j 2 ee best practices

7/31/2019 j 2 Ee Best Practices

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Push your development furtherSunTechDays

J2EE Best Practices usingReal-life Examples.

Carol McDonaldTechnology Evangelist

[email protected]

Sun Tech Days


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eBay Architecture: How to Go

Microsoft IIS

eBayISAPI.dll

MSXML

to here?From there

J2EE ContainerWeb Container

Presentation Tier

EJB Container

Business Tier

Integration Tier

Services

Configur

ation

Logging

Secur

ity

Monolithic Proprietary

Layered Loosely coupled Modular Standards based


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What Is Needed

Learning the technology is

not enough

Industry best practices

Proven solutions

How to avoid bad practices?

Experience and expertise


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Som e Web T ier

Best Prac t ic esand Pat t erns


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Layering

EJB Session Beans

Client Application

Data Transfer Objects

i.e. Managed Entity Values

Business Logic Layer

Service Layer

Domain Layer

Managed Entities

Presentation Layer

Network

ManagedEntities


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Push your development furtherSunTechDaysRationale for Layers

More flexible, extensible:

Presentation Layers

Frequent changes, designed to be flexible

Business Services

Implement use-cases Public interface, resource access

Should remain valid for changes in presentationand data store

Data Layers

Fewer changes, designed to optimize data access


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Layered View (cont.)

Layered View helps to:

Clearly divide responsibilities Decouple business logic completely

Provide a common place for pre-processing and post-processing ofrequests and responses (like logging,translations, transformations, etc.)

Expose a web service interface toexisting business logic


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Push your development furtherSunTechDaysModel View Controller

Client

Problem Domain Services

Enterprise Resources

Controller View

Persistence Layer

Model Layer

Presentation Layer

Thin Browser

HTTP Request HTML Page

Model=business data and rules

View = view ofmodel,presents the user interface

Controllermediates theirinteractions


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Web Tier: Problem

1. Request

???

2. Response

No centralized access pointfor presentation request handling

Web Server

Common RequestProcessingLogic?

Duplicate common

logic in ViewsClient

View

View

View


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Service to Worker

CommandFactory

FrontController

Dispatcher

CommandHelper

1. Request

3. Parse Request

2. Common logic

5. Create

6. Execute

8. Dispatch7. Business

logic

4. Get cmd

ViewHelper

DataBean

View

Client

Servlet

JSP

Java Objects

10. Response

9. Get Data


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Use an MVC Framework

Faster, easier development of

Request processing

Response generation

Use Struts, JSF, Sun ONE ... application framework


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Struts Framework

View Controller Model

JSPw/Struts

Form Bean

ActionServlet

Action

Bean

Java

Bean

Struts-config.xml

SessionBean(s)

EntityBean(s)

Browser

Database


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Push your development furtherSunTechDaysStruts and Core J2EE Patterns

Client

ActionServlet

Action

ActionForward

ActionForm

JSP View

Front Controller Model

View HelperView

ActionMapping

(xml)

ServiceInterface

BusinessService

BusinessDelegate

ServiceLocator

Command

Dispatcher

Response

Request

Uses


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Ebay.com: Presentation Tier

Request

Response

Client

Business

ServiceCommand

Request Handler

Intercepting

Filter

Front

Controller

Navigator Dispatcher

Navigation and Dispatch

View Processor

TransformerHelper

InterceptingFilter

ViewProcessor

Business

Delegate

ServiceLocator

XML

XSLCore J2EE

Pattern

Strategy

Service Interface


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Cache for Performance

Some things can be cached and shared (singleton):

InitialContext object

Anything retrieved from JNDI, EJB Home interfaces

Repeated lookups can be expensive! Use Service LocatorPattern

Some things are cached by individual clients(session):

Cache search results when you are only displaying a few

at a time (non-transactional data) JDBC CachedRowSet

Value List Pattern


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Service Locator Pattern

Use the Service Locator Pattern toCache references obtained by JNDI lookups

(ejb references, datasources, jms)

Repeated lookups can be expensive!


