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<%@taglib uri="http://web.mit.edu/ist/isda/tags/navigation" prefix="nav" %>

Tag descriptions:

Navigation objects and properties

This section details the various object beans which can be exposed through The following section describes all the tags in the navigation tag library.

<nav:setSiteTreeVar> 

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  Unless stated otherwise, these objects are in the edu.mit.isda.navigation package.  Also, all properties of these objects are read-only.  You cannot alter them in any way within a JSP.

SiteTree

This is an object representing the site tree.  There is really only one important property here: homeSection, which corresponds to the topmost url (usually "/") in the site.

Properties

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 Page (and Section)

This is an object representing a page or a section within the site tree.   The basic object is a Page, which has a title and a URL.  A Section is a special type of Page, which contains subpages.  If a Page is not a Section, it does not contain subpages.  (Note that all Section objects are Pages, but not all Page objects are Sections.)   To ease JSP programming, you can just treat all Sections as Pages, and use the "isASection" and "subpages" properties to access section-specific behavior.

Properties

Tag descriptions:

The following section describes the tags in the navigation tag library, as well as giving some example of how they are used in conjunction with the above bean properties

<nav:setSiteTreeVar> 

 This <nav:setSiteTreeVar> action sets a scoped variable to the object representing the site tree.  The site tree bean is useful for a JSP which generates a Site Index or Site Map page.  Once you have set a variable to the site tree bean, you can walk through it with the <nav:treeWalk> and <nav:subTreeWalk> tags.

It is not recommended to save the site tree to session or application scope for later use, as it will possibly be stale (if pages have been added or removed without restarting the webapp).  Instead, just use <nav:setSiteTreeVar> again when you need the most recent site tree.

Syntax

<nav:setSiteTreeVar \[var="_var_"\] \[scope="*page*\|request\|session\|application"\] />

Attributes

Example

<nav:setSiteTreeVar var="theSiteTree" />
The Site Tree was last updated at <fmt:formatDate value="${theSiteTree.lastUpdated}" pattern="h:mm:ss a" />

<nav:treeWalk> and <nav:subtreeWalk>

The <nav:treeWalk> and <nav:subtreeWalk> actions allow you to recursively walk through the site tree (or any tree structure). The idea is that the body of the <nav:treeWalk> tag is performed for every branch of the tree. The body of the <nav:treeWalk> tag must contain the <nav:subtreeWalk> tag, which indicates where to include the sub-branches in the tree walk. It's much easier to look at an example than to explain what I mean.

Note that this is a simple tag, so you may not include jsp scripting elements (<% ... %>, <%= ... %>, etc.) inside the body of the <nav:treeWalk> tag. You must use only JSP tags inside the body. 

Also note that if you try to walk the same node twice, an exception will be thrown.  This prevents infinite regress in the case of faulty logic or a cyclical tree object. 

It is not recommended to save the site tree to session or application scope for later use, as it will possibly be stale (if pages have been added or removed without restarting the webapp).  Instead, just use <nav:setSiteTreeVar> again when you need the most recent site tree.

Syntax

<nav:setSiteTreeVar \[var="_var_"\] \[scope="*page*\|request\|session\|application"\] />

Attributes

Example

<nav:setSiteTreeVar var="theSiteTree" />
The Site Tree was last updated at <fmt:formatDate value="${theSiteTree.lastUpdated}" pattern="h:mm:ss a" />

<nav:treeWalk> and <nav:subtreeWalk>

The <nav:treeWalk> and <nav:subtreeWalk> actions allow you to recursively walk through the site tree (or any tree structure). The idea is that the body of the <nav:treeWalk> tag is performed for every branch of the tree. The body of the <nav:treeWalk> tag must contain the <nav:subtreeWalk> tag, which indicates where to include the sub-branches in the tree walk. It's much easier to look at an example than to explain what I mean.

Note that this is a simple tag, so you may not include jsp scripting elements (<% ... %>, <%= ... %>, etc.) inside the body of the <nav:treeWalk> tag. You must use only JSP tags inside the body. 

Also note that if you try to walk the same node twice, an exception will be thrown.  This prevents infinite regress in the case of faulty logic or a cyclical tree object. 

Syntax

<nav:treeWalk \[root="_theRootObject_"\] \[var="_currentNodeObjectVar_"\] \[depth="_currentDepthVar_"\] >
&nbsp; ...
&nbsp; <nav:subtreeWalk subroot="_subNodeObject_" />
&nbsp; ...
</nav:treeWalk>

Attributes

Example

The following example performs a fairly simple walk through the site tree, producing a set of nested bulleted lists representing all the sections/pages and subpages/subsections in the site. 

<nav:setSiteTreeVar var="theSiteTree" />
<h3><ul><li>
  <nav:treeWalk root="${theSiteTree.homeSection}" var="page">
     <a href="${page.url}"          ><c:out value="${page.title}" /></a>:<br/>
       <ul><c:forEach items="${page.subpages}" var="subpage">
         <li><nav:subtreeWalk subroot="${subpage}" /></li>
       </c:forEach></ul>
  </nav:treeWalk>
</li></ul></h3>

<nav:setBreadcrumbVar> 

 This <nav:setBreadcrumbVar> action sets a scoped variable to an object representing the breadcrumb for a particular target url in the site.   In this case, the breadcrumb object is a list of the target's ancestor pages, starting from the home page of the site and ending at the target page.  This is useful for a JSP which generates a breadcrumb for the current page.   Once you have set a variable to a breadcrumb object, you can iterate through it within a <c:forEach> tag.

