cz.cuni.versatile.core
Class AbstractValueProvider

java.lang.Object
  cz.cuni.versatile.core.AbstractValueProvider

All Implemented Interfaces:

ValueProvider

Direct Known Subclasses:

ConstantVP

public abstract class AbstractValueProvider

extends java.lang.Object

implements ValueProvider

The default implementation of the ValueProvider interface. It implements the chaining mechanism and all the methods which are generic, independent of a particular attributes/values context. When extending AbstractValueProvider only the following three methods need be implemented:

1. the two-parameter constructor
2. getLocalValue() method
3. hasLocalValue() method

Author:

Jaroslav Gergic

attrName

protected java.lang.String attrName

Attribute name.

See Also:

getAttributeName()

defaultProvider

protected ValueProvider defaultProvider

Next-in-the-chain value provider (default).

See Also:

getDefault()

AbstractValueProvider

public AbstractValueProvider(java.lang.String attrName,
                             ValueProvider defaultValue)

Public Constructor

Parameters:

attrName - an attribute name in a given attributes/values context

defaultValue - a default value provider (fall-back), can be null

getAttributeName

public final java.lang.String getAttributeName()

Description copied from interface: ValueProvider

Returns attribute name.

Specified by:

getAttributeName in interface ValueProvider

Returns:

a unique name of the attribute this ValueProvider is bound to.

See Also:

ValueProvider.getAttributeName()

getValue

public final java.lang.Object getValue()

Description copied from interface: ValueProvider

Returns attribute value. (Recursive for the entire chain of ValueProvider instances.)

Specified by:

getValue in interface ValueProvider

Returns:

the current value of the attribute at the time of invocation

See Also:

ValueProvider.getValue()

hasValue

public final boolean hasValue()

Description copied from interface: ValueProvider

Checks whether the attribute is currently set. (Recursive for the entire chain of ValueProvider instances.)

Specified by:

hasValue in interface ValueProvider

Returns:

true if the value is set for any ValueProvider in the chain, false otherwise

See Also:

ValueProvider.hasValue()

getDefault

public final ValueProvider getDefault()

Description copied from interface: ValueProvider

Returns the next ValueProvider in the chain.

Specified by:

getDefault in interface ValueProvider

Returns:

the next ValueProvider in the chain or null when invoked for the tail of the chain.

See Also:

ValueProvider.getDefault()

toPreferenceChain

public PreferenceChain toPreferenceChain()

Description copied from interface: ValueProvider

Takes the current snapshot of the ValueProvider chain returning a list of values in the ValueProvider chain. A value is appended to the chain for those value providers, where hasLocaleValue() returns true.

Remarks: Any item in the result PreferenceChain can be the desired property value as well as a PreferenceChain or a PreferenceBag of property values as returned by an individual ValueProvider in the chain. The purpose of this method is mainly for diagnostics (tuning and debugging).

Specified by:

toPreferenceChain in interface ValueProvider

Returns:

PreferenceChain object - a list of values - can be an empty list.

See Also:

ValueProvider.toPreferenceChain()