I have never used JNLP, and I have no web/war server already running so I will install it from sratch:
Which to use?
GlassFish
Tomcat
Apache
Jetty
Another?
I wonder if someone already using JNLP could make any recomendation for the server.
I just want a blank page with a button in the middle for starting the application nothing more, nothing less.
If you use only JNLP you don't need Java server. JNLP is client side. Simple http server like Apache HTTP Server should be OK. HTTP server will be better solution than use of web container/Java EE server because JNLP (usually) is a static content. Even lighthttpd should be enough.
As already stated any server capable to serve HTTP will do. If your WebStart application is not signed by itself (i.e. you code-signed the corresponding Jar files) you could probably consider to publish the JNLP plus its resources via HTTPS. This way your clients will know that the software they are going to execute came from its rightful origin. Although unsigned WebStart applications are restricted in their privileges on the client's machine it still is a measure to elicit trust in your clients. On the other hand this requires more configuration effort with regard to the server you chose.
If your application will need some extended privileges on the client's machine such as access to the file system then I would recommend that you do sign your jar files to gain the necessary privileges automatically (don't forget to specify them in a element within your JNLP).
These are the default restrictions for unsigned WebStart apps:
No access to local disk.
All your jars must be downloaded from the same host. Note, however, that you can download extensions and JREs from any host as long as they are signed and trusted.
Network connections are allowed only to host from which your jars were downloaded. ("Phone home restriction.")
No security manager can be installed.
No native libraries (not even in extensions).
Limited access to system properties. (The application has read/write access to all system properties defined in the jnlp file, as well as read-only access to the same set of properties as applets
You dont need a server to run JNLP(Webstart).. This is how webstart works
it simply is an application that can be started over the web, this would be the procedure from the user perspective:
user goes to yourwebsite.com
user see's link: run my awesome app
user clicks link, which downloads .jnlp file
user runs the jnlp file through java web start (part of java SE, user requires java runtime environment JRE to run this)
java web start reads jnlp to get information about the server that holds the corresponding application
jar files get downloaded automatically (the first time) and then the application starts
user gets bored and closes application
the next day, user comes back and clicks your link again
application is already downloaded, so it starts right away
user gets bored again and closes your application
1 day later, you decide to update your application and you deploy the new jar file on your
server, replacing one of the old files
after 2 days user clicks your link again
java web start recognizes that the user has a different version, downloads update automatically and starts the application again
...
..
.
Related
I have to call .exe file on client.
But I dont understand sevler-client communication using Applets.
So few Q:
1.Can I do my task using Applets?
2.Does applets jar methods called on server?
Thanks in advance.
Applet does not maintain a state-full communication between client and server.
It is a Java application that runes inside the browser and has an access to a local system resources (if signed) and existing browser session, i.e. can use the same cookies to perform HTTP calls within the same Server-Side session.
1) Yes, you can do you task in Applet as in any other java application, however, in case of Applet it must be signed with the digital signature: http://www.oracle.com/technetwork/java/javase/tech/java-code-signing-1915323.html#60
2) No. All the classpath dependencies Applet may have, will be downloaded and cached on the client machine. See http://docs.oracle.com/javase/tutorial/deployment/deploymentInDepth/index.html
File system access is often not allowed as applets can (should) run in a sandbox limited-privileges environment. So running an exe file is possible only if the applet has proper permissions. Typically they are given such permissions when signed.
That being said, try not to use applets and write proper Java applications instead. You can always wrap the Java app in an applet, so that it is started from the applet.
Not so sure what you mean by the second question.
We have a web application hosted on this webLogic server on a UNIX machine. Its primarily a JSP/Servlet based app. Whenever we do a modification/enhancemment to any one of those JSps or servlets, I precompile them on my local and deploy them on the UNIX system. For example, if there is a file called GetIdServlet.class, we usually rename the existing file to say GetIdServlet.class1 and then put in the new file as GetIdServlet.class. This is just to be able to revert back to the original file in case they are needed. However, I notice very strange behaviour. The application loses some functionality whenever we stop and start the server. The functionality may be back on the next or a few restarts after that. For example, a submit button that is supposed to direct it to the next page just stops working. It may start working after a few restart.
However on my local(Eclipse + webLogic) there is absolutely no issue. Everything works fine. Any ideas on what's going wrong?
You are using Unix Environment and i assume that the local desk setup used is windows OS or MAC. thus, when you copy the class files you are using some tool like WinSCP.
in case so, then please set the copy settings of such tool to use binary method of copying the files.
