Plain Old Java Object (POJO) example

Start with a Plain Old Java™ Object (POJO, in this example) that contains all of the business logic for your extension.

For example:

public class Extension {
   public static void log(String msg) {
      System.out.println(msg);
   }
}

In this case, the POJO contains a single method. Your typical extension contains more logic. For example:

static class FESIExtension implements JSExtension {
   public void initializeExtension(JSGlobalObject go) throws JSException {
      // Create the prototype
      final JSObject prototype = go.makeJSObject();

      prototype.setMember("log", new JSFunctionAdapter() {
         public Object doCall(JSObject thisObject, Object[] args)
               throws JSException {
            if (args.length >= 1) {
               Extension.log(args[0].toString());
            }

            return null;
         }
      });

      final JSObject obj = go.makeJSObject(prototype);

      // This is the name of the object to be used in JavaScript Code
      go.setMember("CustomExtension", obj);

      go.setMember("log", new JSFunctionAdapter() {
         public Object doCall(JSObject thisObject, Object[] args)
               throws JSException {
            if (args.length >= 1) {
               Extension.log(args[0].toString());
            }

            return null;
         }
      });

      go.setMember("Logger", new JSFunctionAdapter() {
         public Object doNew(JSObject thisObject, Object[] args)
               throws JSException {
            JSGlobalObject go = thisObject.getGlobalObject();
            JSObject proto = go.makeJSObject();

            proto.setMember("log", new JSFunctionAdapter() {
               public Object doCall(JSObject thisObject, Object[] args)
                     throws JSException {
                  if (args.length >= 1) {
                     Extension.log(args[0].toString());
                  }

                  return null;
               }
            });
            final JSObject obj = go.makeJSObject(proto);
            return obj;
         }
      });
   }
}

This FESI extension has three main parts:

First, the extension makes a JSObject named prototype and adds the method “log” to prototype:

final JSObject prototype = go.makeJSObject();

prototype.setMember("log", new JSFunctionAdapter() {
   public Object doCall(JSObject thisObject, Object[] args)
         throws JSException {
      if (args.length >= 1) {
         Extension.log(args[0].toString());
      }

      return null;
   }
});
 
go.setMember("CustomExtension", obj);

The prototype JSObject is then added to the JSGlobalObject with the name CustomExtension. This addition allows scripts to call:

CustomExtension.log("message");

The second part of the extension creates a global function named log.

go.setMember("log", new JSFunctionAdapter() {
   public Object doCall(JSObject thisObject, Object[] args)
         throws JSException {
      if (args.length >= 1) {
         Extension.log(args[0].toString());
      }

      return null;
   }
});

Now, a script can call:

log("message");

The third part of the extension creates a constructor that can be called from scripts. For example:

go.setMember("Logger", new JSFunctionAdapter() {
   public Object doNew(JSObject thisObject, Object[] args)
         throws JSException {
      JSGlobalObject go = thisObject.getGlobalObject();
      JSObject proto = go.makeJSObject();

      proto.setMember("log", new JSFunctionAdapter() {
         public Object doCall(JSObject thisObject, Object[] args)
               throws JSException {
            if (args.length >= 1) {
               Extension.log(args[0].toString());
            }

            return null;
         }
      });
      final JSObject obj = go.makeJSObject(proto);
      return obj;
   }
});

With this constructor, scripts can do the following:

var logger = new Logger();
logger.log("message");