04/08/2003. Survive the test of time. We make the net work. J2EE Best Practices

Transcription

1 We make the net work J2EE Best Practices

2 Carol McDonald Technology Evangelist Sun Microsystems

3 Speaker s Qualifications Carol McDonald Is a Technology Evangelist at Sun Microsystems Speaks around the world at Sun Tech Days, and conferences Is a Sun Certified Java Programmer

4 Overall Presentation Goal Learn how to design 3-Tier Business Systems using Enterprise JavaBeans (EJB ) specification

5 Presentation Agenda J2EE Architecture Fundamentals J2EE Blueprints Design Web Tier Best Practices EJB Tier Best Practices Web Services Best Practices

6 The J2EE Framework Browsers HTML EJB JSP JDBC TM Rich Desktops SOAP, XML RMI, CORBA SOAP, XML JSPs/ Servlets/ Frameworks EJBs JMS J2EE Connectors Existing Apps XHTML/WML Devices Services SOAP XML Web Tier Transaction Tier J2EE TM / Sun ONE Server

7 Logical Tiering Desktop Desktop Client Client Handheld Handheld Client Client Telephone Telephone Client Client Desktop Desktop Presentation Presentation Handheld Handheld Presentation Presentation Telephone Telephone Presentation Presentation Search Search Catalog Catalog Checkout Checkout View View Product Product Detail Detail Legacy Legacy Order System Order System External External Payment Payment System System Catalog Catalog RDBMS RDBMS Order Order System System Payment Payment System System Catalog Catalog Database Database Resources Resources Client Client Presentation Presentation Business Business Integration Integration

8 Partition Functionality Into Tiers Presentation Control Business Services Persistent Domain Objects Asynchronous Messaging Servlet Session Publish Presentation Layout Entity Message Receive JSP

9 Architecture Fundamentals: Tiers Logical distribution of functionality Each tier knows only about the vertical layer next to it promotes: Skill separation, parallel development Extensibility, code reusue Maintainability Scalability, Physical distributability

10 2-Dimensional Framework Client Appli- cation Presen- tation Business Integration Resources Virtual JSP/Servlet API EJB API JDBC, JMS, Upper Web Server App Server Middleware Lower OS Environ. OS Environ. OS Environ. Hardware Presentation Hosts Business Hosts Integratio n Hosts Client Presentation Business Integration Resource

11 Architecture Fundamentals: Layers Layers Logical separation of logic Spans tiers Separates business logic from infrastructure services Don't have to reinvent/develop infrastructure Easier development and maintenance

12 Presentation Agenda J2EE Architecture Fundamentals J2EE Blueprints Design Web Tier Best Practices EJB Tier Best Practices Web Services Best Practices

13 J2EE Blueprints: Guidelines and Best practices for J2EE applications includes: Application (source code) Java Pet Store Book FREE:

14 Core J2EE Patterns Patterns Catalog Best Practices Refactoring Bad Practices Core J2EE Patterns Released JavaOne 2001

15 What is a Pattern?

16 What Are Patterns? Patterns are about communicating Problems and Solutions Recurring within a context Expert solutions J2EE Patterns: Collection of best practices for the J2EE platform Create a common vocabulary

17 Refactoring Refactoring: Improving the design of existing Code - Martin Fowler Occurs after code is written or after design is completed Good/bad to better!

18 1. Requirements Analysis Select Products Customer Checkout

19 2. Object Oriented Analysis Category name Media hgth Width uri Product 1..* id name description 1 0..* active getname() getdescription() isactive() setactive() getitems() Group objects into Components: Define cohesive classes Simplify Interface UserInterface Consider transaction boundaries maintainproduct()() 1..* Item id sku color 1 0..* LineItem id item : Item order : Order price 1..* 1 ContactInfo id address city state postalcode 1..* 1 1..* 1 Inventory item : id amount Order id orderitems date account : Account Account id name phone 1..* 0..1

20 3. Group Objects into Components Define cohesive classes Consider transaction boundaries Simplify contracts

21 3. Group Objects into Components Category name Product 1..* id name description 1 0..* active 1..* Item id sku color 1..* 1 Inventory item : id amount Catalog Media products hgthcategoriest width uri getname() getdescription() isactive() setactive() getitems() 1 0..* LineItem id item : Item order : Order price 1..* 1 Order id orderitems date account : Account 1..* Group objects into Components: Define cohesive classes UserInterface Simplify Interface maintainproduct()() Consider transaction boundaries ContactInfo id address city state postalcode 1..* 1 Account id name phone 0..1

