I would like to implement a java application (server application) that can download a new version (.jar file) from a given url, and then update itself at runtime.
What is the best way to do this and is it possible?
I guess that the application can download a new .jar file and start it. But how should I do the handover, e.g. know when the new application is started and then exit. Or is there a better way to do this?
The basic structure of a solution is as follows:
There is a main loop responsible for repeatedly loading the latest version of the app (if required) and launching it.
The application does its thing, but periodically checks the download URL. If it detects a new version it exits back to the launcher.
There are a number of ways you could implement this. For example:
The launcher could be a wrapper script or binary application that starts a new JVM to run the application from a JAR file that gets replaced.
The launcher could be a Java application that creates a classloader for the new JAR, loads an entrypoint class and calls some method on it. If you do it this way, you have to watch for classloader storage leaks, but that's not difficult. (You just need to make sure that no objects with classes loaded from the JAR are reachable after you relaunch.)
The advantages of the external wrapper approach are:
you only need one JAR,
you can replace the entire Java app,
any secondary threads created by the app, etc will go away without special shutdown logic, and
you can also deal with recovery from application crashes, etc.
The second approach requires two JARs, but has the following advantages:
the solution is pure Java and portable,
the changeover will be quicker, and
you can more easily retain state across the restart (modulo leakage issues).
The "best" way depends on your specific requirements.
It should also be noted that:
There are security risks with auto-updating. In general, if the server that provides the updates is compromised, or if the mechanisms for providing the updates are susceptible to attack, then auto-updating can lead to a compromise of the client(s).
Pushing a update to a client that cause damage to the client could have legal risks, and risks to your business' reputation.
If you can find a way to avoid reinventing the wheel, that would be good. See the other answers for suggestions.
I am currently developing a JAVA Linux Daemon and also had the need to implement an auto-update mechanism. I wanted to limit my application to one jar file, and came up with a simple solution:
Pack the updater application in the update itself.
Application: When the application detects a newer version it does the following:
Download update (Zipfile)
Extract Application and ApplicationUpdater (all in the zipfile)
Run updater
ApplicationUpdater: When the updater runs it does the following:
Stop the Application (in my case a daemon via init.d)
Copy the downloaded jar file to overwrite current Application
Start the Application
Cleanup.
Hope it helps someone.
I've recently created update4j which is fully compatible with Java 9's module system.
It will seamlessly start the new version without a restart.
This is a known problem and I recommend against reinventing a wheel - don't write your own hack, just use what other people have already done.
Two situations you need to consider:
App needs to be self-updatable and keep running even during update (server app, embedded apps). Go with OSGi: Bundles or Equinox p2.
App is a desktop app and has an installer. There are many installers with update option. Check installers list.
I've written a Java application that can load plugins at runtime and start using them immediately, inspired by a similar mechanism in jEdit. jEdit is open source so you have the option of looking to see how it works.
The solution uses a custom ClassLoader to load files from the jar. Once they're loaded you can invoke some method from the new jar that will act as its main method. Then the tricky part is making sure you get rid of all references to the old code so that it can be garbage collected. I'm not quite an expert on that part, I've made it work but it wasn't easy.
First way: use tomcat and it's deploy facilities.
Second way: to split application on two parts (functional and update) and let update part replace function part.
Third way: In your server appliction just download new version, then old version releases bound port, then old version runs new version (starts process), then old version sends a request on application port to the new version to delete old version, old version terminates and new version deletes old version. Like this:
This isn't necessarily the best way, but it might work for you.
You can write a bootstrap application (ala the World of Warcraft launcher, if you've played WoW). That bootstrap is responsible for checking for updates.
If an update is available, it will offer it to the user, handle the download, installation, etc.
If the application is up to date, it will allow the user to launch the application
Optionally, you can allow the user to launch the application, even if it isn't up to date
This way you don't have to worry about forcing an exit of your application.
If your application is web based, and if it is important that they have an up to date client, then you can also do version checks while the application runs. You can do them at intervals, while performing normal communication with the server (some or all calls), or both.
