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![54
Copyright 2002 © Paulo Merson
EJB Example
// EJB client (stand-alone application)
public class CartClient {
public static void main(String[] args) {
try {
CartHome home = (CartHome)initial.lookup("MyCart");
Cart shoppingCart = home.create("Duke DeEarl", "123");
shoppingCart.addBook("The Martian Chronicles");
shoppingCart.addBook("2001 A Space Odyssey");
shoppingCart.remove();
} catch (BookException ex) {
System.err.println("Caught a BookException: "
+ ex.getMessage());
} catch (Exception ex) {
System.err.println("Caught an unexpected exception!");
}
}
}](https://image.slidesharecdn.com/j2ee-240113172828-1760d941/85/J2EE-ppt-54-320.jpg)
![54
Copyright 2002 © Paulo Merson
EJB Example
// EJB client (stand-alone application)
public class CartClient {
public static void main(String[] args) {
try {
CartHome home = (CartHome)initial.lookup("MyCart");
Cart shoppingCart = home.create("Duke DeEarl", "123");
shoppingCart.addBook("The Martian Chronicles");
shoppingCart.addBook("2001 A Space Odyssey");
shoppingCart.remove();
} catch (BookException ex) {
System.err.println("Caught a BookException: "
+ ex.getMessage());
} catch (Exception ex) {
System.err.println("Caught an unexpected exception!");
}
}
}](https://image.slidesharecdn.com/j2ee-240113172828-1760d941/75/J2EE-ppt-54-2048.jpg)
J2EE.ppt
- 1. 1 Copyright 2002 ©Paulo Merson J2EE – Building Component-based Enterprise Web Applications 05/09/2002 Paulo Merson
- 2. 2 Copyright 2002 ©Paulo Merson Agenda 1. Application servers 2. What is J2EE? Main component types Application Scenarios J2EE APIs and Services 3. EJB – a closer look 4. Examples
- 3. 3 Copyright 2002 ©Paulo Merson 1. Application Servers In the beginning, there was darkness and cold. Then, … Centralized, non-distributed terminals mainframe terminals
- 4. 4 Copyright 2002 ©Paulo Merson Application Servers In the 90’s, systems should be client- server
- 5. 5 Copyright 2002 ©Paulo Merson Application Servers Today, enterprise applications use the multi-tier model
- 6. 6 Copyright 2002 ©Paulo Merson Application Servers “Multi-tier applications” have several independent components An application server provides the infrastructure and services to run such applications
- 7. 7 Copyright 2002 ©Paulo Merson Application Servers Application server products can be separated into 3 categories: J2EE-based solutions Non-J2EE solutions (PHP, ColdFusion, Perl, etc.) And the Microsoft solution (ASP/COM and now .NET with ASP.NET, VB.NET, C#, etc.)
- 8. 8 Copyright 2002 ©Paulo Merson J2EE Application Servers Major J2EE products: BEA WebLogic IBM WebSphere Sun iPlanet Application Server Oracle 9iAS HP/Bluestone Total-e-Server Borland AppServer Jboss (free open source)
- 9. 9 Copyright 2002 ©Paulo Merson Web Server and Application Server Web Server (HTTP Server) App Server 1 App Server 2 Internet Browser HTTP(S)
- 10. 10 Copyright 2002 ©Paulo Merson 2. What is J2EE? It is a public specification that embodies several technologies Current version is 1.3 J2EE defines a model for developing multi-tier, web based, enterprise applications with distributed components
- 11. 11 Copyright 2002 ©Paulo Merson J2EE Benefits High availability Scalability Integration with existing systems Freedom to choose vendors of application servers, tools, components Multi-platform
- 12. 12 Copyright 2002 ©Paulo Merson J2EE Benefits Flexibility of scenarios and support to several types of clients Programming productivity: Services allow developer to focus on business Component development facilitates maintenance and reuse Enables deploy-time behaviors Supports division of labor
- 13. 13 Copyright 2002 ©Paulo Merson J2EE Benefits Don’t forget to say that Java is cool!
