Core J2EE Patterns 2

8/7/2019 Core J2EE Patterns 2

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Patterns & Design Expertise Center

Sun Software Services

Core J2EE Patterns, Frameworks andMicro Architectures

January 2004


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Agenda

Patterns Core J2EE Pattern Catalog Background

J2EE Progressive Refactoring

Pattern Frameworks

Micro Architecture Web Worker Micro Architecture Example

Messaging Micro Architecture Example Q&A


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Architectural Decisions Produce

Varying Results

.Net J2EE


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What Is A Pattern?

Solution to a recurring problem in a context

Context : What is the environment like? Problem : What do I want to do? Solution : How do I do it?


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Patterns are...

Abstractions Discovered, not created

Difficult to see the appropriategranularity

Mined from good designs

Refactoring targets


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Core J2EE Patterns

Core J2EE Patterns are platform patterns. The context is bounded by the J2EE platform Built upon non-platform patterns GoF


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Core J2EE Patterns Book

1

st

Edition June 2001 15 Patterns categorized bytiers: Presentation Business

Integration Lots of Code Samples Design Considerations Bad Practices Refactorings

2nd Edition JavaOne, June 2003 21 patterns Micro-architecture


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Core J2EE Patterns Book

Client TierBrowser, Applets, Applications, Clients

Presentation TierJSP, Servlets, UI Elements

Business TierEJB and Business Objects

Integration Tier

JDBC, JMS, Connectors

Resource TierDatabases, Systems Legacy

J2EE Pattern Catalog

Addresses 3 Tiers


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Pattern Format

Extensibility

Problem Forces

Solution Structure

Interaction

Consequences

Strategies


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Pattern Strategies

Pattern is abstract and a strategy is(more) concrete

Extensibility


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Pattern Relationships


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Presentation-Tier Patterns

Intercepting Filter Front Controller

Composite View

View Helper

Service to Worker

Dispatcher View Context Object

Application Controller

new

new


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Business Tier Patterns Business Delegate

Session Facade

Service Locator

Transfer Object

Composite Entity

Transfer Object Assembler

Value List Handler

Business Object

Application Service new

new


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Integration Patterns

Data Access Object Service Activator

Domain Store

Web Service Broker

new

new


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New Patterns Facts

Patterns represent abstractions emerging fromusing existing patterns in complexapplications and flesh out pattern language(Context Object, Application Controller,

Business Object, etc.). New patterns rely on POJO stereotype

New patterns identify a web container only

scenario Domain Store addresses Transparent

Persistence (JDO and the like)

Updated for J2EE 1.4 and Web Services


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Presentation Tier Patterns Intercepting Filter

Front Controller

Context Object

Application Controller View Helper

Composite View

Service To Worker

Dispatcher View


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Context Object

Problem: You want to avoid using protocol-specific system

information outside of its relevant context

Forces:

You have components and services that need access tosystem information

You want to decouple application components andservices from the protocol specifics of systeminformation

You want to expose only the relevant APIs within acontext


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Context Object

Solution: Use a Context Object to encapsulate state in a

protocol-independent way to be sharedthroughout your application


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Context Object Strategies Request Context Strategies

Request Context Map Strategy

Request Context POJO Strategy

Request Context Validation Strategy

Configuration Context Strategies

JSTL Configuration Strategy

Security Context Strategies

General Context Object Strategies

Context Object Factory Strategy

Context Object Auto-population Strategy


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Problem: You want to centralize and modularize action

and view management

Forces:

You want to reuse action-management andview-management code

You want to improve code modularity andmaintainability

You want dynamic lookup and dispatch to target


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Solution: Use an Application Controller to centralize

retrieval and invocation of request-processingcomponents, such as commands and views.


