CSE298 CSE300 CSE.RU-1.1 Distributed Object Computing and Java - Web Application- Pinglei Zhou Junming Wang Chaopeng Zhou Computer Science & Engineering.

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Distributed Object Computing and JavaDistributed Object Computing and Java--Web ApplicationWeb Application--

Pinglei ZhouJunming Wang Chaopeng Zhou

Computer Science & Engineering DepartmentThe University of Connecticut

191 Auditorium Road, Box U-155Storrs, CT 06269-3155

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MotivationMotivation

Web Application DevelopmentWeb Application Development Development of Internet and the WWW Traditional way for for dynamic Web

Application

Java Features Support Web ApplicationJava Features Support Web Application Servlet Enterprise JavaBeans JDBC Java and XML RMI …..

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Overview of the PresentationOverview of the Presentation

Overview Traditional Web Programming

Brief Introduction of Enterprise System With J2EE

Description and Evaluation Java-Support Description and Evaluation Java-Support Web ProgrammingWeb Programming

Conclusion and Future Work

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Traditional Web Programming & JavaTraditional Web Programming & Java

HTML ProgrammingHTML Programming

CGI ProgrammingCGI Programming

Scripting LanguageScripting Language

Active Server PagesActive Server Pages

Java-Based Web ProgrammingJava-Based Web Programming

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Generic Enterprise System & JavaGeneric Enterprise System & Java

Enterprise user Interface• AWT & SwingEnterprise Data Enabling• JDBC Distributing Enterprise Communications Enabling• RMICommon Services for Distributed Communications• JINIEnterprise Systems Assurance• Java Security ModelEnterprise Web Application• ServletEnterprise Model Components• EJB

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Why Dynamic Web Page ?Why Dynamic Web Page ?

The Web Page Is Based On Data The Web Page Is Based On Data Submitted by the UserSubmitted by the User

The Web Page Is Derived From Data The Web Page Is Derived From Data That Changes FrequentlyThat Changes Frequently

The Web Page Uses Information From The Web Page Uses Information From Corporate Database or Other Server-Side Corporate Database or Other Server-Side SourcesSources

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System ArchitectureSystem Architecture

Client Program

EJBs

Oracle Database

Servlet

JDBCJDBC

Servlet

JDBC

Middle Tier

Presentation Tier

Data Tier

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Servlet Examples UserServlet Examples User

Processing and/or store data Processing and/or store data submitted by over HTTPS using an submitted by over HTTPS using an HTML formHTML form

Allowing collaboration between Allowing collaboration between peoplepeople

Being a community of active agentsBeing a community of active agents

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Advantages Over Traditional CGIAdvantages Over Traditional CGI

EfficientEfficient

PowerfulPowerful

PortablePortable

SecureSecure

Each resquest each threadStore the program in momery after terminated

Talk Directly to the Web ServerMultiple servlets can share data

Standard Java API

A Servlet can be run by a Servlet Engine in a restrictive Sandbox

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Servlets vs. Applets

Servlets• Server-side Java programs

• Implements the javax.servlet.Servlet interface

Faceless

Applets• Client-side Java programs

• Subclassing the java.applet.Applet class

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Java Servlet Architecture

Host Machine A

Web Server Platform

Servlet Container

Configureation Service

Management Services

Request Handling

ResponseHandling

SessionManagement

ServletRequest

GenericServlet

ServletResponse

HttpServletRequest

HttpServlet

HttpServlet

Response

HttpSession

Cookie

Host Machine B

Web Client Web Client

Net W ork

Net W ork

Java ServletComponent

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Typical Servlet Life CycleTypical Servlet Life Cycle

Init

Service

Service

Service

Service

Service

ServiceService

Service

Destroy

Thread 1 Thread 2 Thread 3

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Servlet’s JobServlet’s Job

Read any data send by the user

Look up other information about the request that is embedded in the HTTP

Process the request and generate the results

Format the result inside a document

Send the document back to the client

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Three Tiers Architecture of Servlet Web Application

