JNA示例程序java.lang.NoClassDefFoundError [英] JNA example program java.lang.NoClassDefFoundError

问题描述

我可以编译这个JNA示例代码（来自 https://github.com/的第2步） twall / jna /＃getting_started ）：

I can compile this JNA example code (from step 2 of https://github.com/twall/jna/#getting_started):

package com.sun.jna.examples;

import com.sun.jna.Library;
import com.sun.jna.Native;
import com.sun.jna.Platform;

/** Simple example of JNA interface mapping and usage. */
public class HelloWorld {

    // This is the standard, stable way of mapping, which supports extensive
    // customization and mapping of Java to native types.
    public interface CLibrary extends Library {
        CLibrary INSTANCE = (CLibrary)
            Native.loadLibrary((Platform.isWindows() ? "msvcrt" : "c"),
                               CLibrary.class);

        void printf(String format, Object... args);
    }

    public static void main(String[] args) {
        CLibrary.INSTANCE.printf("Hello, World\n");
        for (int i=0;i < args.length;i++) {
            CLibrary.INSTANCE.printf("Argument %d: %s\n", i, args[i]);
        }
    }
}

...使用 javac -classpath。：jna.jar -g HelloWorld.java 没有错误。 （我现在下载了jna.jar并将它放在与HelloWorld.java相同的目录中。）

...using javac -classpath .:jna.jar -g HelloWorld.java without error. (I downloaded jna.jar and put it in the same directory as HelloWorld.java for now.)

但是当我使用 java运行它时 - classpath。：jna.jar HelloWorld ，我得到：

But when I run it using java -classpath .:jna.jar HelloWorld, I get:

Exception in thread "main" java.lang.NoClassDefFoundError: HelloWorld (wrong name: com/sun/jna/examples/HelloWorld)
    at java.lang.ClassLoader.defineClass1(Native Method)
    at java.lang.ClassLoader.defineClass(ClassLoader.java:620)
    at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:124)
    at java.net.URLClassLoader.defineClass(URLClassLoader.java:260)
    at java.net.URLClassLoader.access$100(URLClassLoader.java:56)
    at java.net.URLClassLoader$1.run(URLClassLoader.java:195)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.net.URLClassLoader.findClass(URLClassLoader.java:188)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:306)
    at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:268)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:251)
    at java.lang.ClassLoader.loadClassInternal(ClassLoader.java:319)

我在Mac OS X和Linux上得到完全相同的异常。

I get the exact same exception on Mac OS X and Linux.

如何让它运行？

推荐答案

这个例子（以及绝大多数java类）使用套餐：

This example (as well as vast majority of java classes) uses packages:

package com.sun.jna.examples;

为了正确编译/运行它，你需要从root文件夹运行javac / java （例如com所在的文件夹）：

In order to compile / run it properly you need to run javac / java from the "root" folder (e.g. folder where "com" is located):

假设您有一个名为 examples 的文件夹。您将 jna.jar 和源代码都放在其中保留文件夹结构：

Let's say you have a folder called examples. You'd put both the jna.jar and the source code in it preserving folder structure:

/examples
 jna.jar
 /com
   /sun
      /jna
         /examples
           HelloWorld.java

您使用以下编译和运行：

You compile and run using:

javac -classpath .:jna.jar -g com/sun/jna/examples/HelloWorld.java

java -classpath .:jna.jar com.sun.jna.examples.HelloWorld

注意前一种情况下的路径分隔符和后者中的点。

Note the path separators in the former case and dots in the latter.

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