是否可以找到给定包中的所有类或接口？（快速查看 eg Package，似乎没有。）
Jonik
问问题
468406 次
27 回答
405
由于类加载器的动态特性，这是不可能的。类加载器不需要告诉虚拟机它可以提供哪些类，它们只是对类的请求，并且必须返回一个类或抛出一个异常。
但是，如果您编写自己的类加载器，或检查类路径及其 jar，则可以找到此信息。这将通过文件系统操作，而不是反射。甚至可能有一些库可以帮助您做到这一点。
如果有生成或远程交付的类，您将无法发现这些类。
正常的方法是在某处注册您需要在文件中访问的类，或在不同的类中引用它们。或者只是在命名时使用约定。
附录：反射库将允许您在当前类路径中查找类。它可用于获取包中的所有类：
Reflections reflections = new Reflections("my.project.prefix");
Set<Class<? extends Object>> allClasses =
reflections.getSubTypesOf(Object.class);
于 2009-02-06T13:47:57.080 回答
202
您可能应该看看开源反射库。有了它，您可以轻松实现您想要的。
首先，设置反射索引（这有点乱，因为默认情况下禁用搜索所有类）：
List<ClassLoader> classLoadersList = new LinkedList<ClassLoader>();
classLoadersList.add(ClasspathHelper.contextClassLoader());
classLoadersList.add(ClasspathHelper.staticClassLoader());
Reflections reflections = new Reflections(new ConfigurationBuilder()
.setScanners(new SubTypesScanner(false /* don't exclude Object.class */), new ResourcesScanner())
.setUrls(ClasspathHelper.forClassLoader(classLoadersList.toArray(new ClassLoader[0])))
.filterInputsBy(new FilterBuilder().include(FilterBuilder.prefix("org.your.package"))));
然后您可以查询给定包中的所有对象：
Set<Class<?>> classes = reflections.getSubTypesOf(Object.class);
于 2012-03-05T17:29:44.580 回答
141
Google Guava 14 包含一个新类，该类ClassPath具有三种扫描顶级类的方法：
getTopLevelClasses()getTopLevelClasses(String packageName)getTopLevelClassesRecursive(String packageName)
有关更多信息，请参阅ClassPathjavadocs。
于 2012-11-20T16:06:26.023 回答
132
您可以使用此方法1 ，该方法使用ClassLoader.
/**
* 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此方法最初取自http://snippets.dzone.com/posts/show/4831，由 Internet 档案馆存档，链接到现在。该片段也可在https://dzone.com/articles/get-all-classes-within-package获得。
于 2009-02-06T13:49:40.853 回答
117
春天
此示例适用于 Spring 4，但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 仍标记为@Beta，因此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
}
}
于 2014-01-29T12:15:09.273 回答
42
你好。我一直对上述解决方案（以及其他网站）有一些问题。
作为开发人员，我正在为 API 编写插件。API 阻止使用任何外部库或第 3 方工具。该设置还包含 jar 或 zip 文件中的代码以及直接位于某些目录中的类文件。因此，我的代码必须能够围绕每个设置工作。经过大量研究，我想出了一种方法，该方法至少适用于所有可能设置的 95%。
下面的代码基本上是永远有效的矫枉过正的方法。
编码：
此代码扫描给定包中包含的所有类。它只适用于当前的所有类ClassLoader。
/**
* Private helper method
*
* @param directory
* The directory to start with
* @param pckgname
* The package name to search for. Will be needed for getting the
* Class object.
* @param classes
* if a file isn't loaded but still is in the directory
* @throws ClassNotFoundException
*/
private static void checkDirectory(File directory, String pckgname,
ArrayList<Class<?>> classes) throws ClassNotFoundException {
File tmpDirectory;
if (directory.exists() && directory.isDirectory()) {
final String[] files = directory.list();
for (final String file : files) {
if (file.endsWith(".class")) {
try {
classes.add(Class.forName(pckgname + '.'
+ file.substring(0, file.length() - 6)));
} catch (final NoClassDefFoundError e) {
// do nothing. this class hasn't been found by the
// loader, and we don't care.
}
} else if ((tmpDirectory = new File(directory, file))
.isDirectory()) {
checkDirectory(tmpDirectory, pckgname + "." + file, classes);
}
}
}
}
/**
* Private helper method.