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Push your development furtherSunTechDaysBusiness Delegate

Client

independent fromejb tier

Ejb detailshidden

Mock objects can

be used to testclient w/o ejb tier


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Tips for Servlets

Servlets are Multithreaded

Avoid use of shared modified class variables

Synchronize only small blocks in code

Remove servlet sessions when they

are no longer needed: In logoff call session.invalidate()

On client side, dont access your EJBsdirectly, use service locator withbusiness delegate


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Servlet Tips

DO use high performance J2EE

design patterns MVC, Service Locator

DONT hold resources explicitlyfree them

DONT intensively processimmutable objects.


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Tips for JSPs

Avoid scriptlets in JSP

Use JSTL (JSP 2.0 Standard Tag Libraries):

Pass data to JSP in Servlet request notsession

If JSP does not use the HTTP session

Use to preventHTTP Sessions from being automatically created


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Som e EJ B Tier

Best Prac t ic es

and Pat t erns


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Push your development furtherSunTechDaysDo you need EJBs?

Do you need declarativetransactional support?

Do you need to distribute yourbusiness logic?

Do you need JMS, JAX-RPC, RMI?

Do you need to support multipleclient types?

Do you need method-level securityon your objects?

Do you need a standards-basedarchitecture?


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Architecting Applications

Functional requirements captured

via use-cases

Use-cases implemented using MVC &

Command design patterns Implement Business Logic as a Service


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Use case realization

View Items

Any User

View Items

Any user can view any itemsavailable for bidding or sale


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AssembleData

Use case

Biz logic

Convert toBiz Command

CentralizeRequest Hndlg

View Items Design Requirements

RetrieveData

Item/Auctionspecificbiz logic


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ApplicationController

FrontController

SessionFacade

BusinessDelegate

View Items Design

ServiceLocator

ApplicationService

TransferObject

Assembler

TransferObject

Value ListHandler

Data AccessObject


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WEB Tier

PresentationBusiness Logic &

Messaging Fabric

Data Integration

& Persistence

Core Application Design Patterns

FRONT

CONTROLLERVIEW

COMMAND

object

Request Response

MODEL

DATA

TRANSFER

OBJECT

BUSINESS

SERVICE

FACADE

Value List Handler

DATA

ACCESS

OBJECT

DATA

TRANSFER

OBJECT

SessionEJB

Servlet

JSP

Java Objects

Session EJB


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Data Transfer Object

A lot of network traffic

Reduced network traffic

with Data Transfer Object

ClientObject CustomerEntityBean CustomerInfoEntityBean

Before

ClientObject

CustomerEntityBean

CustomerInfoEntityBean

After

GetCustomerInfo()

GetCustomerInfo()

GetCity()

GetState()

GetZipCode()

GetCity()

GetState()

GetZipCode()

Networkboundary

Networkboundary

Create()

Create()


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Value List Handler

For querying, filtering, anddisplaying large amountsof data:

Value List Handler handlesthe search, caches resultsand provides a filterableand traversable result set

Client ValueListHandler

ValueList ValueObject

DataAccessObject

Interface

ValueListiterator

+GetSize():int+getCurrentElement():Object+getPreviousElements(count:int):List+getNextElements(count:int):List+resetIndex():void


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Sequence Diagram

1: Create

2: Execute Search

3: Get Next

4: Get Previous

5: Get Current

6: Get Size

3.2: Return Sub-list

4.2: Return Sub-list

5.2: Return Value Object

6.2: Return Size

2.1: Execute Search

2.1.2: Return Value List

3.1: Get Sub-list

4.1: Get Sub-list

5.1: Get Current

6.1: Get Size

2.1.1: Create

Client

ValueListHandler

DataAccessObject

ValueList

ValueListiterator


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Data Access Object

BusinessObject DataAccessObject DataSource

ValueObject

Uses Encapsulates

creates/uses

obtains/modifies


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eBay.com: Business Tier

Data

Source

Dispatch

Application

Controller

BusinessLogic/Data

TransferObject

DAO

ApplicationService

Persistence

ContextObject

TransferObject

Assembler

BusinessObject

ValueList

Handler

Domain

Store

Core J2EE

Pattern

Strategy

Command


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Direct Entity Bean access results in excessive network overhead

and multiple transactions

Dont:

EJB

Network

Client

Direct Bean Access

Do:

EJBNetwork

Client

Facade

Session Facade pattern


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Push your development furtherSunTechDaysSession Facade pattern

EntityBean 1

EntityBean 2

JavaObject

DataAccess

Object 2

Data

AccessObject 1

1. doThis(...)

