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Developing Enterprise Applications Using Java School of Technology of Setubal Setubal, Portugal April 8, 2002 Qusay H. Mahmoud School of Computing Science Simon Fraser University, Vancouver, B.C., Canada [email protected] http://www.javacourses.com Copyright © 2002 Qusay H. Mahmoud 1 Objectives Understand the architecture of the J2EE Understand the technologies involved in J2EE Know how to build web-based enterprise applications Know what effort is involved in development http://www.javacourses.com Copyright © 2002 Qusay H. Mahmoud 2 Agenda The J2EE Platform and SDK The J2EE APIs Web Components (Servlets, JSPs) Enterprise JavaBeans Technology (EJBs) Duke’s Bank Application Security issues Web Services Online Resources http://www.javacourses.com Copyright © 2002 Qusay H. Mahmoud 3 Enterprise Applications Enterprise is a synonym for distributed Distributed computation done by programs interacting over the network Enterprise is a hot buzzword Reputation for complexity Enterprise computing takes place in a heterogeneous network Involve the use of many different network protocols http://www.javacourses.com Copyright © 2002 Qusay H. Mahmoud 4 Buzzword: N-tier apps Used to describe applications that reside on client and several servers http://www.javacourses.com Copyright © 2002 Qusay H. Mahmoud 5 Why Java? It helps alleviate intimidating aspects of enterprise computing Java is portable (Write Once, Run Everywhere) Enterprise APIs form a single standard layer on top of various proprietary or vendor-enhanced APIs The elegance of Java and OO power make the APIs simpler, easier to understand, and easier to use http://www.javacourses.com Copyright © 2002 Qusay H. Mahmoud 6 Java Platforms [Source: Sun Microsystems Website] http://www.javacourses.com Copyright © 2002 Qusay H. Mahmoud 7 J2EE Platform Brings the benefits of component-based development to enterprise applications Components are Simpler to develop Portable Reusable http://www.javacourses.com Copyright © 2002 Qusay H. Mahmoud 8 J2EE Components Server-side components Enterprise JavaBeans (EJBs) Java Servlets JavaServer Pages (JSPs) Client-side components Application client Configured via deployment descriptors Deployed into containers http://www.javacourses.com Copyright © 2002 Qusay H. Mahmoud 9 J2EE Components packed into Modules Enterprise Beans (JAR file) Classes Deployment descriptor Web Components (WAR file) Servlet classes, JSPs, HTML, images Web application deployment descriptor Application Clients Classes Application client deployment descriptor http://www.javacourses.com Copyright © 2002 Qusay H. Mahmoud 10 J2EE Applications Packed into Enterprise ARchives (EAR file) Configured via application deployment descriptors <application> <display-name>BankApp</display-name> <module> <ejb>account-ejb.jar</ejb> </module> … <module> <web> <web-uri>bank.war</web-uri> <context-root>bank</context-root> </web> </module> </application> http://www.javacourses.com Copyright © 2002 Qusay H. Mahmoud 11 J2EE Standard APIs JDBC Java Naming and Directory Interface (JNDI) Java Message Service (JMS) Remote Method Invocation (RMI) Enterprise JavaBeans (EJBs) Technologies Servlets JavaServer Pages (JSPs) http://www.javacourses.com Copyright © 2002 Qusay H. Mahmoud 12 Other J2EE APIs J2EE Connectors Java Transaction API (JTA) JavaIDL RMI-IIOP Java Transaction Service (JTS) JavaMail http://www.javacourses.com Copyright © 2002 Qusay H. Mahmoud 13 Multi-tiered Architecture Advantages: Decouples accessing of data from end-user applications Encourages component-based code reusability http://www.javacourses.com Copyright © 2002 Qusay H. Mahmoud 14 J2EE SDK J2EE Server Cloudscape database Application deployment tool Create and edit deployment descriptors Package components and J2EE applications Verify and deploy J2EE applications Download: http://java.sun.com/j2ee/download.html http://www.javacourses.com Copyright © 2002 