*
* @param connection
* the connection to the jar
* @param pckgname
* the package name to search for
* @param classes
* the current ArrayList of all classes. This method will simply
* add new classes.
* @throws ClassNotFoundException
* if a file isn't loaded but still is in the jar file
* @throws IOException
* if it can't correctly read from the jar file.
*/
private static void checkJarFile(JarURLConnection connection,
String pckgname, ArrayList<Class<?>> classes)
throws ClassNotFoundException, IOException {
final JarFile jarFile = connection.getJarFile();
final Enumeration<JarEntry> entries = jarFile.entries();
String name;
for (JarEntry jarEntry = null; entries.hasMoreElements()
&& ((jarEntry = entries.nextElement()) != null);) {
name = jarEntry.getName();
if (name.contains(".class")) {
name = name.substring(0, name.length() - 6).replace('/', '.');
if (name.contains(pckgname)) {
classes.add(Class.forName(name));
}
}
}
}
/**
* Attempts to list all the classes in the specified package as determined
* by the context class loader
*
* @param pckgname
* the package name to search
* @return a list of classes that exist within that package
* @throws ClassNotFoundException
* if something went wrong
*/
public static ArrayList<Class<?>> getClassesForPackage(String pckgname)
throws ClassNotFoundException {
final ArrayList<Class<?>> classes = new ArrayList<Class<?>>();
try {
final ClassLoader cld = Thread.currentThread()
.getContextClassLoader();
if (cld == null)
throw new ClassNotFoundException("Can't get class loader.");
final Enumeration<URL> resources = cld.getResources(pckgname
.replace('.', '/'));
URLConnection connection;
for (URL url = null; resources.hasMoreElements()
&& ((url = resources.nextElement()) != null);) {
try {
connection = url.openConnection();
if (connection instanceof JarURLConnection) {
checkJarFile((JarURLConnection) connection, pckgname,
classes);
} else if (connection instanceof FileURLConnection) {
try {
checkDirectory(
new File(URLDecoder.decode(url.getPath(),
"UTF-8")), pckgname, classes);
} catch (final UnsupportedEncodingException ex) {
throw new ClassNotFoundException(
pckgname
+ " does not appear to be a valid package (Unsupported encoding)",
ex);
}
} else
throw new ClassNotFoundException(pckgname + " ("
+ url.getPath()
+ ") does not appear to be a valid package");
} catch (final IOException ioex) {
throw new ClassNotFoundException(
"IOException was thrown when trying to get all resources for "
+ pckgname, ioex);
}
}
} catch (final NullPointerException ex) {
throw new ClassNotFoundException(
pckgname
+ " does not appear to be a valid package (Null pointer exception)",
ex);
} catch (final IOException ioex) {
throw new ClassNotFoundException(
"IOException was thrown when trying to get all resources for "
+ pckgname, ioex);
}
return classes;
}
这三种方法使您能够找到给定包中的所有类。
你像这样使用它：
getClassesForPackage("package.your.classes.are.in");
说明：
该方法首先获取当前的ClassLoader. 然后它获取包含所述包的所有资源并迭代这些URLs。然后它创建一个URLConnection并确定我们拥有什么类型的 URl。它可以是目录 ( FileURLConnection)，也可以是 jar 或 zip 文件 ( JarURLConnection) 中的目录。根据连接的类型，我们将调用两种不同的方法。
首先让我们看看如果它是一个FileURLConnection.
它首先检查传递的 File 是否存在并且是一个目录。如果是这种情况，它会检查它是否是类文件。如果是这样，Class将创建一个对象并将其放入ArrayList. 如果它不是类文件而是目录，我们只需迭代它并做同样的事情。所有其他案例/文件将被忽略。
如果URLConnection是JarURLConnection另一个私有辅助方法将被调用。此方法遍历 zip/jar 存档中的所有条目。如果一个条目是类文件并且在包内，Class则将创建一个对象并将其存储在ArrayList.