Example in WinSCP. go to Options->Preferences->Select Transfer in the Side Menu->under the Transfer Mode section, Select Binary option as the Transfer Mode. This will ensure that the binary replica is created on the Unix environment and that no data is lost in the transfer.
I have created an applet that communicates with a MS Access database (or at least, it should). It works fine when I run it through Dr Java or NetBeans, but when I embed the .class file in an html page and open the html page, it seems to run but none of the changes it is supposed to make to the database actually happen and it cannot retrieve data from the database either. What do I need to do?
Note: the html file, the class file, and the java source file are all on my computer, and in the same folder. The html file is not published or anything, I just created it myself to test the applet.
If you want the database on a server, you need to have it on the same server as the applet is on. E.g. Use Jetty and write a Servlet that communicates with the database via JDBC. The applet then has to communicate with your Servlet, maybe as a web service.
applets run in a sandbox environment . if applet requires access to user system resources it needs to be signed.
package your ".class" files in a jar . have an html file outside the jar that references your jar inside applet tag. then sign your applet jar. see http://java.sun.com/developer/onlineTraining/Programming/JDCBook/signed.html
-----------UPDATE------------------------------
There are two ways of connecting to a database on the server side.
1- The hard way. Untrusted applets cannot touch the hard disk of a computer. Thus, your applet cannot use native or other local files (such as JDBC database drivers) on your hard drive. The first alternative solution is to create a digitally signed applet which may use locally installed JDBC drivers, able to connect directly to the database on the server side.
2- The easy way. Untrusted applets may only open a network connection to the server from which they were downloaded. Thus, you must place a database listener (either the database itself, or a middleware server) on the server node from which the applet was downloaded. The applet would open a socket connection to the middleware server, located on the same computer node as the webserver from which the applet was downloaded. The middleware server is used as a mediator, connecting to and extract data from the database
(Comment by OP on the other thread.)
Could you please explain how the applet can "phone home" to its own server?
I suspect the basic problem with your current approach is that the JRE is getting confused as to whether the DB and applet are on the same 'server'. The first thing to do is stop thinking about folders or directories (or their associated URLs), and do everything, including access the applet, via. your local server. So the URL to the applet should be something like..
http://localhost:8080/the/applet.html
Then make sure all calls to the DB are done through the server as well.
One of my requirements is, on load of page, a file is to be created dynamically and downloaded at a particular location on the client's machine.
In case the file is already present, it has to be over written.
is there any way where we can access the client's system and store the file at the required folder?
I feel one cannot access the client machine when the code is being executed on the server..
Senorio:
1-User click on generate document then it took template stream data ,req. data file and then save two file into client machine.
2-After that template open and it fetch the data file from same directory.
Please help me on this. This is an SOS!!
There are probably other solutions, I use a signed applet for this purpose.
As always, there are a few caveats though:
You can't "force" anything against the will of the user. Applets may be disabled in the client's browser, or they may not even have Java installed. Or the target directory might not be writeable by the user.Your server should handle cases where the client doesn't have the correct version of the file gracefully.
You can't do this from the server side obviously but you also really can't do this from a client script either. Browser security will prevent a page script from modifying contents of the file system.
Your only options will be to run a third-party browser plugin software that has elevated permissions.
Examples of such are
Java Applets
Java WebStart
Microsoft Silverlight
ActiveX
Each one is different and most require some level of user interaction to confirm that they allow plugins to run with elevated security.
I'd like to create a service where people can enter external websites, after which the returned source will be modified by my application (for whatever purpose) and then returned to the user.
One would normally redirect all traffic through the server, so that the server is the one accessing the external source. This is because HTML5 and flash sockets cannot access external sources unless the external source has the required policy files (please correct me if this is false). Even if the user wants the client to, it still can't access these external sources if the external source itself does not have such policy file.
My question is: can a Java applet access an external source regardless of it's policy file, if the user allows it to? How is this usually done?
If not, is there anything else I can try? Redirecting all traffic through my server is not an option because of 1. high use of bandwidth and server resources for a free service and 2. a high chance of my server being marked as a spam bot or bandwidth hogger.
Thanks in advance.
Regards,
Tom
If choice of technology is not a problem you can use a Java Web start application.
Your application will be launched from a web page (if that is what you want)
After user-confirmation your application can do everything (similar to native apps)
I have actually done this with a Java web start application that used web services from servers other than the one it was launched from.