docs/plugins/org.eclipse.jst.jsf.doc.dev/html/programmersguide/using_context_resolvers.html

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<title>Using Context Resolvers</title>
  <meta http-equiv="Content-Style-Type" content="text/css">

  <meta http-equiv="Content-Script-Type" content="text/javascript">

  <link rel="stylesheet" href="../../book.css" type="text/css">
  <link rel="stylesheet" href="../tutorials/default_style.css"></head>
<body>
<table summary="" cellpadding="0" cellspacing="0" width="100%">

<tbody><tr valign="bottom">
<td align="left" width="86%">
<h1>Using Context Resolvers</h1>
</td>
</tr>
</tbody>
</table>

<hr>
<h3>Overview</h3>

Context resolvers are an abstraction used by the JSF EL framework to
decouple sources of context information from the way that information
is created.&nbsp; Common examples of such contexts are:

<ul>
<li>a dynamic web project in an Eclipse workspace</li>
<li>a JSP file in a dynamic web project</li>
<li>a particular absolute offset into an IDocument</li>
</ul>

Context resolvers allow us to derive interesting information from these contexts such as:
<ul>
<li>what is the current IProject?</li>
<li>where are we in an IRegion or DOM tree?</li>
<li>what JSF EL symbols are available at the current IDocument position?</li>
</ul>

<h3>IStructuredDocumentContext</h3>

A particularly useful context is one in an IStructuredDocument.&nbsp;
An IStructuredDocument represents an SSE document that can be
manipulated in a number of different ways including as a regular
IDocument or as a DOM.&nbsp; The IStructuredDocumentContext points to a
specific absolute offset into such a document.&nbsp; The context can
then be passed to various resolvers to determine information about this
position in the document.
<h3>Context Resolvers</h3>
The following is a list of context resolvers that are available as provisional APIs:
<p></p>
<table style="width: 100%; text-align: left;" border="1" cellpadding="2" cellspacing="2">

  <tbody>
    <tr style="font-weight: bold">
      <td style="vertical-align: top;">Resolver Type<br>
      </td>
      <td style="vertical-align: top;">Purpose<br>
      </td>
    </tr>
    <tr>
      <td style="vertical-align: top;"><a href="../api_reference/org/eclipse/jst/jsf/context/resolver/structureddocument/ITaglibContextResolver.html">ITaglibContextResolver</a></td>
      <td style="vertical-align: top;">Resolves taglib information for the current context such
  as retrieving the tag library information for the current tag.</td>
    </tr>
    <tr>
      <td style="vertical-align: top;"><a href="../api_reference/org/eclipse/jst/jsf/context/resolver/structureddocument/IWorkspaceContextResolver.html">IWorkspaceContextResolver</a></td>
      <td style="vertical-align: top;">Resolves workspace information for the current document
  context such as IFile and IProject.</td>
    </tr>
    <tr>
      <td style="vertical-align: top;"><a href="../api_reference/org/eclipse/jst/jsf/context/resolver/structureddocument/IDOMContextResolver.html">IDOMContextResolver</a></td>
      <td style="vertical-align: top;">Resolves DOM information for the current context such as
  current element and attribute.</td>
    </tr>
    <tr>
      <td style="vertical-align: top;"><a href="../api_reference/org/eclipse/jst/jsf/context/resolver/structureddocument/IMetadataContextResolver.html">IMetadataContextResolver</a></td>
      <td style="vertical-align: top;">Resolves meta-data framework information for a given
  context.<span style="">&nbsp; </span>For example, if the current
  context resolves to an XML attribute, retrieves meta-data associate with that
  attribute/element/uri.</td>
    </tr>
    <tr>
      <td style="vertical-align: top;"><a href="../api_reference/org/eclipse/jst/jsf/designtime/resolver/ISymbolContextResolver.html">ISymbolContextResolver</a></td>
      <td style="vertical-align: top;">Determines what symbols are available or valid within the
  current context.<span style="">&nbsp; </span>For example, if
  context is an EL expression, what bean names are available?</td>
    </tr>
  </tbody>
</table>

<h3>Factories</h3>
Factories exist to create both contexts and context resolvers.&nbsp; These are:
<p></p>
<table style="width: 100%; text-align: left;" border="1" cellpadding="2" cellspacing="2">
  <tbody>
    <tr style="font-weight: bold">
      <td style="vertical-align: top;">Factory Name<br>
      </td>
      <td style="vertical-align: top;">What it does<br>
      </td>
    </tr>
    <tr>
       <td style="vertical-align: top;"><a href="../api_reference/org/eclipse/jst/jsf/context/structureddocument/IStructuredDocumentContextFactory.html">org.eclipse.jst.jsf.context.structureddocument.IStructuredDocumentContextFactory</a>
      </td>
      <td style="vertical-align: top;">Creates new IStructuredDocumentContext objects based on a document and offset.<br>
      </td>
    </tr>
    <tr>
      <td style="vertical-align: top;"><a href="../api_reference/org/eclipse/jst/jsf/context/resolver/structureddocument/IStructuredDocumentContextResolverFactory.html">org.eclipse.jst.jsf.context.resolver.structureddocument.IStructuredDocumentContextResolverFactory</a>
      </td>
      <td style="vertical-align: top;">Creates a new instances of context resolvers for an IStructuredDocumentContext.<br>
      </td>
    </tr>
  </tbody>
</table>

<h3>Adding Factory Delegates</h3>
<p>The existing factories can be extended
using factory delegates.&nbsp; A delegate for
IStructuredDocumentContextFactory allows you to extend the existing
factory to create IStructuredDocumentContext's for document contexts
other than an IStructuredDocumentContext and offset.&nbsp; Similarly,
adding factory delegates to IStructuredDocumentContextResolverFactory
allows you to create context resolvers for structured documents other
than those already supported.</p>

<p>Factory delegates are added programmatically be calling
addFactoryDelegate on the appropriate factory.&nbsp; See the JavaDoc
for <a href="../api_reference/org/eclipse/jst/jsf/context/IDelegatingFactory.html">IDelegatingFactory</a> for more details.</p>

</body></html>