java.lang.UnsatisfiedLinkError 在 java.library.path 中没有 *****.dll [英] java.lang.UnsatisfiedLinkError no *****.dll in java.library.path

问题描述

如何在我的 Web 应用程序中加载自定义 dll 文件?我尝试了以下方法:

How can I load a custom dll file in my web application? I've tried the following:

• 复制了 system32 文件夹中所有必需的 dll 并尝试在 Servlet 构造函数 System.loadLibrary
中加载其中之一
• 将所需的 dll 复制到 tomcat_home/shared/lib 和 tomcat_home/common/lib

• Copied all required dlls in system32 folder and tried to load one of them in Servlet constructor System.loadLibrary
• Copied required dlls into tomcat_home/shared/lib and tomcat_home/common/lib

所有这些dll都在网络应用程序的WEB-INF/lib

All these dlls are in WEB-INF/lib of the web-application

推荐答案

为了使 System.loadLibrary() 工作，库(在 Windows 上，DLL)必须位于某个目录中在您的 PATH 或 在 java.library.path 系统属性中列出的路径上(因此您可以像 java 一样启动 Java -Djava.library.path=/path/to/dir).

In order for System.loadLibrary() to work, the library (on Windows, a DLL) must be in a directory somewhere on your PATH or on a path listed in the java.library.path system property (so you can launch Java like java -Djava.library.path=/path/to/dir).

此外，对于loadLibrary()，您指定库的基本名称，末尾没有.dll.因此，对于 /path/to/something.dll，您只需使用 System.loadLibrary("something").

Additionally, for loadLibrary(), you specify the base name of the library, without the .dll at the end. So, for /path/to/something.dll, you would just use System.loadLibrary("something").

您还需要查看您得到的确切 UnsatisfiedLinkError.如果它说:

You also need to look at the exact UnsatisfiedLinkError that you are getting. If it says something like:

Exception in thread "main" java.lang.UnsatisfiedLinkError: no foo in java.library.path

然后它在您的 PATH 或 java.library.path 中找不到 foo 库 (foo.dll).如果它说:

then it can't find the foo library (foo.dll) in your PATH or java.library.path. If it says something like:

Exception in thread "main" java.lang.UnsatisfiedLinkError: com.example.program.ClassName.foo()V

那么库本身就有问题，因为 Java 无法将应用程序中的本机 Java 函数映射到其实际的本机对应物.

then something is wrong with the library itself in the sense that Java is not able to map a native Java function in your application to its actual native counterpart.

首先，我会在您的 System.loadLibrary() 调用周围放置一些日志，以查看它是否正确执行.如果它抛出异常或者不在实际执行的代码路径中，那么你总是会得到上面解释的后一种UnsatisfiedLinkError.

To start with, I would put some logging around your System.loadLibrary() call to see if that executes properly. If it throws an exception or is not in a code path that is actually executed, then you will always get the latter type of UnsatisfiedLinkError explained above.

作为旁注，大多数人将他们的 loadLibrary() 调用放入具有本机方法的类中的静态初始化块中，以确保它始终只执行一次:

As a sidenote, most people put their loadLibrary() calls into a static initializer block in the class with the native methods, to ensure that it is always executed exactly once:

class Foo {

    static {
        System.loadLibrary('foo');
    }

    public Foo() {
    }

}

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