java 用于反射的Java方法（包扫描）

Posted 2021-05-08

/**
 * Scans all classes accessible from the context class loader which belong
 * to the given package and subpackages.
 *
 * @param packageName The base package
 * @return The classes
 * @throws ClassNotFoundException
 * @throws IOException
 * @see https://dzone.com/articles/get-all-classes-within-package
 */
private static Class[] getClasses(String packageName) throws ClassNotFoundException, IOException {
    ClassLoader classLoader = Thread.currentThread().getContextClassLoader();
    assert classLoader != null;
    String path = packageName.replace('.', '/');
    Enumeration resources = classLoader.getResources(path);
    List dirs = new ArrayList();
    while (resources.hasMoreElements()) {
        URL resource = (URL) resources.nextElement();
        dirs.add(new File(resource.getFile()));
    }
    ArrayList classes = new ArrayList();
    for (Object directory : dirs) {
        classes.addAll(findClasses((File) directory, packageName));
    }
    return (Class[]) classes.toArray(new Class[classes.size()]);
}
    
/**
 * Recursive method used to find all classes in a given directory and
 * subdirs.
 *
 * @param directory   The base directory
 * @param packageName The package name for classes found inside the base
 *                    directory
 * @return The classes
 * @throws ClassNotFoundException
 * @see https://dzone.com/articles/get-all-classes-within-package
 */
private static List findClasses(File directory, String packageName) throws ClassNotFoundException {
    List classes = new ArrayList();
    if (!directory.exists()) {
        return classes;
    }
    File[] files = directory.listFiles();
    for (File file : files) {
        if (file.isDirectory()) {
    	assert !file.getName().contains(".");
    	classes.addAll(findClasses(file, packageName + "." + file.getName()));
        } else if (file.getName().endsWith(".class")) {
    	classes.add(Class.forName(packageName + '.' + file.getName().substring(0, file.getName().length() - 6)));
        }
    }
    return classes;
}

/**
 * Gets a class/classes in a package that are of a given type.
 * org.reflections is required
 */
public Set getClassesInPackage(String pack, Class aClass) {

    Reflections ref = new Reflections(pack, new SubTypesScanner(false));

    // ? extends Fruit is example
    Set<Class<? extends Fruit>> allClasses = ref.getSubTypesOf(aClass);

    return allClasses;
}

/**
 * Gets inherited (all) fields of a given type.
 * 
 * @see http://stackoverflow.com/a/2405757/1766166
 */
public static List<Field> getInheritedFields(Class<?> type) {
    List<Field> fields = new ArrayList<Field>();
    for (Class<?> c = type; c != null; c = c.getSuperclass()) {
        fields.addAll(Arrays.asList(c.getDeclaredFields()));
    }
    return fields;
}