目前列出给定包中所有类的最健壮的机制是ClassGraph，因为它处理尽可能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());
}

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。

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
  }
}

目前列出给定包中所有类的最健壮的机制是ClassGraph，因为它处理尽可能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());
}

是的，你可以使用很少的API，这是我喜欢做的，面对这个问题，我使用hibernate核心&必须找到类，其中注释了某个注释。

使这些自定义注释使用，您将标记哪些类您想要获得。

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 {

}

然后用它来标记你的课

@EntityToBeScanned 
public MyClass{

}

创建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allfoundclassesannotatedwithentitytobescans()方法获取找到的类集。

你将需要下列的参考书目

<!-- 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>