Java Web Start - 流行度

Question

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, eg 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" (ie no security concerns), download speeds are fast (load time is quick) and developers know Java (in the numbers they know html/js/php)).

Answer 1

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, eg 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... :)

Answer 2

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.

Answer 3

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!

Answer 4

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.

Answer 5

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 (eg 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.

Answer 6

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.

Answer 7

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

Answer 8

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.