如何在startElement中使用SAX解析器从XML获取元素的值？

以下是如何使用ContentHandler获取元素值的一个非常基本的示例：

public class YourHandler extends DefaultHandler {

    boolean inFirstNameElement = false;

    public class startElement(....) {
        if(qName.equals("firstName") {
            inFirstNameElement = true;
        }
    }

    public class endElement(....) {
        if(qName.equals("firstName") {
            inFirstNameElement = false;
        }
    }

    public class characters(....) {
        if(inFirstNameElement) {
            // do something with the characters in the <firstName> element
        }
    }
}

如果您有一个简单的示例,则为每个标记设置布尔标记即可.如果您有一个更复杂的场景,您可能更喜欢使用元素名称作为键将标志存储在映射中,或者甚至创建一个或多个映射到XML的Employee类,并在每次< employee>时实例化它们.在startElement中找到,填充其属性,并将其添加到endElement中的Collection.

这是一个完整的ContentHandler示例,适用于您的示例文件.我希望它可以帮助你开始：

public class SimpleHandler extends DefaultHandler {

    class Employee {
        public String firstName;
        public String lastName;
        public String location;
        public Map<String,String> attributes = new HashMap<>();
    }
    boolean isFirstName,isLastName,isLocation;
    Employee currentEmployee;
    List<Employee> employees = new ArrayList<>();

    @Override
    public void startElement(String uri,Attributes atts) throws SAXException {
        if(qName.equals("employee")) {
            currentEmployee = new Employee();
            for(int i = 0; i < atts.getLength(); i++) {
                currentEmployee.attributes.put(atts.getQName(i),atts.getValue(i));
            }
        }
        if(qName.equals("firstName")) { isFirstName = true; }
        if(qName.equals("lastName"))  { isLastName = true;  }
        if(qName.equals("location"))  { isLocation = true;  }
    }

    @Override
    public void endElement(String uri,String qName)
            throws SAXException {
        if(qName.equals("employee")) {
            employees.add(currentEmployee);
            currentEmployee = null;
        }
        if(qName.equals("firstName")) { isFirstName = false; }
        if(qName.equals("lastName"))  { isLastName = false;  }
        if(qName.equals("location"))  { isLocation = false;  }
    }

    @Override
    public void characters(char[] ch,int start,int length) throws SAXException {
        if (isFirstName) {
            currentEmployee.firstName = new String(ch,start,length);
        }
        if (isLastName) {
            currentEmployee.lastName = new String(ch,length);
        }
        if (isLocation) {
            currentEmployee.location = new String(ch,length);
        }
    }

    @Override
    public void endDocument() throws SAXException {
        for(Employee e: employees) {
            System.out.println("Employee ID: " + e.attributes.get("id"));
            System.out.println("  First Name: " + e.firstName);
            System.out.println("  Last Name: " + e.lastName);
            System.out.println("  Location: " + e.location);
        }
    }
}