22 Petstore Business Objects Catalog Category Page Product Item Cart CartList CartItem Customer Account Profile Contact Info Credit Card Address Order Item

23 Group Objects into Components Define cohesive classes Consider transaction boundaries Simplify contracts

24 Session vs Entity Beans Session beans Implement business services Often the verbs in use cases Entity Beans Persistent domain objects Often the nouns in use cases

25 Group objects into Components and Separate Functionality into Tiers Presentation control servlet JSP JSP Java Bean Java Bean Session EJBs Session Facade Catalog Cart Entity EJBs Order Customer Products Items Orders Accounts Presentation Layout Business Services Persistent Objects

26 Presentation Agenda Web Tier Best Practices EJB Tier Best Practices

27 Model View Controller Pattern Model represents the application business data and rules View is a screen representation of model, presents the user interface Controller mediates their interactions

28 Model View Controller request Separate Control From Model data From Presentation of View MVC can be broken into smaller finer grained patterns response JSP view Forward event data Business event Bean model client web EJB tier

29 Refactoring: Separate Business Logic from Presentation Formatting View Formatting Business Logic View Formatting View helper View helper Business Logic View helper

30 Refactoring: Localize Disparate Logic Problem Business logic is intermingled within a JSP view Refactoring Extract business logic into one or more helper classes that can be used by the JSP component or by a controller

31 Refactoring: Separate duplicate Control logic from Presentation Formatting View Front Controller Control Formatting View View Control View Helper Control Formatting Formatting Centralizes Control Remove duplication of logic Improves Reusability

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

33 Front Controller Centralizes Control Improves Manageability of Security Improves Reusability Implementation Strategy: Command and Controller Strategy

34 Service to worker MVC broken into smaller finer grained patterns request Command helper Call business service response client JSP view Select view Get data Web View Helper Data Object EJB tier

35 Service to Worker: Centralizes Control and Improves Modularity and Reuse Improves Application Partitioning cleaner separation of the view from the business processing Improves Role Separation Separates Java coder from HTML designer

36 Use an MVC Framework Faster easier development of request processing Response generation Struts or Sun ONE Application Framework

37 Struts Framework ActionServlet controller Busines Logic Action <<send>> <<call>> JSP (view) Model Value Object <<use>> <<use>> ActionMapping

38 Struts: Patterns Implemented Front Controller Command Request Action Servlet Action Mapping Action Client uses Response Composite View JSP View Action Forward Action Form View Helper

39 Sun ONE Application Framework MVC broken into smaller finer grained patterns

40 Refactoring: Reduce coupling between Web and EJB Tier with Business Delegate Session EJB Business Delegate Session EJB Client Session EJB Client Business Delegate Session EJB Session EJB Business Delegate Session EJB

41 Business Delegate Reduces coupling between Web/Client and EJB tier increases maintainability Hides complexities of remote services Implements failure recovery Retry, Exception Translation exposes simpler uniform interface to EJB tier

42 View Helper and Business Delegate

43 Use Service Locator pattern to cache Resource References EJB client EJB client JNDI JMS client JDBC client EJB client EJB client Service locator JMS client JDBC client JNDI Cache references obtained by JNDI lookups better performance and eliminates duplicate code

44 Service Locator Abstracts complexity of JNDI lookups Uniform lookup for all clients Removes duplicate code Caching Improves performance

45 Three Point Business Delegate View

46 Web Tier Patterns Request Handler Service Interface Request Intercepting Filter Front Controller Command Helper Business Delegate Business Service Client Dispatch Dispatcher Service Locator Response View Processor XML Intercepting Filter View View Helper XSL Core J2EE Pattern Strategy

47 Presentation Agenda J2EE Architecture Fundamentals J2EE Design Process Web Tier Best Practices EJB Tier Best Practices Session EJBs Web Services Best Practices

48 Local verses Remote Interfaces EJB client EJB Object EJB client EJB Object Network Remote Interfaces pass by Value: Serialize/deserialize method parameters Local Interfaces pass by Reference: better performance

49 Local verses Remote Interfaces Remote Interfaces: Key Benefits Easier to scale and cluster More reusable pieces in design Key Drawbacks More complexity due to extra layers Lower performance Data copying because of call-by-value semantics Overheads of remoteness

50 When Local, When Remote? Create distributed islands of local components EJB calls within an application Avoid unnecessary remote calls, prefer local EJB calls across applications Prefer remote for loose coupling