2. getData()

3. process

2. getData()

Session Bean

Entity Bean

Plain Java Object

Use the Session Facade:

To reduce network overhead

To group related updates into transactions

SessionFacade

Client

SessionBean


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Push your development furtherSunTechDaysContainer Managed Transactions


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EJBclient

EJBObject

Network

Local vs. Remote Interfaces

Pass by Value:

Serialize/deserializemethod parameters

Pass by Reference:

Better performance

Remote Interfaces Local Interfaces

EJBclient

EJBObject


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Session EJB tips

Stateless session beans give best

performance, watch use of stateful Remove stateful session beans to

reduce unnecessary passivation

Limit size of objects stored in session

beans (performance for passivation)


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S


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Design Patterns Summary

Value Object Exchanges data J2EE tiers

Service Locator Holds results of JNDI lookups

Value List Handler Handles larger result sets from database queries

Business Delegate Simplifies the coupling between the J2EE Web &

EJB tiers

Session Facade Provide business logic functionality

Data Access Object Isolation layer for interfaces to a systems

resources

Etc. www.sun.com/developer/blueprints/.

S


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Pers is tence

Opt ions

S


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Data Access in J2EE

Formal object-oriented model

EJB container managed persistence Great choice for representing existing databases

JDO

Tabular access

Plain JDBC

JDBC RowSets

Good choice for ease of development Non-relational, non-object data access

Use J2EE Connectors

Sun


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BMP vs. CMP

CMPBean

EJB Container

BMPBean

EJB Container

JDBC

DriverJDBC

SQLJ

SQL

JDBC

Driver

SQL

PersistenceManager

BeanState

Database

BeanState

Database

JDBC

SQLJ

1) Bean provider manages State and Data consistency

2) Bean provider handles relationships and OR Mapping

1) Container manages State and Data consistency

2) Container/PM provides concurrency, relationships and OR Mapping

Sun

O


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Use BMP or DAO for

Dealing with legacy database and/or

other persistence store Previously written complex application

Connector driven data stores, EIS Efficient execution of complicated queries

Bulk updates

Complex joins

Aggregates

Sun

E i B Ti


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Entity Bean Tips

Do not use EJB entity beans for batchloading or queries that return large result

sets. Use Data Access Objetsencapsulating JDBC

Use CMP rather than BMP entity beanwhen possible

Do not call EJB entity bean get & setmethods from client

Wrap with session beans to provide course

grain access and single transaction context

Sun

JDBC Ti


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JDBC Tips

Select a certified, high performancetype 2 JDBC driver

Tune connection pool size Close resources as soon as youre done

with them (in finally)

E.g. Statements, Connections, ResultSets

Use JDBCs PreparedStatement instead

of Statement when possible Turn off Auto-Commit

Group updates into a transaction

Sun

JDBC Ti


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JDBC Tips

JDBC Supports a number of highperformance optimization techniques

Typically you can optimize JDBCperformance by:

Using CachedRowSets

Using setDefaultRowPrefetch

Using statically bound column types Using update batching

Using statement caching

Sun

D t b P f


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Database Performance

Common performance bottleneck

Typical problems: Inefficient queries - sending SQL data

that asks the database to do more work

than necessary Excessive querying - efficient queries

called too frequently

Large Data Sets - processing large setsof data in ResultSets

fSun

CMP 2 0 E tit B


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CMP 2.0 Entity Beans

java.io.Serializable

CMP Entity Bean subclass

(Contains persistence logic)

CMP Entity Bean abstract class(Contains data handling logic)

javax.ejb.EntityBean

javax.ejb.EnterpriseBean

You (bean provider)write this code.

Container provides

this class.

Entity Bean is now anabstract class,container extends it

h d l f hSun

C t i M d R l ti hi


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Container Managed Relationships

1

1

1

M M

1

Local Entity

Local Entity

OrderBean Product

Address

Shipping Address

LineItems ProductOrdered

Client

Order

OrderHome LineItem

EJB TierLocal Entity

P h d l f hSun

A f CMP d CMR


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Push your development further TechDaysAccessors for CMP and CMR

public abstract class OrderBeanimplements EntityBean {

private EntityContext context;

//access methods for cmp fields

public abstract String getOrderID(); //primary keypublic abstract void setOrderID(String id);. . .

