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Apache Struts API Documentation: Package org.apache.struts.taglib.nested
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<H2>
Package org.apache.struts.taglib.nested
</H2>
Nested tags & supporting classes extend the base struts tags to
allow them to relate to each other in a nested nature.
<P>
<B>See: </B>
<BR>
<A HREF="#package_description"><B>Description</B></A>
<P>
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<TD COLSPAN=2><FONT SIZE="+2">
<B>Interface Summary</B></FONT></TD>
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<TR BGCOLOR="white" CLASS="TableRowColor">
<TD WIDTH="15%"><B><A HREF="NestedNameSupport.html"><I>NestedNameSupport</I></A></B></TD>
<TD>This is so that managing classes can tell if a nested tag needs to have its <i>name</i> property set.</TD>
</TR>
<TR BGCOLOR="white" CLASS="TableRowColor">
<TD WIDTH="15%"><B><A HREF="NestedParentSupport.html"><I>NestedParentSupport</I></A></B></TD>
<TD>This interface is so managing classes of the nested tag can identify a tag as a parent tag that other tags retrieve nested properties from.</TD>
</TR>
<TR BGCOLOR="white" CLASS="TableRowColor">
<TD WIDTH="15%"><B><A HREF="NestedPropertySupport.html"><I>NestedPropertySupport</I></A></B></TD>
<TD>This interface is for managing classes of the nested extension, so they can know to set the tag's <i>property</i> property.</TD>
</TR>
<TR BGCOLOR="white" CLASS="TableRowColor">
<TD WIDTH="15%"><B><A HREF="NestedTagSupport.html"><I>NestedTagSupport</I></A></B></TD>
<TD>This is to simply allow managing classes to identify the tags to invoke common methods against them.</TD>
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<B>Class Summary</B></FONT></TD>
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<TD WIDTH="15%"><B><A HREF="NestedPropertyHelper.html">NestedPropertyHelper</A></B></TD>
<TD>A simple helper class that does everything that needs to be done to get the nested tag extension to work.</TD>
</TR>
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<TD WIDTH="15%"><B><A HREF="NestedPropertyTag.html">NestedPropertyTag</A></B></TD>
<TD>NestedPropertyTag.</TD>
</TR>
<TR BGCOLOR="white" CLASS="TableRowColor">
<TD WIDTH="15%"><B><A HREF="NestedReference.html">NestedReference</A></B></TD>
<TD>So that a nested hierarchy can penetrate a dynamic JSP include, this class will hold the details of a bean name and nested property.</TD>
</TR>
<TR BGCOLOR="white" CLASS="TableRowColor">
<TD WIDTH="15%"><B><A HREF="NestedRootTag.html">NestedRootTag</A></B></TD>
<TD>NestedRootTag.</TD>
</TR>
<TR BGCOLOR="white" CLASS="TableRowColor">
<TD WIDTH="15%"><B><A HREF="NestedWriteNestingTag.html">NestedWriteNestingTag</A></B></TD>
<TD>NestedWriteNestingTag.</TD>
</TR>
<TR BGCOLOR="white" CLASS="TableRowColor">
<TD WIDTH="15%"><B><A HREF="NestedWriteNestingTei.html">NestedWriteNestingTei</A></B></TD>
<TD>NestedWriteNestingTei This class will allow the nested:writeNesting tag to actually do what the doc says and make a scripting variable as an option (when "id" is supplied).</TD>
</TR>
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<P>
<A NAME="package_description"><!-- --></A><H2>
Package org.apache.struts.taglib.nested Description
</H2>
<P>
Nested tags & supporting classes extend the base struts tags to
allow them to relate to each other in a nested nature. The fundamental
logic of the original tags don't change, except in that all references
to beans and bean properties will be managed in a nested context. <br>
<br>
<a name="doc.Description"></a>
<div align="Center"> [ <a href="#doc.Intro">Introduction</a>
] [ <a href="#doc.FoundationConcepts">Foundation Concepts - model</a>
] [ <a href="#doc.TaggingConcepts">Foundation Concepts - tags</a>
] [ <a href="#doc.TagList">Nested Tag List</a>
] [ <a href="#doc.PropertyProperty">The "property" Property</a>
] [ <a href="#doc.ImplementationDetails">Implementation Details</a>
] </div>
<hr><a name="doc.Intro"></a>
<h3>Introduction</h3>
<p>The nesting extension provides the ability to define a nested object model
and efficiently represent and manage that model through JSP's custom
tags.</p>
<p>It's written in a layer that extends the current Struts tags, building
on their logic and functionality. The layer enables the tags to be aware
of the tags which surround them so they can correctly provide the nesting
property reference to the Struts system. Struts already supported properties
which use "dot notation" in accessing nested objects and properties.</p>
<pre>e.g. myProperty.childProperty.finalProperty</pre>
<p>Because of this the controller servlet excellently manages this nested
model. These tags are about bringing such ease of management to the JSP
view of the architecture.</p>
<hr><a name="doc.FoundationConcepts"></a>
<h3>Foundation Concepts - model.</h3>
<p> A bean holds a reference to another bean internally, and all access
to that bean is handled through the current bean. This act of having
one bean's access go through another bean is known as "nesting beans".
