Question

I am using java web start as a standard deployment technology for my application. I wants to know what is the difference between offline-allowed and update tag.

offline-allowed says that application can be operate when the client system is disconnected from the network

<update check="background" policy="prompt-update"> :- will mean launch the application while checking the update in background and ask the user if he wants wants to download the updated version or launch the cached version.

I am confused with the offline-allowed, does that mean offline-allowed check if the user machine connected to the server where the application is deployed for the update or it just check normal internet connectivity.

What would be the effect if someone use both tag in their jnlp file.

Overall I wants my application to check for the update in background[using the desktop shortcut not the browser link, I do not want to access the application using browser ever time] and ask whenever update is available but it should also allow application to be launched irrespective of the availability of the server hosting jnlp file.

FYI: my application will need to connect to internet for other operations but I can not gurantee the availability of the server hosting jnlp and other application jar file.

Please let me know if you have any suggestions or questions.

Thanks

Answer 1

When you launch JNLP file first time, it installs the application (defined in JNLP xml file) to JVM (Control Panel -> Java -> General -> View).

update check="background" configuration allows you to synchronize your version with server and install new if server has new one. If you doesn’t have connectivity with server – nothing will happen.

What would be the effect if someone use both tag in their jnlp file.

Second one will be affected.

Here is JNLP example:

<?xml version="1.0" encoding="UTF-8"?>
<jnlp spec="1.0+" codebase="http://172.20.0.69:8080/DemoMonitoring/web/" href="monitoring_webstart.jnlp">
<information>
    <title>Demo monitor 172.20.0.69</title>
    <vendor>Demo</vendor>
    <homepage href="http://www.Demo.com"/>
    <description>Demo Monitoring System</description>
    <description kind="short">Demo Monitoring System User Interface.</description>
    <icon href="./images/ne_app_icon_64.png"/>
    <icon kind="splash" href="./images/splash.jpg"/>
    <icon kind="shortcut" href="./images/ne_app_icon_32.png"/>


    <offline-allowed/>
    <shortcut online="false">
        <desktop/>
        <menu submenu="Prabinas">
            <menu submenu="Product Managing System"/>
        </menu>
    </shortcut>

</information>
<security>
    <all-permissions/>
</security>

<resources>
    <!-- Application Resources -->
    <j2se version="1.6+"
          href="http://java.sun.com/products/autodl/j2se"/>
    <jar href="DemoMonitoringPrototype.jar"  main="true" />
    <jar href="lib/log4j-1.2.8.jar" download="eager" />
    <jar href="lib/commons-logging-1.1.1.jar"/>
    <jar href="lib/gson-1.7.1.jar"/>
    <jar href="lib/xpp3_min-1.1.4c.jar"/>
    <jar href="lib/xstream-1.3.1.jar"/>
    <jar href="lib/httpclient-4.1.1.jar"/>
    <jar href="lib/httpcore-4.1.1.jar"/>
    <jar href="lib/DemoMonitorCommon.jar"/>

</resources>
<application-desc name="Prototype" main-class="com.demo.monitor.root.MainRun" width="500" height="500">           
  </application-desc>
 <update check="background" policy="prompt-update"/> 
</jnlp>