Question

我正在尝试实现一个从套接字读取并返回完整XML文档的XMLReader：

import java.io.File;
import java.io.FileInputStream;
import java.io.InputStream;
import java.util.Stack;
import javax.xml.stream.XMLEventReader;
import javax.xml.stream.XMLInputFactory;
import javax.xml.stream.XMLStreamException;
import javax.xml.stream.events.XMLEvent;

public class MyXmlReader {
  private final XMLInputFactory infactory = XMLInputFactory.newInstance();
  private final InputStream inStream;

  public MyXmlReader(final InputStream inStream){
    this.inStream= inStream;
  }

  private String readUntilEndOfXml() throws XMLStreamException{
    final XMLEventReader eventReader= infactory.createXMLEventReader(inStream);

    final StringBuilder sb= new StringBuilder();
    final Stack<String> openTags= new Stack<String>();
    boolean endOfXml= false;
    while (eventReader.hasNext() && !endOfXml){
      final XMLEvent nextEvent= eventReader.nextEvent();
      sb.append(nextEvent.toString());
      if (nextEvent.isStartElement()){
        openTags.add(nextEvent.toString());
      }else if (nextEvent.isEndElement()){
        openTags.pop();
        if (openTags.isEmpty()){
          endOfXml= true;
        }
      }
    }

    eventReader.close();
    return sb.toString();
  }

  public static void main(String[] args) throws Exception {
    final File f= new File("/tmp/double.xml");
    final MyXmlReader r= new MyXmlReader(new FileInputStream(f));

    String xml;
    while((xml= r.readUntilEndOfXml()) != null){
      System.out.println("Got an XML");
    }
  }
}

但是，如果到达文件的末尾（或从套接字读取时套接字已关闭），我会收到以下异常：

javax.xml.stream.XMLStreamException: ParseError at [row,col]:[1,1]
Message: Premature end of file.
    at com.sun.org.apache.xerces.internal.impl.XMLStreamReaderImpl.next(XMLStreamReaderImpl.java:594)
    at com.sun.xml.internal.stream.XMLEventReaderImpl.nextEvent(XMLEventReaderImpl.java:85)
    at com.siemens.bfr2.plato.MyXmlReader.readUntilEndOfXml(MyXmlReader.java:40)
    at com.siemens.bfr2.plato.MyXmlReader.main(MyXmlReader.java:125)

我期待检查eventReader.hasNext()就足够了。为什么eventReader.hasNext()仍在返回true，实际上没有更多数据？

XMLEventReader：在文件末尾避免ParseError

0 个答案: