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

    Fields
    Modifier and Type | Field and Description
    --- | ---
    `protected Scriptable` | `obj`

    - ### Fields inherited from interface org.mozilla.javascript.Scriptable

      `NOT_FOUND`

  - ### Constructor Summary

    Constructors
    Constructor and Description
    `Delegator()` Create a Delegator prototype.
    `Delegator(Scriptable obj)` Create a new Delegator that forwards requests to a delegee Scriptable object.

  - ### Method Summary

    Methods
    Modifier and Type | Method and 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.
    `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[])`