{"id":193,"date":"2007-09-06T00:00:00","date_gmt":"2007-09-06T00:00:00","guid":{"rendered":"http:\/\/www.strongd.net\/?p=193"},"modified":"2007-09-06T00:00:00","modified_gmt":"2007-09-06T00:00:00","slug":"Logic Empty Tag (...<\/logic:empty>)","status":"publish","type":"post","link":"https:\/\/www.strongd.net\/?p=193","title":{"rendered":"Logic Empty Tag (…<\/logic:empty>)"},"content":{"rendered":"

empty tag –<\/FONT> If the requested variable is either null or an empty string then we use this tag to evaluate the contents contained in the nested body parts of this tag.<\/I><\/FONT><\/H3>
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Tag evaluation of the nested body content occurs only if the specified value is either absent<\/B> (i.e. null<\/CODE>), an empty string<\/B> (i.e. a java.lang.String<\/CODE> with a length of zero), or an empty java.util.Collection<\/CODE> or java.util.Map<\/CODE> <\/B>(tested by the isEmpty() method on the respective interface).<\/FONT><\/P>
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Attributes of Empty Tag<\/B><\/FONT><\/P>
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Attribute Name<\/FONT><\/TH>
\n		Description<\/FONT><\/TH><\/TR><\/THEAD>
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name<\/B><\/FONT><\/TD>
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This attribute specifies a  JSP bean variable which is required to make comparison. <\/FONT><\/P><\/TD><\/TR>
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property<\/B><\/FONT><\/TD>
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The variable contains the property of the bean which is required to make comparison and is specified by the name<\/B><\/CODE> attribute. <\/FONT><\/P><\/TD><\/TR>
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scope<\/B><\/FONT><\/TD>
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This specifies the bean scope within which  the bean is searched  by the name<\/CODE> property, or “any scope” if not specified.<\/FONT><\/P><\/TD><\/TR><\/TBODY><\/TABLE><\/DIV>
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Logic notEmpty Tag (<logic:notEmpty>…<\/logic:notEmpty>) <\/FONT><\/H1>
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notEmpty<\/FONT><\/STRONG> – <\/FONT>If the requested variable is neither null nor an empty string then we use this tag to evaluate the contents contained in the nested body parts of this tag.
<\/I><\/FONT><\/H3>
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Tag evaluation of the nested body content occurs only if the specified value is available<\/B> (i.e.not null<\/CODE>) and is not an empty string (i.e. a java.lang.String<\/CODE> with a length of zero).

Attributes of notEmpty Tag<\/B><\/FONT><\/P>
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Attribute Name<\/FONT><\/TH>
\n		Description<\/FONT><\/TH><\/TR><\/THEAD>
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name<\/B><\/FONT><\/TD>
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This attribute specifies a  JSP bean variable which is required to make comparison.  <\/FONT><\/P><\/TD><\/TR>
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property<\/B><\/FONT><\/TD>
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The variable contains the property of the bean which is required to make comparison and is specified by the name<\/B><\/CODE> attribute. <\/FONT><\/P><\/TD><\/TR>
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scope<\/B><\/FONT><\/TD>
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This specifies the bean scope within which  the bean is searched  by the name<\/CODE> property, or “any scope” if not specified.<\/FONT><\/P><\/TD><\/TR><\/TBODY><\/TABLE><\/DIV>
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 <\/H2>
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Example Illustrating the use of the Empty<\/FONT><logic:empty><\/FONT> and the notEmpty <\/FONT><logic:notEmpty> logic tags<\/FONT>.<\/FONT><\/H2>
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Here you will learn to use the Struts  Logic tags. We will cover an example that will show  a comparison between  the two logic tags (ie..<\/FONT><logic:empty> and the <logic:notEmpty>).<\/FONT><\/P>
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Example code<\/B><\/FONT><\/P>
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Creating an <\/FONT><\/B>Action  Class<\/B><\/FONT><\/P>
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Develop a simple action class <\/FONT>EmptyAction.java.<\/FONT><\/CODE><\/P>
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package <\/B><\/FONT>roseindia.net;<\/FONT>
<\/FONT>
import <\/B><\/FONT>java.io.*;<\/FONT>
import <\/B><\/FONT>java.util.*;<\/FONT>