- 14. 14 Copyright 2002 ©Paulo Merson Main technologies JavaServer Pages (JSP) Servlet Enterprise JavaBeans (EJB) JSPs, servlets and EJBs are application components
- 15. 15 Copyright 2002 ©Paulo Merson JSP Used for web pages with dynamic content Processes HTTP requests (non-blocking call-and-return) Accepts HTML tags, special JSP tags, and scriptlets of Java code Separates static content from presentation logic Can be created by web designer using HTML tools
- 16. 16 Copyright 2002 ©Paulo Merson Servlet Used for web pages with dynamic content Processes HTTP requests (non-blocking call- and-return) Written in Java; uses print statements to render HTML Loaded into memory once and then called many times Provides APIs for session management
- 17. 17 Copyright 2002 ©Paulo Merson EJB EJBs are distributed components used to implement business logic (no UI) Developer concentrates on business logic Availability, scalability, security, interoperability and integrability handled by the J2EE server Client of EJBs can be JSPs, servlets, other EJBs and external aplications Clients see interfaces
- 18. 18 Copyright 2002 ©Paulo Merson J2EE Multi-tier Model
- 19. 19 Copyright 2002 ©Paulo Merson J2EE Application Scenarios Multi-tier typical application
- 20. 20 Copyright 2002 ©Paulo Merson J2EE Application Scenarios Stand-alone client
- 21. 21 Copyright 2002 ©Paulo Merson J2EE Application Scenarios Web-centric application
- 22. 22 Copyright 2002 ©Paulo Merson J2EE Application Scenarios Business-to-business
- 23. 23 Copyright 2002 ©Paulo Merson J2EE Services and APIs Java Message Service (JMS) Implicit invocation Communication is loosely coupled, reliable and asynchronous Supports 2 models: point-to-point publish/subscribe
- 24. 24 Copyright 2002 ©Paulo Merson JMS Point-to-point Destination is “queue”
- 25. 25 Copyright 2002 ©Paulo Merson JMS Publish-subscribe Destination is “topic”
- 26. 26 Copyright 2002 ©Paulo Merson J2EE Services and APIs JNDI - Naming and directory services Applications use JNDI to locate objects, such as environment entries, EJBs, datasources, message queues JNDI is implementation independent Underlying implementation varies: LDAP, DNS, DBMS, etc.
- 27. 27 Copyright 2002 ©Paulo Merson J2EE Services and APIs Transaction service: Controls transactions automatically You can demarcate transactions explicitly Or you can specify relationships between methods that make up a single transaction
- 28. 28 Copyright 2002 ©Paulo Merson J2EE Services and APIs Security Java Authentication and Authorization Service (JAAS) is the new (J2EE 1.3) standard for J2EE security Authentication via userid/password or digital certificates Role-based authorization limits access of users to resources (URLs, EJB methods) Embedded security realm
- 29. 29 Copyright 2002 ©Paulo Merson J2EE Services and APIs J2EE Connector Architecture Integration to non-J2EE systems, such as mainframes and ERPs. Standard API to access different EIS Vendors implement EIS-specific resource adapters Support to Corba clients
- 30. 30 Copyright 2002 ©Paulo Merson J2EE Services and APIs JDBC JavaMail Java API for XML Parsing (JAXP) Web services APIs
- 31. 31 Copyright 2002 ©Paulo Merson 3. EJB – a closer look
- 32. 32 Copyright 2002 ©Paulo Merson Home Interface Methods to create, remove or locate EJB objects The home interface implementation is the home object (generated) The home object is a factory
- 33. 33 Copyright 2002 ©Paulo Merson Remote Interface Business methods available to clients The remote interface implementation is the EJB object (generated) The EJB object acts as a proxy to the EJB instance
- 34. 34 Copyright 2002 ©Paulo Merson
- 35. 35 Copyright 2002 ©Paulo Merson EJB – The Big Picture
- 36. 36 Copyright 2002 ©Paulo Merson EJB at runtime Client can be local or remote
- 37. 37 Copyright 2002 ©Paulo Merson EJB at runtime
- 38. 38 Copyright 2002 ©Paulo Merson Types of EJB EJB Taxonomy Stateful Stateless SessionBean BMP CMP EntityBean MessageDrivenBean EnterpriseBean New!