解析完所有资源后，它（主要方法）返回ArrayList包含给定包中的所有类，当前ClassLoader知道。
如果该过程在任何时候失败，ClassNotFoundException将抛出包含有关确切原因的详细信息。
于 2014-03-17T18:47:16.130 回答
23
目前列出给定包中所有类的最强大的机制是ClassGraph，因为它处理最广泛的类路径规范机制，包括新的 JPMS 模块系统。（我是作者。）
List<String> classNames = new ArrayList<>();
try (ScanResult scanResult = new ClassGraph().acceptPackages("my.package")
.enableClassInfo().scan()) {
classNames.addAll(scanResult.getAllClasses().getNames());
}
于 2016-07-31T01:48:16.207 回答
18
不使用任何额外的库：
package test;
import java.io.DataInputStream;
import java.io.InputStream;
import java.net.URL;
import java.util.ArrayList;
import java.util.List;
public class Test {
public static void main(String[] args) throws Exception{
List<Class> classes = getClasses(Test.class.getClassLoader(),"test");
for(Class c:classes){
System.out.println("Class: "+c);
}
}
public static List<Class> getClasses(ClassLoader cl,String pack) throws Exception{
String dottedPackage = pack.replaceAll("[/]", ".");
List<Class> classes = new ArrayList<Class>();
URL upackage = cl.getResource(pack);
DataInputStream dis = new DataInputStream((InputStream) upackage.getContent());
String line = null;
while ((line = dis.readLine()) != null) {
if(line.endsWith(".class")) {
classes.add(Class.forName(dottedPackage+"."+line.substring(0,line.lastIndexOf('.'))));
}
}
return classes;
}
}
于 2014-02-17T22:48:57.713 回答
13
一般来说，类加载器不允许扫描类路径上的所有类。但通常唯一使用的类加载器是 UrlClassLoader，我们可以从中检索目录和 jar 文件列表（请参阅getURLs）并一一打开以列出可用的类。这种方法称为类路径扫描，在Scannotation和Reflections中实现。
Reflections reflections = new Reflections("my.package");
Set<Class<? extends Object>> classes = reflections.getSubTypesOf(Object.class);
另一种方法是使用Java Pluggable Annotation Processing API编写注释处理器，该处理器将在编译时收集所有带注释的类并构建索引文件以供运行时使用。该机制在ClassIndex库中实现：
// package-info.java
@IndexSubclasses
package my.package;
// your code
Iterable<Class> classes = ClassIndex.getPackageClasses("my.package");
请注意，由于 Java 编译器会自动发现在类路径中找到的任何处理器，因此扫描是完全自动化的，因此不需要额外的设置。
于 2012-12-22T12:02:30.177 回答
8
那这个呢：
public static List<Class<?>> getClassesForPackage(final String pkgName) throws IOException, URISyntaxException {
final String pkgPath = pkgName.replace('.', '/');
final URI pkg = Objects.requireNonNull(ClassLoader.getSystemClassLoader().getResource(pkgPath)).toURI();
final ArrayList<Class<?>> allClasses = new ArrayList<Class<?>>();
Path root;
if (pkg.toString().startsWith("jar:")) {
try {
root = FileSystems.getFileSystem(pkg).getPath(pkgPath);
} catch (final FileSystemNotFoundException e) {
root = FileSystems.newFileSystem(pkg, Collections.emptyMap()).getPath(pkgPath);
}
} else {
root = Paths.get(pkg);
}
final String extension = ".class";
try (final Stream<Path> allPaths = Files.walk(root)) {
allPaths.filter(Files::isRegularFile).forEach(file -> {
try {
final String path = file.toString().replace('/', '.');
final String name = path.substring(path.indexOf(pkgName), path.length() - extension.length());
allClasses.add(Class.forName(name));
} catch (final ClassNotFoundException | StringIndexOutOfBoundsException ignored) {
}
});
}
return allClasses;
}
然后，您可以重载该函数：
public static List<Class<?>> getClassesForPackage(final Package pkg) throws IOException, URISyntaxException {
return getClassesForPackage(pkg.getName());
}
如果你需要测试它：
public static void main(final String[] argv) throws IOException, URISyntaxException {
for (final Class<?> cls : getClassesForPackage("my.package")) {
System.out.println(cls);
}
for (final Class<?> cls : getClassesForPackage(MyClass.class.getPackage())) {
System.out.println(cls);
}
}
如果您的 IDE 没有导入助手：
import java.io.IOException;
import java.net.URI;
import java.net.URISyntaxException;
import java.nio.file.FileSystemNotFoundException;
import java.nio.file.FileSystems;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import java.util.Objects;
import java.util.stream.Stream;
有用：
从您的 IDE
对于 JAR 文件
没有外部依赖
于 2019-11-08T19:57:36.023 回答
5
我整理了一个简单的 github 项目来解决这个问题：
https://github.com/ddopson/java-class-enumerator
它应该适用于基于文件的类路径和 jar 文件。
如果你在签出项目后运行“make”，它会打印出来：
Cleaning...
