org.apache.juneau.svl

Class Var

java.lang.Object

org.apache.juneau.svl.Var

Direct Known Subclasses:

SimpleVar, StreamedVar

public abstract class Var
extends Object

Abstract superclass of all Simple Var Language variables.

Vars are used to convert simple variables of the form "$varName{varKey}" into something else by the VarResolver class.

Subclasses must implement one of the following two methods:

• resolve(VarResolverSession,String) - For simple vars.
• resolveTo(VarResolverSession,Writer,String) - For streamed vars.

Subclasses MUST implement a no-arg constructor so that class names can be passed to the VarResolverBuilder.vars(Class...) method.
They must also be thread safe!

Two direct abstract subclasses are provided to differentiated between simple and streamed vars:

• SimpleVar
• StreamedVar

See Also:

• Overview > juneau-svl > SVL Variables

Constructor Summary

Constructors

Constructor and Description
Var(String name, boolean streamed) Constructor.

Method Summary

Modifier and Type	Method and Description
protected boolean	allowNested() Returns whether nested variables are supported by this variable.
protected boolean	allowRecurse() Returns whether variables in the resolved contents of this variable should also be resolved.
protected String	doResolve(VarResolverSession session, String arg) The method called from VarResolver.
protected String	getName() Return the name of this variable.
abstract String	resolve(VarResolverSession session, String arg) The interface that needs to be implemented for subclasses of SimpleVar.
abstract void	resolveTo(VarResolverSession session, Writer w, String arg) The interface that needs to be implemented for subclasses of StreamedVar.

Methods inherited from class java.lang.Object

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

Constructor Detail

Var

public Var(String name,
           boolean streamed)

Constructor.

Parameters:

name - The name of this variable.

streamed - Whether this variable is 'streamed', meaning the resolveTo(VarResolverSession, Writer, String) method is implemented. If false, then the resolve(VarResolverSession, String) method is implemented.

Method Detail

getName

protected String getName()

Return the name of this variable.

For example, the system property variable returns "S" since the format of the variable is "$S{system.property}".

Returns:

The name of this variable.

allowNested

protected boolean allowNested()

Returns whether nested variables are supported by this variable.

For example, in "$X{$Y{xxx}}", $Y is a nested variable that will be resolved if this method returns true.

The default implementation of this method always returns true. Subclasses can override this method to override the default behavior.

Returns:

true if nested variables are supported by this variable.

allowRecurse

protected boolean allowRecurse()

Returns whether variables in the resolved contents of this variable should also be resolved.

For example, if "$X{xxx}" resolves to "$Y{xxx}", then the $Y variable will be recursively resolved if this method returns true.

The default implementation of this method always returns true.
Subclasses can override this method to override the default behavior.

Important Note

As a general rule, variables that resolve user-entered data should not be recursively resolved as this may cause a security hole.

Returns:

true if resolved variables should be recursively resolved.

doResolve

protected String doResolve(VarResolverSession session,
                           String arg)
                    throws Exception

The method called from VarResolver.

Can be overridden to intercept the request and do special handling.
Default implementation simply calls resolve(String).

Parameters:

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

arg - The inside argument of the variable.

Returns:

The resolved value.

Throws:

Exception - Any thrown exception will be serialized as "{exceptionMessage}"

resolve

public abstract String resolve(VarResolverSession session,
                               String arg)
                        throws Exception

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

Parameters:

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

arg - The inside argument of the variable.

Returns:

The resolved value.

Throws:

Exception - Any thrown exception will be serialized as "{exceptionMessage}"

resolveTo

public abstract void resolveTo(VarResolverSession session,
                               Writer w,
                               String arg)
                        throws Exception

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

Parameters:

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

w - The writer to send the resolved value to.

arg - The inside argument of the variable.

Throws:

Exception - Any thrown exception will be serialized as "{exceptionMessage}"