Quick Table of Contents
  1. Table of Contents
  2. Preface
  3. Section 1: Application Design Concepts and Principles
  4. Section 2: Common Architectures
  5. Section 3: Integration and Messaging
  6. Section 4: Business Tiers Technologies
  7. Section 5: Web Tier Technologies
  8. Section 6: Applicability of Java EE Technology
  9. Section 7: Patterns
  10. Section 8: Security

Section 3: Integration and Messaging

Explain possible approaches for communicating with an external system from a Java EE technology-based system given an outline description of those systems and outline the benefits and drawbacks of each approach.

Challenges in integration:

Four methods of communicating integrating applications exist (Enterprise Integration Patterns):
  1. File Transfer: save data to file and share using file system or File Transfer Protocol (FTP).
  2. Shared Database: save data in common database.
  3. Remote Procedure Invocation: expose methods/procedures for remote invocation: RMI, CORBA, SOAP, XML-RPC or REST.
  4. Messaging: connect to common messaging system to exchange data: JMS.

File Transfer

Benefits: simplest integration style, mostly available on all systems
Drawbacks: delivery depends on polls, insecure, fileformat and naming agreements (case sensitivity Windows/UNIX), file management needed (removal, locking, synchronization)

Share

Benefits: easily exported and mounted by remote file systems
Drawbacks: must share same file system or accessible through share, not (externally) allowed by firewalls, not scalable

FTP

Benefits: reliable file transfer method
Drawbacks: FTP service needed, firewall must open port 21

Shared Database

Benefits: database services like locking and transactions, accessible using standard SQL
Drawbacks: must share same database (poor encapsulation), beware of single-point-of-failure

Remote Procedure Invocation

RMI

Benefits: transparant use of objects, JRMP tunneling through HTTP possible
Drawbacks: must share same classes, no support for transactions/sessions, objects must be serializable

CORBA

Benefits: objects, inter-connecting heterogeneous systems, IIOP tunneling through HTTP possible
Drawbacks: slow, no support for transactions/sessions

REST

Benefits: http protocol, allowed by firewall, no class sharing needed, XML
Drawbacks: slow

SOAP and JAX-WS

Benefits: HTTP protocol, allowed by firewall, Java API, no class sharing needed, XML
Drawbacks: slow

Messaging

Benefits: faster delivery than file transfer, better encapsulation, more reliable than remote procedures, service provided by application server, loose coupling, asynchronous communication possible
Drawbacks: extra component/broker to maintain, lack of standards between heterogeneous systems, not suitable for systems that require synchronous communication

JMS

Benefits: transparant communication between heterogeneous systems, broadcasting (publish/subscribe), asynchronous/synchronous, transactional/non-transactional, knows networks are unreliable (retries until delivery), immediate delivery, disconnected operation
Drawbacks: slower than direct communication

Explain typical uses of web services and XML over HTTP as mechanisms to integrate distinct software components.

Reasons to use XML over HTTP:

XML over HTTP is also called Representational State Transfer (REST). XML over HTTP and SOAP reflect the SOA approach. SOAP is not XML over HTTP, but can be tunneled over HTTP. SOAP with Attachments API for Java (SAAJ) can be used for implementation with Java. SOAP is also mentioned in this section, because of the similarities with XML over HTTP.

SOAP

Benefits:

Drawbacks:

REST

Benefits:

Drawbacks:

Explain how JCA and JMS are used to integrate distinct software components as part of an overall Java EE application.

J2EE Connector Architecture (JCA)

For integrating heterogeneous enterprise information systems (EIS). Connector provided by vendor for use in compliant application server, enabling integration by contract. Connector collaborates with application server to provide: transactions, security, and connection management.

Benefits: vendor connectors allow transparant use of their systems, component is loosely coupled, portability, standard interface, secure, transactions, pooling, interface contract
Drawbacks: not all vendors provide connectors, for Java only

Java Message Service (JMS)

JMS is a standard Java API for enterprise messaging systems. It provides asynchronous communication with one ore more other external systems. Vendors can provide JCA compliant JMS-provider connectors.

Two forms of JMS systems:

  1. point-to-point (named queue)
  2. publish-subscribe (durable/undurable topic subscription)

EIS Integration

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