java 为什么我使用本机代码收到此 UnsatisfiedLinkError？

Why am I getting this UnsatisfiedLinkError with native code?

提问by KNewton

I have a library called HelloWorld.so and a program HelloWorld.java with this content:

我有一个名为 HelloWorld.so 的库和一个包含以下内容的程序 HelloWorld.java：

class HelloWorld {
     private native void print();
     public static void main(String[] args) {
         new HelloWorld().print();
     }
     static {
         System.loadLibrary("HelloWorld");
     }
 }

Now when I try to run HelloWorld.java I get this error:

现在，当我尝试运行 HelloWorld.java 时，出现此错误：

$ /usr/java1.4/bin/java HelloWorld
Exception in thread "main"
java.lang.UnsatisfiedLinkError: no HelloWorld in java.library.path
        at java.lang.ClassLoader.loadLibrary(ClassLoader.java:1491)
        at java.lang.Runtime.loadLibrary0(Runtime.java:788)
        at java.lang.System.loadLibrary(System.java:834)
        at HelloWorld.<clinit>(HelloWorld.java:7)

Any tips?

有小费吗？

采纳答案by KNewton

@mmyers Thank you for responding. We found out that all we had to do was change System.loadLibrary to System.load and pass the full path + filename as argument, worked like a charm.

@mmyers 感谢您的回复。我们发现我们所要做的就是将 System.loadLibrary 更改为 System.load 并将完整路径 + 文件名作为参数传递，就像一个魅力。

Even before doing so, we tried using the "-D" parameter and setting LD_LIBRARY_PATH but we weren't successful.

甚至在这样做之前，我们尝试使用“-D”参数并设置 LD_LIBRARY_PATH 但我们没有成功。

Go figure! :)

去搞清楚！:)

Thanks again, Karen

再次感谢，凯伦

回答by Gonnix

I think some points are helpful when getting this error:

我认为在收到此错误时有些要点会有所帮助：

1. Check consistency of function name in .c files and generated files (.h)
2. Name of jni library based on OS. Ex: In HelloWorld.java,System.loadLibrary("HelloWorld");
   • Solaris: libHelloWorld.so
   • Linux: libHelloWorld.so
   • Win: HelloWorld.dll
   • Mac: libHelloWorld.jnilib
3. When running, add -Djava.library.path=PATH. PATHto place where you put your jni library

1. 检查.c 文件和生成的文件 (.h)中函数名称的一致性
2. 基于操作系统的 jni 库名称。例如：在 HelloWorld.java 中，System.loadLibrary("HelloWorld");
   • 索拉里斯： libHelloWorld.so
   • Linux： libHelloWorld.so
   • 赢： HelloWorld.dll
   • 苹果电脑： libHelloWorld.jnilib
3. 运行时，添加-Djava.library.path=PATH. PATH放置您放置 jni 库的位置

Here is my reference: https://blogs.oracle.com/moonocean/entry/a_simple_example_of_jni

这是我的参考：https: //blogs.oracle.com/moonocean/entry/a_simple_example_of_jni

回答by Austin Adams

I had this problem and fixed it by renaming my library to libHelloWorld.soand following Michael Myers's suggestion. I'm on Arch Linux 64-bit.

我遇到了这个问题，并通过将我的库重命名为libHelloWorld.so并遵循 Michael Myers 的建议来修复它。我在 Arch Linux 64 位上。

HelloWorld.c:

HelloWorld.c：

#include <jni.h>
#include <stdio.h>
#include "HelloWorld.h"

/* shamelessly stolen from the book 'The Java Native Interface: Programmer's
   Guide and Specification' */
JNIEXPORT void JNICALL
Java_HelloWorld_print (JNIEnv *env, jobject obj) {
    printf("Hello World!\n");
}

HelloWorld.java:

HelloWorld.java：

class HelloWorld {
     private native void print();
     public static void main(String[] args) {
         new HelloWorld().print();
     }
     static {
         System.loadLibrary("HelloWorld");
     }
 }

Building and testing:

构建和测试：

$ javac HelloWorld.java
$ javah -classpath . HelloWorld
$ gcc -shared -fPIC -I $JAVA_HOME/include -I $JAVA_HOME/include/linux HelloWorld.c -o libHelloWorld.so
$ java -classpath . -Djava.library.path=. HelloWorld
Hello World!

tl;dr: put libat the beginning of the library's filename

tl; dr：放在lib库文件名的开头

回答by Michael Myers

Where is HelloWorld.so located? You probably need to specify its parent directory using the command-line parameter "-Djava.library.path".

HelloWorld.so 位于哪里？您可能需要使用命令行参数指定其父目录"-Djava.library.path"。

For example, if it's in "/path/libs/HelloWorld.so", add -Djava.library.path=/path/libsas an option when invoking java. For instance, it's "-Djava.library.path=lib"on one of my projects.

例如，如果它在 中"/path/libs/HelloWorld.so"，则-Djava.library.path=/path/libs在调用java. 例如，它"-Djava.library.path=lib"在我的一个项目中。

Edit:Dan Dyer points out that the environment variable LD_LIBRARY_PATHalso can be used for this.

编辑：Dan Dyer 指出环境变量LD_LIBRARY_PATH也可用于此目的。