Servlet Engineer:Servlet class

Server:JWSDK

JDBC

OracleRelationalDatabase

JDK1.3

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Installation and SetupInstallation and Setup

Download and install JDK1.3Download and install JDK1.3

Download Java Servlet 2.2Download Java Servlet 2.2

Any Web Server That Support ServletAny Web Server That Support Servlet

http://java.sun.com/j2se/1.3/

http://java.sun.com/products/servlet/index.html

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Options for Web ServerOptions for Web Server

Apache TomcatApache Tomcat

Java Server Web Development Kit Java Server Web Development Kit (JSWDK)(JSWDK)

Sun’s Java Web ServerSun’s Java Web Server

Http://jakarta.apache.org

Http://java.sun.com/products/servlet/download.html

Http://freeware.thespere.com

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Basic Servlet StructureBasic Servlet Structure

Import java.io.*;

import javax.servlet.*;

import javax.servlet.http.*;

public class SimpelServlet extends HttpServlet {

public void init(ServletConfig config){

…..}

public void doGet(HttpServletRequest req, HttpServletResponse res ) throws ServletException , IOException {

…….}

public void doPost(HttpServletRequest req, HttpServletResponse res)

throws ServletException , IOException {

…….}

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Project Implementation-Three TiersProject Implementation-Three Tiers

Choose product(ProjectFrame.htm)

Create Query(CSE300DOC3.java)

Get Price Data from DB(DatabaseUtilities.javaDriverUtilities.javaDBResult.javaDataUtilities.java)

Present the priceinformation for choseninformation(CSE300DOC3.java)

Re-select

Provide Credit Information(CreditCard.htm)

Create Query(CSE300DOC04.java)

Present the Data toUser

Informationconfirmation

N

Y

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Project UML documentation

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JDBC and JavaJDBC and Java

What is JDBCWhat is JDBC Java Database Connectivity(JDBC) is implemented Java Database Connectivity(JDBC) is implemented

in the java.sql package. JDBC is the mechanism in the java.sql package. JDBC is the mechanism Java application and applets use to perform Java application and applets use to perform database access. database access.

Prior JDBC, the only way to access a database Prior JDBC, the only way to access a database from a Java program was to do the database access from a Java program was to do the database access in C, and use native methods to interface the C in C, and use native methods to interface the C code with Java. JDBC is intended to be a low-level code with Java. JDBC is intended to be a low-level API that is powerful enough to exploit most API that is powerful enough to exploit most features available on commercial relational features available on commercial relational database, but is simple enough to be used by all database, but is simple enough to be used by all levels of programmer. levels of programmer.

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JDBC technology is an API that lets you access JDBC technology is an API that lets you access

virtually any tabular data source from the Java virtually any tabular data source from the Java programming language. It provides cross-DBMS programming language. It provides cross-DBMS connectivity to a wideconnectivity to a widerange of SQL databases, and now, with the new range of SQL databases, and now, with the new JDBC API, it also provides access to other tabular JDBC API, it also provides access to other tabular data sources, such as spreadsheets or flat files.data sources, such as spreadsheets or flat files.

Benefit Benefit a developer can easily connect all corporate data a developer can easily connect all corporate data

even in a heterogeneouseven in a heterogeneous environment environment

JDBC and JavaJDBC and Java

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JDBC Technology Core features (part of the JavaTM 2 SDK, Standard Edition )

Feature Benefit

Result set enhancements Ease of programming

- Scrollable result set Ability to move a result set's cursor to a specific row. This feature is used by GUI tools and for programmatic updating

Updatable result set Ability to use Java programming language commands rather than SQL

New data types support Performance improvement (ability to manipulate large objects such as BLOB and CLOB without bringing them to the client from the DB server)

Batch updates Performance improvement (sending multiple updates to the DB for processing as a batch can be much more efficient than sending update statements separately

(http://www.javasoft.com/products/jdbc/features.html)

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JDBC Optional Package features (the javax.sql package)

(http://www.javasoft.com/products/jdbc/features.html)

JDBC Optional Package features (the javax.sql package)

