jms

Message-Oriented Middleware (MOM) products like IBM MQ, MSMQ, and SonicMQ each had proprietary APIs. Developers had to rewrite code for each MOM vendor, creating vendor lock-in and forcing developers to learn multiple APIs.

JMS is a standard Java API for messaging that abstracts vendor-specific MOM implementations. You write code against the JMS API once, and plug in any compliant JMS provider (MOM implementation) without changing your code — similar to how JDBC abstracts database vendors.

1. JMS API: Developer writes messaging code using standard JMS interfaces
2. Service Provider Interface (SPI): JMS providers (like ActiveMQ, SonicMQ) implement the SPI to connect JMS API to their MOM product
3. JNDI Lookup: Client looks up ConnectionFactory and Destination from JNDI (administrator configures these)
4. Message Types: JMS supports TextMessage, BytesMessage, StreamMessage, ObjectMessage, and MapMessage
5. Two messaging domains: Point-to-Point (Queues) and Publish/Subscribe (Topics) — each has its own interface flavor

• Standardized API — write once, run with any JMS provider
• Two separate interface flavors: PTP (QueueConnection, QueueSession) and Pub/Sub (TopicConnection, TopicSession)
• Core interfaces: ConnectionFactory, Connection, Session, Destination, Producer, Consumer
• MOM products provide guaranteed delivery, fault tolerance, load balancing
• Abstractions away low-level concerns: networking protocol, message format, server location

• Built from: MOM — JMS is an API abstraction over MOM products
• Builds into: MDB — MDBs consume JMS messages via onMessage()
• Related: JNDI — JMS uses JNDI to look up ConnectionFactory and Destination
• Contrasts with: RMI-IIOP — RMI is synchronous; JMS is asynchronous
• Related: JMS Programming Model — step-by-step process to send/receive messages

• JMS 1.0 had separate PTP and Pub/Sub interfaces; JMS 1.1 unified them (but EJB 2.x uses 1.0 style)
• Not all MOM features are exposed through JMS — some vendor-specific features need proprietary APIs
• JMS providers must be configured by administrator before application can use them
• ConnectionFactory and Destination must be looked up via JNDI — they are not created programmatically