JCA

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JCA

• J2EE Connector Architecture
• JCA also called J2C by IBM
• Author Esben P. Graven

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What is JCA?

• A Java standard to access multiple EIS
• By EIS we refer to Applications like CICS, IMS,
  Tandem Pathway, Custom NT Applications etc.
• Based on drivers
• These are called Resource Adapters
• Simple design
• Easy to use
• Easy to develop -)

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Why do we need it ??

• Complements JDBC and JMS
• Non-relational and synchronous (for now)
• Clear analogy to JDBC for NON-RELATIONAL systems
• Avoid the tight coupling using a proprietary
  driver creates
• With a standard available, we can swap either
  source or driver
• Similarity between systems
• Treat disparate/heterogeneous systems as
  homogeneous resources
• Allow for uniform access to heterogeneous
  implementations /protocols
• Create a market for first and third party driver
  developers
• Will generally increase the amount of available
  adapters
• Main target are EAI and general tool support
• Tightly and transparently integrates Transaction
  and Security

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The contents (three parts)

• Common Client Interface (CCI)
• Resembles the coding needed in JDBC to call a
  Stored Procedure
• Has four partsConnection Establishing, Command
  Execution, Result retrieval and Interfaces
  description through metadata
• System Contract
• The SPI for J2EE container to Connection and
  Transactional management and Security
  enforcement
• Resource Adapter (Resembles JDBC driver)
• Implementation of the system contract. Being
  establisment, pool and closing connections,
  besides propagating Security andTransactional
  context

Application server
Container Contract
EJB
CCI API
System Contract
Resource Adapter
Specific API
Mainframe (EIS)
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A detailed picture of components
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Why have both EJB and JCA?

• Thesis 1) Services could also be exposed via
  either proprietary JAVA APIs or JNI on a
  specific platform (e.g. App. Server on OS/390)
• I a) This creates a tight coupling
• II a) Is one way - cross App. server events
  requires Messaging
• III a) - JNI requires App. Server on the given
  platform -JNI do not propagate security and
  transaction context, and proprietary API probably
  will not either
• IV a) Definitely not supportable by tools

• Thesis 2) All implementation will be EJB
• I b) EJB were architected for Business logic.
  Similar discussion could be held on JDBC
• II b) The Ia) and IIa) from above still apply.
  Spaghetti will result
• III b) No PlugnPlay EJBs do not expose similar
  methods, needs mapping
• IV b) Pure EJB will be VERY far into the future.
  If ever (remember Shelf-ware)

Inevitable Result !
Desired Result ?
EJB/APP J2EE server Other shapes
other technology
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Is web services not solving Integration?

• Too loosly coupled
• Web Services provide a uniform standards based
  technique for exposing application functionality
  on the web
• Can not be optimised
• Transactional, Security currently missing
• No Connection pooling
• Costly Marshalling
• UDDI currently not targetfor tool support
• Functional Accessibility
• Which functionality do you wanttoo expose to
  whom - the normalapplication / server challenge
• Internal in app, in the company, on the web

Layers / domains aggregates to each other - they
do NOT shield
B2B domain interaction, unknown /indefinite set
of systems
Web Services
Corporate domain cross application integration,
known/controlled set of systems
EJB
Applicationdevelopment
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Steps in using JCA - if not from a tool

• Establish a JNDI context for your session. User
  name and password are required to access the EIS.
  
• Use the JNDI lookup method to locate the
  ConnectionFactory for the resource adapter.
• Use the ConnectionFactory method getConnection to
  open the connection.
• Use the Connection method createInteraction to
  create a new Interaction instance. All operations
  on the underlying EIS are done through an
  Interaction object.
• Instantiate an object representing the
  InteractionSpec interface.
• Use the ConnectionFactory method getRecordFactory
  to get a reference to the RecordFactory.
• Create Record instances as necessary using the
  appropriate RecordFactory create method, such as
  createIndexedRecord. Be sure to establish whether
  the record is for input, output, or both input
  and output (inout).
• If you are managing your own transaction and
  persistence, begin a transaction so that you can
  recover if a problem occurs.
• Perform the desired operation on the data store.
  The example in this article uses database stored
  procedures to operate on the database. Note that
  the elements in the Record instances need to map
  to the appropriate parameters in the stored
  procedures.
• If you manage your own transaction, commit the
  transaction or rollback if there are errors.
• Close the connection to the EIS

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Code snippet (from JavaWorld)

• Import javax.resource.cci., jaxax.resource.Resour
  ceException
• try
• ConnectionSpec spec new CciConnectionSpec(user,
  password)
• Connection con cf.getConnection(spec)
• Interaction ix con.createInteraction()
• CciInteractionSpec iSpec new
  CciInteractionSpec()
• iSpec.setSchema(user)
• iSpec.setFunctionName("EMPLOYEECOUNT")
• RecordFactory rf cf.getRecordFactory()
• IndexedRecord iRec rf.createIndexedRecord("Inpu
  tRecord")
• Record rec ix.execute(iSpec, iRec)
• Iterator iter ((IndexedRecord)rec).iterator()
• while(iter.hasNext())
• Object obj iter.next()
• if(obj instanceof Integer) count
  ((Integer)obj).intValue()
• con.close()

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Current Limitations

• Application Events
• JCA 1.0 effectively addresses a J2EE application
  client interacting with the external system
  application. The case where an EIS application
  needs to generate an event in or connect to a
  J2EE application server is not handled.
• Asynchronous Work with Applications
• JCA 1.0 tackles interactions with EIS
  applications. It does not handle cases where the
  interactions with the EIS application need to be
  asynchronous.
• Adapter Metadata
• The JCA 1.0 specification does not address
  adapter metadata. A tool that needs to work with
  the JCA adapter does not have a standard way to
  query the adapter about its interactions and
  their expected inputs and outputs.
• Work with XML Based External Systems
• It is becoming more commonplace for external
  systems to expose their functionality in the form
  of an XML based protocol. This common case is
  ignored by the JCA specification and therefore
  different approaches to handling XML based
  external systems are offered by different tool
  vendors and adapter providers.
• CCI as a Mandatory Requirement
• Without making CCI mandatory, tools cannot deal
  with JCA generically.

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A wrong and a right way of INTEGRATION

• With JCA 1.0 communication is one-way and left
  picture is reasonable
• With BEA-JCA or JCA 2.0 communication is
  bi-directional and the right picture is the right
  way

EIS
Meta data repository
Producer
JCA
Producer Consumer
EAI J2EE
EJB
EIS
J C A
J C A
Producer Consumer
Deployed in server to avoid complex code for
transaction/security propagation
EJB
Consumer
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Resources

• "Connect the Enterprise with the JCA," Dirk
  Reinshagen (JavaWorld)
• Part 1. A look at the J2EE Connector Architecture
  (November 2001)
• Part 2. Build your own J2EE Connector
  Architecture adapter (February 2002)
• The JCA page from java.sun.com
  http//java.sun.com/j2ee/connector/
• The Java Community Process's JSR 112 page, from
  which JCA 2.0 will spring http//www.jcp.org/jsr
  /detail/112.jsp