如何在给定的包中找到带注释的方法? [英] How to find annotated methods in a given package?

问题描述

我有一个简单的方法标记注释(类似于Effective Java(第二版)第 35 条中的第一个示例):

I have a simple marker annotation for methods (similar to the first example in Item 35 in Effective Java (2nd ed)):

/**
 * Marker annotation for methods that are called from installer's 
 * validation scripts etc. 
 */
@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.METHOD)
public @interface InstallerMethod {
}

然后，在给定的包(比如 com.acme.installer)中，它有一些包含大约 20 个类的子包，我想找到所有用它注释的方法.(因为我想对单元测试中的所有带注释的方法进行一些检查.)

Then, in a given package (say com.acme.installer), which has a few subpackages containing some 20 classes, I'd like to find all methods that are annotated with it. (Because I'd like to do some checks regarding all the annotated methods in a unit test.)

什么(如果有)是最简单的方法?最好不要添加新的第 3 方库或框架.

What (if any) is the easiest way to do this? Preferably without adding new 3rd party libraries or frameworks.

编辑:澄清一下，显然 method.isAnnotationPresent(InstallerMethod.class) 将是检查方法是否具有注释的方法 - 但这个问题包括找到所有方法.

Edit: to clarify, obviously method.isAnnotationPresent(InstallerMethod.class) will be the way to check if a method has the annotation - but this problem includes finding all the methods.

推荐答案

如果你想自己实现，这些方法会找到给定包中的所有类:

If you want to implement it yourself, these methods will find all the classes in a given package:

/**
 * 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
 */
private Iterable<Class> getClasses(String packageName) throws ClassNotFoundException, IOException
{
    ClassLoader classLoader = Thread.currentThread().getContextClassLoader();
    String path = packageName.replace('.', '/');
    Enumeration<URL> resources = classLoader.getResources(path);
    List<File> dirs = new ArrayList<File>();
    while (resources.hasMoreElements())
    {
        URL resource = resources.nextElement();
        URI uri = new URI(resource.toString());
        dirs.add(new File(uri.getPath()));
    }
    List<Class> classes = new ArrayList<Class>();
    for (File directory : dirs)
    {
        classes.addAll(findClasses(directory, packageName));
    }

    return classes;
}

/**
 * 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
 */
private List<Class> findClasses(File directory, String packageName) throws ClassNotFoundException
{
    List<Class> classes = new ArrayList<Class>();
    if (!directory.exists())
    {
        return classes;
    }
    File[] files = directory.listFiles();
    for (File file : files)
    {
        if (file.isDirectory())
        {
            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;
}

然后您可以使用给定的注释过滤这些类:

Then you can just filter on those classes with the given annotation:

for (Method method : testClass.getMethods())
{
    if (method.isAnnotationPresent(InstallerMethod.class))
    {
        // do something
    }
}

这篇关于如何在给定的包中找到带注释的方法?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！