51 Session With Local Entity Beans Session Bean Local EntityBean Local EntityBean Local EntityBean EJB Tier Local EntityBea n Relationship Reference Local EntityBean

52 Petstore Example: Islands of Local Beans Admin Java Client Admin Web Site WebComp onent WebComp onent WebComp onent Business Delegate Relationship Reference Admin Remote Facade LineItem Purchase Order CreditCard Address

53 Use Declarative Transactions with Session Beans Check Out New Transaction Context Transaction Context propagated Session Bean TC TX_REQUIRES_NEW 1. Update Inventory InventoryEJB TX_REQUIRED TC Transaction Attributes 2. Create Order OrderEJB TX_REQUIRED TC TRANSACTION

54 Wrap Entities With Session Facade Client Business Logic Transaction Logic Entity Bean A Entity Bean B Entity Bean C Client Session Facade Business Logic Entity Bean A Entity Bean B Entity Bean Transaction Logic: C Bean Managed or Container Managed Client or Presentation Tier Network Business Tier Client or Presentation Tier Network Business Tier Improves Perfomance

55 Session Facade: Interaction Entity Bean 1 Client Session Bean Entity Bean POJO 1. dothis(...) Session Facade 2. getdata() 3. process Entity Bean 2 Session Bean Java Object 2. getdata() Data Access Object 1 Data Access Object 2

56 Session Facade: Consequences Provides coarse-grained services fewer network calls Centralizes EJB control, transaction, security Combine updates into fewer transactions Protects expensive resources Promotes uniform access

57 Merge Session Beans Client Interaction #1 Session Entity Client Interaction #1 Facade Entity Client Interaction #2 Session Entity Client Interaction #2 Facade Entity Client Interaction #3 Session Entity Client Interaction #3 Entity Client or Presentation Tier Business Tier Client or Presentation Tier Business Tier

58 Session Bean Summary Session beans Implement use case business services Central place for business logic Use as façade for Entity beans Stateful or stateless Consider what state you keep in your sessions Use declarative (Container managed) transactions. Keep transactions short

59 Presentation Agenda J2EE Architecture Fundamentals J2EE Design Process Web Tier Best Practices EJB Tier Best Practices Entity EJBs Web Services Best Practices

60 Entity Bean Best Practice Use Container Managed Persistence Most portable code Eases development Containers optimize database access Can take advantage of advances in CMP technology in J2EE technology-enabled servers

61 Use Bean Managed Persistence For Dealing with Legacy Database and/or other persistence store Previously written complex BMP application Connector driven data stores, EIS Efficient execution of complicated queries Bulk updates Multi object selects Aggregates (like sorting)

62 Why CMP? containers knows Which field is being accessed whether or not field is in a relation whether of not there is a transaction What is in cache the current clustering environment Container can optimize based on above

63 CMP optimizations agressive 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 in the database

64 Abstract View of an Entity Application Order Address 1 Client 1 1 OrderBean Line Items Shipping Address Product Ordered Product 1 Order Home M LineItem M

65 Bean Managed Persistence Composite Entity Pattern EJB class <<EJBEntity>> OrderEJB orderid : String String orderdate : java.sql.timestamp status : S tring totalprice : double OrderEJB() ejbcreate() ejbremove() setentitycontext() ejbload() ejbstore() ejbfindbyprimarykey() unsetentitycontext() ejbactivate() ejbpassivate() ejbpostcreate() getorderdetails() Dependent Object regular java class LineItem itemno : String qty : int unitprice : double lineno : int LineItem() LineItem() getitemno() getqty() getunitprice() getlineno() setitemno() setqty() setunitprice() setlineno() Dependent Object

66 CMP 2.0 Local Interfaces Client EJB Tier Order OrderHome 1 OrderBean 1 Address Local entity 1 Shipping Address LineItems M M 1 Local entity Product ProductOrdered LineItem Local entity

67 Container Managed Relationships 1-1,1-N, M-N associations Relationships defined via local entity interfaces Declaratively expressed in deployment descriptor Order Remote entity Client OrderHome Address 1 Shipping Address Local entity 1 OrderBean 1 1 LineItems ProductOrdered M M LineItem Local entity Product Local entity

68 CMP 2.0 Abstract Getters/setters for all Container Managed fields Getters/setters for all Container Managed Relactionships return/take local interface types

69 Accessors for CMP and CMR fields 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(); public abstract void setlineitems(collection lineitems);

