如何获取已加载的JNI库列表？

Question

正如主题所说，Java中是否有一种方法可以获取在任何给定时间加载的所有JNI本机库的列表？

Answer 1

如果您愿意，有一种方法可以确定所有当前加载的本机库。已经卸载的库无法确定。

基于Svetlin Nakov（Extract classes loaded in JVM to single JAR）的工作，我做了一个POC，它给你从应用程序类加载器和当前类的类加载器加载的本机库的名称。

首先是没有bu的简化版本....它处理异常，错误消息，javadoc，....

获取类加载器通过反射

存储已加载的库的私有字段

public class ClassScope {
    private static final java.lang.reflect.Field LIBRARIES;
    static {
        LIBRARIES = ClassLoader.class.getDeclaredField("loadedLibraryNames");
        LIBRARIES.setAccessible(true);
    }
    public static String[] getLoadedLibraries(final ClassLoader loader) {
        final Vector<String> libraries = (Vector<String>) LIBRARIES.get(loader);
        return libraries.toArray(new String[] {});
    }
}

像这样调用上面的

final String[] libraries = ClassScope.getLoadedClasses(ClassLoader.getSystemClassLoader()); //MyClassName.class.getClassLoader()

voilá libraries 包含已加载的本机库的名称。

从here

获取完整的源代码

Answer 2

我建立在jitter's solution之上。这允许您找出谁（ClassLoader，Class）加载每个本机库。

import java.lang.reflect.Field;
import java.util.*;
import java.util.Map.Entry;

/**
 * Helper functions for native libraries.
 * <p/>
 * @author Gili Tzabari
 */
public class NativeLibraries
{
    private final Field loadedLibraryNames;
    private final Field systemNativeLibraries;
    private final Field nativeLibraries;
    private final Field nativeLibraryFromClass;
    private final Field nativeLibraryName;

    /**
     * Creates a new NativeLibraries.
     * <p/>
     * @throws NoSuchFieldException if one of ClassLoader's fields cannot be found
     */
    public NativeLibraries() throws NoSuchFieldException
    {
        this.loadedLibraryNames = ClassLoader.class.getDeclaredField("loadedLibraryNames");
        loadedLibraryNames.setAccessible(true);

        this.systemNativeLibraries = ClassLoader.class.getDeclaredField("systemNativeLibraries");
        systemNativeLibraries.setAccessible(true);

        this.nativeLibraries = ClassLoader.class.getDeclaredField("nativeLibraries");
        nativeLibraries.setAccessible(true);

        Class<?> nativeLibrary = null;
        for (Class<?> nested : ClassLoader.class.getDeclaredClasses())
        {
            if (nested.getSimpleName().equals("NativeLibrary"))
            {
                nativeLibrary = nested;
                break;
            }
        }
        this.nativeLibraryFromClass = nativeLibrary.getDeclaredField("fromClass");
        nativeLibraryFromClass.setAccessible(true);

        this.nativeLibraryName = nativeLibrary.getDeclaredField("name");
        nativeLibraryName.setAccessible(true);
    }

    /**
     * Returns the names of native libraries loaded across all class loaders.
     * <p/>
     * @return a list of native libraries loaded
     */
    public List<String> getLoadedLibraries()
    {
        try
        {
            @SuppressWarnings("UseOfObsoleteCollectionType")
            final Vector<String> result = (Vector<String>) loadedLibraryNames.get(null);
            return result;
        }
        catch (IllegalArgumentException | IllegalAccessException e)
        {
            throw new AssertionError(e);
        }
    }

    /**
     * Returns the native libraries loaded by the system class loader.
     * <p/>
     * @return a Map from the names of native libraries to the classes that loaded them
     */
    public Map<String, Class<?>> getSystemNativeLibraries()
    {
        try
        {
            Map<String, Class<?>> result = new HashMap<>();
            @SuppressWarnings("UseOfObsoleteCollectionType")
            final Vector<Object> libraries = (Vector<Object>) systemNativeLibraries.get(null);
            for (Object nativeLibrary : libraries)
            {
                String libraryName = (String) nativeLibraryName.get(nativeLibrary);
                Class<?> fromClass = (Class<?>) nativeLibraryFromClass.get(nativeLibrary);
                result.put(libraryName, fromClass);
            }
            return result;
        }
        catch (IllegalArgumentException | IllegalAccessException e)
        {
            throw new AssertionError(e);
        }
    }

