xml-parsing – 使用JAXB部分解组XML以跳过某些xmlElement

我想使用JAXB将XML文件解组为java对象. XML文件非常大,包含一些我想在某些情况下跳过的节点,以提高性能,因为客户端java程序无法编辑这些元素.

示例XML如下：

<Example id="10" date="1970-01-01" version="1.0"> 
    <Properties>...</Properties>
    <Summary>...</Summary>
    <RawData>
        <Document id="1">...</Document>
        <Document id="2">...</Document>
        <Document id="3">...</Document>
        ------
        ------
    </RawData>
    <Location></Location>
    <Title></Title>
    ----- // more elements
</Example>

我有两个用例：

> unmarshal into Example对象,其中包含Properties,Summaries,RawData等,而不跳过任何RawData. (已完成此部分)
> unmarshal into Example对象,不包括RawData.嵌套在RawData中的元素非常大,因此不希望在此用例中阅读此内容.

现在我想解组XML,以便可以跳过RawData.我尝试过this link提供的技术.

使用上面链接中提供的技术也会跳过RawData之后的所有元素.

我已使用以下代码修复了XMLEventReader的问题：

public class PartialXmlEventReader implements XMLEventReader {

private final XMLEventReader reader;
private final QName qName;
private boolean skip = false;

public PartialXmlEventReader(final XMLEventReader reader,final QName element) {
    this.reader = reader;
    this.qName = element;
}

@Override
public String getElementText() throws XMLStreamException {
    return reader.getElementText();
}

@Override
public Object getProperty(final String name) throws IllegalArgumentException {
    return reader.getProperty(name);
}

@Override
public boolean hasNext() {
    return reader.hasNext();
}

@Override
public XMLEvent nextEvent() throws XMLStreamException {
    while (iSEOf(reader.peek())) {
        reader.nextEvent();
    }

    return reader.nextEvent();
}

@Override
public XMLEvent nextTag() throws XMLStreamException {
    return reader.nextTag();
}

@Override
public XMLEvent peek() throws XMLStreamException {
    return reader.peek();
}

@Override
public Object next() {
    return reader.next();
}

@Override
public void remove() {
    reader.remove();
}

@Override
public void close() throws XMLStreamException {
    reader.close();
}

private boolean iSEOf(final XMLEvent e) {
    boolean returnValue = skip;
    switch (e.getEventType()) {
    case XMLStreamConstants.START_ELEMENT:
        final StartElement se = (StartElement) e;
        if (se.getName().equals(qName)) {
            skip = true;
            returnValue = true;
        }
        break;
    case XMLStreamConstants.END_ELEMENT:
        final EndElement ee = (EndElement) e;
        if (ee.getName().equals(qName)) {
            skip = false;
        }
        break;
    }
    return returnValue;
}

}

虽然Unmarshalling只是将这个eventReader传递给unmarshal方法

final JAXBContext context = JAXBContext.newInstance(classes);
    final Unmarshaller um = context.createUnmarshaller();
    Reader reader = null;
    try {
        reader = new BufferedReader(new FileReader(xmlFile));
        final QName qName = new QName("RawData");
        final XMLInputFactory xif = XMLInputFactory.newInstance();
        final XMLEventReader xmlEventReader = xif.createXMLEventReader(reader);
        final Example example =
                (Example) um.unmarshal(new PartialXmlEventReader(xmlEventReader,qName));
        }
    } finally {
        IoUtils.closeQuietly(reader);
    }

原文地址：https://www.jb51.cc/xml/293132.html