JNI里面处理 C和java字符串互相转换

/*
将 String 类型转成 char*
*/
char*   Jstring2CStr(JNIEnv*   env,   jstring   jstr)
{
char*   rtn   =   NULL;
jclass   clsstring   =   (*env)->FindClass(env,"java/lang/String");
jstring   strencode   =  (*env)->NewStringUTF(env,"GB2312");
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   >   0)
{
rtn   =   (char*)malloc(alen+1);         //new   char[alen+1];
memcpy(rtn,ba,alen);
rtn[alen]=0;
}
(*env)->ReleaseByteArrayElements(env,barr,ba,0);

return rtn;
}

/**
将char* 转成 其他类型
*/
jstring CStr2Jstring( JNIEnv* env, const char* pat )
{
//定义java String类 strClass
jclass strClass = (*env)->FindClass(env,"Ljava/lang/String;");
//获取java String类方法String(byte[],String)的构造器,用于将本地byte[]数组转换为一个新String
jmethodID ctorID = (*env)->GetMethodID(env,strClass, "<init>", "([BLjava/lang/String;)V");
//建立byte数组
jbyteArray bytes = (*env)->NewByteArray(env,(jsize)strlen(pat));
//将char* 转换为byte数组
(*env)->SetByteArrayRegion(env,bytes, 0, (jsize)strlen(pat), (jbyte*)pat);
//设置String, 保存语言类型,用于byte数组转换至String时的参数
jstring encoding = (*env)->NewStringUTF(env,"GB2312");
//将byte数组转换为java String,并输出
return (jstring)(*env)->NewObject(env,strClass, ctorID, bytes, encoding);

}