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Web Design & Development CS506

request, _jspService() method is invoked

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Web Design & Development CS506

Web Design & Develoment

</h3> <br>

<h3> <input type="radio" name = "page" value="java"/>Java

</h3><br>

</form>

</body>

</html>

controller.jsp

Based upon the selection made by the user, this page will redirect the user to respective pages. Those are

web.jspand java.jsp

<html>

<body>

// reading parameter named page

String pageName = request.getParameter("page");

// redirecting user based on selection made

if (pageName.equals("web"))

{

response.sendRedirect("web.jsp");

}

else if (pageName.equals("java") )

{

response.sendRedirect("java.jsp");

}

</body>

</html>

web.jsp

This page is used to display course outline of "web design and development" in a tabular format after

reading them from database. The code is:

// importing java.sql package using page directive, to work with database

<%@page import="java.sql.*"%>

<html>

<body>

<h2> Welcome to Web Design & Development Page </h2>

<h3> Course Outline</h3>

<TR>

<TH>Session No.</TH>

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<TH>Topics</TH>

<TH>Assignments</TH>

</TR>

<%-- start of scriptlet --%>

<% // establishing conection

Class.forName("sun.jdbc.odbc.JdbcOdbcDriver");

String conUrl = "jdbc:odbc:CourseDSN";

Connection con = DriverManager.getConnection(conUrl);

// preparing query using join statements

String sql = " SELECT sessionNo, topic, assignment " +"

FROM Course, SessionDetail" +" WHERE courseName = ? " + "

AND Course.courseId = SessionDetail.courseID";

PreparedStatement pStmt = con.prepareStatement(sql);

// setting parameter value "web".pStmt.setString( 1 , "web");

ResultSet rs = pStmt.executeQuery();

String sessionNo;

String topic;

String assignment;

// iterating over resultset

while (rs.next()) {

sessionNo = rs.getString("sessionNo");

topic = rs.getString("topic");

assignment = rs.getString("assignment");

if (assignment == null){

assignment = "";

}

<%-- end of scriptlet --%>

<%-- The values are displayed in tabular format usingexpressions,

however it can also be done usingout.println(sessionNo) like statements

--%>

<TR>

</TR>

} // end while

</TABLE >

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</center>

</body>

</html>

java.jsp

The code of this page is very much alike of "web.jsp". The only change is in making of query. Here the

value is set "java" instead of "web"

// importing java.sql package using page directive, to work with database

<%@page import="java.sql.*"%>

<html>

<body>

<h2> Welcome to Java Page </h2>

<h3> Course Outline</h3>

<TR>

<TH>Session No.</TH>

<TH>Topics</TH>

<TH>Assignments</TH>

</TR>

<%-- start of scriptlet --%>

// establishing connection

Calss.forName("sun.jdbc.odbc.JdbcOdbcDriver");

String conUrl = "jdbc:odbc:CourseDSN";

Connection con = DriverManager.getConnection(conUrl);

// preparing query using join statements

String sql = " SELECT sessionNo, topic, assignment " +"

FROM Course, SessionDetail" +" WHERE courseName = ? " + "

AND Course.courseId = SessionDetail.courseID";

PreparedStatement pStmt = con.prepareStatement(sql);

// setting parameter value "web".pStmt.setString( 1 , "java");

ResultSet rs = pStmt.executeQuery();

String sessionNo;

String topic;

String assignment;

// iterating over resultset

while (rs.next())

{

sessionNo = rs.getString("sessionNo");

topic = rs.getString("topic");

assignment = rs.getString("assignment");

if (assignment == null)

{

assignment = "";

}

<%-- end of scriptlet --%>

<%-- The values are displayed in tabular format usingexpressions, however it can also be done

usingout.println(sessionNo) like statements

--%>

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<TR>

</TR>

} // end while

</TABLE >

</center>

</body>

</html>

Issues with Last Example

Too much cluttered code in web.jsp and java.jsp. This makes it very difficult to understand (probably you

experienced it by yourself) and to make changes/enhancements.

A single page is doing everything that is really a bad approach while making of web applications. The tasks

performed by web.jspor java.jspare:

Displaying contents (Presentation logic)

Connecting with database (DB connectivity logic)

Results Processing (Business Logic)

Can we simplify it? Yes, the answer lies in the use of JavaBeans technology.

JavaBeans

A java class that can be easily reused and composed together in an application. Any java class that follows

certain design conventions can be a JavaBean.

JavaBeans Design Conventions

These conventions are:

A bean class must have a zero argument constructor

A bean class should not have any public instance variables/attributes (fields)

Private values should be accessed through setters/getters

For boolean data types, use boolean isXXX( ) & setXXX(boolean)

A bean class must be serializable

A Sample JavaBean

The code snippet of very basic JavaBean is given below that satisfies all the conventions described above.

The MyBean.java class has only one instance variable.

public class MyBean implements Serializable { private String name; // zero argument constructor

public MyBean( ){

name = "";

}

// standard setter

public void setName(String n) {

name = n;

}

// standard getter

public String getName( ) {

return name;

}

// any other method

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public void print( ) {

System.out.println("Name is: " + name);

}

} // end Bean class

Example Code: Displaying course outline by incorporating JavaBeans

This example is made by making more enhancements to the last one. Two JavaBeans are included in this

example code. These are CourseOutlineBean& CourseDAO.

The CourseOutlineBean is used to represent one row of the table. It contains the following attributes:

sessionNo

topic

assignment

The CourseDAO (where DAO stands of Data Acess Object) bean encapsulates database connectivity and

result processing logic.

The web.jsp and java.jsp will use both these JavaBeans. The code of these and the JSPs used in this

example are given below.

