| <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"> |
| <html> |
| <head> |
| <meta http-equiv="Content-Type" content="text/html; charset=utf-8"> |
| <title>Contributing EL Variables</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>Contributing EL Variables</h1> |
| |
| </td> |
| </tr> |
| </tbody></table> |
| <hr> |
| <h3>Overview</h3> |
| The JSF tooling provides three ways to contribute EL variables to the framework depending on your goal.<br> |
| <br> |
| If you are a component developer and want to add support for EL |
| variables that are declared by your component tags, you can use the |
| symbol factory extension and meta-data.<br> |
| <br> |
| If you are a tooling developer and you wish to add new sources of |
| variables without changing the behavior of other sources (beans, tag |
| contributed variables), you can use the symbolProvider extension.<br> |
| <br> |
| If you are a tooling developer and you wish to modify the way all |
| variables are resolved, you can use the variableResolver extension.<br> |
| <h3>Symbol Factory Extension and Meta-data<br> |
| </h3> |
| A symbol factory is any factory class that extends |
| <code>org.eclipse.jst.jsf.context.symbol.source.AbstractContextSymbolFactory</code>. |
| Once you create your implementation, you can declare it to the |
| framework using the |
| <a href="../extpts_reference/jsf/org_eclipse_jst_jsf_common_contextSymbolFactory.html">org.eclipse.jst.jsf.common.contextSymbolFactory</a> extension |
| point. In the extension, you need to provide a unique |
| factoryId. This factoryId is used to identify your factory and |
| can then be used in your symbol factory meta-data section. See also the <a href="the_design_time_application_manager.html">Design Time Application Manager</a> for information.<br> |
| <br> |
| Your factory implementation will implement the following method:<br> |
| <div class="code"><pre> |
| protected abstract ISymbol internalCreate(String symbolName, int scope, IAdaptable context, List problems);<br> |
| </pre></div> |
| The symbolName is the one provided by the system, usually corresponding |
| to the tag attribute, that declares the variable. You may use |
| this symbol name or ignore it and use your own, depending on how the |
| variable will be named at runtime. The scope argument is one of |
| ISymbolConstants.SYMBOL_SCOPE_*. The system value is passed in |
| based on meta-data settings if present. Your factory is not |
| obligated to use this scope variable. The IAdaptable context |
| object provides context information about the source of the variable |
| declaration. This is usually an IModelContext object. You |
| can implement the supports() abstract method in such a way to tell the |
| framework work what types of context object you support. |
| The problems list is for future use. In future versions, you will |
| be able to add diagnostic objects to the list that report warnings or |
| errors related to symbol creation. Currently, the list is ignored.<br> |
| <h3>SymbolProvider Extension</h3> |
| JSF has many ways to contribute variables. If the framework has |
| overlooked any or if you have added new ways yourself without affecting |
| the way other variables, such as managed beans, are declared, then you |
| can do so through the |
| <a href="../extpts_reference/jsf/org_eclipse_jst_jsf_common_symbolSourceProvider.html">org.eclipse.jst.jsf.common.symbolSourceProvider</a> |
| extension. Your symbol provider will implement the |
| <code>org.eclipse.jst.jsf.context.symbol.source.ISymbolSourceProviderFactory</code> |
| interface. Every time the framework requests a list of variables |
| through the default VariableResolver and ExternalContext, your provider |
| will be queried for all its symbols at one or more scopes.<br> |
| <br> |
| Note that your symbol provider may not called if:<br> |
| <br><ul> |
| <li>the default variable resolver has been replaced by one that does not call the default external context.</li> |
| <li>the default external context has been replaced by one that does not query the symbol providers.</li> |
| </ul> |
| <h3>VariableResolver Extension</h3> |
| <p>The variable provider extension allows you to register your own design |
| time resolver. You declare your resolver using the |
| <a href="../extpts_reference/jsf/org_eclipse_jst_jsf_core_variableresolver.html">org.eclipse.jst.jsf.core.variableresolver extension point.</a> |
| Your extension will declare a unique id and a class. The class |
| must extend |
| <code>org.eclipse.jst.jsf.designtime.el.AbstractDTVariableResolver</code>. |
| To register your resolver as the active one for a project (note: JSF |
| 1.1 only supports a single variable resolver at a given time. |
| Future versions supporting JSF 1.2 will have a more robust scheme |
| matching what is defined in the newer specification), you use |
| DesignTimeApplicationManager.setVariableResolverProvider specifying the |
| id defined in your extension as the argument.</p> |
| |
| <p>Once your variable resolver is registered and active for a project, all |
| variable resolution requests to the framework will call your |
| implementation. This gives you complete control over how all EL |
| variable symbols are discovered and instantiated by the design time |
| framework.</p> |
| |
| </body></html> |