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Application Controller:Command Handler Strategy


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Business Tier Patterns

Business Delegate Service Locator

Session Facade

Business Object Application Service

Composite Entity

Transfer Object

Transfer Object Assembler

Value List Handler


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Business Object

Problem: You have a conceptual domain model with

business logic and relationships

Forces:

You have a conceptual model containingstructured, interrelated composite objects,complex business logic, validation, rules

You want to centralize business logic and statein an application

You want to increase reusability of businesslogic and avoid duplication of code


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Business Object

Solution: Use Business Objects to separate business data

and logic using an object model


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Application Service

Problem: You want to centralize business logic across

several business-tier components and services

Forces: You want to minimize business logic in service

facades

You have business logic acting on multiple

Business Objects or services You want to encapsulate use case-specific logic

outside of individual Business Objects


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Application Service

Solution: Use an Application Service to centralize and

aggregate behavior to provide a uniform servicelayer


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Integration Tier Patterns

Data Access Object

Service Activator

Domain Store Web Service Broker


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Domain Store

Problem: You want to separate persistence from yourobject model

Forces: You want to avoid putting persistencedetails in your Business Objects

You do not want to use entity beans

Your application might be running in a webcontainer

Your object model uses inheritance andcomplex relationships


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Domain Store

Solution: Use Domain Store to separate persistence from the

object model


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Web Service Broker

Problem: You want to provide access to one or more

services using XML and web protocols

Forces: You want to reuse and expose existing services

to clients

You want to monitor and potentially limit the

usage of exposed services

Your services must be exposed using openstandards


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Web Service Broker

Solution: Use a Web Service Broker to expose and broker

one or more services using XML and webprotocols


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Web Service Broker: Strategies

Custom XML Messaging Strategy

Java Binding Strategy

JAX-RPC Strategy


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Agenda


J2EE Progressive Refactoring Scenarios

Pattern Frameworks Micro Architecture

Web Worker Micro Architecture Example

Messaging Micro Architecture Example Q&A


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J2EE Refactoring

14 Refactorings in the book Presentation Tier:

Hide Presentation Tier specifics from Business

Tier Introduce Synchronizer Token

Business Tier:

Wrap Entities with Session Merge Session Beans


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Hide Presentation Tier specifics...

PresentationComponent

BusinessComponent

HttpServletRequest HttpServletRequest

PresentationTier

BusinessTier


BusinessComponent

HttpServletRequest HttpServletRequest

PresentationTier

BusinessTier


BusinessComponent

HttpServletRequest UserInfo

PresentationTier

BusinessTier


BusinessComponent

HttpServletRequest UserInfo

PresentationTier

BusinessTier


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Introduce Synchronizer Token

DuplicateAllowed

Controller

Presentation

Tier

JSPClient

Request

Duplicate

2

1

2

1

Controller

Presentation

Tier

JSPClient

Request

Duplicate

2

1

2

1

2

1

Controller

Presentation

Tier

JSPClient

Request

Duplicate

2

1

2

1

DuplicateDisallowed

No

Access

TOKENTOKEN


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Wrap Entities With Session

EntityBean

A

EntityBean

B

EntityBean

C

Client

BusinessLogic

TransactionLogic

ClientBusiness

Logic

SessionFacade

EntityBean

A

EntityBean

B

EntityBeanCTransaction Logic:

Bean ManagedorContainer Managed

BusinessTier

BusinessTier

BusinessTier

Client orPresentation

Tier


Tier


Tier


Tier


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Merge Session Beans

BusinessTier

BusinessTier


Tier


Tier


Tier


Tier

BusinessTier

BusinessTier

ClientInteraction

#1

Client

Interaction#2

ClientInteraction

#3

ClientInteraction

#1

Client

Interaction#2

ClientInteraction

#3

Session

Session

Session

Entity

Entity

Entity

Facade

Facade

Entity

Entity

Entity


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Progressive Refactoring Scenarios

Direct Access Introduce DAO

Introduce Application Service

Introduce Service Facade

Introduce Business Objects


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Direct Access

Database

Command

Helper


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Introduce DAO

Database

Command

Helper

DAO


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Introduce Application ServicePOJO Architecture

Database

Command

Helper

DAOApplication

Service


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Introduce Application ServiceEJB Architecture

Command

Business

Delegate

Session

Facade

Helper

Application

Service

DAO


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Design Note: Service Facades

Remote and non-Remote business tier

RemoteFacade

LocalFacade

POJOFacade

SessionFacade

ServiceFacade


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Introduce Service FacadeNon-Remote Business Tier