//access methods for cmr fields

public abstract Collection getLineItems();public abstract void setLineItems(Collection lineItems);

P h d l t f thSun

CMP 2 0 Relationship Handling


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Push your development further TechDaysCMP 2.0 Relationship Handling

In CMP 2.0, you declare fields and

relationships in deployment descriptor Container generates all the necessary code

... define your enterprise beans ...

elements represent container-managedpersistent fields

... define EJB relationships ...

P h d l t f thSun

EJB QL Example


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Push your development further TechDays

EJB QL Example

Find orders for a specific product:

SELECT OBJECT(o)

FROMOrders o, IN(o.lineItems)lWHERE l.product.name = ?1

XML:

findByProduct

LocalHome SELECT OBJECT(o) FROM Order o,IN (o.lineItems) l WHERE I.product.name= ?1

P h d l t f thSun

Advantages of CMP 2 0


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Rich modeling capability on relationships- container manages the relationships,

not you! Referential integrity

Cardinality Cascading delete

Freedom from maintaining interactionswith the data store

EJB Query Language (EJB QL)

Portable code

Advantages of CMP 2.0for developer

P h d l t f thSun


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CMP

P sh o r de elopment f rtherSun

Advantages of CMP 2 0


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Optimization is possible becausepersistent fields are only accessible

via get and set methods Lazy loading

Dirty checking Optimistic locking

Optimization is possible in query

operation

Because Query is defined in deployment

descriptor via EJB QL

Advantages of CMP 2.0for Container

Push your development furtherSunT h

CMP Optimizations


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CMP Optimizations

Aggressive Loading

Loading fields relationships and fields ofchildren in the same query

Lazy Loading

Deferring loading of any data until it is accessed

Dirty Writes

Only update data which has been changedin the database


CMP: Standard Vs


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Standard features

Declarative specification of:

Persistent attributes, abstract schema, relationships,queries for finder/select methods(via EJBQL),

transactional attributes

Vendor specific

O/R mapping, concurrency and consistencysemantics, caching semantics, performanceand usability

CMP: Standard Vs.Vendor Specific Features


Pessimistic Locking


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Pessimistic Locking

Time State inDatabase

1000

200020002000

3000 3000

C2C1

The row is locked for the duration of the transaction

1000


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Push your development furtherSunTech

Usage Guidelines


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Usage Guidelines

Pessimistic

Serialized access Recommended for

beans where

conflicts are boundto happen

Scalability dependson DB and Appserver lockinggranularity

Optimistic

Concurrentaccess

Large-scale

deployment Requires collision

and exceptionhandling

Choices forconflict detection


Data and Caching


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Data and Caching

Static data Keep a local copy, hang on to it in memory,

dont worry about being stale

Near static data

Keep a local copy, hang on to it in memory,

lazily check for updates

Dynamic data

Work on local copy, cache carefully, useoptimistic locking

Hot data

Pessimistic locking


Database Isolation Modes


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Database Isolation Modes

Read Uncommitted Dirty reads, non-repeatable reads and

phantom reads can occur

Read Committed Dirty reads are prevented; non-

repeatable reads and phantom reads

can occur Repeatable Read

Dirty reads and non-repeatable reads

are prevented; phantom reads canoccur

Serializable Dirty reads, non-repeatable reads and

phantom reads are prevented


Entity Bean Caching


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Entity Bean Caching

Commit Option A At the end of the transaction, the instance stays

ready and the instance state is valid Commit Option B

At the end of the transaction, the instance stays

ready but the instance state is NOT valid Commit Option C

At the end of the transaction, neither the instance

nor its state is valid Best Option: Check your app server


Transaction Do's


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Transaction Do s

Do use READ_COMMITTED withOptimistic locking as much as possible

Do use Optimistic locking only andSERIALIZABLE if required.


