Class 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.
    See Also:
    Function, Scriptable
    • Constructor Summary

      Constructors 
      Constructor Description
      Delegator()
      Create a Delegator prototype.
      Delegator​(Scriptable obj)
      Create a new Delegator that forwards requests to a delegee Scriptable object.
    • Method Summary

      All Methods Instance Methods Concrete Methods 
      Modifier and Type Method Description
      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.
      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

        equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
    • Method Detail

      • 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 codeJava 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)
      • 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)
      • 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[])