Table of Contents
The Qpid Messaging API is quite simple, consisting of only a handful of core classes.
A message consists of a standard set
of fields (e.g. subject,
reply-to), an application-defined set of
properties, and message content (the main body of the
message).
A connection represents a network connection to a remote endpoint.
A session provides a sequentially ordered context for sending and receiving messages. A session is obtained from a connection.
A sender sends messages to a target
using the sender.send method. A sender is
obtained from a session for a given target address.
A receiver receives messages from a
source using the receiver.fetch method.
A receiver is obtained from a session for a given source
address.
The following sections show how to use these classes in a simple messaging program.
The following C++ program shows how to create a connection, create a session, send messages using a sender, and receive messages using a receiver.
Example 2.1. "Hello world!" in C++
#include <qpid/messaging/Connection.h>
#include <qpid/messaging/Message.h>
#include <qpid/messaging/Receiver.h>
#include <qpid/messaging/Sender.h>
#include <qpid/messaging/Session.h>
#include <iostream>
using namespace qpid::messaging;
int main(int argc, char** argv) {
std::string broker = argc > 1 ? argv[1] : "localhost:5672";
std::string address = argc > 2 ? argv[2] : "amq.topic";
Connection connection(broker);
try {
connection.open(); (1)
Session session = connection.createSession(); (2)
Receiver receiver = session.createReceiver(address); (3)
Sender sender = session.createSender(address); (4)
sender.send(Message("Hello world!"));
Message message = receiver.fetch(Duration::SECOND * 1); (5)
std::cout << message.getContent() << std::endl;
session.acknowledge(); (6)
connection.close(); (7)
return 0;
} catch(const std::exception& error) {
std::cerr << error.what() << std::endl;
connection.close();
return 1;
}
}Establishes the connection with the messaging broker. | |
Creates a session object, which maintains the state of all interactions with the messaging broker, and manages senders and receivers. | |
Creates a receiver that reads from the given address. | |
Creates a sender that sends to the given address. | |
Reads the next message. The duration is optional, if omitted, will wait indefinitely for the next message. | |
Acknowledges messages that have been read. To guarantee delivery, a message remains on the messaging broker until it is acknowledged by a client. session.acknowledge() acknowledges all unacknowledged messages for the given session—this allows acknowledgements to be batched, which is more efficient than acknowledging messages individually. | |
Closes the connection, all sessions managed by the connection, and all senders and receivers managed by each session. |