This document provides an introduction to the Java Connector Architecture (JCA) and Message-Driven Beans (MDBs). It explains that JCA enables integration between systems and is the base for Java EE servers. It also outlines how MDBs are used to listen for inbound messages from JCA resource adapters. Programming with JCA often involves using provided resource adapters to manage connections and transactions. Message listeners are implemented with MDBs rather than session beans. Payara Micro uses JCA adapters to connect systems on cloud platforms like Apache Kafka and Amazon SQS.

1. Introduction to
JCA and MDB
HASUNUMA Kenji
GlassFish Users Group Japan
k.hasunuma@coppermine.jp
Twitter: @khasunuma

2. What's JCA?
• JCA (Java Connector Architecture)
brings integration between systems
• JCA is also base of Java EE servers
• Almost Java EE developer have been
used JCA

3. JCA Overview
External
System
(e.g. EIS)
Java EE
Resource
Adapter
(.rar)
Web app.
(.war)
Outbound
Inbound
Java Connector
Architecture (JCA)

4. Contracts (1/2)
since JCA 1.0 (J2EE 1.3)
• Connection management
(Connection pooling)
• Transaction management (w/JTA)
• Security management (w/JAAS)

5. Contracts (2/2)
since JCA 1.5 (J2EE 1.4)
• Life cycle management
• Work management
• Transaction inflow management
• Message inflow management

6. Application
Architecture
ConnectionFactory
EJB
Connection
External
System
getConnection
JNDI lookup
Outbound
Inbound
I/F

7. Application
c.f. JMS
ConnectionFactory
EJB
Connection
JMS
broker
getConnection
JNDI lookup
Outbound
Inbound
JMS

8. Application
c.f. JDBC
DataSource
EJB
Connection
RDBMS
getConnection
JNDI lookup
SQL JDBC

9. Programming w/JCA
• Many cases, JCA resource adapter is
provided by each systems
• Recently JCA is mainly used to
manage message inflow
• In JCA 1.7 (Java EE 7/8), properties
are set by annotations

10. Outbound
@ConnectionFactoryDefinition(
name = "java:comp/env/OutboundConnectionFactory",
interfacename = com.example.jca.OutboundConnectionFactory,
resourceAdapter = "some-rar",
...
)
@Stateless
public class ExampleMessageSender {
@Resource(lookup = "java.comp/env/OutboundConnectionFactory")
OutboundConnectionFactory factory;
public void send(...) {
try (OutboundConnection conn = factory.createConnection()) {
...
} catch (Exception e) {
...
}
}
}

11. Attention
• Session Bean SHOULD NOT be used
to listen messages
• SHOULD use Message Driven Bean
(MDB) to listen messages

12. What's MDB?
• EJB specified for listening messages
• Have a callback method and handle
inbound messages provided by JCA
• MDB adapts both async and sync
communication

13. Inbound
@MessageDriven(
activationConfig = {
@ActivationConfigProperty(propertyName = ..., propertyValue = ...),
...
}
)
public class ExampleMessageListener implements MessageListener {
public void onMessage(Message message) {
...
}
}
Callback method invoked by the Resource Adapter

14. Use case: Payara Micro
• Payara Micro connects other systems
on cloud via JCA adapters;
• Apache Kafka
• MQTT (Mosquitto, etc.)
• Amazon SQS
• Microsoft Azure Service Bus

15. Why MQ?
• System/service requirements are
different each other
• Now various systems/services are
integrated on cloud platforms
• MQ (i.g. Async) often resolves
impedance matching between each
systems/services

16. JCA is ...
• JCA (Java Connector Architecture)
brings integration between systems
• JCA is also base of Java EE servers,
e.g. JMS, JDBC
• Almost Java EE developer have been
used JCA as JDBC data source

17. Introduction to JCA and MDB
HASUNUMA Kenji
GlassFish Users Group Japan
k.hasunuma@coppermine.jp
Twitter: @khasunuma