\/**<\/FONT><\/CODE>
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* @author Amit Gupta
* @Web http:\/\/www.roseindia.net
* @Email struts@roseindia.net

<\/A>**\/
<\/FONT>import <\/B><\/FONT>javax.servlet.http.HttpServletRequest;<\/FONT>
import <\/B><\/FONT>javax.servlet.http.HttpServletResponse;<\/FONT>
import <\/B><\/FONT>javax.servlet.ServletException;<\/FONT>
import <\/B><\/FONT>org.apache.struts.action.*;<\/FONT>
<\/FONT>
public class <\/B><\/FONT>EmptyAction <\/FONT>extends <\/B><\/FONT>Action <\/FONT>
{<\/FONT>
  <\/FONT>public <\/B><\/FONT>ActionForward execute<\/FONT>(<\/FONT>ActionMapping mapping,<\/FONT>
    <\/FONT>ActionForm form,<\/FONT>
    <\/FONT>HttpServletRequest request,<\/FONT>
    <\/FONT>HttpServletResponse response<\/FONT>)<\/FONT>
    <\/FONT>throws <\/B><\/FONT>IOException, ServletException <\/FONT>{<\/FONT>
<\/FONT>
      <\/FONT>
<\/FONT>
        <\/FONT>return <\/B><\/FONT>mapping.findForward<\/FONT>(<\/FONT>“success”<\/FONT>)<\/FONT>;<\/FONT>
    <\/FONT>}<\/FONT>
}<\/FONT><\/CODE> <\/P><\/TD><\/TR><\/TBODY><\/TABLE><\/DIV><\/TD><\/TR><\/TBODY><\/TABLE><\/DIV>
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Creating Form Bean<\/FONT><\/B><\/P>
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Our form bean class contains only one property text<\/B>. Here is the code of FormBean <\/FONT>(<\/B>EmptyForm<\/CODE>.java)<\/FONT><\/P>
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package <\/B><\/FONT>roseindia.net;<\/FONT>
<\/FONT>
import <\/B><\/FONT>org.apache.struts.action.*;<\/FONT>

\/**

* @author Amit Gupta
* @Web http:\/\/www.roseindia.net
* @Email struts@roseindia.net
<\/A>
**\/
<\/FONT><\/CODE>
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import <\/B><\/FONT>javax.servlet.http.HttpServletRequest;<\/FONT>
import <\/B><\/FONT>javax.servlet.http.HttpServletResponse;<\/FONT>
<\/FONT>
public class <\/B><\/FONT>EmptyForm <\/FONT>extends <\/B><\/FONT>ActionForm <\/FONT>
{<\/FONT>
    <\/FONT>
    <\/FONT>private <\/B><\/FONT>String text = <\/FONT>“”<\/FONT>;<\/FONT>
   <\/FONT>    <\/FONT>
  <\/FONT>public <\/B><\/FONT>String getText<\/FONT>() <\/FONT>
    <\/FONT>{<\/FONT>
        <\/FONT>return <\/B><\/FONT>text;<\/FONT>
    <\/FONT>}<\/FONT>
    <\/FONT>
    <\/FONT>public <\/B><\/FONT>void <\/B><\/FONT>setText<\/FONT>(<\/FONT>String text<\/FONT>) <\/FONT>
    <\/FONT>{<\/FONT>
    <\/FONT>this<\/B><\/FONT>.text=text;<\/FONT>
  <\/FONT>}<\/FONT>
   <\/FONT>
    <\/FONT>
  <\/FONT>
    <\/FONT>
}<\/FONT><\/CODE> <\/P><\/TD><\/TR><\/TBODY><\/TABLE><\/DIV><\/TD><\/TR><\/TBODY><\/TABLE><\/DIV>
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Defining form Bean in struts-config.xml file<\/FONT><\/B><\/P>
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Add the following entry in the struts-config.xml file for defining the form bean<\/FONT><\/P>
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<form-bean name=”EmptyForm” type=”roseindia.net.EmptyForm”\/><\/TD><\/TR><\/TBODY><\/TABLE><\/DIV>
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 Developing the Action Mapping in the struts-config.xml
<\/FONT><\/B>
Here, Action mapping helps to select the method from the Action class for specific requests.<\/FONT><\/P>
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<action path=”\/EmptyAction”
type=”roseindia.net.EmptyAction”
name=”EmptyForm”
scope=”request”
input=”\/pages\/input.jsp”>
<forward name=”success” path=”\/pages\/output.jsp”\/>
<\/action><\/TD><\/TR><\/TBODY><\/TABLE><\/DIV>
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Developing the <\/FONT>input.jsp<\/FONT> page<\/FONT><\/P>
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<%@ taglib uri=”\/tags\/struts-html” prefix=”html” %>
<%@ taglib uri=”\/tags\/struts-logic” prefix=”logic” %>

