是否有可能找到给定包中的所有类或接口?(快速看了一下e.g. Package,似乎没有。)
当前回答
我是这样做的。我扫描所有的子文件夹(子包),我不尝试加载匿名类:
/**
* Attempts to list all the classes in the specified package as determined
* by the context class loader, recursively, avoiding anonymous classes
*
* @param pckgname
* the package name to search
* @return a list of classes that exist within that package
* @throws ClassNotFoundException
* if something went wrong
*/
private static List<Class> getClassesForPackage(String pckgname) throws ClassNotFoundException {
// This will hold a list of directories matching the pckgname. There may be more than one if a package is split over multiple jars/paths
ArrayList<File> directories = new ArrayList<File>();
String packageToPath = pckgname.replace('.', '/');
try {
ClassLoader cld = Thread.currentThread().getContextClassLoader();
if (cld == null) {
throw new ClassNotFoundException("Can't get class loader.");
}
// Ask for all resources for the packageToPath
Enumeration<URL> resources = cld.getResources(packageToPath);
while (resources.hasMoreElements()) {
directories.add(new File(URLDecoder.decode(resources.nextElement().getPath(), "UTF-8")));
}
} catch (NullPointerException x) {
throw new ClassNotFoundException(pckgname + " does not appear to be a valid package (Null pointer exception)");
} catch (UnsupportedEncodingException encex) {
throw new ClassNotFoundException(pckgname + " does not appear to be a valid package (Unsupported encoding)");
} catch (IOException ioex) {
throw new ClassNotFoundException("IOException was thrown when trying to get all resources for " + pckgname);
}
ArrayList<Class> classes = new ArrayList<Class>();
// For every directoryFile identified capture all the .class files
while (!directories.isEmpty()){
File directoryFile = directories.remove(0);
if (directoryFile.exists()) {
// Get the list of the files contained in the package
File[] files = directoryFile.listFiles();
for (File file : files) {
// we are only interested in .class files
if ((file.getName().endsWith(".class")) && (!file.getName().contains("$"))) {
// removes the .class extension
int index = directoryFile.getPath().indexOf(packageToPath);
String packagePrefix = directoryFile.getPath().substring(index).replace('/', '.');;
try {
String className = packagePrefix + '.' + file.getName().substring(0, file.getName().length() - 6);
classes.add(Class.forName(className));
} catch (NoClassDefFoundError e)
{
// do nothing. this class hasn't been found by the loader, and we don't care.
}
} else if (file.isDirectory()){ // If we got to a subdirectory
directories.add(new File(file.getPath()));
}
}
} else {
throw new ClassNotFoundException(pckgname + " (" + directoryFile.getPath() + ") does not appear to be a valid package");
}
}
return classes;
}
其他回答
你可以使用这个使用ClassLoader的method1。
/**
* 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 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()]);
}
/**
* 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 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;
}
__________ 1 .该方法最初取自http://snippets.dzone.com/posts/show/4831,由互联网档案馆存档,如现在所示。该代码片段也可以在https://dzone.com/articles/get-all-classes-within-package上获得。
FindAllClassesUsingPlainJavaReflectionTest.java
@Slf4j
class FindAllClassesUsingPlainJavaReflectionTest {
private static final Function<Throwable, RuntimeException> asRuntimeException = throwable -> {
log.error(throwable.getLocalizedMessage());
return new RuntimeException(throwable);
};
private static final Function<String, Collection<Class<?>>> findAllPackageClasses = basePackageName -> {
Locale locale = Locale.getDefault();
Charset charset = StandardCharsets.UTF_8;
val fileManager = ToolProvider.getSystemJavaCompiler()
.getStandardFileManager(/* diagnosticListener */ null, locale, charset);
StandardLocation location = StandardLocation.CLASS_PATH;
JavaFileObject.Kind kind = JavaFileObject.Kind.CLASS;
Set<JavaFileObject.Kind> kinds = Collections.singleton(kind);
val javaFileObjects = Try.of(() -> fileManager.list(location, basePackageName, kinds, /* recurse */ true))
.getOrElseThrow(asRuntimeException);
String pathToPackageAndClass = basePackageName.replace(".", File.separator);
Function<String, String> mapToClassName = s -> {
String prefix = Arrays.stream(s.split(pathToPackageAndClass))
.findFirst()
.orElse("");