Transaction Don'ts


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Transaction Don ts

Don't use SERIALIZABLE if itcan be avoided

Don't use pessimistic locks if itcan be avoided


EJB Summary


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EJB Summary

EJB Container Services use appropriately for: Distributedtransactionmanagement

Robust security service

Resource management (threads, sockets, database connections)

Container persistence

Remote accessibility

Dispatch and life-cycle management.

Use EJB 2.0 local interfaces for performance

improvements When running in same JVM.



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Push your development furtherDays

J2EE

Per formanceTips


Tune App Server


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Tune App Server

Execute threads that requests run on

JDBC connection pools

JDBC prepared statement cache size

Correct settings depend on application


Tune Key Container Parameters


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Tune Key Container Parameters

Session timeouts

Stateful session bean and entity beancache

Cache = EJB instances with state

Stateless session and entity bean pools

Pool = EJB instances with no assigned state

Transaction isolation level


Entity Bean


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Push your development furtherDaysEntity Bean

Does

not exist

pooled

ready

NewInstance()

setEntityContext() unsetEntityContext()

ejbCreate()

ejbPostCreate()ejbRemove()

business method

ejbStore()ejbLoad()

ejbFind()

ejbActivate() ejbPassivate()

EjbActivate()

EJB

Instance

EJB

Object

EJBInstance

Bean pool sizeBean cache size


Stateful Session Bean


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us you de elop e t u t eDaysStateful Session Bean

Method-ready

ejbRemove()

business method

does not

exist

1) newInstance()

2) setSessioncontext()

3)ejbCreate() ejbPassivate()

EjbActivate()

passiveEJBInstance

EJB

Object

Bean cache sizeSession time out


Stateless Session Bean


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y pDays

EJBInstance

method-ready

pool

EjbRemove()

Business method

does not

exist

1) newInstance()

2) setSessioncontext()

3)ejbCreate()

Stateless Session Beanand Message Driven Bean

Bean pool size

Push your development furtherSunTechD

Manage Expensive Resources


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y pDaysManage Expensive Resources

Cache EJB homes

Cache data sources Minimize use of HTTP sessions

Release database connections Removeunused stateful session beans

Use local Interfaces


Design Patterns can


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y pDays

Session Facades

Service Locator

Value List Handler Data Transfer Object

Design Patterns canSignificantly Help Performance



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y pDays

Per formance

Test ing


Performance Tips Summary


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y pDays

Performance Tips Summary

Tips for better performance Tune app server and infrastructure

Leverage proven design patterns Design coarse grain EJB interfaces: Value Object

Reduce JNDI look-ups: service locator Use session bean wrappers: session facade

Database access Use JDBC for:

Batch loading: session bean or message bean

Large result sets: value list handler Use CMPrather than BMP Entity Beans Use right isolation level and database

transactional control (locking)



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Days

JMS,

Messaging,

Web Serv ic esJ 2EE Best

Prac t i ces


JMS


80/102

Days

Use JMS forloosely coupledapplications that need reliable,scalabledocument orientedmessage exchange

Including Message-DrivenBeans and JMS in your J2EEapplication can greatly increase

performance, robustness, andefficiency


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Publish and Subscribe


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Days

Traders/Brokers

Price Change

Topic

Example: Stock Price Changes


Message-Driven Bean


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Daysg

Container

Destin-

ation

Consumer

Msg-

drivenBean

Instances

High Scalability, High Throughput

MDB instances are pooled by the container

Allow forasynchronous concurrent message consumptionfrom the same destination

JMSProvider

Container

Queue

MDB

Consumer

MDB

Instances

Msg-DrivenBean Class

Concurrent Asynchronous Processing


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MDB Facade Pattern


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Days

EJBTier

Relationship

Reference

AddressEntity

Order

ApprovalMDB

LineItemEntity

Mailer MDB

CardEntity

AsynchronousMessageDelivery

PurchaseOrder Entity

1:m


XML Message Facade


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yg

EJB Architectural Pattern

ClientJMS

Queues

MessageDrivenBean

Stateless

Session

EJB

Entity

Bean

XML Messaging Facade

Asynchronous Synchronous

Example implementation of XML interaction modelon top of Java interaction model

Entity

Bean

Entity

Bean

XMLValue

ObjectsJavaValueObjects


MDBs Container


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y

Order

Bean

InventoryManagement

Bean

Mail

MessageDrivenBean

JMS Topics

Publish/subscribe

ProcessOrder

ProcureInventory

PurchaseOrder

Queue

TRANSACTION

Managed Transactions


Use JMS for


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y

Designing for event-driven interactions:

Not interface-driven

Loose coupling among participants

Asynchronous communication model

Reliable communication or many to manycommunication model

Serves as an asynchronous facade to asubsystem or an application

Event-Driven Interactions


MDB Join Pattern


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Join pattern MDB collects different messages

Stores to same set of entity beans

SetupOffice

HumanResources

ReserveOffice

ReserveEquipment

Add toPayroll

Happy New Hire

NewHire

Assigned Office

Equipment Info

Furnished Office

Paycheck


Example Problem Tracking


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ExistingSynchronousClient

Access

ProblemSolver

Problem

Rep

Company

EJB Tier

A Session EJB provides thebusiness logic for the Customersor help desk to synchronouslyenter Problem data, or search forsimilar problems

Entity EJBs provide the businesslogic for accessing/updating thedomain Data objects


Extension Solution Internal View


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RemoteHelp DeskNew

Problem

MonthlyReport

ExistingSynchronousClient

Access

ReportRequest

ProblemHandler

ReportGenerator

ProblemSolver

Problem

Rep

Company

EJB Tier


JMS Do's & Don'ts


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Do watch message size

Do only use XML when necessary(lower performance)

Do only use reliable messaging whennecessary (lower performance)


Tips for XML messaging


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Inside your Application dont overuse XML Parsing and processing can cause a performance

hit Use XML for messages between

systems

Within a system just use data objects

Convert the data from XML into a Javaclass as soon as possible Can use JAXB for this

Use XML mainly for transmission


Key Web Service Guidelines


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Structure application in two layers Interaction layer and processing layer

Interaction layer Interface to clients

Receive requests and perform

required translations andtransformations

Delegate request to processing

layer for processing Respond to clients

ServiceClient

Interaction

Layer

ProcessingLayer


Layered View


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Processing layer Process request

Apply business logic

Integrate with EIS

Interact with peers

Layered view helps to: Clearly divide responsibilities

Decouple business logic completely

Expose a web service interface to existingbusiness logic


RPC Simple Client/Service


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Common approaches:

SOAP using JAX-RPC (WSDL) Features:

Stateless and conversation-less Industry examples:

Amazon, Fedex, eBay, credit check,

get Weather, get Stock price

Client ServiceRequest

Response


RPC Style Web Services


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RDBMSEAI ResourceAdapters

LegacySystems

DataBase

ERP

Business

Services

Web

Container

Domain

Objects

WebComponent

EntityEJB

StatelessSession

EJB

DAO

Connector

MDB

JAX-RPC


Collaborative B2B Web Services


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Features: Orchestration, Choreography, Collaboration

Business process defines Message sequence

Asynchronous document exchange

Industry examples:

OTA, Sabre, GM

Business

Process

Service

Service

Service

Service


Document Style Web Services


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RDBMSEAI ResourceAdapters

LegacySystems

DataBase

ERP

BusinessServices

SoapHandler

DomainObjects

EntityEJB

MDB DAO

Connector

MDB

Soap

MessageServices

EntityEJB

MDB

SessionEJB

SessionEJB

BusinessDocument

MsgServiceHandler


JBI and J2EE


100/102

208 Binding

SPI

208 Machine

SPI

Binding Framework

WS-I EDI VAN

SOAP EIS resource AS1/AS2

EJB

Module

(EJB API)

JBI BP Module

(WS-BPEL and

WSDL APIs)

Normalized Message Bus

Web App.

Module

(JSP/Servlet

API)

JMS

MQ

JCA


Sun ONE BPM, Messaging & J2EE


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XML/SOAP/JMS

Business Process Engine

Data

XML Proxy

Rule

Base

(XSLT)

XSLTEngine

MessageBroker

Adapter

C++

Inventory

Rule

Base

(XSLT)

XSLT

Engine

Message

Broker

JMSProvider

MDBServlets

EJBJ2EE

SOAP

WebService



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Carol McDonaldTechnology Evangelist

[email protected]

Sun Tech Days

j 2 ee best practices

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