Qusay H. Mahmoud 15 J2EE SDK Tools j2eeadmin: add/remove resources cleanup: remove deployed apps from server cloudscape: start/stop/query database server deploytool: deploy/undeploy applications j2ee: start/stop J2EE server keytool: create keys and generate certificates packager: package J2EE components realmtool: add/remove J2EE users and import certificates verifier: validate J2EE archive files http://www.javacourses.com Copyright © 2002 Qusay H. Mahmoud 16 J2EE Server Standard containers (EJBs and Web) Life cycle management Concurrent execution Standard platform services Security Transactions Resource connections http://www.javacourses.com Copyright © 2002 Qusay H. Mahmoud 17 J2EE Containers A container is the interface between a component and the low-level platform specific functionality J2EE server provides services in the form of a container for every component type You don’t have to develop these services yourself; you concentrate on solving the business problem http://www.javacourses.com Copyright © 2002 Qusay H. Mahmoud 18 J2EE Containers Before a component can be executed, it must be assembled into a J2EE application and deployed into its container http://www.javacourses.com Copyright © 2002 Qusay H. Mahmoud 19 Web Components Used to generate dynamic Web content Run on the server-side Portable Reusable They can be: Based on the Java Servlet API Based on the JavaServer Pages (JSPs) http://www.javacourses.com Copyright © 2002 Qusay H. Mahmoud 20 HTTP Overview An application-level protocol Supports several request methods ( such as GET and POST) GET http://www.yahoo.com HTTP/1.0 Request Reply http://www.javacourses.com Copyright © 2002 Qusay H. Mahmoud 21 Servlets A servlet is a Java class Functions: Process requests Create replies Deployed into a Web container, which Manages servlet life cycle Maps URLs to servlets Converts HTTP requests and responses to objects http://www.javacourses.com Copyright © 2002 Qusay H. Mahmoud 22 Servlet Example A simple servlet public class HelloServlet extends HttpServlet { public void doGet(HttpServletRequest request, HttpServletResponse response) throws IOException, ServletException { response.setContentType("text/html"); PrintWriter out = response.getWriter(); out.println(“<html><head><title>hello</title></head> "); out.println(<body><h1>Hello</h1></body></html>); } http://www.javacourses.com Copyright © 2002 Qusay H. Mahmoud 23 Servlet as a Mediator Devices that have no support for socket or datagram connections, access ‘net services through a mediator http://www.javacourses.com Copyright © 2002 Qusay H. Mahmoud 24 JavaServer Pages (JSPs) JSP is a document that contains two types of text Template data (HTML, XML, WML) that generates static content JSP elements that generate dynamic content Delegates dynamic processing to EJBs, JavaBeans components, custom tags Translates into and executes as a servlet http://www.javacourses.com Copyright © 2002 Qusay H. Mahmoud 25 JSP Elements Directive controls translation into servlet class <%@ page import=“java.io.*” %> Declaration creates object or method <%! int i %> Scriptlet for dynamic processing <% ArrayList accts = beanManager.getAcountController().getAccountsOfCusto mer(request.getRemoteUser()); %> http://www.javacourses.com Copyright © 2002 Qusay H. Mahmoud 26 JSP: JavaBeans Components Create components and access their properties <jsp:useBean id=“accountHistBean” class=“AccountHistorybean” scope=“request”/> scope: page, request, session, or application <jsp:setProperty name=“accountHistbean” property=“beanManager” value=“<%= beanManager %>” /> value can be a String or a JSP expression <jsp:getProperty name=“accountHistBean” property=“credits” /> http://www.javacourses.com Copyright © 2002 Qusay H. Mahmoud 27 JSP: Custom Tags Extensions to JSP that encapsulate dynamic processing Tag libraries Standard Tag Library (JSR 052) Struts: http://jakarta.apache.org/struts Jakarta Taglibs: http://jakarta.apache.org/taglibs