How to stack received messages and process them in batch - activemq

Question

I'd like to create a consumer which stacks arriving messages, and waits:
until n messages have arrived.
t seconds are elapsed.
to process the whole stack of messages.
Pre-fetching is not what I'm looking for. What I really need is to process messages together.
class MyListener(stomp.ConnectionListener):
def on_message(self, headers, body):
print ("Just received ONE message\n"
"I should wait for n-1 others\n"
"or t seconds before processing")

Answer 1

here an example
import java.util.LinkedList;
import java.util.List;
import javax.jms.Connection;
import javax.jms.JMSException;
import javax.jms.Session;
import javax.jms.TextMessage;
import org.apache.activemq.ActiveMQConnectionFactory;
import org.apache.activemq.ActiveMQMessageConsumer;
public class SimpleConsumerClientAcknowledge {
public static void main(String[] args) throws JMSException {
List<TextMessage> messages = new LinkedList<>();
Connection conn = null;
try {
ActiveMQConnectionFactory cf = new ActiveMQConnectionFactory(
"tcp://localhost:61617?jms.prefetchPolicy.all=200");
conn = cf.createConnection("admin", "admin");
Session session = conn.createSession(false, Session.CLIENT_ACKNOWLEDGE);
ActiveMQMessageConsumer consumer = (ActiveMQMessageConsumer) session
.createConsumer(session.createQueue("Q"));
conn.start();
TextMessage msg = null;
// MAX_MESSAGES have to be < prefetchSize / 2 -->
// jms.prefetchPolicy.all=200
// Once the broker has dispatched a prefetch limit number of
// messages to a consumer it will not dispatch any more messages to
// that consumer until the consumer has acknowledged at least 50% of
// the prefetched messages
int MAX_MESSAGES = 100;
long MAX_WAIT = 60000;
long millis = System.currentTimeMillis();
while ((msg = (TextMessage) consumer.receive(5000)) != null) {
if (msg != null) {
messages.add(msg);
}
if (messages.size() == MAX_MESSAGES || (System.currentTimeMillis() - millis >= MAX_WAIT)) {
millis = System.currentTimeMillis();
treatMessages(messages);
// because session is created with
// Session.CLIENT_ACKNOWLEDGE as an acknowledgeMode consumer
// need to acknowledge manually received messages
consumer.acknowledge();
}
}
} catch (Exception e) {
e.printStackTrace();
} finally {
if (conn != null) {
try {
conn.close();
} catch (Exception e) {
}
}
}
}
private static void treatMessages(List<TextMessage> messages) {
// TODO Auto-generated method stub
messages.clear();
}
}