org.mozilla.javascript
Class Delegator

java.lang.Object
  org.mozilla.javascript.Delegator

All Implemented Interfaces:

Callable, Function, Scriptable

Direct Known Subclasses:

Synchronizer

public class Delegator
extends java.lang.Object
implements Function

This is a helper class for implementing wrappers around Scriptable objects. It implements the Function interface and delegates all invocations to a delegee Scriptable object. The normal use of this class involves creating a sub-class and overriding one or more of the methods. A useful application is the implementation of interceptors, pre/post conditions, debugging.

Author:

Matthias Radestock

See Also:

Function, Scriptable

Field Summary

protected Scriptable

obj

Fields inherited from interface org.mozilla.javascript.Scriptable

NOT_FOUND

Constructor Summary

Delegator()
Create a Delegator prototype.

Delegator(Scriptable obj)
Create a new Delegator that forwards requests to a delegee Scriptable object.

Method Summary

java.lang.Object	call(Context cx, Scriptable scope, Scriptable thisObj, java.lang.Object[] args) Call the function.
Scriptable	construct(Context cx, Scriptable scope, java.lang.Object[] args) Note that if the delegee is null, this method creates a new instance of the Delegator itself rathert than forwarding the call to the delegee.
void	delete(int index) Removes a property from this object.
void	delete(java.lang.String name) Removes a property from this object.
java.lang.Object	get(int index, Scriptable start) Get a property from the object selected by an integral index.
java.lang.Object	get(java.lang.String name, Scriptable start) Get a named property from the object.
java.lang.String	getClassName() Get the name of the set of objects implemented by this Java class.
java.lang.Object	getDefaultValue(java.lang.Class<?> hint) Note that this method does not get forwarded to the delegee if the hint parameter is null, ScriptRuntime.ScriptableClass or ScriptRuntime.FunctionClass.
Scriptable	getDelegee() Retrieve the delegee.
java.lang.Object[]	getIds() Get an array of property ids.
Scriptable	getParentScope() Get the parent scope of the object.
Scriptable	getPrototype() Get the prototype of the object.
boolean	has(int index, Scriptable start) Indicates whether or not an indexed property is defined in an object.
boolean	has(java.lang.String name, Scriptable start) Indicates whether or not a named property is defined in an object.
boolean	hasInstance(Scriptable instance) The instanceof operator.
protected Delegator	newInstance() Crete new Delegator instance.
void	put(int index, Scriptable start, java.lang.Object value) Sets an indexed property in this object.
void	put(java.lang.String name, Scriptable start, java.lang.Object value) Sets a named property in this object.
void	setDelegee(Scriptable obj) Set the delegee.
void	setParentScope(Scriptable parent) Set the parent scope of the object.
void	setPrototype(Scriptable prototype) Set the prototype of the object.

Methods inherited from class java.lang.Object

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

Field Detail

obj

protected Scriptable obj

Constructor Detail

Delegator

public Delegator()

Create a Delegator prototype. This constructor should only be used for creating prototype objects of Delegator.

See Also:

construct(org.mozilla.javascript.Context, org.mozilla.javascript.Scriptable, java.lang.Object[])

Delegator

public Delegator(Scriptable obj)

Create a new Delegator that forwards requests to a delegee Scriptable object.

Parameters:

obj - the delegee

See Also:

Scriptable

Method Detail

newInstance

protected Delegator newInstance()

Crete new Delegator instance. The default implementation calls this.getClass().newInstance().

See Also:

construct(Context cx, Scriptable scope, Object[] args)

getDelegee

public Scriptable getDelegee()

Retrieve the delegee.

Returns:

the delegee

setDelegee

public void setDelegee(Scriptable obj)

Set the delegee.

Parameters:

obj - the delegee

See Also:

Scriptable

getClassName

public java.lang.String getClassName()

Description copied from interface: Scriptable

Get the name of the set of objects implemented by this Java class. This corresponds to the [[Class]] operation in ECMA and is used by Object.prototype.toString() in ECMA.

See ECMA 8.6.2 and 15.2.4.2.