rm -rf build/
Building...
javac -d build/classes src/pro/ddopson/ClassEnumerator.java src/test/ClassIShouldFindOne.java src/test/ClassIShouldFindTwo.java src/test/subpkg/ClassIShouldFindThree.java src/test/TestClassEnumeration.java
Making JAR Files...
jar cf build/ClassEnumerator_test.jar -C build/classes/ .
jar cf build/ClassEnumerator.jar -C build/classes/ pro
Running Filesystem Classpath Test...
java -classpath build/classes test.TestClassEnumeration
ClassDiscovery: Package: 'test' becomes Resource: 'file:/Users/Dopson/work/other/java-class-enumeration/build/classes/test'
ClassDiscovery: Reading Directory '/Users/Dopson/work/other/java-class-enumeration/build/classes/test'
ClassDiscovery: FileName 'ClassIShouldFindOne.class' => class 'test.ClassIShouldFindOne'
ClassDiscovery: FileName 'ClassIShouldFindTwo.class' => class 'test.ClassIShouldFindTwo'
ClassDiscovery: FileName 'subpkg' => class 'null'
ClassDiscovery: Reading Directory '/Users/Dopson/work/other/java-class-enumeration/build/classes/test/subpkg'
ClassDiscovery: FileName 'ClassIShouldFindThree.class' => class 'test.subpkg.ClassIShouldFindThree'
ClassDiscovery: FileName 'TestClassEnumeration.class' => class 'test.TestClassEnumeration'
Running JAR Classpath Test...
java -classpath build/ClassEnumerator_test.jar test.TestClassEnumeration
ClassDiscovery: Package: 'test' becomes Resource: 'jar:file:/Users/Dopson/work/other/java-class-enumeration/build/ClassEnumerator_test.jar!/test'
ClassDiscovery: Reading JAR file: '/Users/Dopson/work/other/java-class-enumeration/build/ClassEnumerator_test.jar'
ClassDiscovery: JarEntry 'META-INF/' => class 'null'
ClassDiscovery: JarEntry 'META-INF/MANIFEST.MF' => class 'null'
ClassDiscovery: JarEntry 'pro/' => class 'null'
ClassDiscovery: JarEntry 'pro/ddopson/' => class 'null'
ClassDiscovery: JarEntry 'pro/ddopson/ClassEnumerator.class' => class 'null'
ClassDiscovery: JarEntry 'test/' => class 'null'
ClassDiscovery: JarEntry 'test/ClassIShouldFindOne.class' => class 'test.ClassIShouldFindOne'
ClassDiscovery: JarEntry 'test/ClassIShouldFindTwo.class' => class 'test.ClassIShouldFindTwo'
ClassDiscovery: JarEntry 'test/subpkg/' => class 'null'
ClassDiscovery: JarEntry 'test/subpkg/ClassIShouldFindThree.class' => class 'test.subpkg.ClassIShouldFindThree'
ClassDiscovery: JarEntry 'test/TestClassEnumeration.class' => class 'test.TestClassEnumeration'
Tests Passed.
