org.dynalang.mop.impl
Class MetaobjectProtocolAdaptor

java.lang.Object
  org.dynalang.mop.impl.MetaobjectProtocolAdaptor

All Implemented Interfaces:

BaseMetaobjectProtocol, CallProtocol, MetaobjectProtocol

public class MetaobjectProtocolAdaptor
extends java.lang.Object
implements MetaobjectProtocol

This class can turn any BaseMetaobjectProtocol into a full MetaobjectProtocol by implementing the MOP methods using only the Base MOP methods. The resulting MOP is fully functional (assuming the underlying Base MOP was too), however the additional MOP methods might not have the most optimal implementation possible.

Version:

$Id: $

Author:

Attila Szegedi

Nested Class Summary

Nested classes/interfaces inherited from interface org.dynalang.mop.BaseMetaobjectProtocol

BaseMetaobjectProtocol.Results

Constructor Summary

MetaobjectProtocolAdaptor(BaseMetaobjectProtocol bmop)
Constructs a new MetaobjectProtocolAdaptor that enhances the adapted BaseMetaobjectProtocol with additional MetaobjectProtocol methods.

Method Summary

java.lang.Object	call(java.lang.Object callable, CallProtocol callProtocol, java.util.Map args) Calls a callable object with named arguments.
java.lang.Object	call(java.lang.Object callable, CallProtocol callProtocol, java.lang.Object... args) Calls a callable object with positional arguments.
java.lang.Object	call(java.lang.Object target, java.lang.Object callableId, CallProtocol callProtocol, java.util.Map args) Calls a method on the target object with supplied named arguments.
java.lang.Object	call(java.lang.Object target, java.lang.Object callableId, CallProtocol callProtocol, java.lang.Object... args) Calls a method on the target object with supplied positional arguments.
BaseMetaobjectProtocol.Results	delete(java.lang.Object target, long propertyId) Behaves as BaseMetaobjectProtocol.delete(Object, Object) with an integer property ID.
BaseMetaobjectProtocol.Results	delete(java.lang.Object target, java.lang.Object propertyId) Deletes an association of a value with a property in the target object.
java.lang.Object	get(java.lang.Object target, long propertyId) Behaves as CallProtocol.get(Object, Object) with an integer property ID.
java.lang.Object	get(java.lang.Object target, java.lang.Object propertyId) Retrieves the property value from the target object.
java.lang.Boolean	has(java.lang.Object target, long propertyId) Behaves as BaseMetaobjectProtocol.has(Object, Object) with an integer property ID.
java.lang.Boolean	has(java.lang.Object target, java.lang.Object propertyId) Tells whether the target object has a particular property.
java.util.Iterator<java.util.Map.Entry>	properties(java.lang.Object target) Returns an iterator over the property ID-value pairs in the target object this MOP knows about (and chooses to expose - not all properties must be exposed; hidden properties are allowed).
java.util.Iterator<? extends java.lang.Object>	propertyIds(java.lang.Object target) Returns an iterator over the property IDs in the target object this MOP knows about (and chooses to expose - not all properties must be exposed; hidden properties are allowed).
BaseMetaobjectProtocol.Results	put(java.lang.Object target, long propertyId, java.lang.Object value, CallProtocol callProtocol) Behaves as BaseMetaobjectProtocol.put(Object, Object, Object,CallProtocol) with an integer property ID.
BaseMetaobjectProtocol.Results	put(java.lang.Object target, java.lang.Object propertyId, java.lang.Object value, CallProtocol callProtocol) Associates a value with a property in the target object.
java.lang.Object	representAs(java.lang.Object object, java.lang.Class targetClass) Returns a representation of the specified target object as an object of the specified target class.
static MetaobjectProtocol[]	toMetaobjectProtocols(BaseMetaobjectProtocol[] protocols) Takes an array of base MOPs and "upgrades" them to a full MOP.

Methods inherited from class java.lang.Object

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

Constructor Detail

MetaobjectProtocolAdaptor

public MetaobjectProtocolAdaptor(BaseMetaobjectProtocol bmop)

Constructs a new MetaobjectProtocolAdaptor that enhances the adapted BaseMetaobjectProtocol with additional MetaobjectProtocol methods.

