What is true about Message-Driven Beans (MDBs)?

Question

Options

• AMDBs can participate in transactions.
• BMDBs are invoked synchronously.
• CEach MDBs can process messages only from a single client.
• DMDBs retain data caches between client calls.

• A
  88% (29)
• B
  3% (1)
• C
  3% (1)
• D
  6% (2)

Explanation

MDBs can participate in transactions (A) because the EJB container can automatically begin and commit/rollback a JMS transaction around the onMessage() method, ensuring message processing is atomic and reliable - this is a core feature of the EJB specification.

Why the distractors are wrong:

• B (synchronous) - MDBs are inherently asynchronous. They listen on a JMS queue or topic and are triggered when a message arrives; the sender never waits for a response.
• C (single client) - MDBs are not bound to a single client. Any producer can send messages to the destination the MDB listens on; MDBs are fully anonymous from the sender's perspective.
• D (retain data between calls) - MDBs are stateless. Like stateless session beans, they hold no conversational state between invocations; each onMessage() call is independent.

Memory tip: Think of an MDB as a stateless session bean that listens instead of waits - it shares the stateless, transaction-capable nature of SLSBs, but fires asynchronously from a JMS destination rather than being called directly by a client.

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