另见我的另一个答案
于 2012-10-24T21:49:59.097 回答
5
这是我的做法。我扫描所有子文件夹（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;
}
于 2016-08-17T20:54:23.710 回答
5
是的，您可以使用很少的 API，这就是我喜欢这样做的方式，遇到了我使用休眠核心的问题，并且必须找到用某个注释进行注释的类。
使这些成为自定义注释，您将使用它标记要选择的类。
import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;
@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.TYPE)
public @interface EntityToBeScanned {
}
然后用它标记你的班级
@EntityToBeScanned
public MyClass{
}
制作具有以下方法的实用程序类
public class ClassScanner {
public static Set<Class<?>> allFoundClassesAnnotatedWithEntityToBeScanned(){
Reflections reflections = new Reflections(".*");
Set<Class<?>> annotated = reflections.getTypesAnnotatedWith(EntityToBeScanned.class);
return annotated;
}
}
调用allFoundClassesAnnotatedWithEntityToBeScanned()方法来获取一组找到的类。
您将需要下面给出的库
<!-- https://mvnrepository.com/artifact/com.google.guava/guava -->
<dependency>
<groupId>com.google.guava</groupId>
<artifactId>guava</artifactId>
<version>21.0</version>
</dependency>
<!-- https://mvnrepository.com/artifact/org.javassist/javassist -->
<dependency>
<groupId>org.javassist</groupId>
<artifactId>javassist</artifactId>
<version>3.22.0-CR1</version>
</dependency>
<!-- https://mvnrepository.com/artifact/org.reflections/reflections -->
<dependency>
<groupId>org.reflections</groupId>
<artifactId>reflections</artifactId>
<version>0.9.10</version>
</dependency>
于 2017-02-08T10:57:15.593 回答
4
如果您在 Spring-land，您可以使用PathMatchingResourcePatternResolver;
PathMatchingResourcePatternResolver resolver = new PathMatchingResourcePatternResolver();
Resource[] resources = resolver.getResources("classpath*:some/package/name/*.class");
Arrays.asList(resources).forEach(r->{
...
});
于 2020-04-30T14:21:04.353 回答
3
您需要查找类路径中的每个类加载器条目：
String pkg = "org/apache/commons/lang";
ClassLoader cl = ClassLoader.getSystemClassLoader();
URL[] urls = ((URLClassLoader) cl).getURLs();
for (URL url : urls) {
System.out.println(url.getFile());
File jar = new File(url.getFile());
// ....
}
如果条目是目录，只需在正确的子目录中查找：
if (jar.isDirectory()) {
File subdir = new File(jar, pkg);
if (!subdir.exists())
continue;
File[] files = subdir.listFiles();
for (File file : files) {
if (!file.isFile())
continue;
if (file.getName().endsWith(".class"))
System.out.println("Found class: "
+ file.getName().substring(0,
file.getName().length() - 6));
}
}
如果条目是文件，并且是 jar，请检查它的 ZIP 条目：
else {
// try to open as ZIP
try {
ZipFile zip = new ZipFile(jar);
for (Enumeration<? extends ZipEntry> entries = zip
.entries(); entries.hasMoreElements();) {
ZipEntry entry = entries.nextElement();
String name = entry.getName();
if (!name.startsWith(pkg))
continue;
name = name.substring(pkg.length() + 1);
if (name.indexOf('/') < 0 && name.endsWith(".class"))
System.out.println("Found class: "
+ name.substring(0, name.length() - 6));
}
} catch (ZipException e) {
System.out.println("Not a ZIP: " + e.getMessage());
} catch (IOException e) {
System.err.println(e.getMessage());
}
}
现在一旦你有了包中的所有类名，你可以尝试用反射加载它们并分析它们是类还是接口等。
于 2013-09-25T08:44:56.843 回答
3
我一直在尝试使用 Reflections 库，但是在使用它时遇到了一些问题，而且我应该包含太多的 jar，只是为了简单地获取包上的类。
我将发布我在这个重复问题中找到的解决方案：如何获取包中的所有类名称？
答案是 sp00m 写的；我添加了一些更正以使其正常工作：
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，只需调用本示例中提到的 sp00n 的 find 方法：如果需要，我已经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();
//...
