java调用linux下的so库

1.编写java类

public class Abc {
    static {
        System.loadLibrary("abc");
    }

    public native static String getAbc();

    public static void main(String s[]) {
        System.out.println(getAbc());
    }
}

终端执行： java Abc.java

再执行：javah Abc 生成Abc.h文件

生成Abc.h的头文件,内容如下:

/* DO NOT EDIT THIS FILE - it is machine generated */
#include </usr/local/jdk1..0_201/include/jni.h>
/* Header for class Abc */

#ifndef _Included_Abc
#define _Included_Abc
#ifdef __cplusplus
extern "C" {
#endif
/*
 * Class:     Abc
 * Method:    getAbc
 * Signature: ()Ljava/lang/String;
 */
JNIEXPORT jstring JNICALL Java_Abc_getAbc
  (JNIEnv *, jclass);

#ifdef __cplusplus
}
#endif
#endif

编写C文件：

#include <stdio.h>
#include "Abc.h"

JNIEXPORT jstring JNICALL Java_Abc_getAbc(JNIEnv *env, jclass t2)
{
    char *ptr = "hello world";

    jstring str ;
    str = (*env)->NewStringUTF(env, ptr);

    return str;
}

生成动态库：gcc test.c -fPIC -shared -o libabc.so

将动态库拷贝至： cp libabc.so /usr/local/jdk1.8.0_201/jre/lib/amd64/

然后终端运行 java Abc

[root@sec javatest]# javac Abc.java

[root@sec javatest]# java Abc

hello world

至此 java调用linux下动态库成功

//测试jstring转char*

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include "Abc.h"

JNIEXPORT jstring JNICALL Java_Abc_getAbc
  (JNIEnv *env, jclass t)
{
    char ptr[] = "hello xxx world";

    jstring str ;
    str = (*env)->NewStringUTF(env, ptr);
    return str;
}

/*
 * Class:     Abc
 * Method:    setBuf
 * Signature: (Ljava/lang/String;)V
 */

char* jstringtochar( JNIEnv *env, jstring jstr )
{
    char* rtn = NULL;
    jclass clsstring = (*env)->FindClass(env,"java/lang/String");
    jstring strencode = (*env)->NewStringUTF(env,"utf-8");
    jmethodID mid = (*env)->GetMethodID(env,clsstring, "getBytes", "(Ljava/lang/String;)[B");
    jbyteArray barr= (jbyteArray)(*env)->CallObjectMethod(env,jstr, mid, strencode);
    jsize alen = (*env)->GetArrayLength(env,barr);
    jbyte* ba = (*env)->GetByteArrayElements(env,barr, JNI_FALSE);
    if (alen > )
    {
   　　 rtn = (char*)malloc(alen + );
   　　 memcpy(rtn, ba, alen);
   　　 rtn[alen] = ;
    }
    (*env)->ReleaseByteArrayElements(env,barr, ba, );
    return rtn;
}

JNIEXPORT void JNICALL Java_Abc_setBuf
  (JNIEnv *env, jclass t, jstring dev)
{
    // jstring 转 char*
   //dev1 = ReleaseStringUTFChars(env, dev);

   char * rtn = NULL;
   rtn = jstringtochar(env, dev);

    printf("[%s]\n", rtn);

}

JNIEXPORT void JNICALL Java_Abc_setBuf2
  (JNIEnv *env, jclass t, jint num)
{
    printf("%d\n", num);
}