org.unix4j.variable

Interface VariableContext

All Superinterfaces:

VariableResolver

All Known Implementing Classes:

DefaultVariableContext

public interface VariableContext
extends VariableResolver

The variable context is an extension of the somewhat simplistic VariableResolver. It extends the resolver by allowing registration of delegate resolvers and adding a convenience method to return converted variable values.

Method Summary

Methods

Modifier and Type	Method and Description
void	addVariableResolver(VariableResolver resolver) Adds a variable resolver to this variable context.
<V> V	getValue(String name, ValueConverter<V> converter) Returns the value of the variable given by name and converts it into the target type <V> using the given converter.
void	removeVariableResolver(VariableResolver resolver) Removes the specified variable resolver if it exists and does nothing otherwise.

Methods inherited from interface org.unix4j.variable.VariableResolver

getValue

Method Detail

addVariableResolver

void addVariableResolver(VariableResolver resolver)

Adds a variable resolver to this variable context. The last recently added resolver has preference over previously added resolvers. This allows hiding of variables for instance to support different variable scopes with the same variable names.

Parameters:

resolver - the resolver to add

removeVariableResolver

void removeVariableResolver(VariableResolver resolver)

Removes the specified variable resolver if it exists and does nothing otherwise. If this resolver exists multiple times, the most recently added object is removed.

Parameters:

resolver - the resolver to remove

getValue

<V> V getValue(String name,
             ValueConverter<V> converter)
           throws IllegalArgumentException

Returns the value of the variable given by name and converts it into the target type <V> using the given converter. Returns null if no such variable exists. An exception is thrown if the conversion fails, or which is indicated by a null value returned by the converter for a non-null input value.

Type Parameters:

V - the target value type

Parameters:

name - the variable name

converter - a converter suitable to convert values into the target type <V>

Returns:

the converted value, or null if the variable does not exist

Throws:

IllegalArgumentException - if the value conversion fails, that is, if the converter returns null for the non-null input value