更好的解析xml的方法 [英] Better way to parse xml

问题描述

我多年来一直在解析这样的XML，我不得不承认，当不同元素的数量变得越来越大时，我发现它有点无聊而且筋疲力尽，这就是我的意思，样本虚拟XML：

I've been parsing XML like this for years, and I have to admit when the number of different element becomes larger I find it a bit boring and exhausting to do, here is what I mean, sample dummy XML:

<?xml version="1.0"?>
<Order>
    <Date>2003/07/04</Date>
    <CustomerId>123</CustomerId>
    <CustomerName>Acme Alpha</CustomerName>
    <Item>
        <ItemId> 987</ItemId>
        <ItemName>Coupler</ItemName>
        <Quantity>5</Quantity>
    </Item>
    <Item>
        <ItemId>654</ItemId>
        <ItemName>Connector</ItemName>
        <Quantity unit="12">3</Quantity>
    </Item>
    <Item>
        <ItemId>579</ItemId>
        <ItemName>Clasp</ItemName>
        <Quantity>1</Quantity>
    </Item>
</Order>

这是相关部分（使用sax）：

This is relevant part (using sax) :

public class SaxParser extends DefaultHandler {

    boolean isItem = false;
    boolean isOrder = false;
    boolean isDate = false;
    boolean isCustomerId = false;
    private Order order;
    private Item item;

        @Override
    public void startElement(String namespaceURI, String localName, String qName, Attributes atts) {
        if (localName.equalsIgnoreCase("ORDER")) {
            order = new Order();
        }

        if (localName.equalsIgnoreCase("DATE")) {
            isDate = true;
        }

        if (localName.equalsIgnoreCase("CUSTOMERID")) {
            isCustomerId = true;
        }

        if (localName.equalsIgnoreCase("ITEM")) {
            isItem = true;
        }
    }

    public void characters(char ch[], int start, int length) throws SAXException {

        if (isDate){
            SimpleDateFormat formatter = new SimpleDateFormat("yyyy/MM/dd");
            String value = new String(ch, start, length);
            try {
                order.setDate(formatter.parse(value));
            } catch (ParseException e) {
                e.printStackTrace();
            }
        }

        if(isCustomerId){
            order.setCustomerId(Integer.valueOf(new String(ch, start, length)));
        }

        if (isItem) {
            item = new Item();
            isItem = false;
        }



    }

}

我想知道有没有办法摆脱这些随着元素数量不断增长的可怕布尔值。必须有一种更好的方法来解析这个相对简单的xml。只是通过查看执行此任务所需的代码行看起来很丑陋。

I'm wondering is there a way to get rid of these hideous booleans which keep growing with number of elements. There must be a better way to parse this relatively simple xml. Just by looking the lines of code necessary to do this task looks ugly.

目前我正在使用SAX解析器，但我对任何其他建议持开放态度（除了DOM，我无法承受内存解析器，我有大量的XML文件）。

Currently I'm using SAX parser, but I'm open to any other suggestions (other than DOM, I can't afford in memory parsers I have huge XML files).

推荐答案

以下是使用JAXB和StAX的示例。

Here's an example of using JAXB with StAX.

输入文件：

<?xml version="1.0" encoding="UTF-8"?>
<Personlist xmlns="http://example.org">
    <Person>
        <Name>Name 1</Name>
        <Address>
            <StreetAddress>Somestreet</StreetAddress>
            <PostalCode>00001</PostalCode>
            <CountryName>Finland</CountryName>
        </Address>
    </Person>
    <Person>
        <Name>Name 2</Name>
        <Address>
            <StreetAddress>Someotherstreet</StreetAddress>
            <PostalCode>43400</PostalCode>
            <CountryName>Sweden</CountryName>
        </Address>
    </Person>
</Personlist>

Person.java：

Person.java:

@XmlRootElement(name = "Person", namespace = "http://example.org")
public class Person {
    @XmlElement(name = "Name", namespace = "http://example.org")
    private String name;
    @XmlElement(name = "Address", namespace = "http://example.org")
    private Address address;

    public String getName() {
        return name;
    }

    public Address getAddress() {
        return address;
    }
}

Address.java：

Address.java:

public class Address {
    @XmlElement(name = "StreetAddress", namespace = "http://example.org")
    private String streetAddress;
    @XmlElement(name = "PostalCode", namespace = "http://example.org")
    private String postalCode;
    @XmlElement(name = "CountryName", namespace = "http://example.org")
    private String countryName;

    public String getStreetAddress() {
        return streetAddress;
    }

    public String getPostalCode() {
        return postalCode;
    }

    public String getCountryName() {
        return countryName;
    }
}

PersonlistProcessor.java：

PersonlistProcessor.java:

public class PersonlistProcessor {
    public static void main(String[] args) throws Exception {
        new PersonlistProcessor().processPersonlist(PersonlistProcessor.class
                .getResourceAsStream("personlist.xml"));
    }

    // TODO: Instead of throws Exception, all exceptions should be wrapped
    // inside runtime exception
    public void processPersonlist(InputStream inputStream) throws Exception {
        JAXBContext jaxbContext = JAXBContext.newInstance(Person.class);
        XMLStreamReader xss = XMLInputFactory.newFactory().createXMLStreamReader(inputStream);
        // Create unmarshaller
        Unmarshaller unmarshaller = jaxbContext.createUnmarshaller();
        // Go to next tag
        xss.nextTag();
        // Require Personlist
        xss.require(XMLStreamReader.START_ELEMENT, "http://example.org", "Personlist");
        // Go to next tag
        while (xss.nextTag() == XMLStreamReader.START_ELEMENT) {
            // Require Person
            xss.require(XMLStreamReader.START_ELEMENT, "http://example.org", "Person");
            // Unmarshall person
            Person person = (Person)unmarshaller.unmarshal(xss);
            // Process person
            processPerson(person);
        }
        // Require Personlist
        xss.require(XMLStreamReader.END_ELEMENT, "http://example.org", "Personlist");
    }

    private void processPerson(Person person) {
        System.out.println(person.getName());
        System.out.println(person.getAddress().getCountryName());
    }
}

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