Parameters:

bmop - the base MOP to enhance.

Method Detail

call

public java.lang.Object call(java.lang.Object callable,
                             CallProtocol callProtocol,
                             java.util.Map args)

Description copied from interface: CallProtocol

Calls a callable object with named arguments.

Specified by:

call in interface CallProtocol

Parameters:

callable - the callable object

callProtocol - a marshaller that should be used by this metaobject protocol to convert the arguments to conform to expected argument types for the call.

args - the named arguments for the callable object. null must be treated as empty map. Usually, the map keys are strings, but it is possible that some protocols support non-string keys.

Returns:

the return value of the call, or a special result. BaseMetaobjectProtocol.Results.notCallable is returned if the protocol can authoritatively decide that the target is not a callable, or is not callable with named arguments. BaseMetaobjectProtocol.Results.doesNotExist is returned if the callable does not exist at all. BaseMetaobjectProtocol.Results.noAuthority is returned if the protocol can not authoritatively decide whether the target is callable.

call

public java.lang.Object call(java.lang.Object target,
                             java.lang.Object callableId,
                             CallProtocol callProtocol,
                             java.util.Map args)

Description copied from interface: MetaobjectProtocol

Calls a method on the target object with supplied named arguments. Must behave identically to:

 Object callable = get(target, callableId);
 if(callable instanceof Results) {
     return callable;
 }
 return call(callable, args);
 

Specified by:

call in interface MetaobjectProtocol

Parameters:

target - the target object

callableId - the ID of the method to call

callProtocol - a marshaller that should be used by this metaobject protocol to convert the arguments to conform to expected argument types for the call.

args - the arguments of the call

Returns:

the result of the invocation, or a special result. Can return any return value that CallProtocol.get(Object, Object) would return while looking up the callable. Can also return any return value that CallProtocol.call(Object, CallProtocol, Map) would return while calling.

call

public java.lang.Object call(java.lang.Object target,
                             java.lang.Object callableId,
                             CallProtocol callProtocol,
                             java.lang.Object... args)

Description copied from interface: MetaobjectProtocol

Calls a method on the target object with supplied positional arguments. Must behave identically to:

 Object callable = get(target, callableId);
 if(callable instanceof Results) {
     return callable;
 }
 return call(callable, args);
 

Specified by:

call in interface MetaobjectProtocol

Parameters:

target - the target object

callableId - the ID of the method to call

callProtocol - a marshaller that should be used by this metaobject protocol to convert the arguments to conform to expected argument types for the call.

args - the arguments of the call

Returns:

the result of the invocation, or a special result. Can return any return value that CallProtocol.get(Object, Object) would return while looking up the callable. Can also return any return value that CallProtocol.call(Object, CallProtocol, Object[]) would return while calling.

call

public java.lang.Object call(java.lang.Object callable,
                             CallProtocol callProtocol,
                             java.lang.Object... args)

Description copied from interface: CallProtocol

Calls a callable object with positional arguments.

Specified by:

call in interface CallProtocol

Parameters:

callable - the callable object

callProtocol - a marshaller that should be used by this metaobject protocol to convert the arguments to conform to expected argument types for the call.

args - the positional arguments for the callable object. null must be treated as empty array.

Returns:

the return value of the call, or a special result. BaseMetaobjectProtocol.Results.notCallable is returned if the protocol can authoritatively decide that the target is not a callable, or is not callable with positional arguments. BaseMetaobjectProtocol.Results.doesNotExist is returned if the callable does not exist at all. BaseMetaobjectProtocol.Results.noAuthority is returned if the protocol can not authoritatively decide whether the target is callable.

delete

public BaseMetaobjectProtocol.Results delete(java.lang.Object target,
                                             long propertyId)

Description copied from interface: MetaobjectProtocol

Behaves as BaseMetaobjectProtocol.delete(Object, Object) with an integer property ID.