For a product I recently worked on, we did version checks upon launch (without a boot strapper app, but before the main window appeared), and during calls to the server. When the client was out of date, we relied on the user to quit manually, but forbid any action against the server.
Please note that I don't know if Java can invoke UI code before you bring up your main window. We were using C#/WPF.
If you build your application using Equinox plugins, you can use the P2 Provisioning System to get a ready-made solution to this problem. This will require the server to restart itself after an update.
I see a security problem when downloading a new jar (etc.), e.g., a man in the middle attack. You always have to sign your downloadable update.
On JAX2015, Adam Bien told about using JGit for updating the binaries.
Sadly I could not find any tutorials.
Source in German.
Adam Bien created the updater see here
I forked it here with some javaFX frontend. I am also working on an automatic signing.
Related
i am currently writing a game on javaFX and i have plans to post it in the website i run in the future (end exploit the Ads while at it). The problem is that after searching around a little it seems there is no way to run a java application on a browser.
Allowing people to run it through the browser would really help sharing the program.
My question is: is there today(2018) any way to run a java application through the web? Though i like java, no browser support seems like a really, really bad idea.
Oh, i also heard of Java Web Start. Although it looks like it is just avoiding the problem (not running in the browser) it seems like a good way to share an application. The problem is that it seems it is (Will be?) deprecated? I am helpless, it is like java isn't even trying anymore...
PS: If it makes any difference my game would be a 2D game with 3rd person view. It will also require some server stuff since players will create "arenas" that others can challenge. I would say my game wouldn't be "simple".
Java Web Start does the job very well—if you are willing to pay for a code signing certificate. (They’re a lot more expensive than regular SSL certificates.) The idea is that a user clicks on a hyperlink on your page, which causes the user’s Java installation to launch your application (possibly after installing it). This requires users to have Java installed beforehand.
If you don’t have the resources or desire to go with a code signing certificate, you can look at https://docs.oracle.com/javase/9/deploy/self-contained-application-packaging.htm. It allows you to create native installation packages for JavaFX applications. The disadvantage: You need each platform to create an installer for it. Meaning, you need Windows to create a Windows installer, OS X to create an OS X installation image, and Linux to create a Linux package. Some may also require signing using native tools.
Java 9 includes the jmod and jlink tools, which are capable of creating a file tree with an executable shell script or .bat file. A major advantage is that you can build such a tree for any platform, regardless of your own platform, if you unpackage the foreign platform’s JDK on your machine. Another advantage is that the user doesn’t need to have Java installed at all. A disadvantage is that the script requires a terminal, unless running on Linux.
Of course, you can just go the manual route and distribute a zip file which contains your .jar file(s), a shell script you’ve written, and a .bat file you’ve written. It’s not elegant, but it’s better than nothing. But it may trip up some non-technical users.
There exist a number of tools which create a native executable from .jar files, but I am not familiar with them (and I prefer to avoid third party tools unless they are truly necessary).
Whatever approach you choose, the answer is the same: You distribute something on your web page which the user downloads and runs. Aside from the download process, the browser is not involved.
What you can’t do is have users run your application inside the browser. That is deprecated, with good reason: It’s a disaster for the browser performance, for the Java runtime, for security, and for the user experience. And Firefox has all but banned plugins, so you’d be locking out a substantial percentage of users.
I read SO q&a about launch java as windows service wrappers, but can't find/choose product, suitable for my requirements :
Wrapper reads all java launch parameters from config file. In registry must be only commands to run wrapper itself - path to exe and maybe path to config. Always grant admin rights to change app parameters in registry is not comfortable.
Working dir and path to application also must be in config. I want to place all wrapper files deep into program, because user not intrested in it.
No dependencies(.net, python, etc). I don't want to extend requirements of my program.
Free for every windows OS, include win64.
Simple and lightweight. Size of my program with all 3rd party jars is 12Mbytes. I don't want to add 20Mbytes wrapper.
Automaticaly restart if app process dies.
Preferably single exe files for all windows platform.
