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Apache Struts API Documentation: Package org.apache.struts.taglib.logic
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<H2>
Package org.apache.struts.taglib.logic
</H2>
The "struts-logic" tag library contains tags that are useful in managing
conditional generation of output text, looping over object collections
for repetitive generation of output text, and application flow management.
<P>
<B>See: </B>
<BR>
<A HREF="#package_description"><B>Description</B></A>
<P>
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<TR BGCOLOR="#CCCCFF" CLASS="TableHeadingColor">
<TD COLSPAN=2><FONT SIZE="+2">
<B>Class Summary</B></FONT></TD>
</TR>
<TR BGCOLOR="white" CLASS="TableRowColor">
<TD WIDTH="15%"><B><A HREF="CompareTagBase.html">CompareTagBase</A></B></TD>
<TD>Abstract base class for comparison tags.</TD>
</TR>
<TR BGCOLOR="white" CLASS="TableRowColor">
<TD WIDTH="15%"><B><A HREF="ConditionalTagBase.html">ConditionalTagBase</A></B></TD>
<TD>Abstract base class for the various conditional evaluation tags.</TD>
</TR>
<TR BGCOLOR="white" CLASS="TableRowColor">
<TD WIDTH="15%"><B><A HREF="EmptyTag.html">EmptyTag</A></B></TD>
<TD>Evalute the nested body content of this tag if the specified value is empty for this request.</TD>
</TR>
<TR BGCOLOR="white" CLASS="TableRowColor">
<TD WIDTH="15%"><B><A HREF="EqualTag.html">EqualTag</A></B></TD>
<TD>Evaluate the nested body content of this tag if the specified variable and value are equal.</TD>
</TR>
<TR BGCOLOR="white" CLASS="TableRowColor">
<TD WIDTH="15%"><B><A HREF="ForwardTag.html">ForwardTag</A></B></TD>
<TD>Perform a forward or redirect to a page that is looked up in the configuration information associated with our application.</TD>
</TR>
<TR BGCOLOR="white" CLASS="TableRowColor">
<TD WIDTH="15%"><B><A HREF="GreaterEqualTag.html">GreaterEqualTag</A></B></TD>
<TD>Evaluate the nested body content of this tag if the specified variable is greater than or equal to the specified value.</TD>
</TR>
<TR BGCOLOR="white" CLASS="TableRowColor">
<TD WIDTH="15%"><B><A HREF="GreaterThanTag.html">GreaterThanTag</A></B></TD>
<TD>Evaluate the nested body content of this tag if the specified variable is greater than the specified value.</TD>
</TR>
<TR BGCOLOR="white" CLASS="TableRowColor">
<TD WIDTH="15%"><B><A HREF="IterateTag.html">IterateTag</A></B></TD>
<TD>Custom tag that iterates the elements of a collection, which can be either an attribute or the property of an attribute.</TD>
</TR>
<TR BGCOLOR="white" CLASS="TableRowColor">
<TD WIDTH="15%"><B><A HREF="IterateTei.html">IterateTei</A></B></TD>
<TD>Implementation of <code>TagExtraInfo</code> for the <b>iterate</b> tag, identifying the scripting object(s) to be made visible.</TD>
</TR>
<TR BGCOLOR="white" CLASS="TableRowColor">
<TD WIDTH="15%"><B><A HREF="LessEqualTag.html">LessEqualTag</A></B></TD>
