是否可以在.jar文件中自动创建目录层次结构？

Question

I'm rarely using java, so my knowledge of modern ecosystem is very limited :(. AFAIK, Java is heavy glued with directory hierarchy and file names: for example, if i have a .jar file with "com.mycompany.myapp.WndMain" class, the corresponding .class file must be named exactly "WndMain.class" (case sensitive!) and be placed into "com/mycompany/myapp" directory tree inside .jar file (that is actually a .zip archive).

But while developing applications i don't want my source code files to be named CamelCase and scattered in some directory trees! It's my source code, after all. I prefer files to be organized the way it's comfortably for me to work with them, not for some stupid compiler and archiver :). I want a clean "src" folder with files like "wnd_main.java", "wnd_about.java" etc. Is it some easy way to automatically generate correct file names and directory structure during compilation, based on actual source code content?

Of course i can create script of my own - via Python, Ruby, Shell or whatever - that will read content of ".java" files, parse "using" and "class" directives, create directory structure, copy files, compile etc... But maybe all of this is already done years ago and all i need is something like "sudo apt-get install javamake"? :)

Answer 1

No, the compiler will not let you declare classes where the declared package name in the file (like package com.mycopmany.myapp ) do not match the actual directory structure on disk.

This seems like a lot of work to go through to avoid having directories in your src hierarchy.

Answer 2

It will be a difficult task, as the package name inside each source file MUST be equal to the directory structure as @mattb said, but you can use some build tool like Ant (the most used one) to create the solution that you are looking for.

For example, if you have your source organized this way:

src
    foo
        class_1.java
        class_2.java
    bar
        class_3.java
        class_4.java

You can use Ant to copy all source files to a temp directory, compile and package then in a .jar, but as I said, you will have some problems, like name colisions (example: you can have classes with the same name in different directoties). All your classes must have different names and all classes must access each other as they are in the same package. All this problem is related to the solution that I propose. You can, off course, modify the code of the files that were copied to the temp directory, but I really don't think that all this is worth of try... I sinceraly recommend that you follow the "way to develop" in Java, using some IDE, following the Java Code Conventions , etc.

Answer 3

This is pointless. It's hard to find a question here.
But I'll try to answer:

1. Java requires your files to be strictly organized acordingly to its classnames.
   Think of Python, which enforces indentation. It does this to eliminate the need
   of coding conventions related to indentation.

2. It does this for your own good , to prevent situations of type:

   How do I find this class in such a big project?
   It turns out I was writing a class / feature that is already present.
   For this project, how should I organize the files? Is there some convention?
   What?! 100 classes defined in a single file?

3. Don't like to work with the files and directory structure manually?
   Use an IDE , it will do that for you.

4. If you still want flexibility on Java, why not try some Java-based languages ?
   Like Groovy, for example. Or Clojure, or Scala, or...
   They all work in the JVM, their syntax is compatible with Java's, but more relaxed and permissive . The same applies to the directory structure. Bonus! You can mix Groovy scripts with Java classes.

Bottom note: Actually, non-public classes don't need to follow this convention .
If by some strange reason you decide to declare one of your classes with package access ,
it won't be accessed from outside your package , but you can give it the name you want.

Answer 4

You don't strictly have to organize your .java files into a directory structure that matches the packages - .class files must be in such a structure but javac will accept a flat structure for .java files - however you will make your life much easier if you do so as pretty much all the higher level Java tools in the world expect you to follow this convention. For example Ant relies on matching between the .java and .class directory structures to be able to tell which .class files are out of date with respect to their corresponding .java . If the structures don't match it will recompile every .java file every time.

However the name of each .java file must match the name of the public class it defines (you can have several classes in one .java file but at most one of them can be public and its name must match the file name). This is a requirement of the compiler, and it's not worth fighting against.

Answer 5

scons build system perfectly creates directory structure according to content of .java files. Installation is as easy as pypm -g install scons .