Delegator.java
/* -*- Mode: java; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-
*
* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
// API class
package org.mozilla.javascript;
/**
* 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.
*
* <p>A useful application is the implementation of interceptors, pre/post conditions, debugging.
*
* @see Function
* @see Scriptable
* @author Matthias Radestock
*/
public class Delegator implements Function, SymbolScriptable {
protected Scriptable obj = null;
/**
* Create a Delegator prototype.
*
* <p>This constructor should only be used for creating prototype objects of Delegator.
*
* @see org.mozilla.javascript.Delegator#construct
*/
public Delegator() {}
/**
* Create a new Delegator that forwards requests to a delegee Scriptable object.
*
* @param obj the delegee
* @see org.mozilla.javascript.Scriptable
*/
public Delegator(Scriptable obj) {
this.obj = obj;
}
/**
* Crete new Delegator instance. The default implementation calls this.getClass().newInstance().
*
* @see #construct(Context cx, Scriptable scope, Object[] args)
*/
protected Delegator newInstance() {
try {
return this.getClass().getDeclaredConstructor().newInstance();
} catch (Exception ex) {
throw Context.throwAsScriptRuntimeEx(ex);
}
}
/**
* Retrieve the delegee.
*
* @return the delegee
*/
public Scriptable getDelegee() {
return obj;
}
/**
* Set the delegee.
*
* @param obj the delegee
* @see org.mozilla.javascript.Scriptable
*/
public void setDelegee(Scriptable obj) {
this.obj = obj;
}
/**
* @see org.mozilla.javascript.Scriptable#getClassName
*/
@Override
public String getClassName() {
return getDelegee().getClassName();
}
/**
* @see org.mozilla.javascript.Scriptable#get(String, Scriptable)
*/
@Override
public Object get(String name, Scriptable start) {
return getDelegee().get(name, start);
}
@Override
public Object get(Symbol key, Scriptable start) {
final Scriptable delegee = getDelegee();
if (delegee instanceof SymbolScriptable) {
return ((SymbolScriptable) delegee).get(key, start);
}
return Scriptable.NOT_FOUND;
}
/**
* @see org.mozilla.javascript.Scriptable#get(int, Scriptable)
*/
@Override
public Object get(int index, Scriptable start) {
return getDelegee().get(index, start);
}
/**
* @see org.mozilla.javascript.Scriptable#has(String, Scriptable)
*/
@Override
public boolean has(String name, Scriptable start) {
return getDelegee().has(name, start);
}
@Override
public boolean has(Symbol key, Scriptable start) {
final Scriptable delegee = getDelegee();
if (delegee instanceof SymbolScriptable) {
return ((SymbolScriptable) delegee).has(key, start);
}
return false;
}
/**
* @see org.mozilla.javascript.Scriptable#has(int, Scriptable)
*/
@Override
public boolean has(int index, Scriptable start) {
return getDelegee().has(index, start);
}
/**
* @see org.mozilla.javascript.Scriptable#put(String, Scriptable, Object)
*/
@Override
public void put(String name, Scriptable start, Object value) {
getDelegee().put(name, start, value);
}
/**
* @see org.mozilla.javascript.SymbolScriptable#put(Symbol, Scriptable, Object)
*/
@Override
public void put(Symbol symbol, Scriptable start, Object value) {
final Scriptable delegee = getDelegee();
if (delegee instanceof SymbolScriptable) {
((SymbolScriptable) delegee).put(symbol, start, value);
}
}
/**
* @see org.mozilla.javascript.Scriptable#put(int, Scriptable, Object)
*/
@Override
public void put(int index, Scriptable start, Object value) {
getDelegee().put(index, start, value);
}
/**
* @see org.mozilla.javascript.Scriptable#delete(String)
*/
@Override
public void delete(String name) {
getDelegee().delete(name);
}
@Override
public void delete(Symbol key) {
final Scriptable delegee = getDelegee();
if (delegee instanceof SymbolScriptable) {
((SymbolScriptable) delegee).delete(key);
}
}
/**
* @see org.mozilla.javascript.Scriptable#delete(int)
*/
@Override
public void delete(int index) {
getDelegee().delete(index);
}
/**
* @see org.mozilla.javascript.Scriptable#getPrototype
*/
@Override
public Scriptable getPrototype() {
return getDelegee().getPrototype();
}
/**
* @see org.mozilla.javascript.Scriptable#setPrototype
*/
@Override
public void setPrototype(Scriptable prototype) {
getDelegee().setPrototype(prototype);
}
/**
* @see org.mozilla.javascript.Scriptable#getParentScope
*/
@Override
public Scriptable getParentScope() {
return getDelegee().getParentScope();
}
/**
* @see org.mozilla.javascript.Scriptable#setParentScope
*/
@Override
public void setParentScope(Scriptable parent) {
getDelegee().setParentScope(parent);
}
/**
* @see org.mozilla.javascript.Scriptable#getIds
*/
@Override
public Object[] getIds() {
return getDelegee().getIds();
}
/**
* Note that this method does not get forwarded to the delegee if the <code>hint</code>
* parameter is null, <code>ScriptRuntime.ScriptableClass</code> or <code>
* ScriptRuntime.FunctionClass</code>. Instead the object itself is returned.
*
* @param hint the type hint
* @return the default value
* @see org.mozilla.javascript.Scriptable#getDefaultValue
*/
@Override
public Object getDefaultValue(Class<?> hint) {
return (hint == null
|| hint == ScriptRuntime.ScriptableClass
|| hint == ScriptRuntime.FunctionClass)
? this
: getDelegee().getDefaultValue(hint);
}
/**
* @see org.mozilla.javascript.Scriptable#hasInstance
*/
@Override
public boolean hasInstance(Scriptable instance) {
return getDelegee().hasInstance(instance);
}
/**
* @see org.mozilla.javascript.Function#call
*/
@Override
public Object call(Context cx, Scriptable scope, Scriptable thisObj, Object[] args) {
return ((Function) getDelegee()).call(cx, scope, thisObj, args);
}
/**
* Note that if the <code>delegee</code> is <code>null</code>, this method creates a new
* instance of the Delegator itself rather than forwarding the call to the <code>delegee</code>
* . This permits the use of Delegator prototypes.
*
* @param cx the current Context for this thread
* @param scope an enclosing scope of the caller except when the function is called from a
* closure.
* @param args the array of arguments
* @return the allocated object
* @see Constructable#construct(Context, Scriptable, Object[])
*/
@Override
public Scriptable construct(Context cx, Scriptable scope, Object[] args) {
Scriptable myDelegee = getDelegee();
if (myDelegee == null) {
// this little trick allows us to declare prototype objects for Delegators
Delegator n = newInstance();
Scriptable delegee;
if (args.length == 0) {
delegee = cx.newObject(scope);
} else {
delegee = ScriptRuntime.toObject(cx, scope, args[0]);
}
n.setDelegee(delegee);
return n;
}
return ((Constructable) myDelegee).construct(cx, scope, args);
}
}