Specified by:

delete in interface MetaobjectProtocol

Parameters:

target - the target object

propertyId - the ID of the property.

Returns:

see BaseMetaobjectProtocol.delete(Object, Object).

delete

public BaseMetaobjectProtocol.Results delete(java.lang.Object target,
                                             java.lang.Object propertyId)

Description copied from interface: BaseMetaobjectProtocol

Deletes an association of a value with a property in the target object.

Specified by:

delete in interface BaseMetaobjectProtocol

Parameters:

target - the target object

propertyId - the ID of the property. Usually a String or an Integer, but other property ID types can also be supported.

Returns:

the status of the operation. If the protocol decides that the property did not previously exist, it will return BaseMetaobjectProtocol.Results.doesNotExist. If the protocol authoritatively decides that the property can not be deleted, it will return BaseMetaobjectProtocol.Results.notDeleteable. If the protocol doesn't have the authority to delete the property, it will leave the object unchanged, and return BaseMetaobjectProtocol.Results.noAuthority. If the operation succeeds, BaseMetaobjectProtocol.Results.ok is returned.

get

public java.lang.Object get(java.lang.Object target,
                            long propertyId)

Description copied from interface: MetaobjectProtocol

Behaves as CallProtocol.get(Object, Object) with an integer property ID.

Specified by:

get in interface MetaobjectProtocol

Parameters:

target - the target object

propertyId - the ID of the property.

Returns:

see CallProtocol.get(Object, Object).

get

public java.lang.Object get(java.lang.Object target,
                            java.lang.Object propertyId)

Description copied from interface: CallProtocol

Retrieves the property value from the target object.

Specified by:

get in interface CallProtocol

Parameters:

target - the target object

propertyId - the ID of the property. Usually a String or an Integer, but other property ID types can also be supported.

Returns:

the property value for the target object. A null value means that the protocol authoritatively decided that the value of the property is null. If the protocol decides that the property does not exist, it will return BaseMetaobjectProtocol.Results.doesNotExist. If the protocol decides that the property exists, but is not readable, it will return BaseMetaobjectProtocol.Results.notReadable. If the protocol can not make an authoritative decision, it will return BaseMetaobjectProtocol.Results.noAuthority.

has

public java.lang.Boolean has(java.lang.Object target,
                             long propertyId)

Description copied from interface: MetaobjectProtocol

Behaves as BaseMetaobjectProtocol.has(Object, Object) with an integer property ID.

Specified by:

has in interface MetaobjectProtocol

Parameters:

target - the target object

propertyId - the ID of the property.

Returns:

see BaseMetaobjectProtocol.has(Object, Object).

has

public java.lang.Boolean has(java.lang.Object target,
                             java.lang.Object propertyId)

Description copied from interface: BaseMetaobjectProtocol

Tells whether the target object has a particular property.

Specified by:

has in interface BaseMetaobjectProtocol

Parameters:

target - the target object

propertyId - the ID of the property. Usually a String or an Integer, but other property ID types can also be supported.

Returns:

Boolean.TRUE or Boolean.FALSE if the protocol can authoritatively decide whether the target has or has not the property, or null if it does not have the authority to decide.

properties

public java.util.Iterator<java.util.Map.Entry> properties(java.lang.Object target)

Description copied from interface: BaseMetaobjectProtocol

Returns an iterator over the property ID-value pairs in the target object this MOP knows about (and chooses to expose - not all properties must be exposed; hidden properties are allowed).

Specified by:

properties in interface BaseMetaobjectProtocol

Parameters:

target - the target object

Returns:

an iterator over all the property ID-value pairs.

propertyIds

public java.util.Iterator<? extends java.lang.Object> propertyIds(java.lang.Object target)

Description copied from interface: MetaobjectProtocol

Returns an iterator over the property IDs in the target object this MOP knows about (and chooses to expose - not all properties must be exposed; hidden properties are allowed).

