用C如何编写给java使用的动态库

//1:编写[CallC.java],用于生成C头文件,C包含此头文件编写方法

//CallC.java
    public class CallC
    {
        static
        {
            System.loadLibrary("useC");  //注册库文件名、C生成的库文件在windows下为useC.dll linux下生成为libuseC.so
         }
        //声明的本地方法,可以写多个
        public  staitc native int useC(int flag,String path,String action);
           
    }

//2:执行[javac CallC.java] ，生成CallC.class

//3:执行[javah -classpath . CallC] 生成CallC.h ，制定classpath为当前路径

//4:编写[CallC.cpp]  拷贝jin.h和jin_md.h到代码目录 修改CallC.h 里面头文件, 如果系统有这些头文件则不需处理

//CallC.cpp
#include "CallC.h"

#include <stdio.h>
#include <stdlib.h>

JNIEXPORT jint JNICALL Java_CallC_useC
  (JNIEnv * env , jclass arg, jint jmethods , jstring jname, jstring jparam)
{
    unsigned char *name = NULL;
    unsigned char *param = NULL;
    int methods = jmethods;
    char cmd_buf[256] = {0};\
    int nRet = 0 ;
    
    if(jparam)
    {
        name =  (unsigned char *)env->GetStringUTFChars( jname, JNI_FALSE );
    }
    if(jparam)
    {
        param = (unsigned char *)env->GetStringUTFChars( jparam, JNI_FALSE );
    }
    
     printf("name = %s\n",name); 
   printf("param = %s\n",param); 
   printf("methods = %d\n" , methods);
   
    
    
    switch(jmethods)
    {
        case 1:
            {
                sprintf(cmd_buf,"%s %s" ,name ,  param);
                printf("%s\n" , cmd_buf);
                system(cmd_buf);
                break;
            }
        default :
            {
                nRet = 1;
                break;
            }
    }

  
   
     // 通知虚拟机本地代码不再需要通过 str 访问 Java 字符串。
  env->ReleaseStringUTFChars( jname, (const char *)name ); 
  env->ReleaseStringUTFChars( jparam, (const char *)param );
    return 0;  

}

 

//5:执行[g++ -Wl,--kill-at -shared -fPIC -o  useC.dll CallC.cpp] 编译代码，生成useC.dll  

//6:编写[UseC.java]测试代码

public class UseC
{
    public static void main(String argv[])
    {
          int result = CallC.useC(1 , "dir" , "/a:-d");    
          System.out.print(result);
    }
}

//7:执行[javac -cp . UseC.java]编译java测试源码  

//8:执行[java -Djava_library.path=. -cp . UseC]运行java程序测试动态库

//参考资料 

windows下安装gcc编译环境  http://tieba.baidu.com/p/2826016538

linux下 java JNI调用C语言动态链接库 - JonnyWei的专  http://blog.csdn.net/xiaojianpitt/article/details/5652223

java.lang.UnsatisfiedLinkError解决方法汇集    http://blog.csdn.net/niuxinlong/article/details/4176612