Specified by:

getClassName in interface Scriptable

See Also:

Scriptable.getClassName()

get

public java.lang.Object get(java.lang.String name,
                            Scriptable start)

Description copied from interface: Scriptable

Get a named property from the object. Looks property up in this object and returns the associated value if found. Returns NOT_FOUND if not found. Note that this method is not expected to traverse the prototype chain. This is different from the ECMA [[Get]] operation. Depending on the property selector, the runtime will call this method or the form of get that takes an integer:

JavaScript code	Java code
a.b	a.get("b", a)
a["foo"]	a.get("foo", a)
a[3]	a.get(3, a)
a["3"]	a.get(3, a)
a[3.0]	a.get(3, a)
a["3.0"]	a.get("3.0", a)
a[1.1]	a.get("1.1", a)
a[-4]	a.get(-4, a)

The values that may be returned are limited to the following:

• java.lang.Boolean objects
• java.lang.String objects
• java.lang.Number objects
• org.mozilla.javascript.Scriptable objects
• null
• The value returned by Context.getUndefinedValue()
• NOT_FOUND

Specified by:

get in interface Scriptable

Parameters:

name - the name of the property

start - the object in which the lookup began

Returns:

the value of the property (may be null), or NOT_FOUND

See Also:

Scriptable.get(String, Scriptable)

get

public java.lang.Object get(int index,
                            Scriptable start)

Description copied from interface: Scriptable

Get a property from the object selected by an integral index. Identical to get(String, Scriptable) except that an integral index is used to select the property.

Specified by:

get in interface Scriptable

Parameters:

index - the numeric index for the property

start - the object in which the lookup began

Returns:

the value of the property (may be null), or NOT_FOUND

See Also:

Scriptable.get(int, Scriptable)

has

public boolean has(java.lang.String name,
                   Scriptable start)

Description copied from interface: Scriptable

Indicates whether or not a named property is defined in an object. Does not traverse the prototype chain.

The property is specified by a String name as defined for the get method.

Specified by:

has in interface Scriptable

Parameters:

name - the name of the property

start - the object in which the lookup began

Returns:

true if and only if the named property is found in the object

See Also:

Scriptable.has(String, Scriptable)

has

public boolean has(int index,
                   Scriptable start)

Description copied from interface: Scriptable

Indicates whether or not an indexed property is defined in an object. Does not traverse the prototype chain.

The property is specified by an integral index as defined for the get method.

Specified by:

has in interface Scriptable

Parameters:

index - the numeric index for the property

start - the object in which the lookup began

Returns:

true if and only if the indexed property is found in the object

See Also:

Scriptable.has(int, Scriptable)

put

public void put(java.lang.String name,
                Scriptable start,
                java.lang.Object value)

Description copied from interface: Scriptable

Sets a named property in this object.

The property is specified by a string name as defined for get.

The possible values that may be passed in are as defined for get. A class that implements this method may choose to ignore calls to set certain properties, in which case those properties are effectively read-only.

For properties defined in a prototype chain, use putProperty in ScriptableObject.

Note that if a property a is defined in the prototype p of an object o, then evaluating o.a = 23 will cause set to be called on the prototype p with o as the start parameter. To preserve JavaScript semantics, it is the Scriptable object's responsibility to modify o.

This design allows properties to be defined in prototypes and implemented in terms of getters and setters of Java values without consuming slots in each instance.

The values that may be set are limited to the following:

• java.lang.Boolean objects
• java.lang.String objects
• java.lang.Number objects
• org.mozilla.javascript.Scriptable objects
• null
• The value returned by Context.getUndefinedValue()

Arbitrary Java objects may be wrapped in a Scriptable by first calling Context.toObject. This allows the property of a JavaScript object to contain an arbitrary Java object as a value.

Note that has will be called by the runtime first before set is called to determine in which object the property is defined. Note that this method is not expected to traverse the prototype chain, which is different from the ECMA [[Put]] operation.

Specified by:

put in interface Scriptable

Parameters:

name - the name of the property

start - the object whose property is being set

value - value to set the property to

See Also:

Scriptable.put(String, Scriptable, Object)

put

public void put(int index,
                Scriptable start,
                java.lang.Object value)

Description copied from interface: Scriptable

Sets an indexed property in this object.

The property is specified by an integral index as defined for get.

Identical to put(String, Scriptable, Object) except that an integral index is used to select the property.

Specified by:

put in interface Scriptable

Parameters:

index - the numeric index for the property

start - the object whose property is being set

value - value to set the property to

See Also:

Scriptable.put(int, Scriptable, Object)

delete

public void delete(java.lang.String name)

Description copied from interface: Scriptable

Removes a property from this object. This operation corresponds to the ECMA [[Delete]] except that the no result is returned. The runtime will guarantee that this method is called only if the property exists. After this method is called, the runtime will call Scriptable.has to see if the property has been removed in order to determine the boolean result of the delete operator as defined by ECMA 11.4.1.

