从包中获取所有类

package reflection java

2022-09-03 09:56:10

假设我有一个java包，其中包含所有继承的类，我可以以某种方式获得所有这些类吗？我正在锁定以下行中的某些内容：commandsICommand

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

这样的事情可能吗？

答案 1

下面是一个基本示例，假设类不是 JAR 打包的：

// 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);
    }
}

答案 2

下面是使用 JSR-199 API 的实现，即来自：javax.tools.*

List<Class> commands = new ArrayList<Class>();

JavaCompiler compiler = ToolProvider.getSystemJavaCompiler();
StandardJavaFileManager fileManager = compiler.getStandardFileManager(
        null, null, null);

Location location = StandardLocation.CLASS_PATH;
String packageName = "commands";
Set<JavaFileObject.Kind> kinds = new HashSet<JavaFileObject.Kind>();
kinds.add(JavaFileObject.Kind.CLASS);
boolean recurse = false;

Iterable<JavaFileObject> list = fileManager.list(location, packageName,
        kinds, recurse);

for (JavaFileObject javaFileObject : list) {
    commands.add(javaFileObject.getClass());
}