<TD>Evaluate the nested body content of this tag if the specified variable is less than or equal to the specified value.</TD>
</TR>
<TR BGCOLOR="white" CLASS="TableRowColor">
<TD WIDTH="15%"><B><A HREF="LessThanTag.html">LessThanTag</A></B></TD>
<TD>Evaluate the nested body content of this tag if the specified variable is less than the specified value.</TD>
</TR>
<TR BGCOLOR="white" CLASS="TableRowColor">
<TD WIDTH="15%"><B><A HREF="MatchTag.html">MatchTag</A></B></TD>
<TD>Evalute the nested body content of this tag if the specified value is a substring of the specified variable.</TD>
</TR>
<TR BGCOLOR="white" CLASS="TableRowColor">
<TD WIDTH="15%"><B><A HREF="MessagesNotPresentTag.html">MessagesNotPresentTag</A></B></TD>
<TD>Evalute the nested body content of this tag if the specified value is not present for this request.</TD>
</TR>
<TR BGCOLOR="white" CLASS="TableRowColor">
<TD WIDTH="15%"><B><A HREF="MessagesPresentTag.html">MessagesPresentTag</A></B></TD>
<TD>Evalute to <code>true</code> if an <code>ActionMessages</code> class or a class that can be converted to an <code>ActionMessages</code> class is in request scope under the specified key and there is at least one message in the class or for the property specified.</TD>
</TR>
<TR BGCOLOR="white" CLASS="TableRowColor">
<TD WIDTH="15%"><B><A HREF="NotEmptyTag.html">NotEmptyTag</A></B></TD>
<TD>Evalute the nested body content of this tag if the specified value is not empty for this request.</TD>
</TR>
<TR BGCOLOR="white" CLASS="TableRowColor">
<TD WIDTH="15%"><B><A HREF="NotEqualTag.html">NotEqualTag</A></B></TD>
<TD>Evaluate the nested body content of this tag if the specified variable and value are not equal.</TD>
</TR>
<TR BGCOLOR="white" CLASS="TableRowColor">
<TD WIDTH="15%"><B><A HREF="NotMatchTag.html">NotMatchTag</A></B></TD>
<TD>Evalute the nested body content of this tag if the specified value is not a substring of the specified variable.</TD>
</TR>
<TR BGCOLOR="white" CLASS="TableRowColor">
<TD WIDTH="15%"><B><A HREF="NotPresentTag.html">NotPresentTag</A></B></TD>
<TD>Evalute the nested body content of this tag if the specified value is not present for this request.</TD>
</TR>
<TR BGCOLOR="white" CLASS="TableRowColor">
<TD WIDTH="15%"><B><A HREF="PresentTag.html">PresentTag</A></B></TD>
<TD>Evalute the nested body content of this tag if the specified value is present for this request.</TD>
</TR>
<TR BGCOLOR="white" CLASS="TableRowColor">
<TD WIDTH="15%"><B><A HREF="RedirectTag.html">RedirectTag</A></B></TD>
<TD>Generate a URL-encoded redirect to the specified URI.</TD>
</TR>
</TABLE>
<P>
<A NAME="package_description"><!-- --></A><H2>
Package org.apache.struts.taglib.logic Description
</H2>
<P>
<p>The "struts-logic" tag library contains tags that are useful in managing
conditional generation of output text, looping over object collections
for repetitive generation of output text, and application flow management.