70 Entity Bean CMP 2.0 CMP 2.0 fields and relationships accessed only by get/set methods allows container to: Lazily load fields as they are accessed Group field loading Optimized writes Cluster wide caching (depending on vendor) Automatic join of data in relationships Automatic creation of table in DB

71 Container Implements abstract persistence schema Extends Entity bean and implements local object classes Implements get/set methods Manages all persistent state and relationships, including referential integrity at runtime Implements bean s lifecycle contract ejbload, ejbstore, Performs concurrency control Maps query language to target datastore

72 Advantages Rich, flexible, portable modeling Supports complex coarse-grained to fine-grained object modeling Optimizable, Scalable Supports lazy loading Supports dirty detection/efficient updates Enables different caching strategies, concurrency control strategies Enables query optimization

73 Presentation Agenda J2EE Architecture Fundamentals J2EE Design Process Web Tier Best Practices EJB Tier Best Practices JMS Message Driven Beans Web Services Best Practices

74 JMS Use JMS for loosely coupled applications that need reliable, scalable document/message exchange

75 JMS Communication JMS Provider Producer Destination Consumer Loosely coupled: Producer doesn't need to know consumers, or consumer method arguments Reliable: Message is stored until it can be delivered Asynchronous Producer is not blocked, Consumer does not have to be available

76 JMS Messaging Advantages Store and Forward Scalability Fault tolerance Decoupling Routing Delivery when available Different clients Clustered Message Brokers

77 JMS Messaging Publish/Subscribe Queues

78 Point-to-Point Order and Fulfillment XML JMS Queue XML JMS Warehouse Java Pet Store

79 Publish and Subscribe Stock Price Changes Price Change Topic Traders/Brokers

80 Enterprise XML Messaging: JMS Enterprise Application Integration, Business Process Integration Broadcast Business Event Intranet Servers Business process update Topic Queue Servers Queue Business process update Office Systems

81 Example JMS: Workflow Order Entry Web Server Credit Verification Assign Order # Customer # Billing System De- Compose Order CD Fulfillment Book Fulfillment Video Fulfillment Assemble Package Warehouse Management Bill Customer Payment Ship Package Accounts Receivable Collection Order Complete EDI Gateway Modem Special Order Shipment Tracking EDI Gateway FAX Server

82 JMS persistent messages can have guaranteed delivery Producer 4) Send() return 1) Send 3) Ack 2) Persist JMS Provider 7) Remove 5) Receive 6) Ack Consumer Persistent Store

83 JMS producers can participate in Distributed Transactions TRANSACTION CheckOut EJB EJB EJB update send update Order DB JMS msg Queue Inventory DB

84 Message-Driven Bean High Scalability MDB instances are pooled by the container Allow for asynchronous concurrent message consumption from the same destination Container JMS Provider Desti Consume MDB n- Consumer r ation Queue Container Msgdriven MDB Instances Bean Instances Msg-driven Bean Class

85 MDBs can participate in Distributed Transactions TRANSACTION Purchase Order Queue Publish/subscribe MessageDrivenBean Mail JMS Topics Process Order Procure Inventory <Entity EJB> Order Bean <Entity EJB> Inventory Management Bean

86 MDB Facade Pattern With Local Entity Beans Asynchronous message delivery Order Approval MDB Relationship Reference Line Item Entity 1:m Purchase Order Entity Mailer MDB Address Entity EJB Tier Card Entity

87 Use JMS for Event-Driven Interactions Designing for Event-driven interactions: Loose coupling among participants Not interface driven Your choice: Message Driven Beans Serves as an asynchronous facade to a subsystem or an application

88 Message Driven Bean Join Pattern Join pattern MDB Collects different messages Stores to same set of entity beans Reserve Equipment Equipment Info Setup Office Furnished Office Human Resources NewHire Reserve Office Assigned Office Add to Payroll Paycheck Happy New Hire

89 Modeling Workflow With JMS Designate activity boundaries with Send messages to destinations Receive messages with MDBs Broadcast events with Topics for fan-out Use Join MDB pattern for fan-in Use transactions for guaranteed message delivery Separate transition logic from business logic by using Transition Delegates

90 PetStore Order Processing Scenario Asynchronously send Purchase Order document to the order fulfillment center Requirements: Async interaction Document centric Guaranteed delivery Transactional semantics Petstore Website PO Fulfillment Center

91 Example From the Pet Store Application Web Site MDB Manage Order Flow MDB MDB Queue MDB Verify Credit Transition Delegate Topic MDB Ship Order Notify Customer MDB MDB Transition Delegate Topic Queue Transition Delegate MDB Invoice Order

