What Is Needed. Learning the technology is not enough Industry best practices Proven solutions How to avoid bad practices? a Real-life Example.

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1 1 Push J2EE your Best development Practices further using a Real-life Example. Casey Chan nology Evangelist casey.chan@sun.com Push ebay your Architecture: development furtherhow to Go From there Microsoft IIS ebayisapi.dll MSXML to here? J2EE Container Web Container Services Presentation Tier EJB Container Tier Integration Tier Configuration Logging Security 1 2 Monolithic Layered Proprietary Loosely coupled Modular Standards based What Is Needed Push Core your J2EE development Patterns further Learning the technology is not enough Industry best practices Proven solutions How to avoid bad practices? Collection of best practices and Patterns for for J2EE architecture Also J2EE architecture bad practices and refactorings Based on Sun Java Center Services experience Proven solutions Reuse design Robust and scalable architecture Improve quality Flexibility and maintainability Create a common vocabulary 3 4

2 2 Java Push your TM BluePrints development further Program Agenda Java TM nology Series books Designing Enterprise Applications with the J2EE Platform, 2nd Edition Covers J2EE TM 1.3 platform features Designing Web Services with the J2EE Platform (available soon) Sample applications Java Pet Store Demo Java Adventure Builder Demo Concrete code for the BluePrints guidelines Starting points for your applications Web Tier best practices EJB Tier best practices Persistence Options Container Managed Persistence 5 6 Layering Some Web Tier Best Practices and Patterns Web Tier or Network EJB Session Beans Presentation Layer Data Transfer s i.e. Data Values Logic Layer Service Layer Entity EJBs Domain Layer Persistent Entities 7 8

3 3 Rationale for Layers Model Push your development View Controller further More flexible, extensible: Presentation Layers Frequent changes, design to be flexible Services Implement use-cases Public Service interface Interface should remain valid for changes in presentation and data store Data Layers Fewer changes, designed to optimize data access Model = business data and rules, shared by all clients Controller defines the application behaviour, interprets user actions and maps them into actions performed on the model View = renders the contents of the Model Thin Browser Presentation Layer Model Layer HTTP Request Controller View Problem Domain Services HTML Page Persistence Layer Enterprise Resources Model Push your development View Controller further Response Request Forward Event JSP View Servlet Controller Data Event Bean Model Web EJB Tier MVC Pattern Model Separate: Model data Control Presentation of view 12 Service to Worker = MVC Pattern with more detail Servlet JSP Java s 1. Request 2. Common logic 10. Response 3. Parse Request Front Controller View 9. Get Data 8. Dispatch View Helper Data Bean 4. Get cmd 6. Execute Command Factory Dispatcher 5. Create Command Helper 7. logic

4 4 Push Use your an development MVC Framework further Struts MVC Framework Use Struts, JSF, or Sun Java Studio... application framework Frameworks provide a skeleton which you can extend Faster, easier development of Request processing Response generation Improve Design Modularity Maintainability View 1 View Servlet (Controller) Struts-config.xml Form Bean Model Push Struts your development and Core further J2EE Patterns Push Ebay.com: your development Presentation further Tier Request Front Controller Servlet Mapping (xml) Command Model Service Request Intercepting Filter Request Handler Front Controller Command? Service Navigation and Dispatch Navigator Dispatcher Uses Response View Processor XML 15 View JSP View Forward Dispatcher Form View Helper 16 Response Intercepting Filter View Processor Transformer Helper XSL Core J2EE Pattern Strategy

5 5 Push your development Delegate further Push Ebay.com: your development Presentation further Tier independent from ejb tier Request Intercepting Filter Request Handler Front Controller Command Service Interface Delegate Service Ejb details hidden Navigator Navigation Dispatcher and Dispatch Service Locator Mock objects can be used to test client w/o ejb tier Response Intercepting Filter View Processor View Processor Transformer Helper XML XSL Core J2EE Pattern Strategy Push Cache your development for Performance further Some things can be cached and shared, use a singleton: InitialContext object (JNDI object used for lookups) Anything retrieved from JNDI, EJB Home interfaces Repeated lookups can be expensive! Use Service Locator Pattern Some things are user specific, cached in session: Cache search results when you are only displaying a few at a time (static data) Value List Pattern 19