</p>
<a name="doc.Description"></a>
<p> </p>
<div align="Center"> <a href="#doc.Introduction">[Introduction]</a>
<a href="#doc.Functionality">[Logic Functionality]</a>
<a href="#doc.Properties">[Logic Properties]</a>
<a href="#doc.Examples">[Logic Examples]</a>
</div>
<p></p>
<hr /=""> <a name="doc.Intro"></a>
<h3>Introduction<a name="doc.Introduction"></a>
</h3>
<p> The Logic library supplies tags that are useful for manipulating
presentation logic without the use of scriptlets.</p>
<p><br>
</p>
<div align="Center"><img src="doc-files/logicUML.gif" alt="Logic Tag UML" >
<br>
</div>
<p></p>
<a name="doc.Functionality"></a>
<h3>Logic Tag Functionality<a name="doc.Functionality"></a>
</h3>
<p> The functionality of the logic tags can be divided into four groups:</p>
<p><b>Value Comparisons -</b> The purpose of these tags is to print out the
body of the tag if the comparison evaluates to <i>true. </i></p>
<ul>
<li><b><a href="../../../../../../userGuide/struts-logic.html#equal">equal,</a>
<a href="../../../../../../userGuide/struts-logic.html#notEqual">notEqual</a>
</b> </li>
<li><b><a href="../../../../../../userGuide/struts-logic.html#greaterEqual">greaterEqual</a>
, <a href="../../../../../../userGuide/struts-logic.html#lessEqual">lessEqual</a>
</b></li>
<li><b><a href="../../../../../../userGuide/struts-logic.html#greaterThan">greaterThan</a>
,<a href="../../../../../../userGuide/struts-logic.html#lessThan"> lessThan</a>
</b></li>
</ul>
<p><b>Substring Matching -</b> The purpose of these tags is to match substrings
inside of other Strings</p>
<ul>
<li><b><a href="../../../../../../userGuide/struts-logic.html#match">match</a>
, <a href="../../../../../../userGuide/struts-logic.html#notMatch">notMatch</a>
</b></li>
</ul>
<p><b>Presentation Location -</b> The purpose of these tags is to change
the location of the presentation page</p>
<ul>
<li><a href="../../../../../../userGuide/struts-logic.html#forward"><b>forward</b></a>
</li>
<li><a href="../../../../../../userGuide/struts-logic.html#redirect"><b>redirect</b></a>
</li>
</ul>
<p><b>Collection Utilities -</b>The purpose of these tags is to handle Collections</p>
<ul>
<li><a href="../../../../../../userGuide/struts-logic.html#iterate"><b>iterate</b></a>
</li>
</ul>
<h3>Logic Tag Properties<a name="doc.Properties"></a>
</h3>
<p>Each of the four groups of logic tags have a common set of attributes
associated with them. :</p>
<blockquote>
<p><b>Value Comparisons</b> (equal, notEqual, greaterEqual, lessEqual,
greaterThan, lessThan, present, notPresent)</p>
<p>Each of the value comparison tags takes a <i>value</i> and compares
it to the value of a comparison attribute. If the value given can be
successfully converted to a <i>float</i> or <i>double</i>, then a number
comparison is performed on the value given and the value of the comparison
attribute. Otherwise a String comparison is performed. You have to specify
one of the comparison attributes: <i>cookie</i>, <i>header</i>, <i>parameter</i>
, <i>property</i> or <i>name. </i>For each of the examples, the tag "<i>
someComparisonTag"</i>can be replaced by any of the value comparison
tags.</p>
<ul>
<li>value - the value to which this tag is going to compare, used in
conjunction with one of the comparison attributes: <i>cookie</i>, <i>
header</i>, <i>parameter</i>, <i>and property</i> and/or <i>name. </i></li>
<li>cookie - the name of the cookie to compare to <i>value</i>
<ul>
<li>example:
<pre><logic:<i>someComparisonTag</i> value="someUserName" cookie="userName"><br> User Logged In<br></logic:<i>someComparisonTag</i>><br></pre>
</li>
</ul>
</li>
<li>header - the name of the HTTP header to compare to <i>value</i>
<ul>
<li>example:
<pre><logic:<i>someComparisonTag</i> value="en_US" header="Accept-Language"><br> Welcome English-speaking User*<br></logic:<i>someComparisonTag</i>><br></pre>
</li>
<li>
<p>*Note: See the section in the user's guide on <a href="../../../../../../userGuide/building_view.html#i18n">
Internationalized Messages</a>
to do things like this better.</p>
</li>
</ul>
</li>
<li>name - the variable to be compared to <i>value</i> 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.
<ul>
<li>example:
<pre><%<br> String testString = "pantalones";<br> pageContext.setAttribute("testString", testString, PageContext.PAGE_SCOPE);<br>%><br><jsp:useBean id="testString" scope="page" type="java.lang.String" /><br><logic:<i>someComparisonTag</i> name="testString" value="pantalones"><br> Usted tiene pantalones!<br></logic:<i>someComparison</i>><br></pre>
</li>
</ul>
</li>
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