使用Java WebStart创建桌面应用程序的最佳实践

Question

Hope I can explain this clearly. I am creating a desktop application that has dependencies on other external jar files. For example, my application is Spring-based so there are some SpringFramework jar files that I will need in my application.

I am using Java WebStart to 'launch' this desktop application. (As to why I am doing this is that I need to execute this customised desktop application via the website that we are building).

However I ran into troubles when I executing my desktop application by clicking on the jnlp description file. It gives errors stating that there is no class definition for some of the classes that my desktop application is using. I then realise that my desktop application when packaged as a JAR file, it didnt include my other JAR dependencies with it. Hence the reason for the error.

I guess, I could include the external JAR dependencies in my desktop JAR file but this would make my desktop JAR file quite large. And this will be then make the download of my JAR file slow due to the large JAR file since clicking on the JNLP descriptor file will always source from the desktop JAR file from the server. (unless I can 'tell' the JNLP descriptor not to download if there is no new version on the server.)

Anyway, I was thinking if this is an acceptable approach where my desktop JAR file will not include the JAR dependencies but only references to it. When my desktop application launches, it will check if these dependencies are available on the desktop, and if it is not available, it will call another JNLP descriptor that will download the external JAR files and copy them to a pre-determined location that my desktop application references. Will this work? or is there a simpler solution to my problem?

thanks

Answer 1

The JNLP file should include references to both your main file but also all needed libraries. This is standard functionality and you should do it that way.

Note that you should have a time stamp in your file names to avoid cache problems when updating code.

Answer 2

You need to have your JNLP reference the additional jars you have. Yes this will take slightly longer to download, but as long as you are not including a bunch of jars that you don't need this should not take very long. Web Start is smart enough to not re-download jars that have not changed on subsequent start ups of the same application. I have Java Web Start applications that have several large jars and this works just fine.

As far as putting the extra jars on the user's machine, I would not advise this. If you are going to do that, then there is not much of a point to use Web Start and you might as well install the entire program on the desktop.

Answer 3

其他答案涵盖了大多数基础，但我想我应该补充一点，将多余的Jar标记为download ='lazy'可能是有意义的。