有没有办法让jena将Json-ld读入模型？

Question

我在这里使用的很多东西都不是很有经验。这是针对我们要构建使用语义结构化数据的软件的学校项目。

我以json-ld格式从Frost api（https://frost.met.no/）获取气象数据。我想把它读成耶拿模型。我对jena是否支持这一点感到有些困惑。

import com.mashape.unirest.http.HttpResponse;
import com.mashape.unirest.http.JsonNode;
import com.mashape.unirest.http.Unirest;
import com.mashape.unirest.http.exceptions.UnirestException;
import org.apache.jena.rdf.model.Model;
import org.apache.jena.rdf.model.ModelFactory;

import java.io.ByteArrayInputStream;
import java.io.InputStream;


public class Main {
    public static void main(String[] args) {
        //authentication for the frost api. I have a feeling i shouldn't share this online
        String auth = "######";

        // I use unirest to make the request to the api
        HttpResponse<JsonNode> response = null;
        try {
            response = Unirest.get("https://frost.met.no/sources/v0.jsonld?country=Norge").
                    basicAuth(auth, "").
                    asJson();
        } catch (UnirestException e) {
            e.printStackTrace();
        }

        // Get the data as string. Remove context tag as it gives an error:
        // "org.apache.jena.riot.RiotException: loading remote context failed: https://frost.met.no/schema"
        // I'm assuming this is a problem on the api side. If anyone has any insights feel free to share
        String jsonString = response.getBody().toString();
        jsonString = jsonString.replace("\"@context\":\"https://frost.met.no/schema\",", "");

        // Print the json-ld string. Looks like it should.
        System.out.println(jsonString);

        //convert json-ld string into InputStream as is required by the read() function.
        InputStream targetStream = new ByteArrayInputStream(jsonString.getBytes());
        Model model = ModelFactory.createDefaultModel() ;

        try {
            model.read(targetStream, "", "JSON-LD") ;
        } catch (final Exception e){
            System.out.println(e.toString());
        }

        // Write model to console. This seems to output an empty model
        model.write(System.out, "JSON-LD");

    }
}

响应我看起来像这样：

{
    "@context": "https://frost.met.no/schema",
    "@type": "SourceResponse",
    "apiVersion": "v0",
    "license": "https://creativecommons.org/licenses/by/3.0/no/",
    "createdAt": "2019-03-27T14:00:46Z",
    "queryTime": 0.534,
    "currentItemCount": 1685,
    "itemsPerPage": 1685,
    "offset": 0,
    "totalItemCount": 1685,
    "currentLink": "https://frost.met.no//auth//sources/v0.jsonld?country=Norge",
    "data": [
        {
            "@type": "SensorSystem",
            "id": "SN100",
            "name": "PLASSEN",
            "shortName": "Plassen",
            "country": "Norge",
            "countryCode": "NO",
            "geometry": {
                "@type": "Point",
                "coordinates": [
                    12.5039,
                    61.1349
                ],
                "nearest": false
            },

还有更多，但它只是关于不同SensorSystems的更多数据。

我没有错误，但它输出的模型似乎是空的：

{
  "@id" : "_:b0",
  "@type" : "file:///C:/Users/bm_93/Desktop/Fag/INFO216/SemesterOppgave/SourceResponse"
}

我做得对吗？这是jena支持的吗？

如果没有，有什么办法可以将这个json数据变成jena模型吗？

Answer 1

Jena支持JSON-LD读写。

我们无法查看您尝试阅读的输入，因为它位于登录后面，但通常如果存在@context链接，则解析器需要检索该上下文，否则将无法读取JSON-LD正确。

上下文的URL是https://frost.met.no/schema，但据我所知，这是一个网页的URL，并且没有在那里发布的JSON-LD上下文。所以它看起来像Frost API的一个问题。

您始终可以将响应视为普通JSON ...