Custom triggers - pull and push mechanism

The examples provided in this topic demonstrate how to create time-based and event-based triggers, pull (link TriggerDemo) and push (SimpleMessageListenerContainer) mechanisms using the SDK package.

Example: Time-based triggers - Pull mechanism

The required conditions of triggering are tested at the regular interval, in seconds.

A trigger checks the database (DB) at regular intervals and if the SQL (DB) value that a user provides is more than 0, then the timer-based trigger is triggered.
When the event occurs, it runs the consumer.accept(<RecordValue Instance>) method and triggers an associated bot.
It verifies the conditions at each run.
Add the valid DB driver in the build gradle file to run this example.

This example is an extension of the timer-based trigger (TriggerDemo) and demonstrates the trigger pull mechanism.

Note: This is an illustrative example and do not use it in the production environment.

@BotCommand(commandType = BotCommand.CommandType.Trigger)
@CommandPkg(label = "JDBC Query Trigger", description = "JDBC Query Trigger", icon = "jdbc.svg", name = "jdbcQueryTrigger",
		return_type = RECORD, return_name = "TriggerData", return_description = "Available keys: triggerType")
public class DBStatus {
	
	private static Logger logger = LogManager.getLogger(DBStatus.class);
	
	
	// Map storing multiple tasks
	private static final Map<String, TimerTask> taskMap = new ConcurrentHashMap<>();
	private static final Timer TIMER = new Timer(true);

	@TriggerId
	private String triggerUid;
	@TriggerConsumer
	private Consumer consumer;

	/*
	 * Starts the trigger.
	 */
	@StartListen
	public void startTrigger(
			@Idx(index="1", type = AttributeType.TEXT)
			@Pkg(label = "Provide the database driver class")
			@NotEmpty
			String driverClassName,
			
			@Idx(index="2", type = AttributeType.TEXT)
			@Pkg(label = "Provide the Jdbc connection string")
			@NotEmpty
			String jdbcUrl,
			
			@Idx(index="3", type = AttributeType.TEXT)
			@Pkg(label = "Provide the user Name")
			@NotEmpty
			String userName,
			
			@Idx(index="4", type = AttributeType.CREDENTIAL)
			@Pkg(label = "Provide the password")
			@NotEmpty
			SecureString password,
			
			@Idx(index="5", type = AttributeType.TEXT)
			@Pkg(label = "Provide the SQL to check the records")
			@NotEmpty
			String sqlQuery,
			
			@Idx(index = "6", type = AttributeType.NUMBER)
			@Pkg(label = "Provide the interval to query in seconds", default_value = "300", default_value_type = DataType.NUMBER)
			@GreaterThan("0")
			@NumberInteger
			@NotEmpty
			Double interval) {
		
		DataSource dataSource = getDataSource(driverClassName, jdbcUrl, userName, password);
		
		TimerTask timerTask = new TimerTask() {

			@Override
			public void run() {
				logger.debug("checking DB");
				try {
					if(checkRecordsExist(dataSource.getConnection(), sqlQuery)){
						consumer.accept(getRecordValue());
						return;
					}
				} catch (SQLException e) {
					logger.warn(e.getMessage(),e);
					logger.warn("Trigger is still running.");
				}
				logger.debug("no records found");

			}
		};

		taskMap.put(this.triggerUid, timerTask);
		TIMER.schedule(timerTask, interval.longValue(), interval.longValue());
	}

	private RecordValue getRecordValue() {
		List<Schema> schemas = new LinkedList<>();
		List<Value> values = new LinkedList<>();
		schemas.add(new Schema("triggerType"));
		values.add(new StringValue("DBStatus"));

		RecordValue recordValue = new RecordValue();
		recordValue.set(new Record(schemas,values));
		return recordValue;
	}
	/*
	 * Cancel all the tasks and clear the map.
	 */
	@StopAllTriggers
	public void stopAllTriggers() {
		taskMap.forEach((k, v) -> {
			if (v.cancel()) {
				taskMap.remove(k);
			}
		});
	}

	/*
	 * Cancel the task and remove from the map
	 *
	 * @param triggerUid
	 */
	@StopListen
	public void stopListen(String triggerUid) {
		if (taskMap.get(triggerUid).cancel()) {
			taskMap.remove(triggerUid);
		}
	}

    public static DataSource getDataSource(String driverClassName, String url, String userName,SecureString password) {
    	BasicDataSource ds = new BasicDataSource();
    	ds.setDriverClassName(driverClassName);
    	ds.setUrl(url);
    	ds.setUsername(userName);
    	ds.setPassword(password.getInsecureString());
        return ds;
    }
	
    public static boolean checkRecordsExist(Connection con, String query)
    	    throws SQLException {
			