}
于 2013-12-03T17:52:35.430 回答
3
我刚写了一个util类，里面有测试方法，你可以看看~
IteratePackageUtil.java：
package eric.j2se.reflect;
import java.util.Set;
import org.reflections.Reflections;
import org.reflections.scanners.ResourcesScanner;
import org.reflections.scanners.SubTypesScanner;
import org.reflections.util.ClasspathHelper;
import org.reflections.util.ConfigurationBuilder;
import org.reflections.util.FilterBuilder;
/**
* an util to iterate class in a package,
*
* @author eric
* @date Dec 10, 2013 12:36:46 AM
*/
public class IteratePackageUtil {
/**
* <p>
* Get set of all class in a specified package recursively. this only support lib
* </p>
* <p>
* class of sub package will be included, inner class will be included,
* </p>
* <p>
* could load class that use the same classloader of current class, can't load system packages,
* </p>
*
* @param pkg
* path of a package
* @return
*/
public static Set<Class<? extends Object>> getClazzSet(String pkg) {
// prepare reflection, include direct subclass of Object.class
Reflections reflections = new Reflections(new ConfigurationBuilder().setScanners(new SubTypesScanner(false), new ResourcesScanner())
.setUrls(ClasspathHelper.forClassLoader(ClasspathHelper.classLoaders(new ClassLoader[0])))
.filterInputsBy(new FilterBuilder().includePackage(pkg)));
return reflections.getSubTypesOf(Object.class);
}
public static void test() {
String pkg = "org.apache.tomcat.util";
Set<Class<? extends Object>> clazzSet = getClazzSet(pkg);
for (Class<? extends Object> clazz : clazzSet) {
System.out.println(clazz.getName());
}
}
public static void main(String[] args) {
test();
}
}
于 2013-12-09T17:11:40.733 回答
3
@RunWith(Parameterized.class)使用 Maven 时， Aleksander Blomskøld 的解决方案不适用于我的参数化测试。测试命名正确，并且在找到但未执行的位置：
-------------------------------------------------------
T E S T S
-------------------------------------------------------
Running some.properly.named.test.run.with.maven.SomeTest
Tests run: 0, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 0.123 sec
这里报告了一个类似的问题。
就我而言@Parameters，是在包中创建每个类的实例。在 IDE 中本地运行时，测试运行良好。但是，在运行 Maven 时，没有找到使用 Aleksander Blomskøld 解决方案的类。
我确实使它与以下片段一起工作，该片段的灵感来自 David Pärsson 对 Aleksander Blomskøld 的回答的评论：
Reflections reflections = new Reflections(new ConfigurationBuilder()
.setScanners(new SubTypesScanner(false /* don't exclude Object.class */), new ResourcesScanner())
.addUrls(ClasspathHelper.forJavaClassPath())
.filterInputsBy(new FilterBuilder()
.include(FilterBuilder.prefix(basePackage))));
Set<Class<?>> subTypesOf = reflections.getSubTypesOf(Object.class);
于 2017-06-29T06:17:21.920 回答
2
几乎所有答案都使用Reflections或从文件系统读取类文件。如果您尝试从文件系统中读取类，则在将应用程序打包为 JAR 或其他格式时可能会出错。此外，您可能不想为此目的使用单独的库。
这是另一种纯java方法，不依赖于文件系统。
import javax.tools.JavaFileObject;
import javax.tools.StandardJavaFileManager;
import javax.tools.StandardLocation;
import javax.tools.ToolProvider;
import java.io.File;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.regex.Pattern;
import java.util.stream.Collectors;
import java.util.stream.StreamSupport;
public class PackageUtil {
public static Collection<Class> getClasses(final String pack) throws Exception {
final StandardJavaFileManager fileManager = ToolProvider.getSystemJavaCompiler().getStandardFileManager(null, null, null);
return StreamSupport.stream(fileManager.list(StandardLocation.CLASS_PATH, pack, Collections.singleton(JavaFileObject.Kind.CLASS), false).spliterator(), false)
.map(javaFileObject -> {
try {
final String[] split = javaFileObject.getName()
.replace(".class", "")
.replace(")", "")
.split(Pattern.quote(File.separator));
final String fullClassName = pack + "." + split[split.length - 1];
return Class.forName(fullClassName);
} catch (ClassNotFoundException e) {
throw new RuntimeException(e);
}
})
.collect(Collectors.toCollection(ArrayList::new));
}
}
Java 8 不是必须的。您可以使用 for 循环而不是流。你可以像这样测试它
public static void main(String[] args) throws Exception {
final String pack = "java.nio.file"; // Or any other package
PackageUtil.getClasses(pack).stream().forEach(System.out::println);
}
于 2015-09-28T17:51:49.607 回答
2
我找不到这么简单的东西剪短的工作。所以就在这里，我在搞砸了一段时间后自己做了：
Reflections reflections =
new Reflections(new ConfigurationBuilder()
.filterInputsBy(new FilterBuilder().includePackage(packagePath))
.setUrls(ClasspathHelper.forPackage(packagePath))
.setScanners(new SubTypesScanner(false)));
Set<String> typeList = reflections.getAllTypes();
于 2019-11-18T09:50:09.170 回答
1
如果您没有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。
于 2010-03-03T18:32:21.037 回答
1
值得一提
如果您想拥有某个包下所有类的列表，可以使用Reflection以下方式：
List<Class> myTypes = new ArrayList<>();
Reflections reflections = new Reflections("com.package");
for (String s : reflections.getStore().get(SubTypesScanner.class).values()) {
myTypes.add(Class.forName(s));
}
这将创建一个类列表，稍后您可以根据需要使用它们。
于 2015-12-15T14:51:41.223 回答
1
这是非常有可能的，但是没有像Reflections它这样的额外库很难......
