递归XML解析器

时间:2012-11-08 18:43:03

标签: java xml recursion xml-parsing

我有以下xml文件:

<?xml version="1.0"?>
<CONFIG>
    <FUNCTION>
        <NAME>FUNCT0</NAME>
        <CALLS>
            <FUNCTION>
            <NAME>FUNCT0_0</NAME>
            </FUNCTION>
        </CALLS>
        <CALLS>
            <FUNCTION>
            <NAME>FUNCT0_1</NAME>
            </FUNCTION>
        </CALLS>
    </FUNCTION>
    <FUNCTION>
        <NAME>FUNCT1</NAME>
    </FUNCTION>
</CONFIG>

我有一个名为FunctionInfo的类,它存储一个函数的名称,还包含一个ArrayList,用于包含函数调用的子函数。

我希望最终得到一个包含顶级函数的ArrayList,然后以递归方式将它们的子函数存储在对象中。

我需要这个才能无限期地递归。

我的问题是编写可以执行此任务的递归XML解析器的最简单方法是什么?

编辑:我在Java工作。

谢谢:)

2 个答案:

答案 0 :(得分:6)

除非您的文件很大,否则您可以使用java DOM解析器(DOM解析器将文件保存在内存中)

给定一个节点(从根开始),你可以枚举它的子节点,然后递归地在每个子节点上调用相同的函数。

import java.io.IOException;
import java.util.ArrayList;
import java.util.List;

import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.parsers.ParserConfigurationException;

import org.w3c.dom.Document;
import org.w3c.dom.Element;
import org.w3c.dom.Node;
import org.w3c.dom.NodeList;
import org.xml.sax.SAXException;

public class RecursiveDOM {
    public static void main(final String[] args) throws SAXException, IOException, ParserConfigurationException {
        new RecursiveDOM("file.xml");
    }

    public RecursiveDOM(final String file) throws SAXException, IOException, ParserConfigurationException {
        final DocumentBuilderFactory dbfac = DocumentBuilderFactory.newInstance();
        final DocumentBuilder docBuilder = dbfac.newDocumentBuilder();
        final Document doc = docBuilder.parse(this.getClass().getResourceAsStream(file));
        final List<String> l = new ArrayList<String>();
        parse(doc, l, doc.getDocumentElement());
        System.out.println(l);
    }

    private void parse(final Document doc, final List<String> list, final Element e) {
        final NodeList children = e.getChildNodes();
        for (int i = 0; i < children.getLength(); i++) {
            final Node n = children.item(i);
            if (n.getNodeType() == Node.ELEMENT_NODE) {
                list.add(n.getNodeName());
                parse(doc, list, (Element) n);
            }
        }
    }

}

结果:

[FUNCTION, NAME, CALLS, FUNCTION, NAME, CALLS, FUNCTION, NAME, FUNCTION, NAME]

答案 1 :(得分:1)

此外,您可以考虑使用JAXB(将类映射到XML),这将导致java类的树,如果正确实现,每个类都可以实现特定类型的函数,以便可以递归地“计算”树。 / p>

这是一个基本的JAXB实现,使用Config.unmarshal从InputStream重建它:

import java.io.OutputStream;
import java.io.Reader;

import javax.xml.bind.JAXBContext;
import javax.xml.bind.JAXBException;
import javax.xml.bind.Marshaller;
import javax.xml.bind.Unmarshaller;
import javax.xml.bind.annotation.XmlElement;
import javax.xml.bind.annotation.XmlRootElement;

public class TestJAXB {

    public static void main(final String[] args) throws JAXBException {
        final Function e5 = new Function("N5", null);
        final Function e6 = new Function("N6", null);
        final Function e4 = new Function("N4", null);
        final Function e2 = new Function("N2", ((new Call[] { new Call(e4) })));
        final Function e3 = new Function("N3", ((new Call[] { new Call(e5) })));
        final Function e1 = new Function("N1", ((new Call[] { new Call(e2), new Call(e3) })));
        new Config(new Function[] { e1, e6 }).marshall(System.out);
    }

    @XmlRootElement(name = "CONFIG")
    static class Config {
        @XmlElement(name = "FUNCTION")
        private Function[] functions;

        public Config(final Function[] f) {
            this.functions = f;
        }

        protected Config() {
        }

        public void marshall(final OutputStream out) throws JAXBException {
            final JAXBContext jaxbContext = JAXBContext.newInstance(this.getClass());
            final Marshaller marshaller = jaxbContext.createMarshaller();
            marshaller.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT, Boolean.TRUE);
            marshaller.marshal(this, out);
        }

        public final static Config unmarshall(final Reader r) throws JAXBException {
            final JAXBContext jaxbContext = JAXBContext.newInstance(Config.class);
            final Unmarshaller unmarshaller = jaxbContext.createUnmarshaller();
            return (Config) unmarshaller.unmarshal(r);
        }

    }

    @XmlRootElement(name = "FUNCTION")
    static class Function {
        @XmlElement(name = "NAME")
        String name;

        @XmlElement(name = "CALLS")
        Call[] calls;

        public Function(final String name, final Call[] calls) {
            this.name = name;
            this.calls = calls;
        }

        protected Function() {
        }

    }

    @XmlRootElement(name = "CALL")
    static class Call {
        @XmlElement(name = "FUNCTION")
        Function f;

        protected Call() {
        }

        public Call(final Function f) {
            this.f = f;
        }

    }
}