return s.replaceFirst(prefix, "")
.replaceAll(File.separator, ".");
};
return StreamSupport.stream(javaFileObjects.spliterator(), /* parallel */ true)
.filter(javaFileObject -> javaFileObject.getKind().equals(kind))
.map(FileObject::getName)
.map(fileObjectName -> fileObjectName.replace(".class", ""))
.map(mapToClassName)
.map(className -> Try.of(() -> Class.forName(className))
.getOrElseThrow(asRuntimeException))
.collect(Collectors.toList());
};
@Test
@DisplayName("should get classes recursively in given package")
void test() {
Collection<Class<?>> classes = findAllPackageClasses.apply(getClass().getPackage().getName());
assertThat(classes).hasSizeGreaterThan(4);
classes.stream().map(String::valueOf).forEach(log::info);
}
}
PS:为了简化处理错误的样板文件等,我在这里使用了vavr和lombok库
其他实现可以在我的GitHub daggerok/java-reflection-find- annotation -classes-or-methods repo中找到
如果您不使用任何动态类加载器,您可以搜索类路径,并为每个条目搜索目录或JAR文件。
春天
这个例子是针对Spring 4的,但是您也可以在早期版本中找到类路径扫描器。
// create scanner and disable default filters (that is the 'false' argument)
final ClassPathScanningCandidateComponentProvider provider = new ClassPathScanningCandidateComponentProvider(false);
// add include filters which matches all the classes (or use your own)
provider.addIncludeFilter(new RegexPatternTypeFilter(Pattern.compile(".*")));
// get matching classes defined in the package
final Set<BeanDefinition> classes = provider.findCandidateComponents("my.package.name");
// this is how you can load the class type from BeanDefinition instance
for (BeanDefinition bean: classes) {
Class<?> clazz = Class.forName(bean.getBeanClassName());
// ... do your magic with the class ...
}
谷歌番石榴
注意:在版本14中,API仍然被标记为@Beta,所以在生产代码中要小心。
final ClassLoader loader = Thread.currentThread().getContextClassLoader();
for (final ClassPath.ClassInfo info : ClassPath.from(loader).getTopLevelClasses()) {
if (info.getName().startsWith("my.package.")) {
final Class<?> clazz = info.load();
// do something with your clazz
}
}
我一直在尝试使用Reflections库,但在使用它时遇到了一些问题,而且为了简单地获取包上的类,我应该包含太多的jar。
我将在这个重复的问题中发布一个解决方案:如何在包中获得所有类的名称?
答案由sp00m撰写;我添加了一些更正,使其工作:
import java.io.File;
import java.io.IOException;
import java.net.URL;
import java.util.Enumeration;
import java.util.LinkedList;
import java.util.List;
public final class ClassFinder {
private final static char DOT = '.';
private final static char SLASH = '/';
private final static String CLASS_SUFFIX = ".class";
private final static String BAD_PACKAGE_ERROR = "Unable to get resources from path '%s'. Are you sure the given '%s' package exists?";
public final static List<Class<?>> find(final String scannedPackage) {
final ClassLoader classLoader = Thread.currentThread().getContextClassLoader();
final String scannedPath = scannedPackage.replace(DOT, SLASH);
final Enumeration<URL> resources;
try {
resources = classLoader.getResources(scannedPath);
} catch (IOException e) {
throw new IllegalArgumentException(String.format(BAD_PACKAGE_ERROR, scannedPath, scannedPackage), e);
}
final List<Class<?>> classes = new LinkedList<Class<?>>();
while (resources.hasMoreElements()) {
final File file = new File(resources.nextElement().getFile());
classes.addAll(find(file, scannedPackage));
}
return classes;
}
private final static List<Class<?>> find(final File file, final String scannedPackage) {
final List<Class<?>> classes = new LinkedList<Class<?>>();
if (file.isDirectory()) {
for (File nestedFile : file.listFiles()) {
classes.addAll(find(nestedFile, scannedPackage));
}
//File names with the $1, $2 holds the anonymous inner classes, we are not interested on them.
} else if (file.getName().endsWith(CLASS_SUFFIX) && !file.getName().contains("$")) {
final int beginIndex = 0;
final int endIndex = file.getName().length() - CLASS_SUFFIX.length();
final String className = file.getName().substring(beginIndex, endIndex);
try {
final String resource = scannedPackage + DOT + className;
classes.add(Class.forName(resource));
} catch (ClassNotFoundException ignore) {
}
}
return classes;
}
}
要使用它,只需调用本例中提到的sp00n的find方法: 如果需要的话,我还添加了类实例的创建。
List<Class<?>> classes = ClassFinder.find("com.package");
ExcelReporting excelReporting;
for (Class<?> aClass : classes) {
Constructor constructor = aClass.getConstructor();
//Create an object of the class type
constructor.newInstance();
//...
}
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