这很难，因为你没有完整的工具来获取类名。
而且，我拿了我ClassFinder班级的代码：
package play.util;
import java.io.File;
import java.io.IOException;
import java.util.ArrayList;
import java.util.Enumeration;
import java.util.List;
import java.util.jar.JarEntry;
import java.util.jar.JarFile;
/**
* Created by LINKOR on 26.05.2017 in 15:12.
* Date: 2017.05.26
*/
public class FileClassFinder {
private JarFile file;
private boolean trouble;
public FileClassFinder(String filePath) {
try {
file = new JarFile(filePath);
} catch (IOException e) {
trouble = true;
}
}
public List<String> findClasses(String pkg) {
ArrayList<String> classes = new ArrayList<>();
Enumeration<JarEntry> entries = file.entries();
while (entries.hasMoreElements()) {
JarEntry cls = entries.nextElement();
if (!cls.isDirectory()) {
String fileName = cls.getName();
String className = fileName.replaceAll("/", ".").replaceAll(File.pathSeparator, ".").substring(0, fileName.lastIndexOf('.'));
if (className.startsWith(pkg)) classes.add(className.substring(pkg.length() + 1));
}
}
return classes;
}
}
于 2017-05-26T13:06:42.600 回答
0
基于@Staale 的回答，为了不依赖第三方库，我将通过检查第一个包的物理位置来实施文件系统方法：
import java.io.File;
import java.io.FileFilter;
import java.util.ArrayList;
...
Class<?>[] foundClasses = new Class<?>[0];
final ArrayList<Class<?>> foundClassesDyn = new ArrayList<Class<?>>();
new java.io.File(
klass.getResource(
"/" + curPackage.replace( "." , "/")
).getFile()
).listFiles(
new java.io.FileFilter() {
public boolean accept(java.io.File file) {
final String classExtension = ".class";
if ( file.isFile()
&& file.getName().endsWith(classExtension)
// avoid inner classes
&& ! file.getName().contains("$") )
{
try {
String className = file.getName();
className = className.substring(0, className.length() - classExtension.length());
foundClassesDyn.add( Class.forName( curPackage + "." + className ) );
} catch (ClassNotFoundException e) {
e.printStackTrace(System.out);
}
}
return false;
}
}
);
foundClasses = foundClassesDyn.toArray(foundClasses);
于 2014-08-29T16:57:38.033 回答
0
纯java：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：为了简化处理错误等的样板，我在这里vavr和lombok库中使用
其他实现可以在我的 GitHub daggerok/java-reflection-find-annotated-classes-or-methods repo 中找到
于 2019-05-27T21:22:11.583 回答
-1
如果您只是想加载一组相关的类，那么 Spring 可以帮助您。
Spring 可以在一行代码中实例化实现给定接口的所有类的列表或映射。列表或映射将包含实现该接口的所有类的实例。
话虽如此，作为从文件系统中加载类列表的替代方法，只需在要加载的所有类中实现相同的接口，而不管包如何，并使用 Spring 为您提供所有这些类的实例。这样，您可以加载（和实例化）所有您想要的类，而不管它们在什么包中。
另一方面，如果您想要将它们全部放在一个包中，那么只需让该包中的所有类都实现给定的接口。
请注意，接口本身不必声明任何方法 - 它可以完全为空。
要注入实现给定接口的类列表，请使用以下代码行...
@Autowired
private List<ISomeInterface> implementationList;
也可以使用 Spring 注入类的 Map。如果有兴趣了解如何阅读文档。
最后，我将提供另一种比搜索整个文件系统树更优雅的解决方案。
创建一个自定义注释来构建应用它的类的目录 - 类似于@ClassCatalog。
于 2017-10-04T22:22:50.170 回答
-5
这是不可能的，因为可能不会加载包中的所有类，而您总是知道类的包。
于 2009-02-06T13:46:48.817 回答