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Stomp is a text-orientated wire protocol that allows Stomp clients to communicate with Stomp Brokers.
Stomp clients are available for several languages and platforms making it a good choice for interoperability.
HornetQ provides native support for Stomp. To be able to send and receive Stomp
messages, you must configure a NettyAcceptor with a protocol parameter set to stomp:
<acceptor name="stomp-acceptor"> <factory-class>org.hornetq.core.remoting.impl.netty.NettyAcceptorFactory</factory-class> <param key="protocol" value="stomp"/> <param key="port" value="61613"/> </acceptor>
With this configuration, HornetQ will accept Stomp connections on the port 61613 (which is the default port of the Stomp brokers).
See the stomp example which shows how to configure a HornetQ server
with Stomp.
When consuming messages in stomp, it's preferrable to use Acknowledge consumers, otherwise the server will send messages as fast as it can to the client (i.e. no flow control). Refer to the parameter stomp-consumer-credits for more information.
Stomp clients deals with destinations when sending messages and subscribing. Destination names are simply strings which are mapped to some form of destination on the server - how the server translates these is left to the server implementation.
In HornetQ, these destinations are mapped to addresses and
queues. When a Stomp client sends a message (using a SEND frame), the specified destination is mapped to an address. When a Stomp
client subscribes (or unsubscribes) for a destination (using a SUBSCRIBE
or UNSUBSCRIBE frame), the destination is mapped to a HornetQ
queue.
Well behaved STOMP clients will always send a DISCONNECT frame before closing their connections. In this case the server will clear up any server side resources such as sessions and consumers synchronously. However if STOMP clients exit without sending a DISCONNECT frame or if they crash the server will have no way of knowing immediately whether the client is still alive or not. STOMP connections therefore default to a connection-ttl value of 1 minute (see chapter on connection-ttl for more information. This value can be overridden using connection-ttl-override.
If you need a specific connection-ttl for your stomp connections without affecting the connection-ttl-override setting, you can configure your stomp acceptor with the "connection-ttl" property, which is used to set the ttl for connections that are created from that acceptor. For example:
<acceptor name="stomp-acceptor"> <factory-class>org.hornetq.core.remoting.impl.netty.NettyAcceptorFactory</factory-class> <param key="protocol" value="stomp"/> <param key="port" value="61613"/> <param key="connection-ttl" value="20000"/> </acceptor>
The above configuration will make sure that any stomp connection that is created from that acceptor will have its connection-ttl set to 20 seconds.
Please note that the STOMP protocol version 1.0 does not contain any heartbeat frame. It is therefore the user's
responsibility to make sure data is sent within connection-ttl or the server will assume the client is dead and clean up server
side resources. With Stomp 1.1 users can use heart-beats to maintain the life cycle of stomp
connections.
As explained in Chapter 9, Mapping JMS Concepts to the Core API, JMS destinations are also mapped to HornetQ addresses and queues. If you want to use Stomp to send messages to JMS destinations, the Stomp destinations must follow the same convention:
send or subscribe to a JMS Queue by prepending the queue name
by jms.queue..
For example, to send a message to the orders JMS Queue, the
Stomp client must send the frame:
SEND
destination:jms.queue.orders
hello queue orders
^@
send or subscribe to a JMS Topic by prepending the topic name
by jms.topic..
For example to subscribe to the stocks JMS Topic, the Stomp
client must send the frame:
SUBSCRIBE
destination:jms.topic.stocks
^@
Stomp is mainly a text-orientated protocol. To make it simpler to interoperate with
JMS and HornetQ Core API, our Stomp implementation checks for presence of the content-length header to decide how to map a Stomp message to a JMS Message
or a Core message.
If the Stomp message does not have a content-length header, it will be mapped to a JMS
TextMessage or a Core message with a single nullable
SimpleString in the body buffer.
Alternatively, if the Stomp message has a content-length header, it will be mapped to a JMS
BytesMessage or a Core message with a byte[] in the body
buffer.
The same logic applies when mapping a JMS message or a Core message to Stomp. A Stomp
client can check the presence of the content-length header to determine
the type of the message body (String or bytes).
When receiving Stomp messages via a JMS consumer or a QueueBrowser, the messages have
no properties like JMSMessageID by default. However this may bring some inconvenience to
clients who wants an ID for their purpose. HornetQ Stomp provides a parameter to enable
message ID on each incoming Stomp message. If you want each Stomp message to have a unique ID,
just set the stomp-enable-message-id to true. For example:
<acceptor name="stomp-acceptor"> <factory-class>org.hornetq.core.remoting.impl.netty.NettyAcceptorFactory</factory-class> <param key="protocol" value="stomp"/> <param key="port" value="61613"/> <param key="stomp-enable-message-id" value="true"/> </acceptor>
When the server starts with the above setting, each stomp message sent through this
acceptor will have an extra property added. The property key is
hq-message-id and the value is a String representation of a long type internal
message id prefixed with "STOMP", like:
hq-message-id : STOMP12345
If stomp-enable-message-id is not specified in the configuration, default
is false.
HornetQ also support Stomp over Web Sockets. Modern web browser which support Web Sockets can send and receive Stomp messages from HornetQ.
To enable Stomp over Web Sockets, you must configure a NettyAcceptor
with a protocol parameter set to stomp_ws:
<acceptor name="stomp-ws-acceptor">
<factory-class>org.hornetq.core.remoting.impl.netty.NettyAcceptorFactory</factory-class>
<param key="protocol" value="stomp_ws"/>
<param key="port" value="61614"/>
</acceptor>
With this configuration, HornetQ will accept Stomp connections over Web Sockets on the
port 61614 with the URL path /stomp. Web browser can
then connect to ws://<server>:61614/stomp using a Web Socket to
send and receive Stomp messages.
A companion JavaScript library to ease client-side development is available from GitHub (please see its documentation for a complete description).
The stomp-websockets example shows how to configure HornetQ server to
have web browsers and Java applications exchanges messages on a JMS topic.
StompConnect is a server that can act as a Stomp broker and proxy the Stomp protocol to the standard JMS API. Consequently, using StompConnect it is possible to turn HornetQ into a Stomp Broker and use any of the available stomp clients. These include clients written in C, C++, c# and .net etc.
To run StompConnect first start the HornetQ server and make sure that it is using JNDI.
Stomp requires the file jndi.properties to be available on the
classpath. This should look something like:
java.naming.factory.initial=org.jnp.interfaces.NamingContextFactory java.naming.provider.url=jnp://localhost:1099 java.naming.factory.url.pkgs=org.jboss.naming:org.jnp.interfaces
Make sure this file is in the classpath along with the StompConnect jar and the HornetQ
jars and simply run java org.codehaus.stomp.jms.Main.