ClassLoaderExample.java

    //A GET method in my stupid REST service for example.....
    public Response sendMsg(String content, @QueryParam("msgType") String msgType) {
        //Open class loader in try-with-resource 
        //Use null in constructor if you don't want to use parent class loader. 
        //In this case it's useful because I don't load any class from system classpath.
        try (URLClassLoader clsLoader = URLClassLoader.newInstance(new URL[] {new URL("file:/lib/ACM_0.1.0.jar")}, null)){
            
            Class<?> clazz = clsLoader.loadClass("com.hs.acm.client.message.in." + msgType);
            
            Object msgObj = clazz.newInstance();
            
            AcmClientReqMsg msg = (AcmClientReqMsg) msgObj;
            msg.setAgentID("test agent ID " + clazz.getSimpleName());
            msg.setTransID(new BigInteger(130, random).toString(32));
            
            TextMessage jsonMsg = session.createTextMessage(gson.toJson(msg));
            producer.send(dest, jsonMsg);
        } catch (ClassNotFoundException ex) {
            logger.error("Invalid message type", ex);
            return Response.status(Response.Status.BAD_REQUEST).build();
        } catch (InstantiationException | IllegalAccessException ex) {
            logger.error("Cannot create message object: ", ex);
            return Response.status(Response.Status.INTERNAL_SERVER_ERROR).build();
        } catch (IOException ex) { 
            logger.error("Cannot close class loader: ", ex);
            return Response.status(Response.Status.INTERNAL_SERVER_ERROR).build();
        }
        return Response.status(200).entity("Ok").build();
    }