6 6 ServiceLocator code Push ServiceLocator your development further code 01 public class ServiceLocator { 02 private InitialContext ic; 03 private Map cache; 04 private static ServiceLocator me; private ServiceLocator() { 07 ic = new InitialContext(); 08 cache =new HashMap(); 09 } 10 public static ServiceLocator getinstance() { 11 if (me == null) { 12 me = new ServiceLocator(); 13 } 14 return me; 15 } public EJBHome getremotehome(string jndihomename, Class classname){ 02 EJBHome home = null; 03 if (cache.containskey(jndihomename)) { 04 home = (EJBHome) cache.get(jndihomename); 05 } else { 06 objref = ic.lookup(jndihomename); 07 obj = PortableRemote.narrow(objref, classname); 08 home = (EJBHome)obj; 09 cache.put(jndihomename, home); 10 } 11 return home; 12 } code Push Tips your for development Servlet further Performance 01 ServiceLocator servicelocator = 02 ServiceLocator.getInstance(); 03 try { 04 ProjectHome projecthome =(ProjectHome) 05 servicelocator.gethome( ProjectHome.class );... Servlets are Multithreaded Avoid use of shared modified class variables Synchronize only small blocks in code Don't store a lot of data in the HTTP Session Remove servlet sessions when they are no longer needed: In logoff call session.invalidate() 23 24

7 7 Servlet Tips Tips for JSPs DO use high performance J2EE design patterns MVC, Service Locator DON T hold resources explicitly free them 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 object not session If JSP does not use the HTTP session Use <%page session="false"%> to prevent HTTP Sessions from being automatically created Push Do your development need EJBs? further Some EJB Tier Best Practices and Patterns 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 Clustering for Scalability? 27 28

8 8 Push Architecting your development Applications further Push ebay your Use development case further realization ebay Case Study ebay Case Study View Items Functional requirements captured via use-cases Use-cases implemented using MVC & Command design patterns Implement Logic as Services Verbs in use cases help define services Noun in use cases help define business data objects Any User View Items by category Any user can view auction items by category Push View your Items development Design furtherrequirements View Items Design ebay Case Study ebay Case Study Centralize Request Hndlg Front Controller Convert to Biz Command Use case Biz logic Assemble Data Command Delegate Session Facade Transfer Assembler Value List Handler Transfer Retrieve Data by category Service Locator Data Access 31 32

9 9 Data Transfer EJB GetCity() Network boundary Before GetState() GetZipCode() DON'T DO too much network traffic Item Info Data Transfer EJB A Data Transfer encapsulates a set of data values to return to the client in one network transfer GetItemInfo() Return DTO 34 After GetCity() GetState() GetZipCode() Network boundary DO Reduce network traffic with Data Transfer Push Data your Access development further Use DAO for read-only tabular access to a large set of data, when query results are large and short-lived DataAccess DataSource Uses Encapsulates obtains/modifies Use Data Access s to encapsulate data-access logic creates/uses -provides a simplified interface for performing complex JDBC operations -allows decoupling of data-access optimizations Transfer 36

10 10 EJB Tier patterns Data Access (DAO) public class FacadeEJB implements SessionBean { protected EbayDAO dao; public void ejbcreate() { try { dao = EbayDAOFactory.getDAO(); } catch (EbayDAOSysException se) { throw new EJBException(se.getMessage()); } } public ListChunk getitems(string categoryid, int startindex, int count, Locale locale) { try { return dao.getitems(categoryid, startindex, count, locale); } catch (EbayDAOSysException se) { throw new EJBException(se.getMessage()); } } 37. } Value List Handler Push Example your development Caching further Results Interface ValueListIterator +GetSize():int +getcurrentelement(): +getpreviouselements(count:int):list +getnextelements(count:int):list +resetindex():void For querying, filtering, and displaying large amounts of data: Value List Handler handles the search, can cache results and provides a traversable result set (value list / batch) Create Execute Search Get Next Return Sub List Stateful Session ValueListHandle ValueListiterator r Execute Search Return Value List Get Sub-list ValueList Create DataAccessObjec t ValueListHandler <<List>> ValueList Transfer Get Previous Return Sub-list Get Sub-list Return Sub-list Get Current Return Value Get Current DataAccess Get Size Return Size Get Size 39 40

11 11 Returning Push your development Search further Results Options 41 ValueList Handler as a Stateful Session EJB caches search results, and returns sub list ValueList Handler as Stateless Session EJB: Select * FROM item WHERE id=? LIMIT [count] OFFSET [startindex] Instead of Value list could use JDBC 2.0 scrollable ResultSet but keeps JDBC data source connection open! (J2SE 1.5 will have disconnected scrollable ResultSet) 42 Stateless Example Create ValueListHandle ValueListiterator r Execute Search (index, count) Execute Search (index, count) Create Return Sub List Execute Search (index+count, count) Return Sub List Stateless Session Return sub List DataAccessObjec t Execute Search (index+count, count) Return sub List Select * FROM item WHERE id=? LIMIT [count]offset [startindex] Create ValueList 44 Push Session your development Facade further pattern Session Bean Entity Bean Plain Java 1. dothis(...) 2. getdata() 3. process Use the Session Facade: Session Facade Entity Bean 1 Entity Bean 2 Session Bean Java 2. getdata() Data Access 1 Data Access 2 provide a simple interface to a complex subsystem of enterprise beans Fine-grained entity beans...fascade -> POJOs/DTO to client Enforce a clear and strict separation of business logic from presentation and data logic

