How to Build an E-Commerce Application using J2EE. Carol McDonald Code Camp Engineer

Transcription

1 How to Build an E-Commerce Application using J2EE Carol McDonald Code Camp Engineer

2 Code Camp Agenda J2EE & Blueprints Application Architecture and J2EE Blueprints E-Commerce Application Design Enterprise JavaBeans (EJB ) Designing and implementing the Business Model: Entity Beans, Stateless and Stateful Session Beans Servlets, Java ServerPages (JSP ) Designing and architecting the "View" or Presentation logic Assembling and Deploying the J2EE Application: Transactions JTS and JTA Describe how the sample application uses the transaction capabilities of the J2EE platform to simplify component development. Security How to use J2EE security to safeguard your e-commerce application

3 Download Code Camps All slides with notes are on your CD You can download this and other Code Camps : EJB, Java Performance, J2ME, JINI, JMS, JSP, XML under Events: Developer Code Camps ALSO You can also ask questions there Listen to audiocasts

4 J2EE & Blueprints Agenda Application Architecture and J2EE Sun BluePrints Design Guidelines Architecture of the sample application

5 Architecture and the Cube Architecting your application Using Tiers and Layers affect the application Capabilities

6 Capabilities = Non-Functional System Requirements Availability: service is accessible Reliability: consistency of application and transactions Capacity: can serve # users Extensibility: can add functionality Flexibility: can support changes Performance: good response time Scalability: can support increased load

7 Example Architecture Requirements E-Commerce Apps: Many Clients, lots of reading, less updating, low contention Need High performance and scalability for Reading data Insurance Intranet App: Fewer Clients, Low concurrency High transaction isolation level, Need Higher Consistency Reliability of Updates to DB more important than performance for Reading data

8 The Relationships between the Elements of Architecture Architecting your application Using Tiers and Layers affect the application Capabilities

9 J2EE Platform Specification Applet Container Web Container EJB Container Applet HTTP/ HTTPS JSP Servlet RMI EJB J2SE App Client Container App Client HTTP/ HTTPS JNDI JMS JTA RMI JavaMail J2SE JAF RMI/IIOP JDBC JNDI JMS JTA JavaMail JAF RMI/IIOP JDBC JNDI JMS RMI/IIOP J2SE JDBC J2SE Components run within Container. Database Container provides Runtime environment, J2SE & J2EE APIs, and remote communication

10 Layers of Services: The Application Server provides services to the Container, which in turn provides services to the EJB. Application Server Client O R B Application EJB Container EJB Container Services EJB Application Server Services Naming Transactions Operating System Services Environment Services Persistence DB

11 Layers Layers are abstractions of underlying implementation Each Layer hides implementation details of layer below The Container provides components services of the layers below Advantages: Easier development, maintenance for high performance, scalability Does not require developer to know complex details of distributed protocols, concurrency, transactions, load balancing, security, resource pooling and sharing

12 Application Server : Key Services Thread Allocation Developer Dispatching Object Pooling Session Management, Caching Applications Servers are primarily Resource Managers Applications Servers Manage: dispatching, thread allocation, pools, caches, load balancing, clusters

13 What features might you look for in an Application Server? Transaction Management Load Balancing Security Clustering

14 EJB Container Services Application Server Persistence Life Cycle Container State Management EJB EJB EJB Transaction Remote Interface Security Transaction manager

15 Components Monolithic: 1 binary file Recompiled & linked for any changes Components: plug-gable Parts. Implementation separated from Interface, only Interface published hides implementation details Better design, easier updates Better Flexibility, Extensibility

16 Architecture and the Cube

17 n-tier Architecture with J2EE Clients Application Server EIS Tier Java clients RMI / IIOP network network Container Beans RDBMS Data Base C++, VB.. clients HTTP PeopleSoft SAP R/3 HTML Web Server Browser clients Legacy Systems

18 Tiers Tiers separate functionality Presentation Logic, Business Logic, Data Schema Advantages: One tier can be changed without changing the rest= easier updates Lower deployment and maintenance costs. Capabilities go up: Flexibility, Extensibility

19 Capabilities Non-Functional Requirements With Good Architecture, Layering, Tiers, Load Balancing, Clustering, Transaction Mgmt, Security Web Server App Server R O U T E R Web Server R O U T E R App Server Web Server App Server Reliability, Availability, Extensibility, Flexibility, Scalability, Goes up

20 Why J2EE? Gives you the Advantages of a Standardized Layered, Tier Architecture: Simplifies the complexity of a building n-tier applications. Standardizes an API between components and application server container. J2EE Application Server and Containers provide the framework Services

21 Agenda J2EE & Blueprints J2EE Architecture Sun BluePrints Design Guidelines Architecture of the sample application

22 The J2EE Platform Has a Rich Set of APIs Firewall Client Client Application Server Enterprise JavaBean Enterprise Information Systems (EIS): Client Client Client Web Server JSP, Servlet, HTML, XML Enterprise JavaBean Relational- Database, Legacy Applications, ERP Systems Other Services: JNDI, JMS, JavaMail Client Tier Middle Tier EIS Tier

23 Why J2EE Blueprints Rich APIs Similar Problems Blue Prints More than one way of doing things Need to leverage time-tested solutions Don t reinvent the wheel Provides Answers, Examples of Best Practices

