juneau-doc/docs/Topics/02.juneau-marshall/27.SimpleVariableLanguage/02.VarResolvers.html

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VarResolvers and VarResolverSessions

<p>
	The main class for performing variable resolution is {@link oaj.svl.VarResolver}.
	Two methods are provided for resolving variables:
</p>
<ul class='javatree'>
	<li class='jc'>{@link oaj.svl.VarResolver}
	<ul>
		<li class='jm'>{@link oaj.svl.VarResolver#resolve(String) resolve(String)} 
			- Resolves variables and returns the results as a simple string.
		<li class='jm'>{@link oaj.svl.VarResolver#resolveTo(String,Writer) resolveTo(String,Writer)} 
			- Resolves variables and sends results to a writer.
	</ul>
</ul>
<p>
	Var resolvers can rely on the existence of other objects.
	For example, {@link oaj.config.vars.ConfigVar} relies on the existence of a {@link oaj.config.Config}.
	This is accomplished through the following:
</p>
<ul class='spaced-list'>
	<li>Context-objects - Objects set on the resolver.
	<li>Session-objects - Objects set on the resolver session.
</ul>
<p>
	The following two classes are identical in behavior except for which objects they can access:
</p>
<ul class='javatree'>
	<li class='jc'>{@link oaj.svl.VarResolver} - Has access to context objects only.
	<li class='jc'>{@link oaj.svl.VarResolverSession} - Has access to context and session objects.
</ul>
<p>
	Context and session objects are set through the following methods:
</p>
<ul class='javatree'>
	<li class='jm'>{@link oaj.svl.VarResolverBuilder#contextObject(String,Object)} - Context objects.
	<li class='jm'>{@link oaj.svl.VarResolverSession#sessionObject(String,Object)} - Session objects.
	<li class='jm'>{@link oaj.svl.VarResolver#createSession(Map)} - Session objects.
</ul>
<p>
	Both kinds of objects are accessible through the following method:
</p>
<ul class='javatree'>
	<li class='jm'>{@link oaj.svl.VarResolverSession#getSessionObject(Class, String, boolean)}
</ul>
<p>
	Var resolvers can be cloned and extended by using the {@link oaj.svl.VarResolver#builder()} method.
	Cloning a resolver will copy it's {@link oaj.svl.Var} class names and context objects.
</p>

<h5 class='figure'>Example:</h5>
<p class='bpcode w800'>
	<jc>// Create a resolver that copies the default resolver and adds $C and $A vars.</jc>
	VarResolver myVarResolver = VarResolver.<jsf>DEFAULT</jsf>
		.builder()
		.vars(ConfigVar.<jk>class</jk>, ArgsVar.<jk>class</jk>)
		.build();
</p>