Support de cours J2EE en pdf

(1)

Real-life Examples.

Carol McDonald

Technology Evangelist

carol.mcdonald@sun.com

(2)

Microsoft IIS eBayISAPI.dll MSXML

… to here?

From there…

J2EE™ Container Web Container Presentation Tier EJB™ Container Business Tier Integration Tier Services Configuration Logging Securit y  _Monolithic  Proprietary  _Layered  Loosely coupled  _Modular  _{Standards based}

(3)



_{Learning the technology is}

not enough



_{Industry best practices}



_{Proven solutions}



_{How to avoid bad practices?}



_{Experience and expertise}

(4)

 _{Platform Patterns for J2EE}™

architecture

 _{Based on our experience}

 _{Collection of best practices for J2EE}™

platform

 _J2EE™

architecture refactorings and bad practices

 _{Create a common vocabulary}

 _{Proven solutions}

 Reuse design

 Robust and scalable architecture

 Improve quality

(5)

Some Web Tier

Best Practices

(6)

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 Managed Entities

(7)

 _{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 presentation}

and data store

 _{Data Layers}

(8)



_{Layered View helps to:}

 _{Clearly divide responsibilities}

 _{Decouple business logic completely}

 _{Provide a common “place” for}

pre-processing and post-pre-processing of

requests and responses (like logging, translations, transformations, etc.)

 _{Expose a web service interface to}

(9)

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 of}_model, _{presents the user interface}  Controller mediates their interactions

(10)

1. Request

???

2. Response

No centralized access point

for presentation request handling

Web Server

Common Request Processing Logic? Duplicate common logic in Views Client View View View

(11)

Command Factory Front Controller Dispatcher Command Helper 1. Request 3. Parse Request 2. Common logic 5. Create 6. Execute 8. Dispatch 7. Business logic 4. Get cmd View Helper Data Bean View Client Servlet JSP Java™ Objects 10. Response 9. Get Data

(12)

 _{Faster, easier development of}

 Request processing

 Response generation

(13)

View Controller Model JSP w/Struts Form Bean Action Servlet Action Bean Java Bean Struts-config.xml Session Bean(s) Entity Bean(s) Browser Database

(14)

Client Action Servlet Action Action Forward Action Form JSP View

Front Controller Model

View Helper View Action Mapping (xml) Service Interface Business Service Business Delegate Service Locator Command Dispatcher Response Request Uses

(15)

Request Response Client Business Service Command Request Handler Intercepting Filter Front Controller Navigator Dispatcher

Navigation and Dispatch

View Processor Transformer Helper Intercepting Filter View Processor Business Delegate Service Locator XML XSL Core J2EE Pattern Strategy Service Interface

(16)

 _{Some things can be cached and shared (singleton):}

 InitialContext object

 Anything retrieved from JNDI, EJB Home interfaces

 Repeated lookups can be expensive! Use Service Locator Pattern

 _{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

(17)

Use the Service Locator Pattern to

Cache references obtained by JNDI lookups (ejb references, datasources, jms)

(18)



_Client

independent from

ejb tier



_{Ejb details}

hidden



_{Mock objects can}

be used to test

client w/o ejb tier

(19)



_{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, don’t access your EJBs}

directly, use service locator with

business delegate

(20)



_{DO use high performance J2EE}

design patterns

 _{MVC, Service Locator}



_{DON’T hold resources – explicitly}

free them



_{DON’T intensively process}

(21)



_{Avoid scriptlets in JSP}

 _{Use JSTL (JSP 2.0 Standard Tag Libraries):}

 <c:forEach var="item" values="${cart}">



_{Pass data to JSP in Servlet request not}

session



_{If JSP does not use the HTTP session}

 Use <%page session="false"%> to prevent HTTP Sessions from being automatically created

(22)

Some EJB Tier

Best Practices

(23)



_{Do you need declarative}

transactional support?



_{Do you need to distribute your}

business logic?



_{Do you need JMS, JAX-RPC, RMI?}



_{Do you need to support multiple}

client types?



_{Do you need method-level security}

on your objects?