Feature Benefit

JNDI support Ease of deployment (gives JDBC driver independence, makes JDBC applications easier to manage)

Connection pooling Performance improvement (a connection pool is a cache of database connections that is maintained in memory, so that the connections may be reused)

Distributed transactions

Important for implementing a distributed transaction processing system

JavaBeansTM (RowSet objects)

Send data across a network to thin clients, such as web browsers, laptops, PDAs, and so on

Access any tabular data source, even spreadsheets or flat files Make results sets scrollable or updatable when the JDBC driver

does not support scrollability and updatability Encapsulate a driver as a JavaBeans component for use in a GUI

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JDBC SecurityJDBC Security

Most Java security is centered on the applet and its capacities as code downloaded via the Internet or Intranet.

restricted in their access to the client machine and cannot read or write to files on that machine.

the only machine to which they are allowed to make a database connection is the machine from which they were downloaded.

These restrictions are relaxed when applets are run using applet runners such as the Java Appletviewer or the HotJava browser (Art Taylor 1997)

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JAVA and JDBCJAVA and JDBC

Rather than simply being used to “bring life to Rather than simply being used to “bring life to Web pages”, Java with database now can fill the Web pages”, Java with database now can fill the role of database –aware applications for a role of database –aware applications for a variety of needsvariety of needs currently common gateway interface (CGI)

applications are required to access databases from within Web browsers

Java applets with JDBC now have the potential to provide the functionality with more direct programming and the potential for improved performance.

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Java Applet Java Applet

A Java applet is a small, compact application A Java applet is a small, compact application downloaded as Java bytecodes over the Internet downloaded as Java bytecodes over the Internet by a World Wide Web browser.by a World Wide Web browser. programs represent one of the more common

uses of a Java application and can perform most of the functions of a regular Java application

An applet can either trusted or untrusted. A trusted applet has convinced the Java virtual machine that it can be trusted either by providing a cryptographic key or some other means. Once trusted, this applet could have access to local data.

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Java AppletJava Applet

An applet that has not provided some means of authentication is considered untrusted and would not have access to any local data. This applet could, however. Open a database connection back to the server from which it was downloaded.

An applet is designed to embedded in a Web page and then to supplement the HTML page being rendered by the browser.

Because an applet is a Java program, it is much easier to perform complex functions with an applet than with HTML, which is not a program language.

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Java AppletJava Applet

An applet can use GUI interface. Some GUI An applet can use GUI interface. Some GUI facilities are available as part of an HTML page, facilities are available as part of an HTML page, but Java allows a finer level of programming but Java allows a finer level of programming with the GUI controls.with the GUI controls.

Java applet make the programming of special-Java applet make the programming of special-purpose applications simpler and practically purpose applications simpler and practically eliminate the software distribution cost for these eliminate the software distribution cost for these programs. When combined with JDBC to programs. When combined with JDBC to enable access to relational databases, the enable access to relational databases, the possibility for special-purpose Java applet is possibility for special-purpose Java applet is greatly expanded. greatly expanded.

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Applet IssuesApplet Issues

There are also a number of issues to be considered. There are also a number of issues to be considered. These are especially issues that must be considered These are especially issues that must be considered

with all Web applications, specially performance with all Web applications, specially performance and security. and security. Access bandwidth over the Internet tends to

vary and impacts performance. An application that access a database through the Internet most likely will perform worse than the same application run over the local network.

An applet downloaded over the Internet operates within a fairly restrictive set of security rules. The object of these rules is to protect the interest of the user by protecting their client machine, but the programmer of the applet must consider these rules when designing the application.

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Applet IssuesApplet Issues

In general, normal unsigned applets are considered untrustworthy and are not allowed access to any local database or local files.

An applet that manages to convince the local Java machine that it can be trusted by providing a password or cryptographic key

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JDBC ApplicationJDBC Application

Java JDBC can be two-tiered (conventional Java JDBC can be two-tiered (conventional client-server) or three-tiered(partitioned client-server) or three-tiered(partitioned application).application).

