java - 我需要有关如何正确解析的帮助

Question

我正在学习如何进行 XML 解析，并收到了一个解析 XML 文件的作业，如下所示:

<?xml version="1.0" ?>
<deliveries>
    <van id="VID-12345">
        <package>
            <product taxable="true" productName="Headphones" isbn="123456" unitPrice="10.00" quantity="1"/>
            <product taxable="false" productName="Milk" isbn="234567" unitPrice="2.00" quantity="2"/>
            <customer lastName="Adams" firstName="Maurice" streetAddress="123 4th St" zipCode="13126" accountNumber="ACCT-54321"/>
        </package>
        <package>
            <product taxable="true" productName="Snickers" isbn="345678" unitPrice="1.00" quantity="1"/>
            <product taxable="false" productName="Milk" isbn="234567" unitPrice="2.00" quantity="1"/>
            <customer lastName="Baxter" firstName="Robert" streetAddress="234 5th St" zipCode="13126" accountNumber="ACCT-65432"/>
        </package>
    </van>
    <cart id="VID-23456">
        <package>
            <product taxable="true" productName="Snickers" isbn="345678" unitPrice="1.00" quantity="1"/>
            <customer lastName="Charles" firstName="Steven" streetAddress="345 6th St" zipCode="13126" accountNumber="ACCT-76543"/>
        </package>
    </cart>
</deliveries>

我需要将其解析为如下所示:

Van (VID-12345)
    Customers
        Adams, Maurice at 123 4th St, 13126
        Baxter, Robert at 234 5th St, 13126
Cart (VID-23456)
    Customers
        Charles, Steven at 345 6th St, 13126

我如何解析它看起来像这样？我读过很多教程，但它们要么使用非常复杂的 XML，要么使用非常简单的 XML 作为示例，但我认为这与创建列表和创建要解析的对象有关。我已经尝试了很多小时来寻找解决方案，但无法找到正确的方法。一个解决方案会很好，但即使是一个提示(和教程链接)也有助于指导我。我真的很感谢任何帮助。这也是我到目前为止所得到的:

public class MyHandler extends DefaultHandler {

    public void startElement(String uri, String localName, String qName, Attributes attributes) throws SAXException {

        if (qName.equalsIgnoreCase("van")) {
            System.out.println("---=== Report ===---");
            System.out.println("Van (" + attributes.getValue("id") + ")");
        }
        if (qName.equalsIgnoreCase("customer")) {
            System.out.println("    Customer");
            System.out.println("        " + attributes.getValue("lastName") + ", " + attributes.getValue("firstName") + " at " + attributes.getValue("streetAddress") + ", " + attributes.getValue("zipCode"));
        }
        if (qName.equalsIgnoreCase("cart")) {
            System.out.println("Cart (" + attributes.getValue("id") + ")");
            System.out.println("---=== End of Report ===---");
        }
    }
}

结果(看起来确实错误):

---=== Report ===---
Van (VID-12345)
    Customer
        Adams, Maurice at 123 4th St, 13126
    Customer
        Baxter, Robert at 234 5th St, 13126
Cart (VID-23456)
---=== End of Report ===---
    Customer
        Charles, Steven at 345 6th St, 13126

Answer 1

这样写:

public class MyHandler extends DefaultHandler {
    @Override
    public void startDocument() throws SAXException {
        System.out.println("---=== Report ===---");
    }
    @Override
    public void endDocument() throws SAXException {
        System.out.println("---=== End of Report ===---");
    }
    @Override
    public void startElement(String uri, String localName, String qName, Attributes attributes) throws SAXException {
        if (qName.equalsIgnoreCase("van")) {
            System.out.println("Van (" + attributes.getValue("id") + ")");
            System.out.println("    Customers");
        }
        if (qName.equalsIgnoreCase("cart")) {
            System.out.println("Cart (" + attributes.getValue("id") + ")");
            System.out.println("    Customers");
        }
        if (qName.equalsIgnoreCase("customer")) {
            System.out.println("        " + attributes.getValue("lastName") + ", " + attributes.getValue("firstName") + " at " + attributes.getValue("streetAddress") + ", " + attributes.getValue("zipCode"));
        }
    }
}

如果您不想要 Customers 行(如果没有)，那么您需要跟踪是否已经打印了该行，例如像这样:

public class MyHandler extends DefaultHandler {
    private boolean firstCustomer;
    @Override
    public void startDocument() throws SAXException {
        System.out.println("---=== Report ===---");
    }
    @Override
    public void endDocument() throws SAXException {
        System.out.println("---=== End of Report ===---");
    }
    @Override
    public void startElement(String uri, String localName, String qName, Attributes attributes) throws SAXException {
        if (qName.equalsIgnoreCase("van")) {
            System.out.println("Van (" + attributes.getValue("id") + ")");
            firstCustomer = true;
        }
        if (qName.equalsIgnoreCase("cart")) {
            System.out.println("Cart (" + attributes.getValue("id") + ")");
            firstCustomer = true;
        }
        if (qName.equalsIgnoreCase("customer")) {
            if (firstCustomer) {
                firstCustomer = false;
                System.out.println("    Customers");
            }
            System.out.println("        " + attributes.getValue("lastName") + ", " + attributes.getValue("firstName") + " at " + attributes.getValue("streetAddress") + ", " + attributes.getValue("zipCode"));
        }
    }
}

输出(来自上述两个版本)

---=== Report ===---
Van (VID-12345)
    Customers
        Adams, Maurice at 123 4th St, 13126
        Baxter, Robert at 234 5th St, 13126
Cart (VID-23456)
    Customers
        Charles, Steven at 345 6th St, 13126
---=== End of Report ===---