_{Do you need a standards-based}

(24)



_{Functional requirements captured}

via use-cases



_{Use-cases implemented using MVC &}

Command design patterns

(25)

View Items

Any User

View Items

Any user can view any items available for bidding or sale

(26)

Assemble Data Use case Biz logic Convert to Biz Command Centralize Request Hndlg Retrieve Data Item/Auction specific biz logic

(27)

Application Controller Front Controller Session Facade Business Delegate Service Locator Application Service Transfer Object Assembler Transfer Object Value List Handler Data Access Object

(28)

WEB Tier

Presentation Business Logic & Messaging Fabric Data Integration & Persistence FRONT CONTROLLER VIEW 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

(29)

A lot of network traffic

Reduced network traffic with Data Transfer Object Client Object Customer EntityBean CustomerInfo EntityBean Before Client Object Customer EntityBean CustomerInfo EntityBean After GetCustomerInfo() GetCustomerInfo() GetCity() GetState() GetZipCode() GetCity() GetState() GetZipCode() Network boundary Network boundary Create() Create()

(30)

 _{For querying, filtering, and}

displaying large amounts of data:

 Value List Handler handles

the search, caches results and provides a filterable and traversable result set

Client ValueListHandler <<List>> ValueList ValueObject DataAccessObject Interface ValueListiterator +GetSize():int +getCurrentElement():Object +getPreviousElements(count:int):List +getNextElements(count:int):List +resetIndex():void

(31)

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

(32)

BusinessObject DataAccessObject DataSource

ValueObject

Uses Encapsulates

creates/uses

(33)

Data Source Dispatch Application Controller Business Logic/Data Transfer Object DAO Application Service Persistence Context Object Transfer Object Assembler Business Object Value List Handler Domain Store Core J2EE Pattern Strategy Command

(34)

Direct Entity Bean access results in excessive network overhead and multiple transactions

Don’t:

EJB

Network

Client

Direct Bean Access

Do: EJB Network Client F a c a d e

(35)

Entity Bean 1 Entity Bean 2 Java™ Object Data Access Object 2 Data Access Object 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}

Session Facade

Client

Session Bean

(36)

(37)

EJB client EJB Object Network Pass by Value: Serialize/deserialize method parameters Pass by Reference: Better performance

Remote Interfaces _{Local Interfaces}

EJB client

EJB Object

(38)



_{Do use session beans as a service facade}

 _{With local interfaces: Faster than remote}

 _{Container managed transactions: calls to}

entity beans within one transaction!



_{DO design fine-grained components}

as Java™ classes



_{DO minimize the number of service calls}

(39)



_{Stateless session beans give best}

performance, watch use of stateful



_{Remove stateful session beans to}

reduce unnecessary passivation

 Bean.remove()



_{Limit size of objects stored in session}

(40)



_{DO NOT store large amount of data}

in Stateful SessionEJB



_{DO NOT access entity EJBs remotely}



_{DO NOT implement fine-grained}

(41)

 _{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.

(42)

Persistence

Options

(43)



_{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}

(44)

CMP Bean EJB Container BMP Bean EJB Container JDBC Driver JDBC SQLJ SQL JDBC Driver SQL Persistence Manager Bean State Database Bean State 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

(45)



_{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}

(46)



_{Do not use EJB entity beans for batch}

loading or queries that return large result

sets. Use Data Access Objets

encapsulating JDBC



_{Use CMP rather than BMP entity bean}

when possible



_{Do not call EJB entity bean get & set}

methods from client

 _{Wrap with session beans to provide course}

(47)



_{Select a certified, high performance}

type 2 JDBC driver



_{Tune connection pool size}



_{Close resources as soon as you’re done}

with them (in finally)

 _{E.g. Statements, Connections, ResultSets…}



_{Use JDBC’s PreparedStatement instead}

of Statement when possible



_{Turn off Auto-Commit}

(48)



_{JDBC Supports a number of high}

performance optimization techniques



_{Typically you can optimize JDBC}

performance by:

 _{Using CachedRowSets}

 _{Using setDefaultRowPrefetch}

 _{Using statically bound column types}

 _{Using update batching}

(49)



_{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 sets}

(50)

<<interface>>

java.io.Serializable

CMP Entity Bean subclass (Contains persistence logic) CMP Entity Bean abstract class

(Contains data handling logic) <<interface>>

javax.ejb.EntityBean

<<interface>>

javax.ejb.EnterpriseBean

You (bean provider) write this code.

Container provides this class.

(51)

1 1 1 M _M 1 Local Entity Local Entity OrderBean Product Address Shipping Address LineItems ProductOrdered Client Order OrderHome _LineItem EJB Tier Local Entity

(52)

public abstract class OrderBean implements EntityBean {

private EntityContext context; //access methods for cmp fields

public abstract String getOrderID(); //primary key

public abstract void setOrderID(String id);

. . .

//access methods for cmr fields

public abstract Collection getLineItems();

(53)



_{In CMP 2.0, you declare fields and}

relationships in deployment descriptor

 _{Container generates all the necessary code}

<ejb-jar>

<enterprise-beans>

... define your enterprise beans ...