It is not recommended to save the breadcrumb to session or application scope for later use, as it will possibly be stale (if pages have been added or removed without restarting the webapp).  Instead, just use <nav:setBreadcrumbVar> again when you need the most recent breadcrumb.

Syntax

<nav:setBreadcrumbVartreeWalk \[urlroot="_"targetUrltheRootObject_"\] \[var="_varcurrentNodeObjectVar_"\] \[scopedepth="*page*\|request\|session\|application"\] />

Attributes

Example

The following example gets and displays a breadcrumb for the currently requested page, since the "url" attribute is not set.  (Tip: This can be saved into its own JSP which is included in all JSPs on the web site to give a consistent breadcrumb look and feel and to avoid code duplication.)

<nav:setBreadcrumbVar var="breadcrumb" />
<c:forEach var="page" items="${breadcrumb}" varStatus="status">
<c:if test="${not status.first}">&gt;</c:if><a href="${page.url}"       ><c:out value="${page.title}" /></a>
</c:forEach>

<nav:setPageVar> 

"_currentDepthVar_"\] >
  ...
&nbsp; <nav:subtreeWalk subroot="_subNodeObject_" />
&nbsp; ...
</nav:treeWalk>

Attributes

Example

The following example performs a fairly simple walk through the site tree, producing a set of nested bulleted lists representing all the sections/pages and subpages/subsections in the site. 

<nav:setSiteTreeVar var="theSiteTree" />
<h3><ul><li>
  <nav:treeWalk root="${theSiteTree.homeSection}" var="page">
     <a href="${page.url}"              ><c:out value="${page.title}" /></a>:<br/>
       <ul><c:forEach items="${page.subpages}" var="subpage">
         <li><nav:subtreeWalk subroot="${subpage}" /></li>
       </c:forEach></ul>
  </nav:treeWalk>
</li></ul></h3>

<nav:setBreadcrumbVar> 

 This <nav:setBreadcrumbVar>  This <nav:setPageVar> action sets a scoped variable to an object representing the navigation information for a particular target url in the site.   breadcrumb for a particular target url in the site.   In this case, the breadcrumb object is a list of the target's ancestor pages, starting from the home page of the site and ending at the target page.  This is useful for a JSP which needs to know, for example, the list of links generates a breadcrumb for the current page or section.   Once you have set a variable to a breadcrumb object, you can iterate through it within a <c:forEach> tag.

It is not recommended to save the page object breadcrumb to session or application scope for later use, as it will possibly be stale (if pages have been added or removed without restarting the webapp).  Instead, just use <nav:setPageVar> setBreadcrumbVar> again when you need the most recent page objectbreadcrumb.

Syntax

<nav:setPageVarsetBreadcrumbVar \[url=_"targetUrl_"\] \[var="_var_"\] \[scope="*page*\|request\|session\|application"\] />

...

Example

The following example gets and displays a bulleted list of all links underneath breadcrumb for the currently requested page, since the "url" attribute is not set.  (Tip: This can be saved into its own JSP which is included in all JSPs on the web site to give a consistent subnavigation breadcrumb look and feel and to avoid code duplication.)

<nav:setPageVar var="page"/:setBreadcrumbVar var="breadcrumb" />
<c:forEach var="page" items="${breadcrumb}" varStatus="status">
<c:forEach var="subpage" itemsif test="${pagenot status.subpagesfirst}" >
&bull; <agt;</c:if><a href="${subpagepage.url}"           ><c:out value="${subpagepage.title}" /></a><br/>a>
</c:forEach>

Navigation objects and properties

This section details the various object beans which can be exposed through the above tags.  Unless stated otherwise, these objects are in the edu.mit.isda.navigation package.  Also, all properties of these objects are read-only.  You cannot alter them in any way within a JSP.

SiteTree

This is an object representing the site tree.  There is really only one important property here: homeSection, which corresponds to the topmost url (usually "/") in the site.

Properties

...

:forEach>

<nav:setPageVar> 

 This <nav:setPageVar> action sets a scoped variable to an object representing the navigation information for a particular target url in the site.   This is useful for a JSP which needs to know, for example, the list of links for the current page or section.  

It is not recommended to save the page object to session or application scope for later use, as it will possibly be stale (if pages have been added or removed without restarting the webapp).  Instead, just use <nav:setPageVar> again when you need the most recent page object.

Syntax

<nav:setPageVar \[url=_"targetUrl_"\] \[var="_var_"\] \[scope="*page*\|request\|session\|application"\] />

Attributes

Example

The following example displays a bulleted list of all links underneath the currently requested page, since the "url" attribute is not set.  (Tip: This can be saved into its own JSP which is included in all JSPs on the web site to give a consistent subnavigation look and feel and to avoid code duplication.)

<nav:setPageVar var="page"/>
<c:forEach var="subpage" items="${page.subpages}" >
&bull; <a href="${subpage.url}"           ><c:out value="${subpage.title}" /></a><br/>
</c:forEach>