SVL Variables

Variables are defined through the Var API. The API comes with several predefined variables and is easily extensible.

The following is an example of a variable that performs URL-Encoding on strings.

// First create our var.
public class UrlEncodeVar extends SimpleVar {

    // Must have a no-arg constructor!
    public UrlEncodeVar() {
        super("UE");
    }

    // The method we must implement
    @Override
    public String resolve(VarResolverSession session, String key) {
        return URLEncoder.encode(key, "UTF-8");
    }
}

// Next create a var resolver that extends the existing DEFAULT resolver
// that supports resolving system properties.
VarResolver varResolver = VarResolver.DEFAULT
    .copy()
    .vars(UrlEncodeVar.class)
    .build();

// Retrieve a system property and URL-encode it if necessary.
String myProperty = varResolver.resolve("$UE{$S{my.property}}");

The following shows the class hierarchy of the Var class:

Var - Superclass of all vars.SimpleVar - Superclass of all vars that return strings.DefaultingVar - Variables that define a default value if the resolve method returns null.MapVar - Variables that pull values from maps.MultipartVar - Variables that consist of 2 or more comma-delimited arguments.StreamedVar - Superclass of all vars that stream their value to writers.

The following is the list of default variables defined in all modules:

Module	Class	Pattern
juneau-svl	PropertyVar	$P{key[,default]}
juneau-svl	EnvVariablesVar	$E{key[,default]}
	SystemPropertiesVar	$S{key[,default]}
	EnvFileVar	$EF{key[,default]}
	DotenvVar	$DE{key[,default]}
	ArgsVar	$A{key[,default]}
	ManifestFileVar	$MF{key[,default]}
	HtmlWidgetVar	$W{name}
juneau-config	ConfigVar	$C{key[,default]}
juneau-rest-server	FileVar	$F{path[,default]}
	ServletInitParamVar	$I{name[,default]}
	LocalizationVar	$L{key[,args...]}
	RequestAttributeVar	$RA{key1[,key2...]}
	RequestFormDataVar	$RF{key1[,key2...]}
	RequestHeaderVar	$RH{key1[,key2...]}
	RequestPathVar	$RP{key1[,key2...]}
	RequestQueryVar	$RQ{key1[,key2...]}
	RequestSwaggerVar	$RS{key}
	RequestVar	$R{key1[,key2...]}
	SerializedRequestAttrVar	$SA{contentType,key[,default]}
	SwaggerVar	$SS{key1[,key2...]}
	UrlVar	$U{uri}
	UrlEncodeVar	$UE{uriPart}

$P{...} is the unified property-stack resolver. It walks the configured Settings property source precedence (local overrides, global overrides, args, system properties, environment, .env, and any custom sources). Use $S{...} / $E{...} / $EF{...} / $DE{...} / $A{...} / $MF{...} / $C{...} when you need a source-specific lookup.

See also

• REST Server SVL Variables