We Keep Coding

RPG (iSeries) Modernization using JTOpen - What is possible?

We would be in near future implementing a solution to modernize our iSeries applications
written as RPG programs with some stored procedures, and our preferred way is leveraging the latest and greatest of what Java has to offer in this space.
From googling and checking other questions here on STOVFlow, JTOpen seems to be the defacto
library/toolset which has worked for most and I was encouraged to see that Tomcat runs on an I-series box with out any issues.
With this as the background, I am thinking of the following as the high level sol arch
Install IBM JRE and use JTOpen's capabilities to invoke RPG Programs and in some cases directly call the stored procedures running on DB2
Have Tomcat host a modern web application built using Grails and other frameworks (Camel, Smooks) to provide an application logic layer which would fill any mediations, transformations required for the old functionality to be offered to the user from a browser
Questions-
If any one of you has been involved in such an exercise, please share the pitfalls with this approach
Is there a significant performance drop with respect to response times for the end user?
Would it be better to some how expose the JT400 code as web services and run the web app on a different machine altogether consuming these web services?

Be very careful with calling RPG from Java because RPG is not threadsafe without some changes.

When I was at COMMON, the best product I felt on the market was Profound UI. There are several others from a variety of vendors. Most of these products do not use Java. Java on the i tends to be slow. (There are things that can be done to make it faster, but native is always faster.) You'll pay the price for these products, but just imagine how much time it would take you to do this yourself. For the above, I was quoted in the $20+ thousand range. But like all i products prices vary greatly based on system.
To directly answer your questions:
I have been doing research on modernization as time allows, the products weren't quite there yet (at the time I looked) to use it for what we wanted to use it for (before COMMON 2011). Now it looks like it might work.
This really depends on your system. A newer system will have less problems than an older system. Web will always be slower than the green-screen. Hands-down entry people won't like it. Executives and younger people will love it.
Your slow point is running the business logic. It wouldn't matter which server the HTML is coming from.

I've found that for all practical purposes an AS/400 behaves like an AIX box seen from Java code, and you must use jt400 (jtOpen) to communicate with the AS/400 specific features like data queues, files etc. This works pretty well, but the slowness of invoking the JVM pressures Java based solutions to be long running.
Note also that QTEMP is generally unavailable as a mechanism to keep state due to the nature of prestarted jobs.
Under V6R1 Java 6 is available and runs pretty well in the "new technology" edition. You can then run almost all Java based solutions, including web servers like Jetty in it. Note that Java defaults to code page 819 when accessing IFS files directly. Windows clients using AS/400 as a network drive uses a compatible code page.

chat website in jsp/servlet

I want to devlelop a chat website using JSP/Servlets and Tomcat. I have following questions:
Can the website handle load (1000 people at one time) without slowing down?
Will it cause the website to slow down? What is the ideal server configuration for this kind of website? Note that I don't have a huge budget to host.
How can I implement server push?
Will PHP or JSP be ideal for such website?

Depends entirely on hardware/software. It will obviously run faster on a Quadcore Xeon server from 2010 than an Octa Pentium Pro server from 2000. It will also obviously run and scale better if the code is written efficiently and the server is configured to an optimum.
See 1. I'd suggest to use the NIO connector in Tomcat.
You can use Comet for this. In Tomcat, it's available by AIO (Advanced IO).
Depends entirely on your own skillset. But technically, JSP/Servlet will likely scale better with this.

why re-invent the wheel? Just use an XMPP client. Here are some good clients and claros in particular is a good one.

PHP Communicating w/ Java program

We're come across a problem here at my company and I'm trying to find the best solution.
Software was recently purchased that utilizes a Java program to get the tax for a certain shipment. The site that needs this was written in PHP4. How can I communicate between the two?
It was suggested to use files to communicate but that was horribly slow since the Java program needed to be recompiled every time. So, what is the best solutions to this:
Create a mutli-threaded Java server and use PHP to send/receive the info.
Some other type of file-writing method
Something cool that I dont even know about.
Thanks in advance!
Edit:
I understand the importance of web services but why would this be more efficient that using a mutli-threaded socket-based java server? The only thing connecting to this web services will be my PHP program, no one else. It seems like it might be overkill for my simple task. Am I mistaken? If so, why? Thanks.

Wrap the Java program in a Web Service, and invoke it from PHP. You can even use caching in the Web Service, to optimize performance.

Why not dump the info into a database and have some sort of schedualed job read from it once and a while?
You can always use Quercus which allows you to run PHP in a Tomcat Servlet container.

Web Services is the elegant solution. But in many cases I found much practical to go for a quick-and-dirty solution: start a Java server that communicates using a lightweight communication protocol (none of the heavyweight stuff like XML from Web Services) - example: Apache Thrift. The write a very light client, that takes parameters from command line and writes the output to the console. The client can be in Java or even in other languages, like C++ (Apache Thrift supports that). Then you call the client with system() or with exec() from PHP.
This is not a solution I would ever recommend for production, but it's great for prototyping. Quick and dirty and flexible and extremely modest learning curve (if you already use light-weight communication between your Java processes).