The first bean is known as the parent bean. The bean which it references,
is known as a child bean. The terms "parent" and "child" are commonly
used to describe the model's hierarchy. </p>
<p><b>A simple example...</b><br />
Take an object which represents a monkey. The monkey's job is to pick
bunches of bananas. On each bunch picked hangs many bananas. If this
case was translated to bean objects, the monkey object would have a reference
to the bunch objects he picked, and each bunch object would hold a reference
to the bananas hanging in the bunch. </p>
<p><b>To describe this...</b><br />
The monkey object is the parent to the bunch object, and the bunch
object is a child of the monkey object. The bunch object is parent to
its child banana objects, and the child banana objects children of the
bunch object. The monkey is higher in the hierarchy than the bananas,
and the bananas lower in the hierarchy to the bunches. </p>
<p> One special term to remember is for the most parent class, which is
known as the "root" object which starts the hierarchy. </p>
<hr><a name="doc.TaggingConcepts"></a>
<h3>Foundation Concepts - tags.</h3>
<p> What the tags provide is an efficient way or representing the above
models within JSP tag markup. As a result the tags take on similar relationships
to each other. A tag can be the parent of another, and similarly be a
child of a parent tag. However the most important part to remember, is
that the properties of parent tags define the nested property for the
child tags' properties. </p>
<p> One issue which may confuse the new developer, is that even though
a tag is a parent tag in a markup sense (the opening tag and closing tag
are either side of another tag) does not immediately mean that the child
tag will be relative to that tag. Why? Some tags make bad parents. In other
words, they're not logical steps in defining a hierarchy. </p>
<p> For example the relationship between the select tag and the options
tag. The html:options tag "must" be surrounded by a parent html:select
tag. </p>
<pre>eg:<br> <html:select name="myBean" property="mySelectProperty" ><br> <html:options name="myBean" property="myOptionsProperty" ><br> </html:select></pre>
<p> In the nested context, this would cause undesired results if the select
tag was a parent. The bean reference would become... </p>
<pre> mySelectProperty.myOptionsProperty</pre>
...which when translated, Struts would go to the value of the select
property and then try to get your options list from that returned value.
The extended logic tags are the same. You don't want to extend your properties
within the objects the logic tags are evaluating.
<p> To get manage this, the tags in the nested extension are categorised
into parent tags and non-parent tags. Those which implement <code>org.apache.struts.taglib.nested.NestedParentSupport</code>
are classed as parents, and the nested system knows they define levels
in the nested hierarchy. Every other tag, does not, and will be skipped
if found to be a "markup parent" (like our select tag) and not a "nested
parent". </p>
<p> There are also the special case of starting off the hierarchy with
a "root" tag. These tags are what the extension requires to provide them
with the bean by which the structure will be based on. </p>
<hr><a name="doc.TagList"></a>
<h3>Nested Tag List.</h3>
<p> Here's a list of tags in the nested extension, grouped by parent/context
functionality. "root", "nested parent", "markup parent" & "basic".
</p>
<p><b>Root Tags</b>
<table border="1">
<tbody>
<tr>
<th>markup name</th>
<th>brief description</th>
</tr>
<tr>
<td>html:form</td>
<td>For backwards compatibility, you can use the typical form tag
to implement your nested hierarchy.</td>
</tr>
<tr>
<td>nested:form</td>
<td>An extension of the above <code>html:form</code>, this is just
to provide definition in the nested tag library.</td>
</tr>
<tr>
<td>nested:root</td>
<td>When you don't want to configure a form, you can use any bean
which is in "scope" by specifying its name within this tag.</td>
</tr>
</tbody>
</table>
</p>
<br />
<p><b>Nested Parent Tags</b> (Affect the hierarchy)
<table border="1">
<tbody>
<tr>
<th>markup name</th>
<th>brief description</th>
</tr>
<tr>
<td>nested:nest</td>
<td>This tag executes no logic, simply representing a nesting level
for the rest of the markup to relate to.</td>
</tr>
<tr>
<td>nested:iterate</td>
<td>Extension of <code>logic:iterate</code> you can use it to iterate
through a list, and have all child references nest within the
beans returned from this iterated collection.</td>
</tr>
</tbody>
</table>
</p>
<br />
<p><b>Markup Parent Tags</b> (marked-up like parent tags, but don't affect
the hierarchy)
<table border="1">
<tbody>
<tr>
<th>markup name</th>
<th>brief description</th>
</tr>
<tr>
<td>nested:select</td>
<td><code>html:select</code> extension. Provides the logic to render
a select box in Html.</td>
</tr>
<tr>
<td>nested:empty</td>
<td><code>logic:empty</code> extension.</td>
</tr>
<tr>
<td>nested:notEmpty</td>
<td><code>logic:notEmpty</code> extension.</td>
</tr>
<tr>
<td>nested:equal</td>
<td><code>logic:equal</code> extension.</td>
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