Specified by:

propertyIds in interface MetaobjectProtocol

Parameters:

target - the target object

Returns:

an iterator over the property IDs.

put

public BaseMetaobjectProtocol.Results put(java.lang.Object target,
                                          long propertyId,
                                          java.lang.Object value,
                                          CallProtocol callProtocol)

Description copied from interface: MetaobjectProtocol

Behaves as BaseMetaobjectProtocol.put(Object, Object, Object,CallProtocol) with an integer property ID. Associates a value with a property in the target object.

Specified by:

put in interface MetaobjectProtocol

Parameters:

target - the target object

propertyId - the ID of the property. Usually a String or an Integer, but other property ID types can also be supported.

value - the new value for the property

callProtocol - a marshaller that is used to convert the value in case the property can only accept values of certain types, and the metaobject protocol allows automatic coercing to those types.

Returns:

the previous value of the property, or a special value. A null value means that the protocol authoritatively decided that the previous value of the property is null. If the protocol decides that the property does not exist, and can not be created, it will return BaseMetaobjectProtocol.Results.doesNotExist. If the protocol can not set the new value, it will return BaseMetaobjectProtocol.Results.notWritable. If the protocol doesn't have the authority to put the new property value, it will leave the object unchanged, and return BaseMetaobjectProtocol.Results.noAuthority. If the operation succeeds, BaseMetaobjectProtocol.Results.ok is returned.

put

public BaseMetaobjectProtocol.Results put(java.lang.Object target,
                                          java.lang.Object propertyId,
                                          java.lang.Object value,
                                          CallProtocol callProtocol)

Description copied from interface: BaseMetaobjectProtocol

Associates a value with a property in the target object.

Specified by:

put in interface BaseMetaobjectProtocol

Parameters:

target - the target object

propertyId - the ID of the property. Usually a String or an Integer, but other property ID types can also be supported.

value - the new value for the property

callProtocol - a marshaller that is used to convert the value in case the property can only accept values of certain types, and the metaobject protocol allows automatic coercing to those types.

Returns:

a value indicating the outcome of the operation. If the protocol decides that the property does not exist, and can not be created, it will return BaseMetaobjectProtocol.Results.doesNotExist. If the protocol authoritatively decides that the property is read-only, it will return BaseMetaobjectProtocol.Results.notWritable. If the property has a limitation on types it can take as values, and the supplied marshaller is not able to provide a suitable representation, then the value of the property is not changed, and BaseMetaobjectProtocol.Results.noRepresentation is returned. Finally, if the protocol doesn't have the authority to put the new property value, it will leave the property value unchanged, and return BaseMetaobjectProtocol.Results.noAuthority. If the operation succeeds, BaseMetaobjectProtocol.Results.ok is returned.

representAs

public java.lang.Object representAs(java.lang.Object object,
                                    java.lang.Class targetClass)

Description copied from interface: CallProtocol

Returns a representation of the specified target object as an object of the specified target class. Typical supported target classes would be wrappers for Java primitive types that map to native types of the higher level languages. I.e. if an object is used as a boolean expression, then the language would ask the protocol to interpret it as boolean by calling representAs(Boolean.TYPE).

Specified by:

representAs in interface CallProtocol

Parameters:

object - the object to represent

targetClass - the target class for representation.

Returns:

the representation that must be instance of the targetClass, or in case targetClass is primitive, of its adequate boxing class. It can also be a special value to indicate conversion failure: BaseMetaobjectProtocol.Results.noAuthority is returned if the marshaller can not authoritatively decide on a representation; BaseMetaobjectProtocol.Results.noRepresentation is returned if the marshaller can authoritatively decide that the requested representation is not possible. representation of null should be null, except when the target class is a primitive type in which case BaseMetaobjectProtocol.Results.noRepresentation should be returned.

toMetaobjectProtocols

public static MetaobjectProtocol[] toMetaobjectProtocols(BaseMetaobjectProtocol[] protocols)

Takes an array of base MOPs and "upgrades" them to a full MOP. If any element of the input array is already a full mop, it is left unchanged. If it is a base MOP, it is wrapped in an instance of MetaobjectProtocolAdaptor.

Parameters:

protocols - the input array of base MOPs

Returns:

an array of full MOPs.