CourseOutlineBean.java

package vu;

import java.io.*;

public class CourseOutlineBean implements Serializable{

private int sessionNo;

private String topic;

private String assignment;

// no argument constructor

public CourseOutlineBean() {

sessionNo = 0;

topic = "";

assignment = "";

}

// setters

public void setSessionNo(int s){

sessionNo = s;

}

public void setTopic(String t){

topic = t;

}

public void setAssignment(String a){

assignment = a;

}

// getterspublic

int getSessionNo( ){

return sessionNo;

}

public String getTopic( ){

return topic;

}

public String getAssignment( ){

return assignment;

}

} // end class

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CourseDAO.java

package vu;

import java.io.*;

import java.sql.*;

import java.util.*;

public class CourseDAO implements Serializable{

private Connection con;

public CourseDAO() {

establishConnection();

}

//********** establishConnection method ************* method used to make connection with

databaseprivate

void establishConnection(){

try{

// establishing conection

Class.forName("sun.jdbc.odbc.JdbcOdbcDriver");

String conUrl = "jdbc:odbc:CourseDSN";

con = DriverManager.getConnection(conUrl);

}catch(Exception ex){

System.out.println(ex);

}

//*********** retrieveCourseList method ********************

public ArrayList retrieveCourseList(String cName){

ArrayList courseList = new ArrayList();

try{

String sql = " SELECT sessionNo, topic, assignment " +"

FROM Course, SessionDetail" +"

WHERE courseName = ? " + "

AND Course.courseId = SessionDetail.courseID ";

PreparedStatement pStmt = con.prepareStatement(sql);

pStmt.setString(1, cName);

ResultSet rs = pStmt.executeQuery();

int sNo;

String topic;

String assignment;

while ( rs.next() ) {

sNo = rs.getInt("sessionNo");

topic = rs.getString("topic");

assignment = rs.getString("assignment");

if (assignment == null)

{

assignment = "";

}

// creating a CourseOutlineBean object

CourseOutlineBean cBean = new CourseOutlineBean();

cBean.setSessionNo(sNo);

cBean.setTopic(topic);cBean.setAssignment(assignment);

// adding a bean to arraylist

courseList.add(cBean);

}

}catch(Exception ex){

System.out.println(ex);

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} finally {

// to close connection

releaseResources();

}

// returning ArrayList object

return courseList;

} // end retrieveCourseOutline

//********** releaseResources method ********************

private void releaseResources(){

try{

if(con != null){

con.close();

}

}catch(Exception ex){

System.out.println();

}

} // end releaseResources

}//end CourseDAO

index.jsp

This page is used to display the course options to the user in the radio button form.

<html>

<body>

<h2>Select the page you want to visit</h2>

Web Design & Develoment

</h3> <br>

<h3> <input type="radio" name = "page" value="java"/>Java

</h3><br>

</form>

</body>

</html>

controller.jsp

Based on user selection, redirects the user to desired page.

<html>

<body>

String pageName = request.getParameter("page");

if (pageName.equals("web")) {

response.sendRedirect("web.jsp");

} else if (pageName.equals("java") )

{

response.sendRedirect("java.jsp");

}

</body>

</html>

web.jsp

This page is used to display course outline of "web design and development" in a tabular format after

reading them from database. Moreover, this page also uses the JavaBeans (CourseOutlineBean &

CourseDAO).

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Web Design & Development CS506

<%@page import="java.util.*" %>

<%-- importing vu package that contains the JavaBeans--%>

<%@page import="vu.*" %>

<html>

<body>

<h2> Welcome to Web Design & Development Course </h2>

<h3> Course Outline</h3>

<TR>

<TH>Session No.</TH>

<TH>Topics</TH>

<TH>Assignments</TH>

</TR>

<%-- start of scriptlet --%>

// creating CourseDAO object

CourseDAO courseDAO = new CourseDAO();

// calling retrieveCourseList() of CourseDAO class and

// passing "web" as value. This method returns ArrayListArrayList

courseList = courseDAO.retrieveCourseList("web");

CourseOutlineBean webBean = null;

// iterating over ArrayList to display course outline

for(int i=0; i<courseList.size(); i++){

webBean = (CourseOutlineBean)courseList.get(i);

<%-- end of scriptlet --%>

<TR>

</TR>

} // end for

</TABLE >

</center>

</body>

</html>

java.jsp

The code contains by this page is almost same of web.jsp. Here, "java" is passed to retieveCourseList( )

method. This is shown in boldface.

<%@page import="java.util.*" %>

<%-- importing vu package that contains the JavaBeans--%><%@page import="vu.*" %>

<html>

<body>

<h2> Welcome to Java Course </h2>

<h3> Course Outline</h3>

<TR>

<TH>Session No.</TH>

<TH>Topics</TH>

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Web Design & Development CS506

<TH>Assignments</TH>

</TR>

<%-- start of scriptlet --%>

// creating CourseDAO object

CourseDAO courseDAO = new CourseDAO();

// calling retrieveCourseList() of CourseDAO class and

// passing "java" as value. This method returns ArrayList

ArrayList courseList = courseDAO.retrieveCourseList("java");

CourseOutlineBean javaBean = null;

// iterating over ArrayList to display course outline

for(int i=0; i<courseList.size(); i++){

javaBean = (CourseOutlineBean)courseList.get(i);

<%-- end of scriptlet --%>

<TR>

</TR>

} // end for

</TABLE >

</center>

</body>

</html>

References:

Entire material for this handout is taken from the book JAVA A Lab Course by Umair Javed.

This material is available just for the use of VU students of the course Web Design and

Development and not for any other commercial purpose without the consent of author.

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