- 39. 39 Copyright 2002 ©Paulo Merson Session Bean Stateful session bean: Retains conversational state (data) on behalf of an individual client If state changed during this invocation, the same state will be available upon the following invocation Example: shopping cart
- 40. 40 Copyright 2002 ©Paulo Merson Session Bean Stateless session bean: Contains no user-specific data Business process that provides a generic service Container can pool stateless beans Example: shopping catalog
- 41. 41 Copyright 2002 ©Paulo Merson Entity Bean Represents business data stored in a database persistent object Underlying data is normally one row of a table A primary key uniquely identifies each bean instance Allows shared access from multiple clients Can live past the duration of client’s session Example: shopping order
- 42. 42 Copyright 2002 ©Paulo Merson Entity Bean Bean-managed persistence (BMP): bean developer writes JDBC code to access the database; allows better control for the developer Container-managed persistence (CMP): container generates all JDBC code to access the database; developer has less code to write, but also less control
- 43. 43 Copyright 2002 ©Paulo Merson Message-Driven Bean Message consumer for a JMS queue or topic Benefits from EJB container services that are not available to standard JMS consumers Has no home or remote interface Example: order processing – stock info
- 44. 44 Copyright 2002 ©Paulo Merson 4. Examples JSP example Servlet example EJB example
- 45. 45 Copyright 2002 ©Paulo Merson JSP example
- 46. 46 Copyright 2002 ©Paulo Merson JSP example <%@ page import="hello.Greeting" %> <jsp:useBean id="mybean" scope="page" class="hello.Greeting"/> <jsp:setProperty name="mybean" property="*" /> <html> <head><title>Hello, User</title></head> <body bgcolor="#ffffff" background="background.gif"> <%@ include file="dukebanner.html" %> <table border="0" width="700"> <tr> <td width="150"> </td> <td width="550"> <h1>My name is Duke. What's yours?</h1> </td> </tr>
- 47. 47 Copyright 2002 ©Paulo Merson JSP example <tr> <td width="150" </td> <td width="550"> <form method="get"> <input type="text" name="username" size="25"> <br> <input type="submit" value="Submit"> <input type="reset" value="Reset"> </td> </tr> </form> </table> <% if (request.getParameter("username") != null) { %> <%@ include file="response.jsp" %> <% } %> </body> </html>
- 48. 48 Copyright 2002 ©Paulo Merson Servlet example public class HelloWorldServlet extends HttpServlet { public void service(HttpServletRequest req, HttpServletResponse res) throws IOException { res.setContentType("text/html"); PrintWriter out = res.getWriter(); out.println("<html><head><title>Hello World Servlet</title></head>"); out.println("<body><h1>Hello World!</h1></body></html>"); } }
- 49. 49 Copyright 2002 ©Paulo Merson EJB Example // Shopping Cart example // Home interface public interface CartHome extends EJBHome { Cart create(String person) throws RemoteException, CreateException; Cart create(String person, String id) throws RemoteException, CreateException; }
- 50. 50 Copyright 2002 ©Paulo Merson EJB Example // Remote interface public interface Cart extends EJBObject { public void addBook(String title) throws RemoteException; public void removeBook(String title) throws BookException, RemoteException; public Vector getContents() throws RemoteException; }
- 51. 51 Copyright 2002 ©Paulo Merson EJB Example // Enterprise bean class public class CartEJB implements SessionBean { String customerName, customerId; Vector contents; private SessionContext sc; public void ejbCreate(String person) throws CreateException { if (person == null) { throw new CreateException("Null person not allowed."); } else { customerName = person; } customerId = "0"; contents = new Vector(); }
- 52. 52 Copyright 2002 ©Paulo Merson EJB Example public void ejbCreate(String person, String id) throws CreateException { if (person == null) { throw new CreateException("Null person not allowed."); } else { customerName = person; } IdVerifier idChecker = new IdVerifier(); if (idChecker.validate(id)) { customerId = id; } else { throw new CreateException("Invalid id: " + id); } contents = new Vector(); }
- 53. 53 Copyright 2002 ©Paulo Merson EJB Example public void addBook(String title) { contents. addElement(title); } public void removeBook(String title) throws BookException { boolean result = contents.removeElement(title); if (result == false) { throw new BookException(title + " not in cart."); } } public Vector getContents() { return contents; } . . . }
- 54. 54 Copyright 2002 ©Paulo Merson EJB Example // EJB client (stand-alone application) public class CartClient { public static void main(String[] args) { try { CartHome home = (CartHome)initial.lookup("MyCart"); Cart shoppingCart = home.create("Duke DeEarl", "123"); shoppingCart.addBook("The Martian Chronicles"); shoppingCart.addBook("2001 A Space Odyssey"); shoppingCart.remove(); } catch (BookException ex) { System.err.println("Caught a BookException: " + ex.getMessage()); } catch (Exception ex) { System.err.println("Caught an unexpected exception!"); } } }
- 55. 55 Copyright 2002 ©Paulo Merson Questions
- 56. 56 Copyright 2002 ©Paulo Merson Sources & Resources Java 2 Platform Enterprise Edition Specification, v1.3 Designing Enterprise Applications with the Java 2, Enterprise Edition. Nicholas Kassen and the Enterprise Team Does the App Server Maket Still Exist? Jean- Christophe Cimetiere The State of The J2EE Application Server Market. Floyd Marinescu
- 57. 57 Copyright 2002 ©Paulo Merson Sources & Resources The J2EE Tutorial. Sun Microsystems IBM WebSphere Application Server manuals BEA WebLogic Server manuals www.java.sun.com/j2ee www.theserverside.com