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.

1. 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");

2. 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");

3. 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");
   

Parent topic: Migration of custom FESI extensions to the IBM JSEngine