameResolver(new Identity())
                        .withDataType(Object.class)
                        .build();
            // @formatter:on
        }

        public Subscription<String> subscribe(final String channelID, final SubscriptionListener<String, Object> handler) throws SDKException {
            return subscriber.subscribe(channelID, handler);
        }
        public void disconnect() {
            subscriber.disconnect();
        }
        private static final class Identity implements SubscriptionNameResolver<String> {
            @Override
            public String apply(String id) {
                return id;
            }
        }
        public static void main( String[] args )
        {
           cred crede = new cred(); 
           String uRl = "https://xxx.cumulocityiox.com"; 
           CumulocityCredentials rC = new CumulocityCredentials(crede.name,crede.pass);
           PlatformParameters parameters = new PlatformParameters(uRl,rC, new ClientConfiguration());
           CepCustomNotificationsSubscriber t = new CepCustomNotificationsSubscriber(parameters);

           System.out.println(t.toString() + " - " + t.CEP_CUSTOM_NOTIFICATIONS_URL.toString()); // It prints an integer number corresponding to the subscriber t.
// Now how to listen to the events on the channel and get the desired data.                       
        }
    }

由于我们能够获得一些整数值来验证与服务器的连接。但是现在下一点是如何监听事件的频道并获取这些事件。任何帮助将不胜感激。

Answer 1

我以为你创建了一个像这样的 cep 模块

insert into
  SendNotification
select
  e.event as payload,
  "customevent/" || e.event.source.value as channelName
from
  EventCreated e;

如果您创建频道"自定义事件/累积城系统-ID"的订阅，您将能够获得这些事件

在您的 Java 代码中，只需添加以下行（使用 lambda 表达式）

t.subscribe("/customevent/1191201", new  SubscriptionListener (){
        @Override
        public void onNotification(Subscription s, Object r) {
            // here come the notification of the desired channel. The Object r is the event desired.
            System.out.println(r);
        }
        @Override
        public void onError(Subscription s, Throwable thrwbl) {
            // errors will come here
        }

    });

和

System.out.println(r);

将打印类似的东西

{creationTime=2017-01-26T19:00:15.837+01:00, c8y_Position=Position 
[lat=4, lng=-71.80, alt=67, accuracy=null],    
self=http://yourTenant.cumulocity.com/event/events/1202018, 
time=2017-01-    26T13:00:15.000-05:00, id=1202018, source={name=Lancer 
UBL142,
self=http://yourTenant.cumulocity.com/inventory/managedObjects/1191201, 
id=1191201}, text=Estado,Idle mode (Parking), type=c8y_LocationUpdate}

请注意，"/customevent/1191201"是您想要的channelId。

希望这有帮助！