<s:if> test expression evaluation for boolean value doesn't work as expected

Use struts tag to create a variable like this

<s:set var="bool_val" value="true" />
expression evaluated value : 
<s:if test="%{#bool_val == true}">
    TRUE
</s:if><s:else>
    FALSE
</s:else>

Here is a sample tutorial.

There is a shorter version to the one suggested by Visruth CV :

<s:set var="foo" value="true" />

expression evaluated value : 
<s:if test="foo">
    TRUE
</s:if><s:else>
    FALSE
</s:else>

In case you want to check the boolean value against an Action attribute, here is the way to go :

class FooAction extends ActionSupport {
    private Boolean _bar = true;

    public Boolean isBar() { return _bar; }
}

And in the jsp file :

expression evaluated value : 
<s:if test="isBar()">
    TRUE
</s:if>
<s:else>
    FALSE
</s:else>

You can't use a scriptlet variable in Struts tags unless you put this variable to the value stack. But you'd better not use a scriptlet variable, but the variable value.

<%@ taglib prefix="s" uri="/struts-tags" %>

<%boolean bool_val=true;%>
real value : <%=bool_val%><br/>
expression evaluated value : 
<s:set var="bool_val"><%=bool_val%></s:set>
<s:if test="#bool_val == 'true'">
    TRUE
</s:if><s:else>
    FALSE
</s:else>