JNI中jstring 、const char* 、string相互转换函数_jni string const char *-优快云博客

char* Jstring2CStr(JNIEnv* env, jstring jstr)

{
char*   rtn   =   NULL;
jclass   clsstring   =   env->FindClass("java/lang/String");
jstring   strencode   =   env->NewStringUTF("GB2312");
jmethodID   mid   =   env->GetMethodID(clsstring,   "getBytes",   "(Ljava/lang/String;)[B");
jbyteArray   barr=   (jbyteArray)env->CallObjectMethod(jstr,mid,strencode);
jsize   alen   =   env->GetArrayLength(barr);
jbyte*   ba   =   env->GetByteArrayElements(barr,JNI_FALSE);
if(alen   >   0)
{
rtn   =   (char*)malloc(alen+1);         //new   char[alen+1];
memcpy(rtn,ba,alen);
rtn[alen]=0;
}
env->ReleaseByteArrayElements(barr,ba,0);
return rtn;
}

std::string jstring2str(JNIEnv* env, jstring jstr)
{
    char*   rtn   =   NULL;
    jclass   clsstring   =   env->FindClass("java/lang/String");
    jstring   strencode   =   env->NewStringUTF("GB2312");
    jmethodID   mid   =   env->GetMethodID(clsstring,   "getBytes",   "(Ljava/lang/String;)[B");
    jbyteArray   barr=   (jbyteArray)env->CallObjectMethod(jstr,mid,strencode);
    jsize   alen   =   env->GetArrayLength(barr);
    jbyte*   ba   =   env->GetByteArrayElements(barr,JNI_FALSE);
    if(alen   >   0)
    {
        rtn   =   (char*)malloc(alen+1);
        memcpy(rtn,ba,alen);
        rtn[alen]=0;
    }
    env->ReleaseByteArrayElements(barr,ba,0);
    std::string stemp(rtn);
    free(rtn);
    return   stemp;

}

 
  jstring str2jstring(JNIEnv* env, 
  const  
  char 
  * pat) 
 
  { 
 
  //定义java String类 strClass 
 
  jclass strClass = (env)->FindClass( 
  "Ljava/lang/String;" 
  ); 
 
  //获取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(strClass,  
  "<init>" 
  , 
  "([BLjava/lang/String;)V" 
  ); 
 
  //建立byte数组 
 
  jbyteArray bytes = (env)->NewByteArray(strlen(pat)); 
 
  //将char* 转换为byte数组 
 
  (env)->SetByteArrayRegion(bytes, 
  0 
  , 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( 
  "GB2312" 
  ); 
 
  //将byte数组转换为java String,并输出 
 
  return  
  (jstring)(env)->NewObject(strClass, ctorID, bytes, encoding); 
 
  }