Docs/examples for JSAdapter

[Jim Laskey (Oracle)]

In Nashorn, there is no need to wrap classes/types in JavaScript objects.  You can work with them directly or extended them directly.  As an example,

jjs> var ArrayList = Java.type("java.util.ArrayList");  // or var ArrayList = java.util.ArrayList;
jjs> var Arrays = Java.type("java.util.Arrays");
jjs> var list = new ArrayList();
jjs> list.add("a");
true
jjs> list.add("b");
true
jjs> list.add("c");
true
jjs> list.addAll(Arrays.asList(["d", "e", "f"]));
true
jjs> list.addAll(Arrays.asList("g", "h", "i"));
true
jjs> for each(var e in list) print(e);
a
b
c
d
e
f
g
h
i

Is there a specific example of something you want to translate?  We can help you out.

Cheers,

-- Jim






On 2013-10-22, at 1:02 PM, Rick Bullotta <rick.bullotta at thingworx.com> wrote:

> In Rhino, you register custom adapters in a “wrap factory” that tells the script engine to use these adapters for accessing instances of those classes/types.  What’s the analog in Nashorn?  Can custom types implement interfaces that Nashorn will use?
>  
> From: Jim Laskey (Oracle) [mailto:james.laskey at oracle.com] 
> Sent: Tuesday, October 22, 2013 11:52 AM
> To: Rick Bullotta
> Cc: nashorn-dev at openjdk.java.net
> Subject: Re: Docs/examples for JSAdapter
>  
> In general the Nashorn docs start here. https://wiki.openjdk.java.net/display/Nashorn/Nashorn+Documentation, but as you point out, we seem to be lacking JSAdapter details.  I should start an FAQ.
>  
> From the javadoc (cd make; ant javadoc # ./dist/javadoc/index.html)
>  
> ·         public final class NativeJSAdapter
> ·         extends ScriptObject
> This class is the implementation of the Nashorn-specific global object named JSAdapter. It can be thought of as the Proxy equivalent for JavaScript. NativeJSAdapter calls specially named JavaScript methods on an adaptee object when property access/update/call/new/delete is attempted on it. Example:
>     var y = {
>                 __get__    : function (name) { ... }
>                 __has__    : function (name) { ... }
>                 __put__    : function (name, value) {...}
>                 __call__   : function (name, arg1, arg2) {...}
>                 __new__    : function (arg1, arg2) {...}
>                 __delete__ : function (name) { ... }
>                 __getIds__ : function () { ... }
>             };
>  
>     var x = new JSAdapter(y);
>  
>     x.i;                        // calls y.__get__
>     x.foo();                    // calls y.__call__
>     new x();                    // calls y.__new__
>     i in x;                     // calls y.__has__
>     x.p = 10;                   // calls y.__put__
>     delete x.p;                 // calls y.__delete__
>     for (i in x) { print(i); }  // calls y.__getIds__
>  
> JavaScript caller of adapter object is isolated from the fact that the property access/mutation/deletion are really calls to JavaScript methods on adaptee.
> 
> JSAdapter constructor can optionally receive an "overrides" object. Properties of overrides object is copied to JSAdapter instance. When user accessed property is one of these, then adaptee's methods like __get__, __put__ etc. are not called for those. This can be used to make certain "preferred" properties that can be accessed in the usual/faster way avoiding proxy mechanism. Example:
> 
>      var x = new JSAdapter({ foo: 444, bar: 6546 }) {
>           __get__: function(name) { return name; }
>       };
>  
>      x.foo;           // 444 directly retrieved without __get__ call
>      x.bar = 'hello'; // "bar" directly set without __put__ call
>      x.prop           // calls __get__("prop") as 'prop' is not overridden
>  
> It is possible to pass a specific prototype for JSAdapter instance by passing three arguments to JSAdapter constructor. So exact signature of JSAdapter constructor is as follows:
>      JSAdapter([proto], [overrides], adaptee);
>  
> Both proto and overrides are optional - but adaptee is not. When proto is not passed JSAdapter.prototype is used.
> ·          
> 
> As well as the test ./test/script/basic/jsadapter.js
>  
> var obj = new JSAdapter() {
>     __get__: function(name) {
>         print("getter called for '" + name + "'"); return name;
>     },
> 
>     __put__: function(name, value) {
>         print("setter called for '" + name + "' with " + value);
>     },
> 
>     __call__: function(name, arg1, arg2) {
>         print("method '" + name + "' called with " + arg1 + ", " + arg2);
>     },
> 
>     __new__: function(arg1, arg2) {
>         print("new with " + arg1 + ", " + arg2);
>     },
> 
>     __getIds__: function() {
>         print("__getIds__ called");
>         return [ "foo", "bar" ];
>     },
> 
>     __getValues__: function() {
>         print("__getValues__ called");
>         return [ "fooval", "barval" ];
>     },
> 
>     __has__: function(name) {
>         print("__has__ called with '" + name + "'");
>         return name == "js";
>     },
> 
>     __delete__: function(name) {
>         print("__delete__ called with '" + name + "'");
>         return true;
>     }
> };
> 
> // calls __get__
> print(obj.foo);
> 
> // calls __put__
> obj.foo = 33;
> 
> // calls __call__
> obj.func("hello", "world");
> 
> // calls __new__
> new obj("hey!", "it works!");
> 
> for (i in obj) {
>     print(i);
> }
> 
> for each (i in obj) {
>     print(i);
> }
> 
> var x = "foo" in obj;
> print(x);
> 
> var y = "js" in obj;
> print(y);
> 
> print(delete obj.prop);
> 
> print(obj["js"]);
> obj["js"] = "javascript";
> print(obj["javascript"]);
> 
> Hope that helps.  Is there a specific question?
>  
> Cheers,
>  
> -- Jim
>  
> On 2013-10-22, at 11:50 AM, Rick Bullotta <rick.bullotta at thingworx.com> wrote:
> 
> 
> Hi, all.
> 
> I've been searching everywhere for any form of documentation or substantive examples as to how JSAdapter works in Nashorn, as it is an essential piece of the puzzle for many of us who will naturally be migrating from Rhino.
> 
> Can anyone provide and additional info?
> 
> Thanks,
> 
> Rick
> ThingWorx
> 
>