动态加载java类文件的方法 [英] Method to dynamically load java class files

问题描述

什么是动态加载java类文件的好方法，以便编译成jar的程序可以读取目录中的所有类文件并使用它们，以及如何编写文件以使它们具有必要的包

我相信这是一个 ClassLoader

我建议您从下面的示例开始，加载不在类路径中的类文件。

  //在包含类文件的目录的根目录上创建一个File对象
文件file = new File（c：\\myclasses \\）; 
 
 try {
 //将文件转换为URL 
 URL url = file.toURL（）; // file：/ c：/ myclasses / 
 URL [] urls = new URL [] {url}; 
 
 //使用目录
创建一个新的类加载器classLoader cl = new URLClassLoader（urls）; 
 
 //加载类; MyClass.class应该位于
 //目录文件：/ c：/ myclasses / com / mycompany 
 Class cls = cl.loadClass（com.mycompany.MyClass）; 
} catch（MalformedURLException e）{
} catch（ClassNotFoundException e）{
} 
  

What would be a good way to dynamically load java class files so that a program compiled into a jar can read all the class files in a directory and use them, and how can one write the files so that they have the necessary package name in relation to the jar?

解决方案

I believe it's a ClassLoader you're after.

I suggest you start by looking at the example below which loads class files that are not on the class path.

// Create a File object on the root of the directory containing the class file
File file = new File("c:\\myclasses\\");

try {
    // Convert File to a URL
    URL url = file.toURL();          // file:/c:/myclasses/
    URL[] urls = new URL[]{url};

    // Create a new class loader with the directory
    ClassLoader cl = new URLClassLoader(urls);

    // Load in the class; MyClass.class should be located in
    // the directory file:/c:/myclasses/com/mycompany
    Class cls = cl.loadClass("com.mycompany.MyClass");
} catch (MalformedURLException e) {
} catch (ClassNotFoundException e) {
}

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