WA1104 J2EE Best Practices and Patterns with WebSphere V5 Course Outline 1. Introduction Java Web Application Architecture J2EE Architecture Web Application Programming Model – MVC Patterns Factory Method Singleton Command Modeling the Structure Aspect of Command Pattern Modeling the Behavior Aspect of Command Pattern Facade Adapter Proxy Publish-Subscribe Modeling the Structural Aspect of the Publish-Subscribe Pattern Modeling the Behavioral Aspect of the Publish-Subscribe Pattern 2. Presentation Tier Patterns Why use the intercepting filter pattern? Uses for Filtering What is a filter? Features of filters The Filter interface How a filter works In what order? A simple logging filter Configuring the filter Mapping the filter The Web Deployment Descriptor Common filter tasks Request and Response Wrappers How Struts uses this design pattern? Front Controller Pattern Command and Controller Strategy Advantages of command and controller strategy How Struts uses this strategy? View Helper Pattern Use JavaBean as result bean helper Use custom tag for display logic written in Java Components of a Tag library JSTL Overview Use Access Beans as business delegates How Struts uses this pattern Problem Solution 1 – use jsp:include Solution 2 – use Struts templates Transform View Pattern The Music Collection Example – Sample XML file The Music Collection Example – Retrieving owner details The Music Collection Example – Retrieving the core data The Music Collection Example – Current Output Transformation with Java Reading an XML Transforming to HTML Transforming to System.out 3. Presentation Tier Design Considerations HttpSession Why on the server? WebSphere V5 Session Management URL Rewriting Do not store large Object Graphs in HttpSession The problem The design pattern that fixes it A client side fix Struts implementation Typical validation rules Client-side validations Jakarta commons validation framework features Not resetting JavaBeans between requests Passing HttpServletRequest to business tier Best Practice 1: Dynamic caching Dynamic caching - continued Best Practice 2: Disable the HTTP access logs Best Practice 3: Tune the number of client threads 4. Business and Integration Tier Patterns Business Delegate Pattern How it works Data Transfer Object Pattern DTO Example (Output) DTO Example (Input) Role of DTO in MVC Access Beans Types of Access Beans Data Class Access Bean Data Class Programming Model Access Bean Constructor Generating Access Beans Generating a Data Class Generating an EJB Factory Using EJB Factory and Data Class Deleting the Access Bean Value Object Pattern Multiple Value Objects Best Practice – derive EJB from the Value Object Composite Entity Pattern An example Class Diagram How the client interacts Value Object Assembler Value List Handler How does it work? Design Considerations Service Locator Data Access Object (DAO) DAO Implementation Guidelines Service Activator MDB- Integrating JMS and EJB Message-Driven Beans Are Different From Other EJBs Message-Driven Beans are Stateless Message-Driven Bean Interfaces Example: Message Counter Class MessageCounter Class MessageCounter Processing the Message Deployment Descriptor Entry 5. Business and Integration Tier Best Practices Exception Handling Use java:comp to locate resources Use Container Authentication Use JDBC Connection Pooling Prepared Statement Cache Release JDBC Resources Optimize database first DB2 Tuning - MaxAppls DB2 Tuning - MaxAgents DB2 Tuning - Buffer Pool Tuning DB2 Tuning - Configuring buffpage DB2 Tuning - Evaluating the buffer pool size DB2 Tuning - Monitoring the database buffer pool DB2 Tuning - reorgchk Set CMP EJB Method Access Intent Carefully Class Loader Class Loader Hierarchy WebSphere Class Loaders WebSphere Class Loaders Hierarchy Class Loading Isolation Options Complete Isolation Medium Isolation Minimal Isolation Which option to use? Configuring the Class Loading Policy Configuring Application Server Policy Configuring Applications WAR Class Loader Policy Configuring the Options WSAD Project Structure Using log4j from an WebSphere application Using Log4J Example servlet using log4j 6. Other EJB Patterns Session Façade Session Façade Pattern Session Façade Miscellaneous Details Message Façade Pattern Message Façade Message façade pattern shortcomings Version Number pattern Sequence Blocks Stored Procedures for Autogenerated Keys Fast Lane Pattern 7. Transaction Management What is a transaction? ACID properties Transaction demarcation Resource managers Isolation levels WebSphere - Setting Isolation Level for EJB WebSphere - CMP EJB Access Intent WSAD - Setting Access Intent WSAD - Setting Data Source Isolation Level Basics Manage your own transactions Change isolation level EJB Transaction Basics Transaction Propagation Client Managed Transaction Bean Managed Transaction Container Managed Transaction Transaction Outcome Vetoing Transaction Let the container manage transactions CMT and the Session Façade CMT and other EJBs Transactions and Message Driven Beans Distributed transaction Two-phase commit Aborting a global transaction Optimizations Window of doubt JMS, EJB, XA Using XA-enabled data source Increase concurrency by reducing transaction isolation level Keep transactions short Multi-step wizard “the wrong way” What’s wrong? Multi-step wizard “the right way” 8. Performance Overview Visitor, hit, user Load, throughput, response time Response time Effect of load on the system Saturation and buckle points Scaling Performance and scalability are different! Problem Areas CPU utilization Measure CPU utilization everywhere Symptoms of underutilization What causes underutilization? Network capacity problem? Synchronization problem? Slow external resource? Is the test pushing the system hard enough? Does your system scale? Symptoms of burstiness Infrequent synchronization problem? Test driver synchronization problem? Slow back-end systems? Slow garbage collection? Timeout problems? Erratic network traffic? Symptoms of overutilization The components of CPU usage High User CPU High System CPU High Wait CPU Server hanging Thread dump in WebSphere v5 Thread dump file Uneven cluster loading Load balancer configured correctly? Plan of attack WebSphere routing mechanism WebSphere routing policies Overview What is WPT? Download and install record Configure your system to use record Record a session Output from record Details of running a stress test Best Practices 9. Messaging Tier Patterns Java Message Service JMS Programming: Overview The JMS Interfaces JMS PTP Programming: Example JMS PTP Programming: Example One-to-one (Local) One-to-one (Remote) Request-Reply One-to-Many Many-to-one Many-to-one With Reply Many to Many Hub and Spoke Route to different queues based on message content Break a composite message and process separately Combine related messages to a single message Send Large Messages Using the Memento Pattern 10. Architecting Security Security Functionality Challenge Mechanism Basic Challenge Client Certificates Form-based Authentication Form-based Authentication WebSphere Authentication Mechanism SWAM Authentication Mechanism LTPA Authentication Mechanism User Registry LDAP User Registry Custom User Registry HTTP Single Sign On (SSO J2EE Authorization Model WebSphere Authorization Model EJB Delegation Policies Delegation Scenario Form Based Logout Architecture Guidelines 11. Build and Deployment What is Ant? Writing a Build Script How to run Ant? Using ant from WSAD Running Ant Advanced Task Automating Deployment Deployment Tasks Scripting Environment Central Scripting Objects Launching wsadmin JACL Scripting Patterns Examples Example Script Common Tasks for Applications Common Tasks for Applications Common Configuration Tasks Installing an Application What can I do? What next? 12. JUnit and WSAD What is JUnit? Who uses JUnit? Why JUnit? The xUnit Philosophy A JUnit Test Running the tests Swing-based Test Runner JUnit Basics assertTrue assertEquals assertSame assertNull The failure message The Test Class The Test Method The Test Suite JUnit Design JUnit with Ant JUnit with WSAD Change JUnit version in WSAD Running Tests WSAD Test Runner Icons Rerun an individual test Debug with JUnit Testing Strategies Specific Techniques Testing simple Java classes Testing with databases Testing web applications Test-Driven Design Parting Thoughts 13. Struts Architecture and Overview Review: MVC Model Review: Request, Session and Application What is Struts? Struts Flow Components in Struts The Model The View The Controller Struts Flow struts-config.xml struts-config.xml Content The data-sources element in the struts-config.xml The form-beans element in the struts-config.xml The global-forwards element in the struts-config.xml The action-mappings element in the struts-config.xml Sample struts-config.xml The Role of web.xml for the Application Configuring Struts in the web.xml web.xml Content Steps to Configuring Struts in the web.xml Step 1. Configuring the Action Servlet Instance in the web.xml Action Servlet Config Example Step 2. Configuring the Action Servlet Mapping in web.xml Prefix Mapping Example Extension Mapping Example Step 3. Configuring the Struts Tag Libraries in the web.xml Sample web.xml