    	    Statement stmt = null;
    	    try {
    	        stmt = con.createStatement();
    	        ResultSet rs = stmt.executeQuery(query);
    	        rs.last();
    	        if(rs.getRow() > 0)
    	        	return true;
    	    } catch (SQLException e ) {
    	        throw new BotCommandException("Problem running statemnt", e);
    	    } finally {
    	        if (stmt != null) { stmt.close(); }
    	    }    
    	    return false;
    	}  
	public String getTriggerUid() {
		return triggerUid;
	}
	public void setTriggerUid(String triggerUid) {
		this.triggerUid = triggerUid;
	}
	public Consumer getConsumer() {
		return consumer;
	}
	public void setConsumer(Consumer consumer) {
		this.consumer = consumer;
	}
}

Example: Event-based triggers - Push mechanism

The trigger waits for an event to occur, for example, a message listener to start listening.

An event details are stored in the memory and a message listener waits for a message.
When the event occurs, it runs the consumer.accept(<RecordValue Instance>) method and triggers an associated bot..

The following example shows how to create a simple ActiveMQ message listener (SimpleMessageListenerContainer) to demonstrate the trigger push mechanism.

@BotCommand(commandType = BotCommand.CommandType.Trigger)
@CommandPkg(label = "JMS Trigger", description = "JMS Trigger", icon = "jms.svg", name = "jmsTrigger",
		return_type = RECORD, return_name = "TriggerData", return_description = "Available keys: triggerType")
public class JMSQueue implements SessionAwareMessageListener {

	// Map storing multiple MessageListenerContainer
	private static final Map<String, MessageListenerContainer> taskMap = new ConcurrentHashMap<>();

	@TriggerId
	private String triggerUid;
	@TriggerConsumer
	private Consumer consumer;
	
	//This method is called by MessageListenerContainer when a message arrives.
	// At this point, the trigger get enabled 
	@Override
	public void onMessage(javax.jms.Message message, Session session) throws JMSException {
		consumer.accept(getRecordValue());

	}

	private RecordValue getRecordValue() {
		List<Schema> schemas = new LinkedList<>();
		List<Value> values = new LinkedList<>();
		schemas.add(new Schema("triggerType"));
		values.add(new StringValue("JMSQueue"));

		RecordValue recordValue = new RecordValue();
		recordValue.set(new Record(schemas,values));
		return recordValue;
	}
	/*
	 * Starts the trigger.
	 * 
	 * Use this method to setup the trigger, such as, setup the MessageListenerContainer and start it.
	 */
	@StartListen
	public void startTrigger(@Idx(index = "1", type = AttributeType.TEXT)
	@Pkg(label = "Provide the broker URL")
	@NotEmpty
	String brokerURL, @Idx(index = "2", type = AttributeType.TEXT)
	@Pkg(label = "Provide the queue name")
	@NotEmpty
	String queueName) {
		
		if (taskMap.get(triggerUid) == null) {
			synchronized (this) {
				if (taskMap.get(triggerUid) == null) {
					SimpleMessageListenerContainer messageListenerContainer = new SimpleMessageListenerContainer();
					messageListenerContainer.setConnectionFactory(new PooledConnectionFactory(brokerURL));
					messageListenerContainer.setDestinationName(queueName);
					messageListenerContainer.setMessageListener(this);
					messageListenerContainer.start();
					taskMap.put(triggerUid, messageListenerContainer);

				}
			}
		}

	}

	/*
	 * Cancel all the tasks and clear the map.
	 */
	@StopAllTriggers
	public void stopAllTriggers() {
		taskMap.forEach((k, v) -> {
			v.stop();
			taskMap.remove(k);
		});
	}

	/*
	 * Cancel the tasks and remove from the map
	 *
	 * @param triggerUid
	 */
	@StopListen
	public void stopListen(String triggerUid) {
		taskMap.get(triggerUid).stop();
		taskMap.remove(triggerUid);
	}

	public String getTriggerUid() {
		return triggerUid;
	}

	public void setTriggerUid(String triggerUid) {
		this.triggerUid = triggerUid;
	}

	public Consumer getConsumer() {
		return consumer;
	}

	public void setConsumer(Consumer consumer) {
		this.consumer = consumer;
	}

}

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