Java XML 转 Map 的几种方法

在 Java 中将 XML 转换为 Map 是一个常见的需求，以下是几种实现方式：

使用 DOM 解析器

import org.w3c.dom.*;
import javax.xml.parsers.*;
import java.io.*;
import java.util.*;
public class XmlToMapConverter {
    public static Map<String, Object> xmlToMap(String xmlString) throws Exception {
        DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
        DocumentBuilder builder = factory.newDocumentBuilder();
        Document document = builder.parse(new InputSource(new StringReader(xmlString)));
        Map<String, Object> map = new HashMap<>();
        NodeList nodeList = document.getDocumentElement().getChildNodes();
        for (int i = 0; i < nodeList.getLength(); i++) {
            Node node = nodeList.item(i);
            if (node.getNodeType() == Node.ELEMENT_NODE) {
                map.put(node.getNodeName(), node.getTextContent());
            }
        }
        return map;
    }
}

使用 Jackson 库

import com.fasterxml.jackson.databind.*;
import com.fasterxml.jackson.dataformat.xml.XmlMapper;
import java.util.*;
public class XmlToMapConverter {
    public static Map<String, Object> xmlToMap(String xmlString) throws Exception {
        XmlMapper xmlMapper = new XmlMapper();
        return xmlMapper.readValue(xmlString, new TypeReference<Map<String, Object>>() {});
    }
}

使用 XStream 库

import com.thoughtworks.xstream.XStream;
import java.util.*;
public class XmlToMapConverter {
    public static Map<String, Object> xmlToMap(String xmlString) {
        XStream xstream = new XStream();
        xstream.alias("map", HashMap.class);
        xstream.alias("entry", Map.Entry.class);
        xstream.registerConverter(new MapEntryConverter());
        @SuppressWarnings("unchecked")
        Map<String, Object> map = (Map<String, Object>) xstream.fromXML(xmlString);
        return map;
    }
}
class MapEntryConverter implements Converter {
    // 实现Converter接口方法...
}

使用 Simple XML 库

import org.simpleframework.xml.*;
import org.simpleframework.xml.convert.*;
import org.simpleframework.xml.stream.*;
import java.util.*;
@Root
public class XmlToMapConverter {
    @ElementMap(entry = "entry", key = "key", value = "value", inline = true)
    private Map<String, Object> map;
    public static Map<String, Object> xmlToMap(String xmlString) throws Exception {
        Serializer serializer = new Persister();
        XmlToMapConverter converter = serializer.read(XmlToMapConverter.class, xmlString);
        return converter.map;
    }
}

使用 Apache Commons Digester

import org.apache.commons.digester3.Digester;
import java.util.*;
public class XmlToMapConverter {
    public static Map<String, Object> xmlToMap(String xmlString) throws Exception {
        Digester digester = new Digester();
        Map<String, Object> map = new HashMap<>();
        digester.push(map);
        digester.addSetNext("*/entry", "put");
        digester.addObjectCreate("*/entry", HashMap.class);
        digester.addSetProperties("*/entry", "key", "key");
        digester.addSetNext("*/entry/value", "put");
        return digester.parse(new InputSource(new StringReader(xmlString)));
    }
}

注意事项

1. 嵌套结构处理：上述方法中，只有 Jackson 和 XStream 能很好地处理嵌套的 XML 结构
2. 命名空间：XML 使用命名空间，需要额外处理
3. 属性：有些方法可能无法自动处理 XML 属性
4. 性能：对于大文件，DOM 解析器可能不是最佳选择，考虑使用 SAX 或 StAX

完整示例（Jackson 处理嵌套结构）

import com.fasterxml.jackson.databind.*;
import com.fasterxml.jackson.dataformat.xml.XmlMapper;
import java.util.*;
public class XmlToMapConverter {
    public static Map<String, Object> xmlToMap(String xmlString) throws Exception {
        XmlMapper xmlMapper = new XmlMapper();
        return xmlMapper.readValue(xmlString, new TypeReference<Map<String, Object>>() {});
    }
    public static void main(String[] args) throws Exception {
        String xml = "<root><name>John</name><age>30</age><address><street>123 Main St</street><city>New York</city></address></root>";
        Map<String, Object> map = xmlToMap(xml);
        System.out.println(map);
        // 输出: {name=John, age=30, address={street=123 Main St, city=New York}}
    }
}

选择哪种方法取决于你的具体需求,如 XML 结构复杂度、性能要求和项目依赖情况，Jackson 通常是处理 XML 到 Map 转换的最简单和最灵活的方法。