Service Facade >>Local Facade >>

Local Session Bean | POJO

Command

Service

Facade

Helper

DAO


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Introduce Service FacadeRemote Business Tier

PhysicalBoundary

Service Facade >>Remote Facade >>

Remote Session Bean

Command

Business

Delegate

Service

Facade

Helper

DAO


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Introduce Business Objects

Command

Business

Delegate

Session

Facade

Business

Object

Domain

Store

Helper

Application

Service

DAO


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Agenda





Messaging Micro Architecture Example

Q&A


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Pattern Framework

Set of cooperating patterns Targeting macro problem

Basis for pattern driven design


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Pattern Realization

Realizing patterns to code


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Agenda





Messaging Micro Architecture Example

Q&A


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Micro Architectures

Micro-architectures are building blocks for designingapplications

They represent a higher level of abstraction than theindividual patterns described in the catalog, and areexpressed by a combination of patterns to solve aproblem

Micro-architecture is a prescriptive design leveragingpatterns to solve a larger problem, such as designing asubsystem

Micro-Architectures:

WebWorker Micro Architecture

Messaging Micro Architecture


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Micro Architectures


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Web Worker Micro Architecture Problem:

How do you integrate a J2EE application and a workflowsystem and have the workflow system direct users to theappropriate web page

User 1 User 2 User 3

J2EE

Use Case 1

Page

Logic

Use Case 2

Page

Logic

Use Case 3

Page

Logic

Workflow


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Hire Employee Workflow

i l ll b i


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Hire Employee Collaborationwith Adapters


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i


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Work Adapter Class Diagram



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Messaging Micro Architecture

Messaging >> Async, Web Services

Problem:

How do you provide async, doc-based webservices in J2EE

How do you orchestrate these web services

h i


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Async WS OrchestrationWith J2EE

Invoke

Async Reply(sometime later)Business

Process

Orchestration

(BPEL)

J2EE

WebService

J2EE

WebService

J2EE

WebService

Shi i l


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Shipping Example

Shi i E l


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Shipping Example

Shipper Transporter

A W b S i O h t ti


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Async Web Service Orchestration

Shipping Company contracts Transportersto ship products

Client Web AppOrchestration

Server

Transport 1

Transport 2

Transport 3

Micro ArchitectureMicro Architecture

Bid Request

Bid

Mi A hit t d f P tt


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Micro Architecture composed of Patterns

ContextObject

InterceptingFilter

Web ServiceBroker

ApplicationController

TransporterMessage Context

Message Handler

Service Endpoint, Broker/Mediator, Validation

Routing

ServiceActivator

OrchestrationServer

ApplicationService

Service

W b S i B k


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Web Service Broker

G t Bid I t ti E Ch t


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Get Bids Interaction Eye-Chart

G t Bid I t ti P t 1


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Get Bids Interaction Part 1Transporter

Web Service

Get Bids Interaction Part 2


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Get Bids Interaction Part 2

Create Bid Interaction E e Chart


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Create Bid Interaction Eye-Chart

Create Bid Interaction Part 1


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Create Bid Interaction Part 1Bid App



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Bid App


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ACE: Design To Deplo Ser ice


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ACE: Design To Deploy Service Rapid intuitive design of enterprise

applications

Focus on design rather than coding

Builds upon best practices, patternsand frameworks

Fewer resources, faster development

Automated deployment

DASL S ifi ti L


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DASL: Specification Language

ACE uses a high level domain

modeling language called DASL

DASL is used to specify:

Business Objects, relationships

Core reusable business logic

User interaction

Transactions and Persistence

DASL G hi t l


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DASL: Graphic tools

Summary


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Summary Patterns are great! Use them effectively to improve

software quality

Build New Architecture

Analyse / understand existing Architecture

Refactor Avoid re-inventing the wheel

Promote design re-use

Increase developer productivity, communication

Micro Architectures leverage patterns

Large and growing community around patterns

Stay Connected:


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Stay Connected:

Check out CJP:

http://www.corej2eepatterns.com

Subscribe:

http://archives.java.sun/j2eepatterns-interest.html

Write to us:

[email protected]

Java.Net Patterns Community


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[email protected] January 2004

Thanks!

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Core J2EE Patterns 2