Since you are using PHP4, you may want to just set up a tomcat server that is on a closed network, or just local on the machine of interest, and have it communicate with a servlet, that way you don't have to write a multi-threaded server and deal with creating a communication interface.
If you can upgrade, this page has two other options that may of interest:
http://us3.php.net/manual/en/intro.java.php

Give a look at Quercus
Quercus is Caucho Technology's fast, open-source, 100% Java implementation of the PHP language
I never used it though,

Web Services is the answer. Here's a nice intro link. Your problem is the very reason web services came to the forefront - communication between systems that couldn't ordinarily communicate.
What a web service is essentially going to do is send XML between the PHP and the Java systems. You're going to have to establish an interface for the two, which might be more difficult at the upstart, but you'll reap the benefits later on. In either case, it will be much faster than reading and writing files on the server. Disk I/O are the major bottlenecks on any server.

I may miss something, but if your java program output the needed values, can't you just start the java program from php using exec (http://dk.php.net/manual/en/function.exec.php)

Use the PHP/Java Bridge from sourceforge.net. It is mature, fast and easy to install.

Java Web Start - Popularity

I recently used a Java Web Start application. I launched it from my web browser using an embedded jnlp link in the page I was viewing. The application was downloaded, launched and worked just fine. It had access to my local file-system and remembered my preferences between restarting it.
What I want to know is why are Java Web Start applications not a more popular delivery format for complex applications on the web? Why do developers often spend considerable time & energy replicating desktop functionality in html/javascript when the power of a desktop application could be delivered more easily using Java & Java Web Start?
I know that in some corporate environments, e.g banking, they are relatively popular ways of delivering complex trading applications to clients, but why are they not pervasive across the web as a whole?
(For the sake of discussion let's assume a world where: download sources are "trusted" & applications are "signed" (i.e. no security concerns), download speeds are fast (load time is quick) and developers know Java (in the numbers they know html/js/php)).

I think the reason is not security nor startup time of the app. Let's understand what's behind the scene before we find out the root cause.
Java Control Panel has settings that allow users to use the default browser's proxy settings or to override them. In other words, infrastructure teams are able to customize the Windows or OS installation images to have JVM pre-installed with enterprise proxy settings. So I believe this is not an issue at all.
Java Web Start actually caches all apps with customizable settings in Java Control Panel. Once the app is cached, the app is "installed" just like other apps. Although first time execution may be slow, the second time will be fast due to JVM's smart memory allocation technique. So start up time could be an issue but a lot of web sites (even enterprise internal) are now migrated to portal. A web portal normally contains lots of unused libraries for development purposes due to the fact that the portal itself does not anticipate what kinds of portlets are built and deployed on a specific page. Therefore, downloading a single portal page could consume up to MBs and complete a page in more than 5 seconds; this is only one page and caching helps up to 30% but there are still lots of HTML/Javascript/CSS components required to download every time. With this, I am sure Java Web Start is an advantage here.
Java Web Start does not download again if it is cached as long as the server copy is NOT upgraded. Therefore, if, e.g. a project management software like MS Project, is completed using SmartClient (similar to JWS), the information exchange between the client and server would be purely data without presentation like browser's full page refresh. Even with the help of Ajax, it doesn't eliminate full page download entirely. Besides, a lot of companies consider Ajax to be immature and unsecured still. That is why Ajax is a hot topic in the circles of developers but not within enterprise software yet. With that in mind, JWS apps definitely have more advantages such as how JWS apps are deployed and executed in sandboxes, signed, and have much more interactive GUI.
Other advantages include faster development (easier to debug in code and performance), responsive user interface (does not require Comet Servers to provide PUSH functionality), and executing faster (for sure because client computers renders GUI without translation like HTML/Javascript/CSS, and less data processing).
After all these, I haven't touched the question yet, why JWS is not so famous?
My opinion is that it is the same as Brian Knoblauch's comment, it's without awareness.
IT folks are too attracted by the hype of Web Technologies, Ajax PUSH, GWT, and all those buzz words make them bias towards the fun of using different technologies or to resolve technical challenges instead of what's really working for the clients.
Take a look at Citrix. I think Citrix is actually a great idea. Citrix allows you to build your own app farms behind the scene. There are tons of upgrade and implementation strategies you can go for without impact to client experience. Citrix deployment is extremely easy, stable and secure. Enterprises are still using it. However, I think JWS is even better than Citrix. The idea of JWS is to run apps on client machines instead of hosting tons of server farms where client machines are capable of running these apps themselves. This saves a company a lot of money!!! With JWS, development team can still build business logic and data on server side. However, without the web processing unit and let the client computers do the rendering process, it greatly reduces the amount of network consumption and server processing power.
Another example of why JWS is an amazing idea is Blackberry MDS. Blackberry apps are actually Java apps translated from Javascript. With BB's MDS studio, you use the GUI tool to build BB app GUI, coding GUI logic in Javascript. Then apps are then translated and deployed on a BES server. Then the BES server will distribute these apps to BB. On each BB, it runs a thin Java App with GUI rendering and networking capability only. Whenever the app requires data, it communicates with the BES through web services to consume services from other servers. Isn't this just JWS BB version? It's been extremely successful.
Finally I think JWS is not popular because of how Sun advertises it. BB never advertises how good their BB Java apps are, they believe clients won't even care what is it. BB advertises the benefits of using MDS to develop apps: Fast, Cost Saving, Business Return.
Just my, a bit long, 2 cents... :)

