Best Practices in Java EE Web Development - Learn Java for Web Development - page 131

Listing 3-37. Using Scope

<c:set var="helloVar" value="hello" scope="session" />

We could also have expressed this by providing the value in the body content of the action,
as illustrated in Listing 3-38.

Listing 3-38. Using <c:set>with Body

<c:set var="hello" scope="session" >
helloworld
</c:set>

The value of a variable can also be an EL expression, as illustrated in Listing 3-39.

Listing 3-39. Using an EL Expression in a Value

<c:set var="titleVar" value="${book.title}" scope="session" />

In Listing 3-39, the title property of the book bean is set in the titleVar variable.
Listing 3-40 shows the scriptlet equivalent of <c:set> , as illustrated in Listing 3-36.

Listing 3-40. Scriptlet Equivalent of <c:set>

<%
String helloVar = "hello";
pageContext.setAttribute("helloVar ", helloVar);
%>

Setting the Property of a Speciied Target Object
To be able to set bean properties or map values using <c:set> , we need to use target and property ,
instead of var , which will define the bean and property name to be set. If target is map , for instance,
then property is the name of the key and value is the value for that key.
Here's the syntax:

<c:set value=""value""target=""target"" property=""propertyName""/>

If using a target object, the target must evaluate to a JavaBean or a



java.util.Map object.
If the target is a JavaBean, it must contain the appropriate getter/setter



methods.
Listing 3-41 illustrates how to set a map key using a <c:set> tag.

Listing 3-41. Setting a Map Key using the <c:set>Tag

<c:set target="bookMap" property="id" value="1">

This is equivalent to bookMap.put("id", "1"); . You can also supply the value in the body of the
<c:set> tag.