Jsp examples

Beans and HTML Forms
Usually Beans are used to
represent the data of HTML
forms

Example: Name Form
<html>
<head>
<title>JSP Processong form using a bean</title>
</head>
<body>
<h1>JSP Processing form using a bean</h1>
<form action="doFormBean.jsp" method="GET">
First name: <input type="text" name="firstName"></ br>
Last name: <input type="text" name="lastName">
<p><input type="submit" name="button"
value="Submit Name"></p>
</form>
</body>
</html>

Example: Name Bean
package beans;
public class NameBean
{
private String firstName; // property
private String lastName; // property
public String getFirstName()
{ return firstName; }
public String getLastName()
{ return lastName; }

public void setFirstName(String first)
{ firstName = first; }
public void setLastName(String last)
{ lastName = last; }
}

Example: doFormBean.jsp
<jsp:useBean id="name" class="beans.NameBean" />
<jsp:setProperty name="name" property="*" />
<html>
<head>
<title>JSP Form results using a bean</title>
</head>
<body>
<h1>JSP Form results using a bean</h1>
Hello
<jsp:getProperty name="name" property="firstName" />
<jsp:getProperty name="name" property="lastName" />
</body>
</html>

Note the use of property="*" to set all the bean properties
using the form data values (i.e., GET/POST parameters)

MVC approach
MVC stands for Model-View-Controller
Controller:
controls the application by getting the input
and forwarding the request to the appropriate
page
View:
visual appearance of the output data
Model:
logic, calculations necessary to produce the
data. Sometimes called business logic

MVC Example (Temperature)
Getting the input (Fahrenheit temperature)
form.jsp (user input of temperature)
controller.jsp (dispatch (forward) request)
Displaying the output (Celsius temperature)
response.jsp
Model (logic and calculations done by beans)
TemperatureBean.java (form data)
TemperatureCalculatorBean.java
(does the temperature conversion)

TemperatureBean:

package beans;
public class TemperatureBean
{
private String temperature;

public String getTemperature()
{ return temperature; }

public void setTemperature(String t)
{temperature = t; }
}

TemperatureCalculatorBean:

package beans;
import java.text.DecimalFormat;
public class TemperatureCalculatorBean
{
private double celsius;

public String getTemperature()
{
return
new DecimalFormat("0.00").format(celsius);
}

// continued on next slide

TemperatureCalculatorBean (Contd.):

public void setTemperature(String fahr)
{
double f;
try
{
f = Double.parseDouble(fahr);
}
catch (NumberFormatException e)
{
f = 0.0;
}
celsius = (f - 32.0) * (5.0 / 9.0);
}
}

Forwarding A Page

A JSP can forward the request to another
page using
<jsp:forward page="file.jsp" />
The important idea here is that this new
page receives all the request parameters
of the forwarding page.

controller.jsp:

<jsp:useBean id=" temperature" class="beans.TemperatureBean">
<jsp:setProperty name="temperature" property="*" />
</jsp:useBean>
<% if (request.getParameter("temperature") == null)
{
%>
<jsp:forward page="form.jsp" />
<%
} else {
%>
<jsp:forward page="response.jsp" />
<% }
%>

form.jsp
<html>
<head>
<title>Fahrenheit to Celsius Conversion</title>
</head>
<body>
<h1>Fahrenheit to Celsius Conversion</h1>
<form action="controller.jsp" method="GET">
Fahrenheit temperature:
<input type="text" name="temperature"></ br>
<input type="submit" name="button"
value="Submit Temperature"></p>
</form>
</body>
</html>

response.jsp
<jsp:useBean id="temp" class="beans.Temperature"
property=“*” />
<jsp:useBean id="convert"
class="beans.TempertureCalculatorBean" />
<jsp:setProperty name="convert" property="temperature"
value="<%= temp.getTemperature() %>" />
<html>
<head><title>Fahrenheit to Celsius Conversion</title>
</head><body><h1>Fahrenheit to Celsius Conversion</h1>
<jsp:getProperty name="temp" property="temperature" />
Fahrenheit is
<jsp:getProperty name="convert"
property="temperature" /> Celsius.
<p><a href="controller.jsp">Convert another .. </a>
</p></body></html>

Reference
COS 2206 JSP, Barry G. Adams, Department of Mathematics and
Computer Science, Laurentain University.

Jsp examples

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