java怎么调用C的dll
我做了1个java调用c++的dll
想做一个java调用C的dll就不知道怎么做了

在xx.c里 写
JNIEXPORT jint JNICALL Java_testdll_getValue
(JNIEnv *, jobject)
这些报错 之前在XX.CPP里写可以 c语言不了解 谁有
java调C的dll的例子呀，或者给我讲讲也行 谢谢
[解决办法]
好像是 System.loadLibrary这个吧。
我们的项目里有一段，贴出来参考一下吧

package org.scavino.twain;

import ins.filemanager.fileuploader.FileUploaderConst;
import ins.filemanager.fileuploader.FileUploaderFrame;
import ins.filemanager.fileuploader.FileUploaderParams;

import java.io.BufferedInputStream;
import java.io.BufferedOutputStream;
import java.io.File;
import java.io.FileOutputStream;
import java.io.InputStream;
import java.net.MalformedURLException;
import java.net.URL;
import java.net.URLConnection;
import java.util.StringTokenizer;

import javax.swing.JOptionPane;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

public class JTwain {
private static final Log logger = LogFactory
.getLog(JTwain.class);

    private static final JTwain mInstance = new JTwain();

    protected final String DLL_NAME = "jtwain";
   
    private JTwain() {    
        initLib();
    }
   
    public static JTwain getInstance(){
        return mInstance;
    }

    public native boolean isTwainAvailble();
        
    public native String[] getAvailableSources();
    
    public native String[] acquire();
    
    public native String[] acquire(String sourceName);

    /*
     * Loads the C/JNI Libray
     */
    private void initLib(){

        try {
        String libraryPath = System.getProperty("java.library.path");

    if ((libraryPath == null) 
[解决办法]
 (libraryPath.trim().length() == 0)) {  
    logger.info("");
    return;
    }

    String systemDir = null;
    String firstEntry = null;
    String original;
    String entry;

    StringTokenizer st = new StringTokenizer(libraryPath, ";");
    int i = 0;
    while (i < st.countTokens()) {
    original = st.nextToken();
    entry = original;
    if (i == 0) { 
 
    firstEntry = entry;
    }
    if (entry.endsWith("\\")) {
    entry = entry.substring(0, entry.length() - 1);
    }
    entry = entry.toLowerCase();
    if (entry.endsWith("windows\\system")) {
    systemDir = original;
    break;
    }
    if (entry.endsWith("winnt\\system32")) {
    systemDir = original;
    break;
    }
    if (entry.endsWith("windows\\system32")) {
    systemDir = original;
    File file = new File(original.replace("System32", "SysWow64"));
    if(file.exists()){
    systemDir = file.getPath();
    }
    break;
    }
    
    i++;
    }
    if (systemDir == null) {
    systemDir = firstEntry;
    }
    installFile(new URL(FileUploaderConst.FileUploadURL), systemDir
    + "/jtwain.dll");
    
            System.loadLibrary(DLL_NAME);
        } catch (MalformedURLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
logger.error(e);
}
        
        finally {
            // Send to your logging subsystem
            System.out.println("Loading : " + DLL_NAME + ".dll");
        }
    }
    
    /**
 * dll
 */
protected static void installFile(URL sourceUrl, String destFileName) {
File destFile = new File(destFileName);
if (!destFile.exists()) {
try {
System.err.println("installing file " + destFileName);
destFile.getParentFile().mkdirs();
URLConnection connection = sourceUrl.openConnection();
InputStream is = connection.getInputStream();
FileOutputStream fos = new FileOutputStream(destFile);
byte[] buff = new byte[8192];
BufferedInputStream in = new BufferedInputStream(is,
buff.length);
BufferedOutputStream out = new BufferedOutputStream(fos,
buff.length);
int i;
int count = 0;
while ((i = in.read(buff, 0, buff.length)) != -1) {
out.write(buff, 0, i);
count += i;
}
in.close();
out.close();
} catch (Exception exception) {
exception.printStackTrace();
logger.error(exception); 
 
}
}
}

}