我的launch4j .exe文件无法像我的java文件那样工作。 我想念什么吗？

Question

As someone new to java and bundling programs with code, I was able to successfully get the proper output running a simple new HelloWorld java file. So I believe there are no issues with the java file in terms of compiling it to a class file or running it afterwards, and that I have all the files needed in the java kit to create an executable file. However, I am not sure if I am using launch4j properly to get the .exe, either with setting up the .jar or through the process from making a proper .xml file.

The code below shows what I get when I try to put everything into the .jar file, but I guess the output is an error because a new .jar file isn't produced unless I take out the "m" from the "cvfm" in the jar command. The code does show something about the manifest being added regardless when doing so, yet I still do not get a proper application. After getting the correct output without launch4j, I stopped recreating the .java and .class files and just focused on the .xml when recreating the .jar file achieved no difference. I have tried in launch4j leaving the environment variables blank in the JRE tab or just included the same path of the system variables that the java file worked with correctly in the command prompt, and I have also switched the check of GUI to console in the header tab. Research has also told me to look up a manifest.mf file, to which I don't think I have that precise file in the JDK, but may have found something similar in the kit (at least when looking in typical areas like the bin folder).

C:\JavaTest>jar cvfm HelloWorld.jar HelloWorld.class
java.io.IOException: invalid header field
        at java.util.jar.Attributes.read(Attributes.java:406)
        at java.util.jar.Manifest.read(Manifest.java:234)
        at java.util.jar.Manifest.<init>(Manifest.java:81)
        at java.util.jar.Manifest.<init>(Manifest.java:73)
        at sun.tools.jar.Main.run(Main.java:176)
        at sun.tools.jar.Main.main(Main.java:1288)

C:\JavaTest>jar cvf HelloWorld.jar HelloWorld.class
added manifest
adding: HelloWorld.class(in = 426) (out= 289)(deflated 32%)

I always get a warning about signing when testing the wrapper, but I don't think that has been an issue like an actual error. Due to the nature of the numerous combinations, it is hard to keep track of what caused the differences in issues, but it seems that now leaving the JRE tab blank except for having a min JRE version yields the error "no main manifest attribute" right from the wrapper test in launch4j. Having the very end of the system variable path included in the environment variable field does the same thing. Before trying to recreate the .jar, switching the header to console would create a .exe without errors, but either opening the application would either do nothing or put the same "no main manifest attribute" output in the command prompt. Now, I can't even use launch4j to test wrappers that have the header on console even when building them produces no errors (yet the same error happens when opening the .exe). I am just trying to get the .exe produced from launch4j to provide the same output in the command prompt that I get when typing "java HelloWorld" there.

If I am indeed creating the .jar properly and working with launch4j properly, did I just miss the unlisted step of needing some sort of manifest file to work with launch4j? If so, how would I make sure I got it properly? Would it be seen in a bin folder or completely separate from the JDK? Would I need to move it to my JavaTest folder where the java/class/jar/exe files are? Any help is truly appreciated.

Answer 1

The 'm' in jar cvfm stands for manifest, and implies that you will be providing a file as argument which is the manifest. The f stands for: You will specify the file name.

So, HelloWorld.jar is the argument to the f, and HelloWorld.class is the argument to the m. Your class file, obviously, isn't a valid manifest file, hence why the error occurs.

Generally, use a build tool to make jars, such as maven or gradle. You need a manifest in order to have a Main-Class attribute, and you need a Main-Class attribute to create a runnable jar, and you need a runnable jar to launch4j-ify it.

Make a file named MANIFEST.MF. Create it with a plain text editor. It should contain:

Main-Class: com.foo.thisIsAPackage.YourMainClass

and nothing else.

Then:

jar cvfm HelloWorld.jar MANIFEST.MF YourMainClass.class

note that I'm pretty sure you MUST have a package or this is not going to work.