Logic Equal Tag (<logic:equal>...</logic:equal>)

equal tag - if the requested variable is equal to the specified value then this tag is used to evaluate the contents contained in the nested body parts of this tag.

Compares the variable passed against the specified constant value. The nested body content of this tag is evaluated if the variable and value are equal.

Attribute Name	Description
cookie	The variable contains the cookie value needed to compare .Here the name is specified by this attribute.
header	The variable contains the header value needed to compare whose name is specified by this attribute. The name match is performed in a case insensitive manner.
name	The variable to be compared is the JSP bean specified by this attribute, if `property` is not specified, or the value of the specified property of this bean, if `property` is specified.
parameter	The variable to be compared is the first, or only, value of the request parameter specified by this attribute.
property	The variable contains the bean property value needed to compare ,it is specified by this attribute. The property reference can be simple, nested, and/or indexed.
scope	This specifies the bean scope within which the bean is searched by the `name` property, or "any scope" if not specified.
value	The constant value is specified by other attribute(s) of this tag, needed to compare

Logic notEqual Tag (<logic:notEqual >...</logic:notEqual>)

notEmpty - if the requested variable is not equal to the specified value then this tag is used to evaluate the contents contained in the nested body parts of this tag.

Compares the variable passed against the specified constant value. The nested body content of this tag is evaluated if the variable and value are not equal.

Attributes of notEmpty Tag

Attribute Name	Description
cookie	The variable contains the cookie value needed to compare .Here the name is specified by this attribute.
header	The variable contains the header value needed to compare whose name is specified by this attribute. The name match is performed in a case insensitive manner.
name	The variable to be compared is the JSP bean specified by this attribute, if `property` is not specified, or the value of the specified property of this bean, if `property` is specified.
parameter	The variable to be compared is the first, or only, value of the request parameter specified by this attribute.
property	The variable contains the bean property value needed to compare ,it is specified by this attribute. The property reference can be simple, nested, and/or indexed.
scope	This specifies the bean scope within which the bean is searched by the `name` property, or "any scope" if not specified.
value	The constant value is specified by other attribute(s) of this tag, needed to compare

Example Illustrating the use of the Equal<logic:equal> and the notEqual <logic:notEqual> logic tags.

Here you will learn to use the Struts Logic Equal and notEqual tags. We will cover an example that will show a comparison between the two logic tags (ie..<logic:equal > and the <logic:notEqual >).

Example code

Creating an Action Class

Develop a simple action class LogicAction.java.



package roseindia.net;

 

 import java.io.*;

 import java.util.*;



/**

* @author Amit Gupta * @Web http://www.roseindia.net * @Email [email protected] **/ import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import javax.servlet.ServletException; import org.apache.struts.action.*; public class LogicAction extends Action { public ActionForward execute(ActionMapping mapping, ActionForm form, HttpServletRequest request, HttpServletResponse response) throws IOException, ServletException { return mapping.findForward("success"); } }

Creating Form Bean

Our form bean class contains only one property number. Here is the code of FormBean (LogicForm.java)

package roseindia.net;

    

    import org.apache.struts.action.*;

    

    /**

    

    * @author Amit Gupta

    * @Web http://www.roseindia.net

    * @Email [email protected]

    

    **/

import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; public class LogicForm extends ActionForm { private long number; public long getNumber() { return number; } public void setNumber(long number) { this.number=number; } }

Defining form Bean in struts-config.xml file

Add the following entry in the struts-config.xml file for defining the form bean

<form-bean name="LogicForm" type="roseindia.net.LogicForm" />

Developing the Action Mapping in the struts-config.xml

Here, Action mapping helps to select the method from the Action class for specific requests.

Developing the InputLogic.jsp page

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

<html:html>
<head>
<title>Using <logic> Tags</title>
</head>

<body>
<h1>Using <logic> Tags</h1>

<html:form action="/LogicAction" method ="post">

<h2>Enter a number:</h2>
<html:text property="number"/>

<br>
<h3>The <logic:Equal>tag works if you enter 1</h3>

<h3>else The <logic:notEqual> is processed </h3>

<br>

<html:submit value="Submit"/>

<html:cancel/>
</html:form>
</body>
</html:html>

Developing the output.jsp page 0

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

<HTML>
<HEAD>
<TITLE>Here's Your Data...</TITLE>
</HEAD>

<BODY>
<H3>Here's Your Data...</H3>

<h4>The number entered is:

<bean:write name="LogicForm" property="number"/></h4>

<logic:equal name="LogicForm" property="number" value="1">
<h4>Using the tag <logic:equal ></h4>
Result : Equal
</logic:equal>

<logic:notEqual name="LogicForm" property="number" value="1">
<h4>Using the tag <logic:notEqual > </h4>
Result : notEqual
</logic:notEqual>

</BODY>
</HTML>

Add the following line in the index.jsp to call the form.

<li>
<html:link page="/pages/InputLogic.jsp">Struts File Upload</html:link>
<br>
Example demonstrates how LogicAction Class works.
</li>

Building and Testing the Example 1

To build and deploy the application go to Struts\Strutstutorial directory and type ant on the command prompt. This will deploy the application. Open the browser and navigate to the InputLogic.jsp page. Your browser displays the following page.

Writing value equal to1 to the InputLogic.jsp page displays the working of the Equal Logic tag <logic:equal >

It displays the following out.jsp page 2

Now write any data other than 1 to the InputLogic.jsp to see the working of the notEqual logic tag <logic:notEqual>

The <logic:notEqual > evaluated here displays the output.jsp as

Logic Equal Tag (...)