I try and lookinkg throught different wrappers and tired a bit. Best suitable till now is:
jslwin (http://jslwin.sourceforge.net), but i don't know how mature it is(version 0.99). Also parameter lists in config is a bit complex(need to edit parameters quantity).
winrun4j (http://winrun4j.sourceforge.net), but i don't know how mature it is(version 0.45). Also it needs a special class for working as a service.
Also i try or look throught:
YAJWS (http://yajsw.sourceforge.net/) too big (30mb), can't make it work with custom files layout.
Advanced Installer (http://www.advancedinstaller.com) too big (50mb).
nssm (http://nssm.cc/) store launch parameters in registry(no config)
winsw (https://kenai.com/projects/winsw) .net required, stops after process dies
commons-daemon, procrun (http://commons.apache.org/proper/commons-daemon/index.html) store launch parameters in registry(no config), can't understand this product, i think it's complex.
jsmooth (http://jsmooth.sourceforge.net) complex and old(last update 2007)
javaservice (http://forge.ow2.org/projects/javaservice/) old (last update 2006)
runasservice (http://runasservice.sourceforge.net/) requires .net
windows rktools - sc, instsrv, srvany (http://support.microsoft.com/?scid=kb%3Ben-us%3B137890&x=16&y=7) - store launch parameters in registry(no config)
jwrapper (http://www.jwrapper.com/) seems not what i need. It packs java program in exe file with JRE. It's not about windows services.
firedaemon (http://www.firedaemon.com/) not free. And maybe it's not what i need.
launch4j (http://launch4j.sourceforge.net/) cool ability "search or download java". Maybe i add something like this to simplify installation, but it is still not about subj.
Java service wrapper (http://wrapper.tanukisoftware.com/) not free for win64.
Tell me please which wrappers suits my needs? Or maybe i think wrong about wrappers above and some of them suits my needs to?
I have had similar issues over the years. Its not that they all are inferior, its that they are all pretty hard to integrate nicely with your own project.
You may want to check out stork: https://github.com/fizzed/stork
It'll help create launchers for your Java console or daemon apps, and they will work across all major platforms. There is also a maven plugin in case you wanted to tie it into your existing build process.
I'm not sure if JWrapper will fulfil all the requirements like 1 and 2 in the way that you want it since rather than you dictating how it does the launch and where it puts things etc JWrapper instead handles that stuff in its own way but it does produce executables for win/mac/linux and more importantly it does support windows service installation as well as macos and linux daemon installation:
http://www.jwrapper.com/guide-installing-a-service.html
The service support though is for paid licenses, the free version doesn't currently support it.
Disclosure: I work for JWrapper
I am setting up a little service to allow people to run temporary Minecraft servers on a spare box that's not being put to much use.
The .jar that will start up the Minecraft server will be uneditable, as in they can't upload a new .jar and run that in its place. However, the .jar will be the Bukkit Mod/Wrapper for Minecraft servers, which allows the loading of plugins that are in the form of .jars. What's stopping someone from creating their own plugin and using it to spawn more servers?
How can I prevent someone from using a server plugin to create another server process? I am already planning to make it so that each server will be ran under it's own user account, which wont be accessible to login from.
I'm not familiar with the Minecraft code base.
However you should look into running the code with a SecurityManager. This will enable you restrict many operations (such as being able to exec a new process).
Done correctly, this should enable you to completely lock down the loaded .jar file. It's possible that the Minecraft server does this for you already, it's a fairly obvious thing to want to restrict the activities of downloadable mods.
In linux there is a file called /etc/security/limits.conf.
Read this: http://linux.die.net/man/5/limits.conf.
nproc would limit the number of processes for the user/domain.
I'm looking for a non-webstart/jnlp solution.
I'd like to add to my app an update feature that checks in an ftp or http server and downloads the last version (if there is a newer one) replacing the libs that has been changed.
How can i do that? I want to implement something like JDownloaders updates.
Thanks
It looks like you just described exactly how to do it. Add an update feature that checks an FTP or HTTP server and downloads the latest version.