While it is expected that many applications will While it is expected that many applications will make use of two-tiered application development, make use of two-tiered application development, there are advantages to the three-tiered there are advantages to the three-tiered approachapproach

StateImplementationInterfaceIdentifierPrincipals

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Two-tiered ApplicationTwo-tiered Application

There is a front- end portion of the application that There is a front- end portion of the application that request data. The data is stored on and retrieved request data. The data is stored on and retrieved from a server. The following figure is an example.from a server. The following figure is an example.

Tier Two

Database Instances

Tier OneClient

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Two-tiered ApplicationTwo-tiered Application

This approach has the benefit of moving front-end This approach has the benefit of moving front-end processing off the server where there is usually a processing off the server where there is usually a significant demand for CPU cycles and places significant demand for CPU cycles and places processing on the client where there are usually processing on the client where there are usually plenty of CPU cycles available.plenty of CPU cycles available.

It has the benefit of allowing data collection to be It has the benefit of allowing data collection to be performed in what is usually a rich GUI performed in what is usually a rich GUI environment such as windows. The GUI environment such as windows. The GUI environment requires CPU cycles and fast access to environment requires CPU cycles and fast access to the display device.To run such an application on the display device.To run such an application on the server could require CPU resources that could the server could require CPU resources that could be scarce on a busy server, and significant be scarce on a busy server, and significant bandwidth to the display device. bandwidth to the display device.

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Two-tiered ApplicationTwo-tiered Application

DisadvantageDisadvantage When an application must retrive a large

number of rows from the server and process the rows in application memory , then the traditional two-tiered, client-server model to suffer performance degradation.

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  TTwo-tiered Realization of The CSCC wo-tiered Realization of The CSCC

Project Project

Tier Two

Database Instances

Client

Tier One

WebPageAppletData

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The WebpageThe Webpage

Dreamwaver3 Dreamwaver3

Firework3Firework3

Flash4Flash4

Photoshop5.5Photoshop5.5

Paintshop. Paintshop.

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The AppletThe Applet

Client Program

OracleDatabase

CustomerLogin

OrderData Search

Customer Database Update

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Advantages of this ApproachAdvantages of this Approach

Because the applet runs on the client, so Because the applet runs on the client, so the approach saves Server CPU cycles the approach saves Server CPU cycles and spaces.and spaces.

The cost of the realization is less The cost of the realization is less expensive than three tier’s approaches. expensive than three tier’s approaches. Because it saves one serverBecause it saves one server

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The disadvantages of the approachThe disadvantages of the approach

In a large enterprise, there is a need to control In a large enterprise, there is a need to control data access and enforce enterprise rules.data access and enforce enterprise rules.

If it is supported by the database server, some If it is supported by the database server, some portion of these rules can be enforced using portion of these rules can be enforced using stored procedures on the database server.stored procedures on the database server.

In more complicated business rules, using a In more complicated business rules, using a three tiered approach, a central application tier three tiered approach, a central application tier composed of remote methods and accessed using composed of remote methods and accessed using RMI can be used to enforce these rules. RMI can be used to enforce these rules. Creation and DisposalCreation and Disposal

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Future WorkFuture Work

Because of the equipment restriction, we did not try the application by putting applet and data to the same server.

If we use signed applet, it will spend about $400 to get the ID,certificate.So we can not try the signed applet on the Internet Explorer or Netscape. We only tested the program by using Appletviewer.

If in the future someone has chance , to test the approach in the same server. It will be fine.

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Benefits of Enterprise JavaBeansBenefits of Enterprise JavaBeans

Developer Architecture IndependentDeveloper Architecture Independent Write once, run anywhere (WORA)Write once, run anywhere (WORA) Establish Roles for Application DevelopmentEstablish Roles for Application Development EJBs Takes Care of Transaction ManagementEJBs Takes Care of Transaction Management Provides Distribute Transaction SupportProvides Distribute Transaction Support Creates Portable and Scalable SolutionCreates Portable and Scalable Solution Seamlessly Integrates with CORBASeamlessly Integrates with CORBA Provides for Vendor Specific EnhancementProvides for Vendor Specific Enhancement

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Modeling using Session and Entity EJBs

Use Session Beans for Application Logic

Use Session Beans as the only interface to the Client

Expect Little Reuse of Session Beans

Use Session Beans to Control the Workflow of a Group of Entity Beans

Use Entity Beans to develop a persistent object model

Use Entity Beans to Enforce Accuracy/Integrity of the Database

Insist on Reuse of Entity Beans

Model Domain Objects with a Unique Identity Shared by Multiple Clients

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The Architecture of this Application

J2EE ServerJ2EE Server

… ...

