尝试解析XML文件时Java内存不足

Question

I have a fairly large XML file (~280 MB) and each row in the XML file has many attributes, I want to extract 3 attributes from it and store it somewhere. But I ran out of memory when I do that. My code looks like this:

File xmlFile = new File(xml);
DocumentBuilderFactory dbFactory = DocumentBuilderFactory.newInstance();
DocumentBuilder dBuilder = dbFactory.newDocumentBuilder();
Document doc = null;
try {
    doc = dBuilder.parse(xmlFile);
} catch (SAXException e) {
    e.printStackTrace();
} catch (IOException e) {
    e.printStackTrace();
}

NodeList nList = doc.getElementsByTagName("row");
for (int index = 0; index < nList.getLength(); index++) {
    Node nNode = nList.item(index);
    if (nNode.getNodeType() == Node.ELEMENT_NODE) {
        System.out.print("F1 : " + 
            nNode.getAttributes().getNamedItem("F1").getTextContent());
        System.out.print(" F2: " + 
            nNode.getAttributes().getNamedItem("F2").getTextContent());
        System.out.println(" F3: " + 
            nNode.getAttributes().getNamedItem("F3").getTextContent());
    }
}

This is the error I get:

Exception in thread "main" java.lang.OutOfMemoryError: Java heap space
    at com.sun.org.apache.xerces.internal.dom.DeferredDocumentImpl.getNodeObject(DeferredDocumentImpl.java:974)
    at com.sun.org.apache.xerces.internal.dom.DeferredElementImpl.synchronizeData(DeferredElementImpl.java:121)
    at com.sun.org.apache.xerces.internal.dom.ElementImpl.getTagName(ElementImpl.java:314)
    at com.sun.org.apache.xerces.internal.dom.DeepNodeListImpl.nextMatchingElementAfter(DeepNodeListImpl.java:199)
    at com.sun.org.apache.xerces.internal.dom.DeepNodeListImpl.item(DeepNodeListImpl.java:146)
    at com.sun.org.apache.xerces.internal.dom.DeepNodeListImpl.getLength(DeepNodeListImpl.java:117)
    at Parser.parsePosts(Parser.java:55)
    at Parser.main(Parser.java:72)

How do I change it to prevent going over too much space?

EDIT: Wrote a new parser using SAX, seems to get the job done. The code is:

try {

        SAXParserFactory factory = SAXParserFactory.newInstance();
        SAXParser saxParser = factory.newSAXParser();

        DefaultHandler handler = new DefaultHandler() {
            public void startElement(String uri, String localName,String qName, 
                    Attributes attributes) throws SAXException {
                System.out.print(attributes.getValue("F1") + " ");
                System.out.print(attributes.getValue("F2") + " ");
                System.out.println(attributes.getValue("F3"));
            }
        };

        saxParser.parse("file.xml", handler);

    } catch (Exception e) {
        e.printStackTrace();
    }

Answer 1

There are two ways to solve your problem. You can either increase the maximum memory on your application or use sax to parse your xml file.

Answer 2

Try the parameter -Xmx<size> when you run to increase the size of your heap.

Eg, java -Xmx500m <filename>

Answer 3

您将不得不增加Java VM的内存限制：设置-Xmx = 2048或其他足够大的值。