Blog

Understanding JCA Outbound resource adapter

Posted by Kylin Soong on Oct 20, 2015 categorized as javaee

JCA(Java EE Connector Architecture) eatures three different types of resource adapters: Outbound, Inbound, Bi-directional, the Outbound resource adapter allows the application to communicate to the Enterprise Information System (EIS). A typical example, define datasource(-ds.xml) connect to Database(Oracle, Mysql) in WildFly/JBoss container is base on JCA Outbound resource adapter. This article we will dive into the details of JCA Outbound resource adapter.

Architecture

As below figure, the Java Connector Architecture specification consists of a number of outbound components:

JCA outbound

Application - The application uses the

  • ConnectionFactory: Used to create a connection. In WildFly/JBoss, the connection factory is looked up by JNDI. the main methods defined in javax.resource.cci.ConnectionFactory including:
public Connection getConnection() throws ResourceException;
public Connection getConnection(ConnectionSpec properties throws ResourceException;
  • Connection: The connection contains the Enterprise Information System (EIS) specific operations, and use to operate/interact with EIS.

Application Server - Like many other JEE specifications, Connection Manager and Connection Event Listener in JCA are for vendor, in WildFly/JBoss, IronJacamar(http://www.ironjacamar.org/) used to implement these api definition, it play a role as Application Server.

  • ConnectionManager: The connection manager handles all managed connections in regards to pooling, transaction and security. The key method of javax.resource.spi.ConnectionManager is
public Object allocateConnection(ManagedConnectionFactory mcf, ConnectionRequestInfo cxRequestInfo) throws ResourceException;

this method gets called by the resource adapter’s connection factory instance. This lets connection factory instance (provided by the resource adapter) pass a connection request to the ConnectionManager instance.

  • ConnectionEventListener: The connection event listener allows the connection manager to know the status of each managed connection. The javax.resource.spi.ConnectionEventListener extends java.util.EventListener and provide the following methods:
public void connectionClosed(ConnectionEvent event);
public void localTransactionStarted(ConnectionEvent event);
public void localTransactionCommitted(ConnectionEvent event);
public void localTransactionRolledback(ConnectionEvent event);
public void connectionErrorOccurred(ConnectionEvent event);

Resource Adapter - Usually, this component are plugable, it can add to JEE container like WildFly/JBoss as a plugin. To develop a Resource Adapter, 4 interfaces need to implement, javax.resource.cci.ConnectionFactory and javax.resource.cci.Connection which we already refered in above. javax.resource.spi.ManagedConnectionFactory and javax.resource.spi.ManagedConnection which we will introduce below.

  • ManagedConnectionFactory: Use to create both javax.resource.cci.ConnectionFactory and javax.resource.spi.ManagedConnection, the main methods it defined including:
public Object createConnectionFactory(ConnectionManager cxManager) throws ResourceException;
public Object createConnectionFactory() throws ResourceException;
public ManagedConnection createManagedConnection(Subject subject, ConnectionRequestInfo cxRequestInfo) throws ResourceException;
public ManagedConnection matchManagedConnections(Set connectionSet, Subject subject, ConnectionRequestInfo  cxRequestInfo) throws ResourceException;
  • ManagedConnection: The managed connection represents a physical connection to the target Enterprise Information System (EIS). The managed connection notifies the application server of events such as connection closed and connection error.