Remember that you cannot download and overwrite a file which is in use. So you have two options for a design from where I sit:
When you start up the application, copy all of the jar and library files to a /temp folder of some sort before running them. Then, when you download the update, overwrite the files in the original place. The next time the application starts up, it will use the new files.
When you start up the application, first startup an updater. Have it connect to the server and compare all of the file versions. It will be able to overwrite any of the application files because it doesn't use them. It only uses the updater jar. Once this is done and everything has been updated, then start a new process from the updater with the actual application. You will also need to put some code in to be able to update the updater jar. Either make the main application be able to update the updater, or use the first technique and run the updater from a copy of the updater jar.
Remember when you download the files that you should be downloading them to a temporary location and then moving them to the right place when they're done. This will make sure that you never leave your application in a "half-downloaded" state.
Beyond that, getting this to work is going to be about a lot of testing. Good luck!
Have a look at http://code.google.com/p/getdown/
According to this question on stackoverflow it seem to be a viable alternative for web start (at least worth having a look at).
I am currently working on desktop software based on java.It's quite a big code base (more than 40 jar files).
I wish to provide an automatic update functionality. The desktop software constantly checks one back end system to see if there are new versions of the jar files available.
The problem now is: How to replace the updated jar files?
If you deploy your application using Java Webstart (JNLP), you get this mechanism almost for free...
From http://mindprod.com/jgloss/javawebstart.html
The key benefit for Java Web Start is automatic update without having to download the entire program every time.
Easiest would be to check for updates on each startup, download the updates and then launch your application. I think this is the way that Java Web Start works (see aioobes answer).
More complex would be to use either the netbeans or eclipse framework for your application. Both are rather complex and you will have to rewrite your application to work with them. This solution supports live updates.
As far as I am aware there is no easy way to update a running application. It is possible to load new versions of a class with a different classloader, but not possible to unload old versions while they are still referenced.
You can make a little server and a launcher which downloads the newest version, replaces the old one, and starts the jar with:
Runtime.getRuntime().exec("java yourjar -jar");
And you terminate the launcher with:
System.exit(1)
You can also serialize down your state (keep it in memory) and then create a new ClassLoader instance pointing to the new .jar files. Then serialize up your state again using this new classloader. You have just changed the underlaying .jars within a executing product.
Please note that you do not need to change the classloader for everything only for the part that is actually using the .jar files. This can be tricky to conclude what parts that are. And you might get nasty linking errors if done wrongly. So..
.. to keep it simple, use WebStart or a preloader that updates the .jars and then starts the main app (basically what WebStart does for you).
A reason for rolling your own, is that you can use your own format for the .jars, encryption, other packing formats etc.
After reading some answers to many auto-update questions, I thought of a solution. This is how I would implement a secure auto-update for a Java/Kotlin jar application.
Assumption: the installer will contain two jars: a launcher and the main application. Any shortcuts created will point to the launcher, but still be the name of the application. The release will contain the main application and the installer.
The launcher is launched first:
First check if an update has already been downloaded as app_name_update.jar
if an update has been downloaded, rename app_name_update.jar to app_name.jar
Start app_name.jar
This part does not have to be in the launcher, but it's preferred as to not slow down the main application: at this point, the launcher should check for an update (e.g. GitHub releases API) and download it to {CWD}/unverified_app_name_update.jar.
Compare the hash of unverified_app_name_update.jar to an online location containing hashes for all published versions. hashes.txt would be an example found in the same github repository. If the software is open-source, GPG signed commits is a must and the launcher should check if the latest update is a verified commit! If its a proprietary application, keep the hashes.txt at a separate URL from the release where your company does not control the infrastructure (e.g. GitHub).
Main app launched:
No need to check for updates unless updates are mandatory, in which case check for update -> if update found, start loading animation "updating" while you can detect that the launcher is still running. Ensure that the launcher has no race condition while loops!
I found ready project to solve automatically updating.
You can update your app, in your cases you can update jars and resources of your desktop app. The idea of the this is next: wrap you app with starter which can control updating and running you app. In details you can find here.