org.objectweb.jonathan.apis.kernel
Interface Component

All Known Subinterfaces:
Context, Forkable
All Known Implementing Classes:
JAlias, JAssemblage, JAtom, JComponent, JConfigurationFactory.JConfiguration, JContextFactory.JContext, JImplicitFactory, JSequence, LazyComponent, TreeContextFactory.TreeContext

public interface Component

The Component interface represents a component, with a value and a type.


Method Summary
 Component fork()
          "Forks" a copy of the target component.
 Component getComponent(Name name)
          Returns the component contained in the element registered in the target component under the name name.
 Element getElement(Name name)
          Returns the element in the target component identified by name, null if no element exists under name name.
 java.lang.Object getFactoryValue()
           
 int getIntValue()
          Returns the value of the target component, if its class is an integer class.
 Element getReference()
          Returns a distinguished element referencing the target component, if any, null otherwise.
 java.lang.Class getType()
          Returns the type of the target component, as a Class.
 java.lang.Object getValue()
          Returns the value of the target component, if its type is an object reference type.
 java.lang.Object getValue(Name name)
          Returns the value of the element registered in the target context under the name name.
 Element setReference(Element element)
          Sets an element containing the target component.
 

Method Detail

getElement

Element getElement(Name name)
Returns the element in the target component identified by name, null if no element exists under name name.

Parameters:
name - the name of the element to be retrieved;
Returns:
the corresponding element, if any; null otherwise.

getComponent

Component getComponent(Name name)
Returns the component contained in the element registered in the target component under the name name. A call to getComponent(name) is equivalent to getElement(name).getComponent() if the provided name actually corresponds to an element. If it is not the case, null is returned.

Parameters:
name - the name of the element whose component is seeked;
Returns:
the corresponding component, or null.

getValue

java.lang.Object getValue(Name name)
Returns the value of the element registered in the target context under the name name. A call to getValue(name) is equivalent to getElement(name).getValue() if the provided name actually corresponds to an element. If it is not the case, NO_VALUE is returned.

Parameters:
name - the name of the element whose value is seeked;
Returns:
the corresponding value, or NO_VALUE.

getReference

Element getReference()
Returns a distinguished element referencing the target component, if any, null otherwise. Implementations are not required to keep information about a given containing element. It is always legal to return null.

Returns:
an element containing the target component, if any, null otherwise.

setReference

Element setReference(Element element)
Sets an element containing the target component. The provided element should already be initialized as a container of the component. The returned element is the former container, if any. This method MUST be called when a component is referred to by an element.

Parameters:
element - the new element referencing the target component.
Returns:
the former element referencing the target component, if any, null otherwise.

getType

java.lang.Class getType()
Returns the type of the target component, as a Class.

Returns:
the type of the target component, as a Class.

getValue

java.lang.Object getValue()
Returns the value of the target component, if its type is an object reference type.

If the target component is of an integral type, NO_VALUE} is returned.

Returns:
the value of the target component.

getIntValue

int getIntValue()
Returns the value of the target component, if its class is an integer class.

If the target component has an object reference type, Integer.MAX_VALUE is returned.

Returns:
the value of the target component.

getFactoryValue

java.lang.Object getFactoryValue()
                                 throws JonathanException
Throws:
JonathanException

fork

Component fork()
"Forks" a copy of the target component. The returned component is a copy of the target component, sharing the same reference, but *NOT* referred to by this reference.

For basic components, this operation simply duplicates the component structure, but the value is still shared.

In the configuration framework, components contain a specification of their value (in the form of an assemblage, atom, alias... description). The fork() method is used to duplicate the specification, but not the value. It may thus be used to obtain several instances of a component, using getValue() on the returned component.

When the target component is a context, the returned component is a new context, roughly containing the forked versions of the target context's components.

If the target context contains an alias, and if the target T of this alias is in the scope of the context, then the target of the forked alias is a forked instance of T. But if the target is outside the scope of the context, then the target of the forked alias is T itself. The context thus defines a set of components that will be actually duplicated, all links outside the context being preserved.

The same rule applies for assemblages, and other "container" components. For instance, consider an assemblage 'A' made of factory 'F' and configuration 'C', 'C' containing an atom 'At', an alias 'In' to At, and an alias 'Out' to a component 'K' outside 'A'. Then the forked version of 'A' is a new assemblage made of a copy of 'F' and a new configuration containing a copy 'At2' of 'At', an alias 'In2' to 'At2', and an alias 'Out2' to 'K'.

Aliases are treated specifically. Calling the fork() method on an alias is like calling the same method on its target.

Returns:
a forked instance of the target component.