A property can be made permanent by ignoring calls to remove it.

The property is specified by a String name as defined for get.

To delete properties defined in a prototype chain, see deleteProperty in ScriptableObject.

Specified by:

delete in interface Scriptable

Parameters:

name - the identifier for the property

See Also:

Scriptable.delete(String)

delete

public void delete(int index)

Description copied from interface: Scriptable

Removes a property from this object. The property is specified by an integral index as defined for get.

To delete properties defined in a prototype chain, see deleteProperty in ScriptableObject. Identical to delete(String) except that an integral index is used to select the property.

Specified by:

delete in interface Scriptable

Parameters:

index - the numeric index for the property

See Also:

Scriptable.delete(int)

getPrototype

public Scriptable getPrototype()

Description copied from interface: Scriptable

Get the prototype of the object.

Specified by:

getPrototype in interface Scriptable

Returns:

the prototype

See Also:

Scriptable.getPrototype()

setPrototype

public void setPrototype(Scriptable prototype)

Description copied from interface: Scriptable

Set the prototype of the object.

Specified by:

setPrototype in interface Scriptable

Parameters:

prototype - the prototype to set

See Also:

Scriptable.setPrototype(org.mozilla.javascript.Scriptable)

getParentScope

public Scriptable getParentScope()

Description copied from interface: Scriptable

Get the parent scope of the object.

Specified by:

getParentScope in interface Scriptable

Returns:

the parent scope

See Also:

Scriptable.getParentScope()

setParentScope

public void setParentScope(Scriptable parent)

Description copied from interface: Scriptable

Set the parent scope of the object.

Specified by:

setParentScope in interface Scriptable

Parameters:

parent - the parent scope to set

See Also:

Scriptable.setParentScope(org.mozilla.javascript.Scriptable)

getIds

public java.lang.Object[] getIds()

Description copied from interface: Scriptable

Get an array of property ids. Not all property ids need be returned. Those properties whose ids are not returned are considered non-enumerable.

Specified by:

getIds in interface Scriptable

Returns:

an array of Objects. Each entry in the array is either a java.lang.String or a java.lang.Number

See Also:

Scriptable.getIds()

getDefaultValue

public java.lang.Object getDefaultValue(java.lang.Class<?> hint)

Note that this method does not get forwarded to the delegee if the hint parameter is null, ScriptRuntime.ScriptableClass or ScriptRuntime.FunctionClass. Instead the object itself is returned.

Specified by:

getDefaultValue in interface Scriptable

Parameters:

hint - the type hint

Returns:

the default value

See Also:

Scriptable.getDefaultValue(java.lang.Class)

hasInstance

public boolean hasInstance(Scriptable instance)

Description copied from interface: Scriptable

The instanceof operator.

The JavaScript code "lhs instanceof rhs" causes rhs.hasInstance(lhs) to be called.

The return value is implementation dependent so that embedded host objects can return an appropriate value. See the JS 1.3 language documentation for more detail.

This operator corresponds to the proposed EMCA [[HasInstance]] operator.

Specified by:

hasInstance in interface Scriptable

Parameters:

instance - The value that appeared on the LHS of the instanceof operator

Returns:

an implementation dependent value

See Also:

Scriptable.hasInstance(org.mozilla.javascript.Scriptable)

call

public java.lang.Object call(Context cx,
                             Scriptable scope,
                             Scriptable thisObj,
                             java.lang.Object[] args)

Description copied from interface: Function

Call the function. Note that the array of arguments is not guaranteed to have length greater than 0.

Specified by:

call in interface Callable

Specified by:

call in interface Function

Parameters:

cx - the current Context for this thread

scope - the scope to execute the function relative to. This is set to the value returned by getParentScope() except when the function is called from a closure.

thisObj - the JavaScript this object

args - the array of arguments

Returns:

the result of the call

See Also:

Function.call(org.mozilla.javascript.Context, org.mozilla.javascript.Scriptable, org.mozilla.javascript.Scriptable, java.lang.Object[])

construct

public Scriptable construct(Context cx,
                            Scriptable scope,
                            java.lang.Object[] args)

Note that if the delegee is null, this method creates a new instance of the Delegator itself rathert than forwarding the call to the delegee. This permits the use of Delegator prototypes.

Specified by:

construct in interface Function

Parameters:

cx - the current Context for this thread

scope - an enclosing scope of the caller except when the function is called from a closure.

args - the array of arguments

Returns:

the allocated object

See Also:

Function.construct(Context, Scriptable, Object[])