JSP tutorial part 17: JSP property actions

The <jsp:setProperty> Action:

The setProperty action sets the properties of a Bean.

There are two basic ways to use the setProperty action:

1. You can use jsp:setProperty after, but outside of, a jsp:useBean element, as below:

<jsp:useBean id="myName" ... />

.......

<jsp:setProperty name="myName" property="someProperty" .../>

In this case, the jsp:setProperty is executed regardless of whether it is a new bean

or an existing bean.

2. A second context in which jsp:setProperty can appear is inside the body of a

jsp:useBean element, as below:

<jsp:useBean id="myName" ... >

...

<jsp:setProperty name="myName" property="someProperty" .../>

</jsp:useBean>

Here, the jsp:setProperty is executed only if a new object is instantiated, not if an

existing one is found.

Following are the list of attributes associated with setProperty action:

Attribute	Description
name	Designates the bean whose property will be set. The Bean must have been previously defined.
property	Indicates the property you want to set. A value of "*" means that all request parameters whose names match bean property names will be passed to the appropriate setter methods.
value	The value that is to be assigned to the given property. The parameter's value is null, or the parameter does not exist, the setProperty action is ignored.
param	The param attribute is the name of the request parameter whose value the property is to receive. You can't use both value and param, but it is permissible to use neither.

The <jsp:getProperty> Action:

 The getProperty action is used to retrieve the value of a given property and Converts it to a string, and finally inserts it into the output.

The getProperty action has only two attributes, both of which are required.

<jsp:useBean id="myName" ... />

...

<jsp:getProperty name="myName" property="someProperty" .../>

Following is the list of required attributes associated with setProperty action:

Attribute	Description
name	The name of the Bean that has a property to be retrieved. The Bean must have been previously defined.
property	The property attribute is the name of the Bean property to be retrieved.

Building Beans : jsp:useBean:

Format

– <jsp:useBean id="name" class="package.classname" />

Purpose

– Allow instantiation of Java classes without explicit Java programming.

Example:

<jsp:useBean id="book1" class=“org.asr.beans.Book" />

is equivalent to the scriptlet

<% org.asr.beans.Book book1 = new org.asr.beans.Book(); %>

– But jsp:useBean has two additional advantages:

• It is easier to derive object values from request parameters

• It is easier to share objects among pages or servlets

Setting Simple Bean Properties : jsp:setProperty:

Format

– <jsp:setProperty name="name"

property="property"

value="value" />

Purpose

– Allows setting of bean properties (i.e., calls to setXxx methods) without explicit

java programming

Example

– <jsp:setProperty name="book1"

property="title"

value="Core Servlets and JavaServer Pages" />

is equivalent to the following scriptlet

<% book1.setTitle("Core Servlets and JavaServer Pages"); %>

Accessing Bean Properties : jsp:getProperty:

Format

– <jsp:getProperty name="name" property="property" />

Purpose

– Allows access to bean properties (i.e., calls to getXxx methods) without explicit

java programming

Example

<jsp:getProperty name="book1" property="title" />

is equivalent to the following scriptlet

<%= book1.getTitle() %>