HTTPHTMLHTML

Database

JDBC

EJB Server

Session Beans

RMI/IIOP

Web Server

Servlets

Dynamically generated presentation

Entity Beans Entity BeansBusiness Logic

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Component Diagram of Enterprise Component Diagram of Enterprise BeansBeans

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Developing Web-based Application with Developing Web-based Application with J2EEJ2EE

Develop Entity BeansDevelop Entity Beans Develop Session BeansDevelop Session Beans Develop ClientsDevelop Clients Start up the Server & Deploy ToolStart up the Server & Deploy Tool Build the Bean and War Components (Define the Build the Bean and War Components (Define the

deployment descriptor)deployment descriptor) Deploy the ApplicationDeploy the Application

Specify the JNDI name and Web Context name Run the ApplicationRun the Application

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Developing & Deploying Entity BeansDeveloping & Deploying Entity Beans

Define Home InterfaceDefine Home Interface Define Remote InterfaceDefine Remote Interface Define a Primary Key ClassDefine a Primary Key Class Implement the Bean ClassImplement the Bean Class Compile the Above ClassesCompile the Above Classes Set up the Data Source to the DatabaseSet up the Data Source to the Database

With BMP, You Should Create the Database Manually

With CMP, the Container Create the Database at Deploying Time

Define the Deployment Descriptor with Define the Deployment Descriptor with DeploytoolDeploytool

Start J2EE Server and Your are Ready to DeployStart J2EE Server and Your are Ready to Deploy

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Define Home InterfaceDefine Home Interface

The Home Interface Defines the Life Cycle of an The Home Interface Defines the Life Cycle of an Enterprise BeanEnterprise Bean

It Extends javax.ejb.EJBHome InterfaceIt Extends javax.ejb.EJBHome Interface create<create<METHOD>(…)METHOD>(…) Methods Methods

The Return Type Must Be the Entity Bean’s Remote Interface Type

find<METHOD>(…) Methods findByPrimaryKey(PrimaryKey pk) Method is

Mandatory for Entity Beans Home Methods (Only in EJB2.0)Home Methods (Only in EJB2.0)

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Home Interface SampleHome Interface Sample

// Sample entity bean home interface

import javax.ejb.*;

import java.rmi.RemoteException;

import java.util.Collection;

public interface CustomerHome extends EJBHome{

Customer create(String customerID,String name,String address,String password) throws CreateException, RemoteException;

public Customer findByPrimaryKey(String customerID) throws FinderException,RemoteException;

public Collection findByName(String name) throws FinderException,RemoteException;

}

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Define Remote InterfaceDefine Remote Interface

The Remote Interface Defines the Business Methods of an Enterprise Bean

It extends javax.ejb.EJBObject Interface For Every Method in the Remote Interface, There

is a Corresponding Method in the Bean Implementation

import javax.ejb.*;import java.util.Vector;import java.rmi.RemoteException;

public interface Customer extends EJBObject{// simple get and set methodspublic String getName() throws RemoteException;public void setName(String name) throws RemoteException;public String getPassword() throws RemoteException;public void setPassword(String password) throws RemoteException;public String getAddress() throws RemoteException;public void setAddress(String address) throws RemoteException;

}

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import java.io.Serializable;public class AccountPK implements Serializable{

public String accountID;public AccountPK(){}public AccountPK(String accountID){

this.accountID = accountID;}public int hashCode(){

return accountID.hashCode();}public boolean equals(Object other) {

if ((other == null) || !(other instanceof AccountPK))return false;