12 12 Use the Session Facade pattern To Execute complex use cases in a single network call to reduce network overhead Don t: Direct Bean Access EJB Use the Session Facade To group finer grained calls to local entity beans Local vs. Remote Interfaces Remote Interfaces Local Interfaces Network Do: Direct Entity Bean access results in excessive network overhead and multiple transactions Network F ac a d e EJB EJB client Network EJB Pass by Value: Serialize/deserialize method parameters (Coarse logic for distributed) EJB client EJB Pass by Reference: Better performance 45 Direct Entity Bean access results in excessive network overhead 46 Push Design your development your local further & remote EJBs Use Session Facade to group finer grained calls to local EJBs in a Coarse Grained Interface Java Remote Facade WebComp onent WebComp onent Delegate WebComp onent Determine which EJBs will be collocated within same VM Relationship Reference Admin Remote Facade LineItem Purchase Order CreditCard Address 47

13 13 Push ebay.com: your development further Tier Session EJB tips ebay Case Study Command Context Transfer Dispatch Application Controller Application Service Facade Transfer Assembler Logic/Data Domain Store Value List Handler Persistence DAO Data Source Core J2EE Pattern Remove stateful session beans when finished (user logs out) Bean.remove() Limit size of objects stored in session beans due to memory cost and I/O for passivation Strategy Push Stateless your development or Stateful further Session EJB? Push Service your development Tier DON'T further s Stateless session beans are pooled and can service multiple clients give best performance Stateful store conversational state=1 per client (are activated and passivated) For Performance Strive for Statelessness when application has a high number of users convert Stateful to stateless by adding parameters to the bean methods that hold the extra state DO NOT store large amount of data in Stateful SessionEJB DO NOT access of Entity EJBs remotely DO NOT implement fine-grained components as remote EJBs 51 52

14 14 Design Patterns Summary Push Design your development Patterns further Summary Invoke business methods Mediate business processing Locate services Session Facade Obtain composite value objects Value Assembler Transactional Data Components Entity Message Driven Bean Encapsulate data Encapsulate data Access data sources Service Locator Value List handler Encapsulate data Transfer Encapsulate data Locate services Data Access Access business list Access data sources Data Transfer Exchanges data J2EE tiers Service Locator Holds results of JNDI lookups Value List Handler Handles larger result sets from database queries Delegate Simplifies the coupling between the J2EE Web & EJB tiers Session Facade Provide business logic functionality Data Access Isolation layer for interfaces to a systems resources Etc Push Data your Access development Options further in J2EE: Persistence Best Practices -oriented (transactional) data model EJB Container Managed Persistence JDO Great choice for ease and performance Tabular access EJBs should not be simple wrappers on database data rows; they should have business logic. To simply access data, use Plain JDBC encapsulated in a DAO Non-relational, non-object data access, Legacy systems, CRM, SAP Use J2EE Connectors

15 15 BMP vs. CMP Push Effect your development of Good further CMP Optimizations BMP Bean EJB Container CMP Bean EJB Container JDBC SQLJ JDBC Driver Persistence Manager JDBC SQLJ SQL 1) Bean provider manages State and Data consistency 2) Bean provider handles relationships and OR Mapping JDBC Driver SQL Bean State Database 1) Container manages State and Data consistency 2) Container/PM provides concurrency, relationships and OR Mapping Bean State Database Benchmark Score # of Database Calls Simple BMP Optimized BMP CMP Push CMP your 2.0 development Entity further Beans Push Container your development Managed further Relationships Entity Bean is now an abstract class, container extends it <<interface>> java.io.serializable Order Address 1 Shipping Address Local Entity <<interface>> javax.ejb.enterprisebean <<interface>> javax.ejb.entitybean CMP Entity Bean abstract class (Contains data handling logic) CMP Entity Bean subclass (Contains persistence logic) You (bean provider) write this code. Container provides this class. OrderHome EJB Tier OrderBean 1 1 M M Local Entity Product LineItems ProductOrdered LineItem Local Entity

16 16 CMP 2.0 Relationship Handling Example Push your development CMP Wizard further 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> Push Advantages your development of further CMP 2.0 for developer container manages the persistence and the relationships, not you! No SQL or persistence logic in source code Freedom from maintaining interactions with the data store EJB Query Language (EJB QL) Portable code 64 Push Advantages your development of further CMP 2.0 for Container Optimization is possible because persistent fields are only accessible via get and set methods Containers knows Which field is being accessed Whether or not field is in a relation Whether of not there is a transaction What's in cache The current clustering environment Can optimize based on above

17 17 Entity Bean Tips Summary 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 grain access and single transaction context J2EE Patterns and Best Practices are proven solutions Reuse design Robust and scalable architecture Improve quality, performance Flexibility and maintainability Java TM BluePrints Program Designing Enterprise Applications with the J2EE Platform, 2nd Edition Resources: Casey Chan nology Evangelist Java Performance Tuning 67 J2EE Performance Testing 68