耶拿从乌龟读取失败

Question

我刚刚将 jena 库导入到 eclipse 以在 rdf-s 上工作，这是我的第一次尝试，但我无法读取 turtle (.ttl) 文件。

我是这样尝试的：

import java.io.*;
import java.util.*;
import com.hp.hpl.jena.rdf.model.*;

public class Simpsons {

public static void main(String[] args) throws IOException {
    Model model=ModelFactory.createDefaultModel();
    model.read(new FileInputStream("simpsons.ttl"),null);

}

}

我得到的错误如下：

Exception in thread "main" org.apache.jena.riot.RiotException: [line: 1, col: 1 ] Content is not allowed in prolog.
at org.apache.jena.riot.system.ErrorHandlerFactory$ErrorHandlerStd.fatal(ErrorHandlerFactory.java:136)
at org.apache.jena.riot.lang.LangRDFXML$ErrorHandlerBridge.fatalError(LangRDFXML.java:252)
at com.hp.hpl.jena.rdf.arp.impl.ARPSaxErrorHandler.fatalError(ARPSaxErrorHandler.java:48)
at com.hp.hpl.jena.rdf.arp.impl.XMLHandler.warning(XMLHandler.java:209)
at com.hp.hpl.jena.rdf.arp.impl.XMLHandler.fatalError(XMLHandler.java:239)
at org.apache.xerces.util.ErrorHandlerWrapper.fatalError(Unknown Source)
at org.apache.xerces.impl.XMLErrorReporter.reportError(Unknown Source)
at org.apache.xerces.impl.XMLErrorReporter.reportError(Unknown Source)
at org.apache.xerces.impl.XMLErrorReporter.reportError(Unknown Source)
at org.apache.xerces.impl.XMLScanner.reportFatalError(Unknown Source)
at org.apache.xerces.impl.XMLDocumentScannerImpl$PrologDispatcher.dispatch(Unknown Source)
at org.apache.xerces.impl.XMLDocumentFragmentScannerImpl.scanDocument(Unknown Source)
at org.apache.xerces.parsers.DTDConfiguration.parse(Unknown Source)
at org.apache.xerces.parsers.DTDConfiguration.parse(Unknown Source)
at org.apache.xerces.parsers.XMLParser.parse(Unknown Source)
at org.apache.xerces.parsers.AbstractSAXParser.parse(Unknown Source)
at com.hp.hpl.jena.rdf.arp.impl.RDFXMLParser.parse(RDFXMLParser.java:151)
at com.hp.hpl.jena.rdf.arp.ARP.load(ARP.java:119)
at org.apache.jena.riot.lang.LangRDFXML.parse(LangRDFXML.java:142)
at org.apache.jena.riot.RDFParserRegistry$ReaderRIOTFactoryImpl$1.read(RDFParserRegistry.java:142)
at org.apache.jena.riot.RDFDataMgr.process(RDFDataMgr.java:859)
at org.apache.jena.riot.RDFDataMgr.read(RDFDataMgr.java:255)
at org.apache.jena.riot.RDFDataMgr.read(RDFDataMgr.java:241)
at org.apache.jena.riot.adapters.RDFReaderRIOT_Web.read(RDFReaderRIOT_Web.java:62)
at com.hp.hpl.jena.rdf.model.impl.ModelCom.read(ModelCom.java:253)
at assignment2.Simpsons.main(Simpsons.java:11)

请帮助我提出一些想法，因为我不知道会出现什么问题，因为这是我第一次尝试 Jena。我还从某个地方得到了一个提示，我应该执行以下操作：：

看来Jena不太擅长发现RDF序列化 单独在文件中使用，特别是对于使用 URL 寻址的文件。一种 解决这个问题的方法是制作一个获取文件的方法 通过使用字符串函数扩展文件名并返回 Jena 预定义字符串中的适当 RDF 序列化格式。 然后，您可以使用您的方法来读取输入和写入文件 以正确的序列化格式。

但我真的不明白我应该如何编写该方法。

Answer 1

The read method you are using 假定输入格式为RDF/XML。

您需要使用other read methods 之一。

原来是这样：

public static void main(String[] args) throws IOException {
    Model model=ModelFactory.createDefaultModel();
    model.read(new FileInputStream("simpsons.ttl"),null,"TTL");
}

Answer 2

以下程序将读取并遍历 TTL 文件

import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import org.apache.jena.graph.Triple ;
import org.apache.jena.riot.RDFDataMgr ;
import org.apache.jena.riot.lang.PipedRDFIterator;
import org.apache.jena.riot.lang.PipedRDFStream;
import org.apache.jena.riot.lang.PipedTriplesStream;

public class ReadingTTL
{
    public static void main(String... argv) {
        final String filename = "yagoTransitiveType2.ttl";

        // Create a PipedRDFStream to accept input and a PipedRDFIterator to
        // consume it
        // You can optionally supply a buffer size here for the
        // PipedRDFIterator, see the documentation for details about recommended
        // buffer sizes
        PipedRDFIterator<Triple> iter = new PipedRDFIterator<>();
        final PipedRDFStream<Triple> inputStream = new PipedTriplesStream(iter);

        // PipedRDFStream and PipedRDFIterator need to be on different threads
        ExecutorService executor = Executors.newSingleThreadExecutor();

        // Create a runnable for our parser thread
        Runnable parser = new Runnable() {

            @Override
            public void run() {
                // Call the parsing process.
                RDFDataMgr.parse(inputStream, filename);
            }
        };

        // Start the parser on another thread
        executor.submit(parser);

        // We will consume the input on the main thread here

        // We can now iterate over data as it is parsed, parsing only runs as
        // far ahead of our consumption as the buffer size allows
        while (iter.hasNext()) {
            Triple next = iter.next();
            // Do something with each triple
            System.out.println("Subject:  "+next.getSubject());
            System.out.println("Object:  "+next.getObject());
            System.out.println("Predicate:  "+next.getPredicate());
            System.out.println("\n");
        }
    }

}