AccountPK otherPK = (AccountPK) other;return accountID.equals(otherPK.accountID);

}}

Define Primary Key Class for Entity Define Primary Key Class for Entity BeanBean

The Primary Key Class is Used to Uniquely The Primary Key Class is Used to Uniquely Identify an Object Reference to an Entity BeanIdentify an Object Reference to an Entity Bean

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Develop Entity Bean ClassDevelop Entity Bean Class

Implement the Business Logic MethodsImplement the Business Logic Methods Implement ejbCreate<METHOD>(…) Methods Implement ejbCreate<METHOD>(…) Methods

and ejbPostCreate<METHOD>(…) Methodsand ejbPostCreate<METHOD>(…) Methods Implement ejbFind<METHOD>(…) MethodsImplement ejbFind<METHOD>(…) Methods

ejbFindByPrimaryKey(PrimaryKey pk) Method is Mandatory Implement ejbHome<METHOD>(…) Methods Implement ejbHome<METHOD>(…) Methods

(Only in EJB2.0)(Only in EJB2.0) Implement EJB Call Back MethodsImplement EJB Call Back Methods

ejbActivate(): Called When the Bean is Activated ejbPassivate(): Called When the Bean is Passivated ejbLoad(): Forces the Bean to Load State from Database ejbStore() : Forces the Bean to Store State from Database ejbRemove(): Called When Client Calls Remove() setEntityContext(...): Called by Container on Creation unsetEntityContext(): Called by Container Before Being Removed

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Sample Entity Bean ClassSample Entity Bean Class// This is a Container Managed Persistence Beanimport …public class CustomerBean implements EntityBean{ protected EntityContext ctx; public String customerID; … … public CustomerBean(){} // business methods public String getCustomerName() throws RemoteException { return customerName; } public void setName(String name) throws RemoteException { this.customerName=customerName; } // create and finder methods public CustomerPK ejbCreate(…) throws CreateException,RemoteException { this.customerID=customeID; … ;return null; } public void ejbPostCreate(…) throws CreateException,RemoteException{} public CustomerPK ejbFindByPrimaryKey(CustomerPK primaryKey)throws … {} // EJB call back methods public void setEntityContext(EntityContext ctx)throws RemoteException {this.ctx=ctx;} public void unsetEntityContext() throws RemoteException { this.ctx = null; } public void ejbActivate() throws RemoteException {} public void ejbPassivate() throws RemoteException {} public void ejbStore() throws RemoteException{} public void ejbLoad() throws RemoteException{} public void ejbRemove() throws RemoteException{}}

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Developing & Deploying Session BeansDeveloping & Deploying Session Beans

Define the Home InterfaceDefine the Home Interface

Define the Remote InterfaceDefine the Remote Interface

Implement the Bean ClassImplement the Bean Class

Compile Your Code and Define the Deployment Compile Your Code and Define the Deployment Descriptor with DeploytoolDescriptor with Deploytool

Start up J2EE Server and You are Ready to DeployStart up J2EE Server and You are Ready to Deploy

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Develop War ComponentsDevelop War Components

Develop ServletsDevelop Servlets

Compile Your CodeCompile Your Code

Use Deploytool to Assemble Your War ComponentUse Deploytool to Assemble Your War Component Designate Servlet Class EJB References Role Security Transaction

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State Diagram for the ServletsState Diagram for the Servlets

Create a new customer and send mail to the user using Confirm session bean

Newuser Servlet

Charge a customer through Teller bean and display the data.