Examples (we will see them in action) Effort involved in developing custom tags http://www.javacourses.com Copyright © 2002 Qusay H. Mahmoud 28 Enterprise JavaBeans What is an Enterprise Bean? Component for EJB technology Runs on the server Encapsulates business logic Portable Reusable Transactional http://www.javacourses.com Copyright © 2002 Qusay H. Mahmoud 29 How do Enterprise beans simplify development Enterprise bean developer Focuses on solving business problems EJB container Provides system-level services Client developer Focuses on presentation and usability http://www.javacourses.com Copyright © 2002 Qusay H. Mahmoud 30 Type of Enterprise Beans Session beans Entity beans Message-driven beans http://www.javacourses.com Copyright © 2002 Qusay H. Mahmoud 31 What is a Session Bean? Represents a single client in the server A logical extension of the client Transient state – not persistent Examples Sample session beans in action http://www.javacourses.com Copyright © 2002 Qusay H. Mahmoud 32 What is an Entity Bean? Represents a business object in a persistent storage (e.g. a database) Often provides an object view of a database table Examples Sample entity beans in action http://www.javacourses.com Copyright © 2002 Qusay H. Mahmoud 33 What is a Message-Driven Bean? Based on Java Message Service (JMS) technology) Message listener Consumes messages from a queue The onMessage() method is invoked upon message arrival http://www.javacourses.com Copyright © 2002 Qusay H. Mahmoud 34 Structure of an EJB Enterprise Bean Class Implementation Home Interface Life cycle methods Remote Interface Business methods Deployment Descriptor XML file http://www.javacourses.com Copyright © 2002 Qusay H. Mahmoud 35 Duke’s Bank Application Online access to bank accounts Customers – web clients Withdraw and deposit funds Account history Transfer funds Administrators (J2EE application client) Manage customers Manage accounts http://www.javacourses.com Copyright © 2002 Qusay H. Mahmoud 36 Duke’s Bank Application High-level architecture [source: Sun Microsystems Website] http://www.javacourses.com Copyright © 2002 Qusay H. Mahmoud 37 Duke’s Bank Client’s View Defining client’s view with interfaces http://www.javacourses.com Copyright © 2002 Qusay H. Mahmoud 38 Duke’s Bank Application Enterprise Beans http://www.javacourses.com Copyright © 2002 Qusay H. Mahmoud 39 Duke’s Client Application Client: locate, create, deposit http://www.javacourses.com Copyright © 2002 Qusay H. Mahmoud 40 Duke’s Bank Application TxControllerEJB: Deposit http://www.javacourses.com Copyright © 2002 Qusay H. Mahmoud 41 Duke’s Bank Application TxEJB: Create http://www.javacourses.com Copyright © 2002 Qusay H. Mahmoud 42 Duke’s Bank Application Web Component Integration [source: Sun] http://www.javacourses.com Copyright © 2002 Qusay H. Mahmoud 43 Duke’s Bank Application Security Secure each container to secure entire application Use authentication to prove identity Use authorization to restrict access http://www.javacourses.com Copyright © 2002 Qusay H. Mahmoud 44 Application Client Security Admin uses the application client to create customers and accounts Must authenticate to access any management functions by the application client Login screen pops up when the application client is accessed http://www.javacourses.com Copyright © 2002 Qusay H. Mahmoud 45 Duke’s Bank Application Creating a customer account Admin creates the customer record Customer ID is embedded in the customer record Admin uses realmtool to add customer ID, password, group to default realm Realm –add 200 j2ee customer http://www.javacourses.com Copyright © 2002 Qusay H. Mahmoud 46 Duke’s Bank Application Creating an account Admin accesses the application client and creates an account for the customer Create methods in the enterprise bean can only be accessed by users in the admin role The customer ID, found in the customer record, binds the account to the customer http://www.javacourses.com