A major roadblock for Java Webstart is probably that you still need to have a JVM installed before it can even attempt to download and start your application. Everyone has a browser. Not everyone has a JVM.
Edit:
I've since acquired some hands-on webstart experience and can now add these two points:
The Deployment Toolkit script and the modularized JVM released somewhere around Java 1.6u10 make the JVM requirement less problematic since it can automatically download a JVM and the API core and start the program wile downloading the rest.
Web Start is seriously buggy. Even among the Java 1.6 releases there was one which downloaded the entire app every time, and another which downloaded it and then failed with an obscure error message. All in all, I cannot really recommend relying on such a fragile system.

I think it's mostly due to a lack of awareness. It works very well. Quite seamless. App only downloads if it's the first time, there's been an upgrade, or if the end-user has cleared the cache. Great way to deploy full-blown desktop apps that user won't have to worry about manually upgrading!

The problem with Webstart is, that you actually have to 'start' something which isn't at all that fast even with a fast connection, while with a webapp you enter the URL and the app is there.
Also a lot of things can go wrong with webstart. Maybe the intended user doesn't have the privileges needed, or the proxy of webstart is configured wrong, or something went wrong with jre dependencies or there is simply no java installed in the first place. So for the average john doe in the internet it is not at all pleasent.
In controlled environments like a company it is a good and easy solution in many cases.

I've worked on a JWS-deployed application for a few years over a user base of a few thousands and its automatic upgrades are actually a huge pain.
On every update for some reason dozens of users get "stuck in the middle". All you get is the "class not found" exception (if you're lucky), or uninformative "unable to launch" from JWS before it even gets to your code. Looks like the update is half-downloaded. Or, in other words, it does not download and apply the update atomically AND has poor caching so that relaunching the app from the same URL does not fix anything.
There's no way to resolve it other than clearing JWS cache or providing a different URL (e.g. append ?dummyparam=jwssucks at the end). Even I as a developer hit it sometimes and don't see a way around.
When it works, it works. But too often it doesn't, and then it's a huge pain for you and your helpdesk. I would not recommend it for enterprise or mission-critical use.

There is a very big issue namely that it doesn't allow for "start the program instantly and THEN check for and download any updates in the background" deployments, which is what the defacto behaviour of applications are converging to.
I consider this personally so big an annoyance that we are actively looking for another technology which provides that.

From these posts it looks like when using Web start, it is important to make a good care about the server. The "huge pain" of downloading application on every startup may be caused by incorrect time stamp delivered from the server. Here not the application but the server must be configured to use caching properly and not just to disable it. About buggy start, I am not that much sure, but it seems to me that this also may be caused by unreliable connection.
Important advantage of Web start is that it works nicely with OpenJDK under Linux. Clients of some happy developers use Windows only but my clients do not.
HTML and JavaScript, mentioned in the initial question, are lighter approaches that work fine with smaller tasks like animated buttons or even interactive tables. Java niche seems around much more complex tasks.

Java Web Start is kind a successor of Java Applets, and applets got burned around the new millenium.
But, I still think Java Applets are way better than GWT or Javascript hell.
Java Web Start vs Embedded Java Applet

How to connect a Java back end with a .NET front end

I have a bunch of Java code which was written using the Hibernate framework, originally destined to have a front end written using JSPs. However, the requirements for the front end have changed, and we've decided that a desktop client (which will be written in .NET) is a better match for our users.
I don't really want to waste the code that's already been written - can anybody suggest a good set of tools for writing a document-based web services interface that we will be able to access from .NET?
Thanks,
Jim

If you truly want a document based service interface (rather than an RPC style web service architecture), your best bet is going to be creating a SOAP based web service interface.
A quick glance at the Java site shows that the Metro stack might help a bit:
Java Web Services at a Glance

We're developing an application with the exact architecture you describe for a finance application. We reviewed several different options, and have finally landed on using compressed CSV over HTTP.
CSV was chosen since the vast majority of data was going to be displayed in a grid on the front end, we had very large result sets >250k rows on a regular basis, and it compresses really really well.
We also looked at using:
ICE, but declined on that due to licensing costs and the need to reinvent so much.
Google's protocol buffers via servlets, but declined on that due to lack of C# support (as of last fall).
Compressed XML using WOX, but declined on that due to lock-in to a small thesis project for support and XML being too verbose.
The industry supports a couple of different options as well:
SOAP, but that has its own well documented issues.
IIOP, J-Integra has a product called Espresso which will allow you to do RMI from a front end.

I'd personally use some lightweight RPC protocol, be it XML-RPC or a homegrown one. SOAP, IMO, is way too fat and is not as interoperable as it's supposed to be. The simpler the better.

We have a quite large application using a Java RMI server and IIOP.NET for interoperability. We have used IIOP.NET with the Sun RMI and the Bea Weblogic (now Oracle) without major issues.