Running from Web Start

Java Web Start (originally developed by Sun Microsystems) provides a convenient means of downloading the Unravel program to the user's computer, and running it in application mode. Transfer of files to the user's computer is allowed subject to security conditions discussed below being met. The Web Start application is included in the Java Runtime Environment (jre) installation. Web Start is independent of the browser and does not present the significant security risks associated with negligent use of applets.

When the user clicks a link in the browser, pointing to a special JNLP (Java Network Launching Protocol) file urvwbs.jnlp, it will ask "What do you want to do with urvwbs.jnlp?" with Save or Save As options. By default it will save it in the Downloads directory but users can place it in any other location if they wish. Normally the downloaded Unravel application will be launched by double clicking on the downloaded urvwbs.jnlp file. If that does not work it will be necessary to set it to open with javaws.exe in the bin directory for the jre. Permission to download the program and then running it is subject to security conditions being met. Earlier versions of Web Start would present a dialog that let users decide if they are agreeable to allow the program to run from a signed jar. Later versions have more stringent security conditions. In such cases, if the Java Cache Viewer security is set too high running the Unravel program from Web Start will not be possible. To change the security setting go to the Java Conrol Panel, select the Security tab, and set security to appropriate level. Accessing the Java Control Panel varies with computer operating system in use. Possibilities include accessing it through the Java item in the list of items presented or searching for Java. If users are still not permitted to run the Unravel application, it may be necessary for them to include http://www.kenblackbox.com (not with /UnravelRun.htm extension for the page from which it is selected) in the Exception Site list. When security pre-conditions are met the Unravel application will run after the user agrees to allow it to do so. The title of the Unravel application as used in the urvwbs.jnlp file is UnravelJ WebStart. The "J" in UnravelJ is to distinguish it from UnravelC (an earlier version, also available from the website, that was developed using C++ but for Windows users only).

The JNLP file includes information on the program's Java archive file (file with jar extension), the name of the main class for the application, and any other files (e.g. library jar file) required for running the application. The jar files required to run the application are copied from the website to a cache directory on the user's disk. The jar filename in the cache bears no relation to its actual name - Oracle uses a random generator to select name (e.g. urvall.jar would end up with a cache file name like 4c3b82af-1e7c0261).

To run the application, the appropriate Java Virtual Machine (JVM) must be available from the user's computer. This is achieved by having the appropriate jre available (any jre7 or jre8 would be acceptable). Once the application's jar files have been downloaded, The Web Start Unravel program can be launched by:

Web Start has the advantage that it checks for Unravel program updates every time it is run.

When the application is first run in Web Start mode, an additional set of files specific to Web Start mode is downloaded to the application's working directory on the user's computer. The set includes the Readme.htm file that contains links to licence details in Licence.htm and to WebStartAuxFiles.htm. The latter file provides an instruction on how to copy the application files from the cache to the application's working directory. While this copying is not required for either on-line or off-line Web Start operation, it enables the application to be run uninstalled from a simple executable jar file (referred to as UnravelJ Direct to distinguish this method of running the program from the UnravelJ WebStart mode). That results in a significant reduction in start-up time relative to Web Start operation. The copying of the application files may also be useful to users who desire to store a copy of the application on a medium suitable for archiving. Full details on the additional set of files specific to Web Start mode are provided in the Readme.htm file instated when the program is first run in Web Start mode. If the user deletes any one or more files in the set, the missing files will be reinstated the next time the program is run in Web Start mode.

While probably not significant, the set of files downloaded by the Unravel program to the application's working directory, and files extracted from the cache and stored in that directory, will be given the date-time of extraction, not their last-modified date-time.