92 JMS Design Decisions and Recommendations Use XML documents over JMS Use Message-driven beans Use container managed transactions Makes delivery part of transaction Use persistent messages for reliability

93 Presentation Agenda J2EE Architecture Fundamentals J2EE Design Process Web Tier Best Practices EJB Tier Best Practices Web Services Best Practices

94 Web Services Tiered Architecture Internet Web Servers J2EE Application Servers RDBMS Data Base Legacy Systems SOAP HTTP RMI JMS JDBC JMS ERP SAP Message handling Soap Broker Business Logic Enterprise Resources Web Service Processing Business Services Domain Objects EAI

95 XML Messaging Communication Styles RPC-oriented Document-oriented MOM

96 RPC-oriented Style Request Credit check requestor Response Credit check service Synchronous, point to point, msg not persistent Sends data formatted as arguments Must know method arguments, exposes internals object model imposed on the client

97 Document-oriented Style Business Document Order Entry Web Server Assign De- Order # Compose Customer # Order Coffee x Billing Fulfillment System Coffee y Fulfillment Bean z Fulfillment Special Order Assemble Package Warehouse Management Bill Customer Payment Ship Package Shipment Tracking Accounts Receivable Collection Order Complete

98 Document-oriented Style Data formatted as a XML Business Document Useful for larger amounts, coarse-grained data Typically initiates a business process flow Asynchronous service interactions Service object model not imposed on the client Loosely coupled Service only uses the message items it needs, ignores the rest

99 Enterprise XML Messaging JMS Enterprise Application Integration, Business Process Integration Broadcast Business Event Intranet Servers Business process update Topic Queue Servers Queue Business process update Office Systems

100 RPC style Web Services and the J2EE Platform JAX- RPC Soap Handler Business Services Domain Objects EAI Resource Adapters RDBMS Data Base Web Component Stateless Session EJB Entity EJB DAO Connector Legacy Systems MDB ERP

101 Document style Web Services and the J2EE Platform JAXM or JAX-RPC Soap Handler Web Component Message Services MDB Business Services Session EJB Domain Objects Entity EJB EAI Resource Adapters DAO RDBMS Data Base Business Document MDB Session EJB Entity EJB Connector Legacy Systems MDB ERP

102 PetStore example Asynchronous WS Accessing asynchronous services with JAX-RPC Servlet sends requests as JMS API-based EJB Client may receive results via polling or callback Client Web Container JAX-RPC Servlet Endpoint JMS EJB Container MDB Entity Persistence MDB Connector EIS

103 Wrapping Legacy Applications Make available with JAX-RPC API Use Connectors from Web or EJB tier Client Web Container JAX-RPC Servlet Endpoint EJB Container EJB Connector Connector EIS EIS

104 Handling Incoming Documents With EJB Components Fragment and dispatch incoming XML documents to appropriate services Avoids transferring Account Processing unnecessary information Simplifies XML XML Workflow Engine Credit Card Processing processing logic Decouples services DOM Fragment Serialized XML Java Objects Purchase Order Processing

105 Recommendations: J2EE Platform-Based Apps as Web Services remote call concerns: Fine-grained services are flexible but incur network overhead Coarse-grained services minimize overhead but are less flexible Prefer coarse-grained services Consolidate multiple operations Minimizes expensive remote invocations

106 Recommendations: J2EE Platform-Based Apps as Web Services For Object-centric processing model Use RPC with arguments/return values that map well to Java classes For Document-centric processing model Prefer to pass XML documents as javax.xml.transform.source Or pass URLs to XML source documents Pass metadata, processing requirements, etc. in RPC arguments

107 Summary of XML messaging JAX-RPC JAXM JMS Main Concepts remote message MOM method call document Synchronous P2P Yes Yes No+ Publish/Subscribe No No Yes Reliability No Yes * Yes Asynchronous Yes Yes * Yes Non Java clients Yes Yes No XML Support Yes Yes Yes # * with JAXM API Provider + always goes through MOM # XML in form of Text message. No SOAP support

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109 Resources & Summary

110 J2EE Blueprints: Guidelines and Best practices for J2EE applications includes: Application (source code) Java Pet Store Book FREE:

111 Core J2EE Patterns Patterns Catalog Best Practices Refactoring Bad Practices Core J2EE Patterns Released JavaOne 2001

112 In pursuit of the best software in the universe All presentations Audiocasts Demos Codecamp materials Technology briefings code/articles/links/chats/resources