Package org.apache.juneau.commons.svl.vars

Class SystemPropertiesVar

java.lang.Object

org.apache.juneau.commons.svl.Var

org.apache.juneau.commons.svl.SimpleVar

org.apache.juneau.commons.svl.DefaultingVar

org.apache.juneau.commons.svl.vars.SystemPropertiesVar

public class SystemPropertiesVar
extends DefaultingVar

System property variable resolver.

The format for this var is "$S{systemProperty[,defaultValue]}"

Example:

// Create a variable resolver that resolves system properties (e.g. "$S{java.home}") VarResolver varResolver = VarResolver.create().vars(SystemPropertiesVar.class).build(); // Use it! System.out.println(varResolver.resolve("java.home is set to $S{java.home}"));

Since this is a SimpleVar, any variables contained in the result will be recursively resolved.
Likewise, if the arguments contain any variables, those will be resolved before they are passed to this var.

See Also:

• Marshall Simple Variable Language

Field Summary

Fields

Modifier and Type	Field	Description
static final String	NAME	The name of this variable.

Constructor Summary

Constructors

Constructor	Description
SystemPropertiesVar()	Constructor.

Method Summary

Modifier and Type	Method	Description
protected boolean	isStable()	System properties are mutable in principle (via System.setProperty(java.lang.String, java.lang.String)) but treated as stable in normal application code.
String	resolve(VarResolverSession session, String key)	The interface that needs to be implemented for subclasses of SimpleVar.

Methods inherited from class org.apache.juneau.commons.svl.DefaultingVar

doResolve

Methods inherited from class org.apache.juneau.commons.svl.SimpleVar

resolveTo

Methods inherited from class org.apache.juneau.commons.svl.Var

allowNested, allowRecurse, canResolve, getName

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Details

NAME

public static final String NAME

The name of this variable.

See Also:

• Constant Field Values

Constructor Details

SystemPropertiesVar

public SystemPropertiesVar()

Constructor.

Method Details

resolve

public String resolve(VarResolverSession session,
 String key)

Description copied from class: Var

The interface that needs to be implemented for subclasses of SimpleVar.

Specified by:

resolve in class Var

Parameters:

session - The session object used for a single instance of a var resolution.

key - The inside argument of the variable.

Returns:

The resolved value.

isStable

protected boolean isStable()

System properties are mutable in principle (via System.setProperty(java.lang.String, java.lang.String)) but treated as stable in normal application code. This var opts in to compile-time stable-value folding.

Caveat:

If a deployment relies on System.setProperty(java.lang.String, java.lang.String) mutations after VarResolver build, those mutations will not be picked up by templates that were compiled before the mutation. Either re-build the resolver after the property change, or override this method to return false via a subclass.

Overrides:

isStable in class Var

Returns:

Always true for the default implementation.