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JavaBeans are simple classes that are used to develop dynamic WebPages. JavaBeans are required to create dynamic web pages by using separate java classes instead of using java code in a JSP page. It provides getter and setter methods to get and set values of the properties. Using JavaBeans it is easy to share objects between multiple WebPages.
Java Bean Properties:
- getPropertyName () : It is used to read the property. This method is called accessor.
- setPropertyName (): It is used to write the property. This method is called mutator.
useBean Tag
<jsp:useBean> tag is used to instantiate a JavaBean or to locate existing bean instance and assign it to a variable name. Synatx of <jsp:useBean> action tag :
<jsp:usebean id=”bean name” scope=”scope name” class=”packageName.className” beanName=”packageName.className” type=” packageName.className”/>
Where:
- id: It represents variable name assigned to id attribute of useBean tag
- scope: It represents scope in which bean instance has to be located.Scopes may be page,request,session, and application.Default scope is page.
- page : It indicates that bean can be used within JSP page until page sends response to client or forwards request to another resource.
- request : It Indicates bean can be used from any JSP page that processing same request until JSP page sends response to the client.
- session : It indicates that bean can be used from any JSP page invoked in the same session .The Page in which we create bean must have page directive with session=”true”.
- application : It indicates that bean can be used from any JSP page in the same application.
- class : It takes class name to create a bean instance if bean instance not present in given scope.It should have no-argument constructor and should not be an abstract class.
- beanName : It takes class name or expression .
- type : It takes a class or interface name, which can be used with class or beanName attribute. This attribute can be used with or without class or beanName.
useBean Example
Let us create a simple bean class Person.java:
Listing 1:Person.java
package javabeat.net.jsp.beans;
public class Person {
private String firstName = null;
private String lastName = null;
private int age = 0;
public String getFirstName() {
return firstName;
}
public void setFirstName(String firstName) {
this.firstName = firstName;
}
public String getLastName() {
return lastName;
}
public void setLastName(String lastName) {
this.lastName = lastName;
}
public int getAge() {
return age;
}
public void setAge(int age) {
this.age = age;
}
}
Listing 2: beanExample.jsp
<%@ page language='java' contentType='text/html; charset=UTF-8'
pageEncoding='UTF-8'%>
<!DOCTYPE html PUBLIC '-//W3C//DTD HTML 4.01 Transitional//EN' 'http://www.w3.org/TR/html4/loose.dtd'>
<html>
<head>
<meta http-equiv='Content-Type' content='text/html; charset=UTF-8'>
<title>Use Bean Example</title>
</head>
<body>
<jsp:useBean id='date' class='java.util.Date'/>
<jsp:useBean id='person' class='javabeat.net.jsp.beans.Person'>
<jsp:setProperty name='person' property='firstName'
value='joe'/>
<jsp:setProperty name='person' property='lastName'
value='smith'/>
<jsp:setProperty name='person' property='age'
value='10'/>
</jsp:useBean>
<h2>Simple use of bean calling java.util.Date</h2>
Today is <%=date%>
<h2>Example for Accessing JavaBeans Properties</h2>
<p><b>Person First Name:</b>
<jsp:getProperty name='person' property='firstName'/>
</p>
<p><b>Person Last Name:</b>
<jsp:getProperty name='person' property='lastName'/>
</p>
<p><b>Person Age:</b>
<jsp:getProperty name='person' property='age'/>
</p>
</body>
</html>
Execute the beanExample.jsp. Right click on beanExample.jsp and select Run > Run As. Following output would be seen:
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