<cmp-field> elements represent container-managed persistent fields

</enterprise-beans>

<relationships>

... define EJB relationships ... </relationships>

(54)

Find orders for a specific product:

SELECT OBJECT(o)

FROM Orders o, IN (o.lineItems) l

WHERE l.product.name = ?1

 _XML:

<query>

<query-method>

<method-name>findByProduct</method-name>

<method-intf>LocalHome</method-intf>

</query-method>

<ejb-ql>SELECT OBJECT(o) FROM Order o,IN (o.lineItems) l WHERE I.product.name= ?1</ejbql>

(55)



_{Rich modeling capability on relationships}

- container manages the relationships,

not you!

 _{Referential integrity}

 _Cardinality

 _{Cascading delete}



_{Freedom from maintaining interactions}

with the data store



_{EJB™ Query Language (EJB QL)}



_{Portable code}

(56)

(57)



_{Optimization is possible because}

persistent 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

(58)



_{Aggressive Loading}

 _{Loading fields relationships and fields of}

children in the same query



_{Lazy Loading}

 _{Deferring loading of any data until it is accessed}



_{Dirty Writes}

 _{Only update data which has been changed}

(59)



_{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 consistency}

semantics, caching semantics, performance and usability

(60)

Time State in Database Begin Txn read initial balance w/Lock .. balance += 1000 .. Commit 1000 2000 2000 Begin Txn read initial balance w/lock (blocks ..) unblocks balance += 1000 Commit 2000 3000 3000 C2 C1

The row is locked for the duration of the transaction

(61)

Concurrent Access to same Bean (same Primary Key)

Retry

3000 2000

Concurrent Access to same Bean (same Primary Key)

Lock obtained at update time, possible conflict detection with version id column

“ Update-conflict” Detection

Time State in Database Begin Tx Select initial balance .. balance += 1000 update .. Commit 1000 2000 2000 Begin Tx Select initial balance .. balance += 1000 update Exception .. Commit 3000 C2 C1 1000 1000

(62)



_Pessimistic

 _{Serialized access}

 _{Recommended for}

beans where

conflicts are bound

to happen  _{Scalability depends} on DB and App server locking granularity 

_Optimistic

 _Concurrent access  _Large-scale deployment  _{Requires collision} and exception handling  _{Choices for} conflict detection

(63)



_{Static data}

 _{Keep a local copy, hang on to it in memory,}

don’t 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, use}

optimistic locking



_{Hot data}

(64)



_{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 can occur



_Serializable

 _{Dirty reads, non-repeatable reads and}

(65)



_{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

(66)



_{Do use READ_COMMITTED with}

Optimistic locking as much as possible



_{Do use Optimistic locking only and}

(67)



_{Don't use SERIALIZABLE if it}

can be avoided



_{Don't use pessimistic locks if it}

(68)

 _{EJB Container Services – use appropriately for:}

 Distributed transaction management

 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

(69)

J2EE

Performance

Tips

(70)



_{Execute threads that requests run on}



_{JDBC connection pools}



_{JDBC prepared statement cache size}



_{Correct settings depend on application}

(71)



_{Session timeouts}



_{Stateful session bean and entity bean}

cache

 _{Cache = EJB instances with state}



_{Stateless session and entity bean pools}

 _{Pool = EJB instances with no assigned state}

(72)

Does not exist pooled ready NewInstance() setEntityContext() unsetEntityContext() ejbCreate() ejbPostCreate() ejbRemove() business method ejbStore() ejbLoad() ejbFind() ejbActivate() ejbPassivate() EjbActivate() EJB Instance EJB Object EJB Instance

Bean pool size Bean cache size

(73)

Method-ready ejbRemove() business method does not exist 1) newInstance() 2) setSessioncontext() 3)ejbCreate() ejbPassivate() EjbActivate() passive EJB Instance EJB Object

Bean cache size Session time out

(74)

EJB Instance method-ready pool EjbRemove() Business method does not exist 1) newInstance() 2) setSessioncontext() 3)ejbCreate()

and Message Driven Bean

(75)



_Cache

_{“EJB homes”}



_{Cache data sources}



_{Minimize use of HTTP sessions}



_Release

_database

_connections



_Remove

_{unused stateful session}

_beans

(76)



_{Session Facades}



_{Service Locator}



_{Value List Handler}



_{Data Transfer Object}

(77)

Performance

Testing

(78)