Display Servlet

Verify an account by querying Account

beanVerify Servlet

Storefront Servlet

Authenticate user by querying Customer entity bean

Login Servlet

Avail Servlet

Tell what data available by querying ClimateData bean

Return to the main page

Fig. 4 State digram for the servlet

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Develop ServletsDevelop Servlets

Locate the Bean Container Using JNDI & Locate the Bean Container Using JNDI & RMI/IIOPRMI/IIOP

Create the Bean if Necessary (When Business Method Required)

Use the Bean Dispose of the Bean (Call remove() Method)

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How the Client Locates the Home How the Client Locates the Home ObjectObject

Get or Create a JNDI Naming ContextGet or Create a JNDI Naming Context Use the Context to Lookup the EJB Home Object Use the Context to Lookup the EJB Home Object

Through RMI/IIOPThrough RMI/IIOP Use the Home Object to Create the Beans.Use the Home Object to Create the Beans.

try {// Get the JNDI naming contextContext initial = new InitialContext();// Use the context to lookup the EJB home interfaceObject objref = initial.lookup("TheAccount");// Use RMI/IIOP to get the EJB home interfaceaccountHome = (AccountHome)PortableRemoteObject.narrow(objref,AccountHome.class);

}catch(Exception e){

throw new ServletException(e.toString());}

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… ...public class NewuserServlet extends HttpServlet{ private CustomerHome customerHome; public void init() throws ServletException{ try { // Locate the Home Object

Context initial = new InitialContext();Object objref = initial.lookup("TheCustomer");

customerHome = (CustomerHome) PortableRemoteObject.narrow(objref,CustomerHome.class); } catch(Exception e){… … …} }

public void doGet((HttpServletRequest request,...)throws ServletException, IOException{

… … … try{ //Call finder methods or obtain Remote Reference customerHome.findByPrimaryKey(new CustomerPK(customerID)); customerHome.create(…); } … … …

Sample EJB ClientsSample EJB Clients

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Conclusions and Future ResearchConclusions and Future Research

ConclusionsConclusions Easy to Develop with J2EE Flexible Powerful

Future ResearchFuture Research New Feture in EJB2.0

Message-driven Bean

Persistence Provider

etc. Fully Explore EJBs.

JNDI, RMI, JSP, XML, JMS, Java IDL, JTS, JTA, JavaMail, and JAF

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System EvaluationSystem Evaluation

Learning vs. DevelopingLearning vs. Developing

Code LengthCode Length

Efficiency

Influence On Each Approach When Database Influence On Each Approach When Database ChangesChanges

Influence On Each Approaches When Business Rules Change

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Learning vs. DevelopingLearning vs. Developing

EJBsEJBs two months to learn while half a month to

develop

ServletServlet Have to know certain knowledge about Java.

AppletApplet The easiest to learn.

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Code LengthCode Length

EJBsEJBs Shortest code length, lots of duplicate codes.

ServletServlet Has the longest code length

AppletApplet Between EJBs and Servlet.

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Efficiency

EJBsEJBs Has the worst efficiency in the three

approaches

ServletServlet Faster than EJBs

AppletApplet Fastest among the three approaches.

Directly access the database by using the low-level interface

CSE298

CSE300

CSE.RU-1.64

Influence on Each Approach When Influence on Each Approach When Database Changes Database Changes

EJBsEJBs Simply re-designate the data source and re-

deploy the application, no source code change needed.

ServletServlet Have to change code and recompile and re-

deploy.

AppletApplet Have to change code and recompile and re-

deploy

CSE298

CSE300

CSE.RU-1.65

Influence On Each Approaches When Business Rules Change

EJBsEJBs Rewrite the session beans

ServletServlet Can update the rules but not flexible.

AppletApplet Difficult to update or enhance the rule

CSE298

CSE300

CSE.RU-1.66

ConclusionsConclusions

JDBC offers a database-independent means to JDBC offers a database-independent means to enable data for use in Java applicationenable data for use in Java application

Java Servlet architecture provides a component Java Servlet architecture provides a component container model that can result in a significant container model that can result in a significant amount of simplified HTTP communicationamount of simplified HTTP communication

EJB provides a standard component model for EJB provides a standard component model for developing distributing application as developing distributing application as components that operate inside of an EJB components that operate inside of an EJB containercontainer

CSE298

CSE300

CSE.RU-1.67

Future Work

JavaServer PagesJavaServer Pages Combination of markup with Java Code to

produce a dynamic web page

ServletServlet JINI and JavaSpace

Java RMI and IDLJava RMI and IDL Homogeneous & heterogeneous network

environments