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  1. JDK
  2. JDK-8055464

Add a URL scheme handler to reliably launch .jnlp files - java part



    • b03
    • x86
    • generic
    • Verified



        Launching Java Web Start applications from a web page is too unreliable. The current state-of-the-art method seems to be to serve a file with ".jnlp" suffix and MIME-type "application/x-java-jnlp-file". This does not work reliably. See http://crbug.com/10877 for example about the problems with Google Chrome.

          To fix the issue, Java Web Start installer should register an URL Scheme handler to reliably launch Java Web Start applications from web pages. I'd suggest scheme "javaws".

        The only stuff required to start a Java Web Start application from a web page should be

            <a href="javaws://example.com/path/to/awesomeapp.jnlp">Launch the AwesomeApp</a>

        Note that the URL should not require the ".jnlp" suffix. Any URL should be okay. The "javaws" scheme handler should then pass the URL to javaws or javaws.exe binary depending on the OS which should proceed to load the .jnlp file by itself. It should replace the "javaws:" prefix with "https:" to locate the actual resource. Optionally, a fallback to non-SSL connection might be allowed.

        Another cool scheme name instead of "javaws" would be just "java". The scheme URL does not need to promote that this is "javaws" technology but instead it should promote "java" technology.

        Java Web Start is the right way to start bigger Java applications because it allows for easy updating and installing/downloading the application and allows for better UI/UX than Java applets.

        However, there are some roadblocks for launching Java Web Start applications from a web page using common browsers with default settings:

        1. Sun/Oracle failed to create a working browser intergration. See http://crbug.com/10877 for example about Google Chrome / Chromium. Basically the Java plugin fails to implement the required NPAPI stuff to get Firefox and Chrome to reliably forward the MIME-type application/x-java-jnlp-file to javaws / javaws.exe binary.

        2. Sun/Oracle failed to get a real registered MIME-type for Java Web Start .jnlp files. The application/x- prefix technically means draft or private.

        3. Sun/Oracle failed to use URL scheme instead of MIME-type when the intent is that Java Web Start handles the application downloading and launching. For example, if instead of using URL such as https://example.com/app/launch.jnlp Java Web Start were launched as javaws://example.com/app/launch.jnlp things would work much smoother. This is because in this case, the web browser does not need to even load the .jnlp file, it just passes the full URL to the scheme handler (which would be the javaws binary).

        If an URL Scheme handler were used, Java Web Start applications could be *reliably* lanched also from e.g. email messages and instant message chat. Of course, allowing this makes even greater need for correctly sandboxing the application within the JVM.

        Discussion: http://stackoverflow.com/questions/126260/objections-against-java-webstart

        EXPECTED -
        When I click "Launch the AwesomeApp" link on a web page the Java Web Start application "AwesomeApp" should reliably start regardless of the web browser I'm using (assuming that I've previously installed Java JRE).

        If I haven't installed Java JRE, the behavior is browsers dependant but hopefully I would get error message along the lines "AwesomeBrowser cannot handle the URL Scheme 'javaws' or "Select URL Scheme handler for 'javaws://example.com/path/to/AwesomeApp.jnlp&#39;".
        ACTUAL -
        Depends on browser. Currently if I try to use Java Web Start, I'm usually greeted with a "Save as..." dialog once I click a link on a web page (e.g. Google Chrome). After that I must navigate to downloaded file and e.g. double click it to launch the application. In base case, if I'm running suitable browser and I have configured it suitably, the AwesomeApp is launched once I click the link. However, that rarely works out-of-box -- the browser must be configured by hand.

        ---------- BEGIN SOURCE ----------
        <a href="javaws://example.com/path/to/awesomeapp.jnlp">Launch the AwesomeApp</a>

        or simply an URL within an email message:


        ---------- END SOURCE ----------

        Workaround depends on a browser. For example, Google Chrome running on Ubuntu Linux requires following workaround:

        1. Click a link to a .jnlp file
        2. A "Save as..." dialog opens
        3. Save file to somewhere
        4. Notice that there's a new toolbar at the bottom of the browser window saying that the file has been successfully saved.
        5. Notice that there's a tiny down arrow next to the filename.
        6. Click the tiny down arrow
        7. Select "Always open files of this type"
        8. Click the original link again. It now works and will work the next time you try to launch the Web Start Application.


        After the app has been launched 100 times, the automatic launching will fail in Google Chrome and the Save as dialog is raised again (See the chrome bug referenced above).


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                herrick Andy Herrick (Inactive)
                alexp Alexander Potochkin (Inactive)
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