_{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_CMP _{rather than BMP Entity Beans}

 _{Use right}_{isolation level}_{and database}

(79)

JMS,

Messaging,

Web Services

J2EE Best

Practices

(80)



_{Use JMS for}

_{loosely coupled}

applications that need

reliable,

scalable

document oriented

message exchange



_{Including Message-Driven}

Beans and JMS in your J2EE™

application can greatly increase

performance, robustness, and

efficiency

(81)

Java™ Pet Store

JMS JMS

Queue

(82)

Traders/Brokers Price Change

Topic

(83)

Container Desti n-ation Consume r Msg-driven Bean Instances

 _{High Scalability, High Throughput}

 MDB instances are pooled by the container

 Allow for asynchronous concurrent message consumption from the same destination

JMS Provider Container Queue MDB Consumer MDB Instances Msg-Driven Bean Class

(84)



_{Asynchronous Interaction}



_{Concurrent processing}



_{Broadcasting events (messages)}



_{Reliable messaging}



_{Messaging with Transaction Support}



_Scalability



_{Loose Coupling}



_{Batch processing}

(85)

EJB Tier Relationship Reference Address Entity Order Approval MDB LineItem Entity Mailer MDB Card Entity Asynchronous Message Delivery Purchase Order Entity 1:m

(86)

EJB Architectural Pattern

Client _QueuesJMS MessageDriven Bean Stateless Session EJB Entity Bean XML Messaging Facade Asynchronous Synchronous

Example implementation of XML interaction model on top of Java™ interaction model

Entity Bean Entity Bean XML Value Objects Java™ Value Objects

(87)

Order Bean Inventory Management Bean Mail MessageDrivenBean JMS Topics Publish/subscribe Process Order Procure Inventory <Entity EJB> <Entity EJB> Purchase Order Queue TRANSACTION

Managed Transactions

(88)



_{Designing for event-driven interactions:}

 _{Not interface-}_driven

 _{Loose coupling}_{among participants}  _Asynchronous_{communication model}

 _Reliable_{communication or m}_{any to many}

communication model



_{Serves as an asynchronous facade to a}

subsystem or an application

(89)



_{Join pattern}

 _{MDB collects different messages}

 _{Stores to same set of entity beans}

Setup Office Human Resources Reserve Office Reserve Equipment Add to Payroll

Happy New Hire NewHire

Assigned Office Equipment Info

Furnished Office

(90)

Existing Synchronous Client Access Problem Solver Problem Rep Company EJB Tier

 _{A Session EJB provides the}

business logic for the Customers or help desk to synchronously enter Problem data, or search for similar problems

 _{Entity EJBs provide the business}

logic for accessing/updating the domain Data objects

(91)

Remote Help Desk New Problem Monthly Report Existing Synchronous Client Access Report Request Problem Handler Report Generator Problem Solver Problem Rep Company EJB Tier

(92)



_{Do watch message size}



_{Do only use XML when necessary}

(lower performance)



_{Do only use reliable messaging when}

(93)



_{Inside your Application don’t 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 Java™}

class as soon as possible

 _{Can use JAXB for this}

(94)



_{Structure application in two layers}

 _{Interaction layer and processing layer}



_{Interaction layer}

 _{Interface to clients}

 _{Receive requests and perform}

required translations and transformations

 _{Delegate request to processing}

layer for processing

 _{Respond to clients} Service Client Interaction Layer Processing Layer

(95)



_{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 existing}

(96)



_{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 Service

Request

(97)

RDBMS EAI Resource Adapters Legacy Systems Data Base ERP Business Services Web Container Domain Objects Web

Component Entity_EJB

Stateless Session EJB DAO Connector MDB JAX-RPC

(98)

 _Features:

 Orchestration, Choreography, Collaboration

 Business process defines Message sequence

 Asynchronous document exchange

 _{Industry examples:}  OTA, Sabre, GM Business Process Service Service Service Service

(99)

RDBMS EAI Resource Adapters Legacy Systems Data Base ERP Business Services Soap Handler Domain Objects Entity EJB MDB DAO Connector MDB Soap Message Services Entity EJB MDB Session EJB Session EJB Business Document Msg Service Handler

(100)

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

(101)

XML/SOAP/JMS

Business Process Engine Data XML Proxy Rule Base (XSLT) XSLT Engine Message Broker Adapter C++ Inventory Rule Base (XSLT) XSLT Engine Message Broker JMS Provider MDB Servlets EJB J2EE SOAP Web Service

(102)

Carol McDonald

Technology Evangelist

carol.mcdonald@sun.com