如何获取一个包中的所有类?
你不能这样做。类可以通过许多不同的类加载器来引入,包括远程加载器。
/**
* Scans all classloaders for the current thread for loaded jars, and then scans
* each jar for the package name in question, listing all classes directly under
* the package name in question. Assumes directory structure in jar file and class
* package naming follow java conventions (i.e. com.example.test.MyTest would be in
* /com/example/test/MyTest.class)
*/
public Collection<Class> getClassesForPackage(String packageName) throws Exception {
String packagePath = packageName.replace(".", "/");
ClassLoader classLoader = Thread.currentThread().getContextClassLoader();
Set<URL> jarUrls = new HashSet<URL>();
while (classLoader != null) {
if (classLoader instanceof URLClassLoader)
for (URL url : ((URLClassLoader) classLoader).getURLs())
if (url.getFile().endsWith(".jar") // may want better way to detect jar files
jarUrls.add(url);
classLoader = classLoader.getParent();
}
Set<Class> classes = new HashSet<Class>();
for (URL url : jarUrls) {
JarInputStream stream = new JarInputStream(url.openStream()); // may want better way to open url connections
JarEntry entry = stream.getNextJarEntry();
while (entry != null) {
String name = entry.getName();
int i = name.lastIndexOf("/");
if (i > 0 && name.endsWith(".class") && name.substring(0, i).equals(packagePath))
classes.add(Class.forName(name.substring(0, name.length() - 6).replace("/", ".")));
entry = stream.getNextJarEntry();
}
stream.close();
}
return classes;
}
.equals(packagePath)
更改为.startsWith(packagePath)
就可以满足我的需求了。谢谢。 - Jesse Chisholm这里有一个代码片段(链接在此),它可以做到您想要的,前提是类可以在本地找到:
private static Class[] getClasses(String packageName)
throws ClassNotFoundException, IOException {
ClassLoader classLoader = Thread.currentThread().getContextClassLoader();
assert classLoader != null;
String path = packageName.replace('.', '/');
Enumeration<URL> resources = classLoader.getResources(path);
List<File> dirs = new ArrayList<File>();
while (resources.hasMoreElements()) {
URL resource = resources.nextElement();
dirs.add(new File(resource.getFile()));
}
ArrayList<Class> classes = new ArrayList<Class>();
for (File directory : dirs) {
classes.addAll(findClasses(directory, packageName));
}
return classes.toArray(new Class[classes.size()]);
}
private static 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()) {
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;
}
没有全局的方法来做到这一点。话虽如此,如果您知道您的类来自哪里,您可以遍历jar文件或文件系统的目录。
Java没有发现功能。
大多数具有添加(发现)新类的能力的产品都有一个描述“程序扩展”的文本文件或特定目录,您可以在其中放置使用@JG所描述的技巧的类或jar。(这就是Eclipse所做的,并建议在用户可能手动添加新模块的任何解决方案中使用)