在Java中在运行时为本机库添加新路径 [英] Adding new paths for native libraries at runtime in Java

问题描述

是否可以在运行时为本机库添加新路径？
（而不是使用属性java.library.path启动Java），因此在尝试查找时，对 System.loadLibrary（nativeLibraryName）的调用将包含该路径 nativeLibraryName 。
这是可能的，或者这些路径在JVM启动后被冻结了吗？

Is it possible to add a new path for native libraries at runtime ?. (Instead of starting Java with the property java.library.path), so a call to System.loadLibrary(nativeLibraryName) will include that path when trying to find nativeLibraryName. Is that possible or these paths are frozen once the JVM has started ?

推荐答案

没有少量黑客行为似乎是不可能的即访问ClassLoader类的私有字段）

It seems impossible without little hacking (i.e. accessing private fields of the ClassLoader class)

这博客提供了两种方法。

记录中，这是简短版本。

For the record, here is the short version.

选项1：使用新值完全替换java.library.path）

Option 1: fully replace java.library.path with the new value)

public static void setLibraryPath(String path) throws Exception {
    System.setProperty("java.library.path", path);

    //set sys_paths to null so that java.library.path will be reevalueted next time it is needed
    final Field sysPathsField = ClassLoader.class.getDeclaredField("sys_paths");
    sysPathsField.setAccessible(true);
    sysPathsField.set(null, null);
}

选项2：添加新路径当前java.library.path

Option 2: add a new path to the current java.library.path

/**
* Adds the specified path to the java library path
*
* @param pathToAdd the path to add
* @throws Exception
*/
public static void addLibraryPath(String pathToAdd) throws Exception{
    final Field usrPathsField = ClassLoader.class.getDeclaredField("usr_paths");
    usrPathsField.setAccessible(true);

    //get array of paths
    final String[] paths = (String[])usrPathsField.get(null);

    //check if the path to add is already present
    for(String path : paths) {
        if(path.equals(pathToAdd)) {
            return;
        }
    }

    //add the new path
    final String[] newPaths = Arrays.copyOf(paths, paths.length + 1);
    newPaths[newPaths.length-1] = pathToAdd;
    usrPathsField.set(null, newPaths);
}

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