24 J2EE Blueprints Guidelines and Best practices for designing n-tier enterprise applications with J2EE J2EE blueprints include: Book, Designing Enterprise Applications Application (source code) Java Pet Store FREE:

25 Blueprints FREE:

26 J2EE Deliverables J2EE Specification J2EE Reference Implementation J2EE J2EE Compatibility Test Suite J2EE BluePrints

27 Java Pet Store Demo

28 Some Key BluePrints Questions -Issues Faced by Developers When to use Servlets verses JavaServer Pages? Where to store client session state: client-tier, web-tier or EJB tier? Access Data Base Resources via EJB or directly from JSP JavaBean? When to use EJB components? When to use Session Beans and when to use Entity Beans?

29 Design of Sample Application Blueprints Choices: Blueprints Choices: Client tier HTML Clients for End-User Web Access XML for Data externalization (Order procurement) Web Server tier JavaServer Pages (JSP) for dynamic content generation Application Server tier EJB for business logic

30 J2EE Blueprints Guidelines Process for developing an application from requirements, to design, to implementation 1. Scenarios or Use Cases 2. partitioning of functionality into modules 3. Application architecture using Model-View- Controller: 1. assignment of functionality to tiers: 1. Design of the Model 2. Design of the View 3. Design of the Controller 2. object decomposition within tiers

31 1) Sample Application Shopping Scenario 1. Web-based browsing of a product catalog 2. Creation and maintenance of a shopping cart 3. User account creation/ Login 4. Placing orders 5. Secure order processing 1. B2B transactions 2. Externalisation of order data (expressed in XML) 3. Order confirmation using

32 1) Use Case Shopping Scenario Create/Update Customer Account Browse Catalog Customer Login to Customer Account add items to shopping cart <<extend>> <<includes>> check out order items Add Order to Warehouse System (external) <<includes>> Send Receipt

33 Shopping Scenario Sequence Diagram Catalog Controller Shopping Cart Account Order Inventory Mailer : Customer browse products add item to cart add item to cart check out get items in cart get account details create order update inventory send receipt

34 J2EE Blueprints Process for developing an application from requirements, to design, to implementation 1. Scenarios or Use Cases 2. partitioning of functionality into modules 3. Application architecture using Model-View- Controller: 1. assignment of functionality to tiers: 1. Design of the Model 2. Design of the View 3. Design of the Controller 2. object decomposition within tiers

35 2) Divide the Application Into Modules Based on Services (Functionality) Account User Account Module: tracks user account information Catalog Product Catalog Module: provides search for products, and product details Cart Shopping Cart Module: allows user to save selected items for the session. Order Order Processing Module: performs order Processing when user buys the items in the cart.

36 2) Divide the Application Into Modules Based on Services Inventory Inventory Module: maintains information on the number of each type of product in stock. Mail Messaging Module: sends confirmation receipt messages. Control Control Module: control interactions between user (browse, add items, check out) and business objects.

37 Interrelationship of the modules User interface Control browse Catalog new/existing account Account checkout add/remove items Cart Order Inventory Mail

38 J2EE Blueprints Process for developing an application from requirements, to design, to implementation 1. Scenarios or Use Cases 2. partitioning of functionality into modules 3. Application architecture using Model-View- Controller: 1. assignment of functionality to tiers: 1. Design of the Model 2. Design of the View 3. Design of the Controller 2. object decomposition within tiers

39 Divide Application Objects into 3 categories: Model View Controller (MVC) UI Pattern Model represents the application business data and rules View is a screen representation of model, presents the user interface Controller mediates their interactions

40 Model View Controller Design Pattern Entity EJB and Session EJB Get Data To Display Model Business Event View View selection Controller JSP JavaBeans components User event Session EJB And Servlet classes

41 Assignment of Functionality to Tiers Presentation Business Logic Data Presentation Logic Application Requests Business Services Domain Objects Persistence View Controller Model

42 MVC With J2EE Technology Build View in the Web-tier Use JSP components for presentation layout Custom tags and JavaBeans components for presentation logic Build Controller in the Web / EJB tier Servlet for dispatching Session bean for control within business objects Build Model in the EJB tier Session beans for Business Services: Process and Rules Entity beans to maintain model data

43 Assignment of Functionality to Tiers or Vertical Layering #A Presentation Control Business Services Domain Objects Data Access Objects Servlet Session Entity DAO Presentation Layout JSP

44 What are Domain Objects? Domain Objects model the real world entities, nouns in business problem Also known as Data Model, business object model Example User Account, Order, Product, Inventory

45 What are Business Services? Business Services Model the verbs in application Business processes are the services in the use cases Example Browse Catalog Add item to Cart Purchase items

46 Sample Application Architecture Vertical Layering View Controller Session EJBs Entity EJBs Presentation Control servlet Catalog Products Items Controller Shopping Inventory JSP JSP Java Bean Java Bean Mailer Order Account Orders Accounts Presentation Layout Business Services Domain Objects

47 Summary We went over: Advantages of horizontal layers Advantages of Vertical Tiers Affect of Layers and Tiers on Capabilities. the process of architecting the sample application the Model View Controller Design Pattern