    /**
     * Returns a Map from the names of native libraries to the classes that loaded them.
     * <p/>
     * @param loader the ClassLoader that loaded the libraries
     * @return an empty Map if no native libraries were loaded
     */
    public Map<String, Class<?>> getNativeLibraries(final ClassLoader loader)
    {
        try
        {
            Map<String, Class<?>> result = new HashMap<>();
            @SuppressWarnings("UseOfObsoleteCollectionType")
            final Vector<Object> libraries = (Vector<Object>) nativeLibraries.get(loader);
            for (Object nativeLibrary : libraries)
            {
                String libraryName = (String) nativeLibraryName.get(nativeLibrary);
                Class<?> fromClass = (Class<?>) nativeLibraryFromClass.get(nativeLibrary);
                result.put(libraryName, fromClass);
            }
            return result;
        }
        catch (IllegalArgumentException | IllegalAccessException e)
        {
            throw new AssertionError(e);
        }
    }

    /**
     * The same as {@link #getNativeLibraries()} except that all ancestor classloaders are processed
     * as well.
     * <p/>
     * @param loader the ClassLoader that loaded (or whose ancestors loaded) the libraries
     * @return an empty Map if no native libraries were loaded
     */
    public Map<String, Class<?>> getTransitiveNativeLibraries(final ClassLoader loader)
    {
        Map<String, Class<?>> result = new HashMap<>();
        ClassLoader parent = loader.getParent();
        while (parent != null)
        {
            result.putAll(getTransitiveNativeLibraries(parent));
            parent = parent.getParent();
        }
        result.putAll(getNativeLibraries(loader));
        return result;
    }

    /**
     * Converts a map of library names to the classes that loaded them to a map of library names to
     * the classloaders that loaded them.
     * <p/>
     * @param libraryToClass a map of library names to the classes that loaded them
     * @return a map of library names to the classloaders that loaded them
     */
    public Map<String, ClassLoader> getLibraryClassLoaders(Map<String, Class<?>> libraryToClass)
    {
        Map<String, ClassLoader> result = new HashMap<>();
        for (Entry<String, Class<?>> entry : libraryToClass.entrySet())
            result.put(entry.getKey(), entry.getValue().getClassLoader());
        return result;
    }

    /**
     * Returns a list containing the classloader and its ancestors.
     * <p/>
     * @param loader the classloader
     * @return a list containing the classloader, its parent, and so on
     */
    public static List<ClassLoader> getTransitiveClassLoaders(ClassLoader loader)
    {
        List<ClassLoader> result = new ArrayList<>();
        ClassLoader parent = loader.getParent();
        result.add(loader);
        while (parent != null)
        {
            result.add(parent);
            parent = parent.getParent();
        }
        return result;
    }
}

Answer 3

由于Nicolas提到Scala，这是通过JRuby进行抖动解决方案的一种方法（在1.6和1.7中测试）：

require 'java'
import 'java.lang.ClassLoader'
f = ClassLoader.java_class.declared_field('loadedLibraryNames')
f.accessible = true
f.value(ClassLoader.system_class_loader).to_array.to_a

Answer 4

在Clojure中，在REPL上复制/粘贴：

(-> (doto (.getDeclaredField ClassLoader "loadedLibraryNames")
      (.setAccessible true))
    (.get (ClassLoader/getSystemClassLoader)))

Answer 5

在Groovy中（在2.3.3中测试）：

libs = ClassLoader.class.getDeclaredField("loadedLibraryNames")
libs.setAccessible(true)
libraries = libs.get(ClassLoader.getSystemClassLoader())

Answer 6

从2019年1月开始，正确的答案（从jdk9 +起）是：无法再获取已加载库列表。

尽管提到的字段（loadedLibraryNames）在hotspot类型的VM中仍然存在，但在其他字段（例如openj9）中则不存在。另外，如果您在jdk9以上版本上尝试此操作，则会在终端上收到警告，表明该访问权限将在Java 12以上版本中撤消：

WARNING: An illegal reflective access operation has occurred
WARNING: Illegal reflective access by <class> (file:<file>) to method|constructor
WARNING: Please consider reporting this to the maintainers of <file>
WARNING: Use --illegal-access=warn to enable warnings of further illegal reflective access operations
WARNING: All illegal access operations will be denied in a future release

说， *此方法仅适用于非常特定的JVM。不要依赖于此，因为有人可能会使用其他成熟的VM，例如openj9，azul，corretto等。 *自Java 9正式发布以来，它将无法正常运行，但将从Java 12开始使JVM崩溃（或产生意外的输出）。