<html:html>
<head>
<title>Using &lt;logic&gt; Tags<\/title>
<\/head>

<body>
<h1>Using &lt;logic&gt; Tags<\/h1>

<html:form action=”\/EmptyAction” method =”post”>

<h2>Enter your name:<\/h2>
<html:text property=”text”\/>

<br>
<br>

<html:submit value=”Submit”\/>


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

<\/TD><\/TR><\/TBODY><\/TABLE><\/DIV>
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Developing the <\/FONT>output.jsp<\/FONT> page<\/FONT><\/P>
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<%@ 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 text field text:<\/h4>

<bean:write name=”EmptyForm” property=”text”\/>

<logic:notEmpty name=”EmptyForm” property=”text” scope=”request”>
<h4>Using the tag &lt;logic:notEmpty &gt; <\/h4> 
Results:not Empty
<\/logic:notEmpty>


<logic:empty name=”EmptyForm” property=”text” scope=”request”>
<h4>Using the tag&lt;logic:empty &gt;<\/h4> 
Results: Empty
<\/logic:empty><\/FONT>

<\/BODY>
<\/HTML> <\/TD><\/TR><\/TBODY><\/TABLE><\/DIV>
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Add the following line in the index.jsp to call the form.<\/FONT><\/P>
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<li>
<html:link page=”\/pages\/input.jsp”>Struts File Upload<\/html:link>
<br>
Example demonstrates  how EmptyAction Class works.
<\/li>
<\/FONT><\/P>
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Building and Testing the Example <\/FONT><\/B><\/P>
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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 <\/FONT>input.jsp <\/B><\/FONT>page. Your browser displays the following  page.<\/FONT><\/P>
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Writing nothing to the <\/FONT>out.jsp <\/B>page <\/FONT>displays the<\/FONT> working of  the  Empty Logic tag <logic:empty > <\/B><\/FONT><\/P>
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<\/TD><\/TR><\/TBODY><\/TABLE><\/DIV>
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 Writing nothing <\/FONT>displays the following <\/FONT>out.jsp <\/B>page<\/FONT><\/P>
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<\/TD><\/TR><\/TBODY><\/TABLE><\/DIV>
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Now  write any data to the <\/FONT>input.jsp<\/FONT> to see the working of  the notEmpty logic tag<\/B><\/FONT> <logic:notEmpty ><\/FONT><\/B><\/P>
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<\/TD><\/TR><\/TBODY><\/TABLE><\/DIV>
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The<\/FONT> <logic:<\/FONT>notEmpty <\/FONT>> evaluated here displays the <\/FONT>output.jsp<\/FONT> as<\/FONT><\/P>
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<\/TD><\/TR><\/TBODY><\/TABLE><\/DIV>
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<\/DIV><\/p>\n","protected":false},"excerpt":{"rendered":"

empty tag – If the requested variable is either null or an empty string then we use this tag to evaluate the contents contained in the nested body parts of this tag. Tag evaluation of the nested body content occurs only if the specified value is either absent (i.e. null), an empty string (i.e. a java.lang.String … Continue reading Logic Empty Tag (…<\/logic:empty>)<\/span><\/a><\/p>\n","protected":false},"author":2,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[],"tags":[],"class_list":["post-193","post","type-post","status-publish","format-standard","hentry"],"_links":{"self":[{"href":"https:\/\/www.strongd.net\/index.php?rest_route=\/wp\/v2\/posts\/193","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.strongd.net\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.strongd.net\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.strongd.net\/index.php?rest_route=\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/www.strongd.net\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=193"}],"version-history":[{"count":0,"href":"https:\/\/www.strongd.net\/index.php?rest_route=\/wp\/v2\/posts\/193\/revisions"}],"wp:attachment":[{"href":"https:\/\/www.strongd.net\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=193"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.strongd.net\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=193"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.strongd.net\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=193"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}