org.objectweb.fractal.julia.loader
Interface Loader

All Known Implementing Classes:
BasicLoader, BootstrapComponentImpl, DynamicLoader

public interface Loader

An interface to load classes or to generate them on the fly.


Method Summary
 Tree evalTree(Tree tree, Map context)
          Evaluates the given tree in the given context.
 void init(Map context)
          Initializes this loader.
 Class loadClass(String className, Object loader)
          Loads the class whose name is given.
 Class loadClass(Tree classDescriptor, Object loader)
          Loads or generates the class whose descriptor is given.
 Tree loadTree(String name)
          Loads the tree whose name is given.
 Object newObject(Tree objectDescriptor, Object loader)
          Creates and returns the object whose description is given.
 

Method Detail

init

void init(Map context)
          throws Exception
Initializes this loader.

Parameters:
context - the initialization arguments.
Throws:
Exception - if the initialization fails.

loadTree

Tree loadTree(String name)
              throws Exception
Loads the tree whose name is given.

Parameters:
name - a tree name.
Returns:
the tree whose name is given.
Throws:
Exception - if the tree is not found or cannot be loaded.

evalTree

Tree evalTree(Tree tree,
              Map context)
              throws Exception
Evaluates the given tree in the given context. Each leaf node of the given tree whose name begins with ' is replaced by the evaluation of the tree associated to this name in the given context (except if the result of this evaluation is "QUOTE"). For example the evaluation of "('x d)" in a context where x is associated to "(a 'y)", y is associated to "(b 'z)", and z is associated to "QUOTE" gives "((a (b 'z)) d)".

Parameters:
tree - the tree to be evaluated.
context - a map associating names to trees.
Returns:
the evaluated tree.
Throws:
Exception - if a name is not found in the given context. The exception's detail is equal to this name.

newObject

Object newObject(Tree objectDescriptor,
                 Object loader)
                 throws Exception
Creates and returns the object whose description is given.

Parameters:
objectDescriptor - the descriptor of the object to be created. This descriptor must be either of the form "className", or of the form "(classDescriptor arg1 ... argN)". In the first case, "className" must be the fully qualified name of a class. In the second case, "classDescriptor" must be a valid class descriptor (see loadClass). "arg1" ... "argN" can be arbitrary trees.
loader - an optional class loader to load auxiliary classes.
Returns:
an object created according to the given description. If this description is of the form "className", this method returns a new instance of the "className" class (which must have a default public constructor). If the description is of the form "(classDescriptor arg1 ... argN)", the class described by "classDescriptor" is loaded or generated with the loadClass method, and a new instance of this class is created (this class must have a default public constructor). Then, if the arguments "arg1 ... argN" are not empty, the initialize method is used to initialize the previous instance (in this case, the "classDescriptor" class must implement the Initializable interface; the initialize method is called with (arg1 ... argN) as parameter). Finally the previously created object is returned.
Throws:
Exception - if the specified object cannot be created.

loadClass

Class loadClass(String className,
                Object loader)
                throws ClassNotFoundException
Loads the class whose name is given.

Parameters:
className - the fully qualified name of the class to be returned.
loader - an optional class loader to load auxiliary classes.
Returns:
the class whose name is given.
Throws:
ClassNotFoundException - if the specified class is not found.

loadClass

Class loadClass(Tree classDescriptor,
                Object loader)
                throws ClassNotFoundException
Loads or generates the class whose descriptor is given.

Parameters:
classDescriptor - the descriptor of the class to be loaded or dynamically generated. This descriptor must be either of the form "className", or of the form "(objectDescriptor arg1 ... argN)". In the first case, "className" must be the fully qualified name of a class. In the second case, "objectDescriptor" must be a valid object descriptor (see newObject), describing an object that implements the ClassGenerator interface. "arg1" ... "argN" can be arbitrary trees.
loader - an optional class loader to load auxiliary classes.
Returns:
the class whose description is given. If this description is of the form "className", this method returns the "className" class. If the description is of the form "(objectDescriptor arg1 ... argN)", the class generator described by "objectDescriptor" is instantiated with the newObject method, and its generateClass method is used to generate a class (this method is called with classDescriptor as second argument), which is finally returned.
Throws:
ClassNotFoundException - is the specified class cannot be loaded or dynamically generated.