从包中获取所有类 [英] Getting all Classes from a Package

问题描述

假设我有一个java包命令，其中包含所有继承自 ICommand 的类，我可以获得所有不知何故，这些课程？我正在锁定以下内容：

Lets say I have a java package commands which contains classes that all inherit from ICommand can I get all of those classes somehow? I'm locking for something among the lines of:

Package p = Package.getPackage("commands");
Class<ICommand>[] c = p.getAllPackagedClasses(); //not real 

有类似的可能吗？

推荐答案

这是一个基本的例子，假设类不是JAR打包的：

Here's a basic example, assuming that classes are not JAR-packaged:

// Prepare.
String packageName = "com.example.commands";
List<Class<ICommand>> commands = new ArrayList<Class<ICommand>>();
URL root = Thread.currentThread().getContextClassLoader().getResource(packageName.replace(".", "/"));

// Filter .class files.
File[] files = new File(root.getFile()).listFiles(new FilenameFilter() {
    public boolean accept(File dir, String name) {
        return name.endsWith(".class");
    }
});

// Find classes implementing ICommand.
for (File file : files) {
    String className = file.getName().replaceAll(".class$", "");
    Class<?> cls = Class.forName(packageName + "." + className);
    if (ICommand.class.isAssignableFrom(cls)) {
        commands.add((Class<ICommand>) cls);
    }
}

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