Copyright © 2002 Qusay H. Mahmoud 47 Duke’s Bank Application Securing the Web Components Web components are protected when the application is deployed Customer must authenticate to access web components A form-based login pops up when the customer tries to access web component Web component retrieves the customer ID by calling getUserPrincipal() <% ArrayList accts = beanManager.getAccountController().getAccountsOfCusto mer(request.getUserPrincipal().getName()); %> http://www.javacourses.com Copyright © 2002 Qusay H. Mahmoud 48 Duke’s Bank Application Securing the Enterprise Beans Enterprise beans provide methods for creating customer and accounts Method permissions on the home interface restrict account and customer creation to admin role Roles and mapping between users and roles is specified at application deployment time Enterprise beans provide methods for crediting, debiting, transferring funds Methods permission on the remote interface restricts these operations to customer role http://www.javacourses.com Copyright © 2002 Qusay H. Mahmoud 49 Transaction Management Indivisible unit of work Atomic (all or nothing) Committed or rolled back Bean-managed Your code sets transaction boundaries Container-managed EJB container sets boundaries http://www.javacourses.com Copyright © 2002 Qusay H. Mahmoud 50 Resources Connections Types: Database connections Java Message Service API-based objects Mail sessions URLs Resource adapters http://www.javacourses.com Copyright © 2002 Qusay H. Mahmoud 51 Resource Connections Example private String dbName = “java:comp/env/jdbc/BankDB”; InitialContext ic = new InitialContext(); DataSource ds = (DataSource) ic.lookup(dbName); Connection con = ds.getConnection(); http://www.javacourses.com Copyright © 2002 Qusay H. Mahmoud 52 Connector Architecture Enables J2EE components such as EJB to interact with enterprise information systems A resource adapter is a J2EE component that implements the J2EE connector architecture for a specific enterprise information system A resource adapter is analogous to a JDBC driver For JDBC: the outside resource is DBMS For resource adapter: the outside resource is enterprise information system http://www.javacourses.com Copyright © 2002 Qusay H. Mahmoud 53 Web Services Services offered through the web and can be accessed from any web-services enabled machine with Internet access http://www.javacourses.com Copyright © 2002 Qusay H. Mahmoud 54 Online Resources J2EE: http://java.sun.com/j2ee J2EE Tutorial: http://java.sun.com/j2ee/tutorial J2EE white papers: http://java.sun.com/j2ee/white J2EE BluePrints: http://java.sun.com/blueprints http://www.javacourses.com Copyright © 2002 Qusay H. Mahmoud 55 Online Resources JSP Taglibs: http://java.sun.com/products/jsp/taglibraries.html Tomcat http://jakarta.apache.org/tomcat Web Services http://java.sun.com/webservices Deploying Web Services on J2EE: http://developer.java.sun.com/developer/tec hnicalArticles/WebServices/wsj2ee http://www.javacourses.com Copyright © 2002 Qusay H. Mahmoud 56 Thank you Q&A http://www.javacourses.com Copyright © 2002 Qusay H. Mahmoud 57 Copyright Info Java™ and J2EE ™ are registered trademarks of Sun Microsystems, Inc. Part of the slides have been adapted from J2EE Tutorial and JavaOne Sessions 2001. All trademarked product and company names are the property of their respective trademark holders. http://www.javacourses.com Copyright © 2002 Qusay H. Mahmoud 58 Speaker Bio Qusay H. Mahmoud is a faculty member in the School of Computing Science at Simon Fraser University, Canada. He is widely published on the Java programming language, including the MIDP and Palm programming articles for Sun Microsystems Java Developer Connection. Qusay is the author of Distributed Programming with Java (Manning Publications, 1999) and Learning Wireless Java (O’Reilly & Associates, 2002) http://www.cs.sfu.ca/~qmahmoud http://www.javacourses.com Copyright © 2002 Qusay H. Mahmoud 59
