如何无需自定义类将XML数据转换为List<Map<String,String>>？

给定如下XML数据：

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<books>
  <book>
    <name>SCJP</name>
    <author>Kathy Sierra</author>
    <publisher>Tata McGraw Hill</publisher>
    <isbn>856-545456736</isbn>
  </book>
  <book>
    <name>Java Persistence with Hibernate</name>
    <author>Christian Bauer</author>
    <publisher>Manning</publisher>
    <isbn>978-3832180577</isbn>
  </book>
</books>

能否无需自定义类，将该XML数据转换为List<Map<String,String>>或List<Map<String,Object>>格式？

此前尝试用JAXB解组，得到的是自定义Book类的对象列表：

[Book [name=SCJP, author=Kathy Sierra, publisher=Tata McGraw Hill, isbn=856-545456736], 
Book [name=Java Persistence with Hibernate, author=Christian Bauer, publisher=Manning, isbn=978-3832180577]]

期望得到的格式为：

[{name="SCJP", author="Kathy Sierra", publisher="Tata McGraw Hill", isbn="856-545456736"},
{name="Java Persistence with Hibernate", author="Christian Bauer", publisher="Manning", isbn="978-3832180577"}]

可以实现，以下是几种无需自定义类的实现方式：

1. JDK原生DOM解析（无额外依赖） #

直接使用JDK自带的DOM API遍历XML节点，将每个book节点的子节点键值对存入Map，再收集到List中：

import org.w3c.dom.Document;
import org.w3c.dom.Element;
import org.w3c.dom.Node;
import org.w3c.dom.NodeList;
import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import java.io.ByteArrayInputStream;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

public class XmlToMapList {
    public static void main(String[] args) throws Exception {
        String xmlContent = "<?xml version=\"1.0\" encoding=\"UTF-8\" standalone=\"yes\"?>\n" +
                "<books>\n" +
                "  <book>\n" +
                "    <name>SCJP</name>\n" +
                "    <author>Kathy Sierra</author>\n" +
                "    <publisher>Tata McGraw Hill</publisher>\n" +
                "    <isbn>856-545456736</isbn>\n" +
                "  </book>\n" +
                "  <book>\n" +
                "    <name>Java Persistence with Hibernate</name>\n" +
                "    <author>Christian Bauer</author>\n" +
                "    <publisher>Manning</publisher>\n" +
                "    <isbn>978-3832180577</isbn>\n" +
                "  </book>\n" +
                "</books>";

        DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
        DocumentBuilder builder = factory.newDocumentBuilder();
        Document doc = builder.parse(new ByteArrayInputStream(xmlContent.getBytes()));
        doc.getDocumentElement().normalize();

        NodeList bookNodes = doc.getElementsByTagName("book");
        List<Map<String, String>> resultList = new ArrayList<>();

        for (int i = 0; i < bookNodes.getLength(); i++) {
            Node bookNode = bookNodes.item(i);
            if (bookNode.getNodeType() == Node.ELEMENT_NODE) {
                Element bookElement = (Element) bookNode;
                Map<String, String> bookMap = new HashMap<>();

                NodeList childNodes = bookElement.getChildNodes();
                for (int j = 0; j < childNodes.getLength(); j++) {
                    Node child = childNodes.item(j);
                    if (child.getNodeType() == Node.ELEMENT_NODE) {
                        Element childElement = (Element) child;
                        bookMap.put(childElement.getTagName(), childElement.getTextContent().trim());
                    }
                }
                resultList.add(bookMap);
            }
        }

        // 输出结果
        System.out.println(resultList);
    }
}

2. 使用Jackson XML（需引入依赖） #

Jackson提供了XML解析支持，可以直接将XML映射为List<Map<String,String>>，无需自定义类：

首先添加Maven依赖：

<dependency>
    <groupId>com.fasterxml.jackson.dataformat</groupId>
    <artifactId>jackson-dataformat-xml</artifactId>
    <version>2.15.2</version>
</dependency>

实现代码：

import com.fasterxml.jackson.dataformat.xml.XmlMapper;
import java.util.List;
import java.util.Map;

public class JacksonXmlToMapList {
    public static void main(String[] args) throws Exception {
        String xmlContent = "<?xml version=\"1.0\" encoding=\"UTF-8\" standalone=\"yes\"?>\n" +
                "<books>\n" +
                "  <book>\n" +
                "    <name>SCJP</name>\n" +
                "    <author>Kathy Sierra</author>\n" +
                "    <publisher>Tata McGraw Hill</publisher>\n" +
                "    <isbn>856-545456736</isbn>\n" +
                "  </book>\n" +
                "  <book>\n" +
                "    <name>Java Persistence with Hibernate</name>\n" +
                "    <author>Christian Bauer</author>\n" +
                "    <publisher>Manning</publisher>\n" +
                "    <isbn>978-3832180577</isbn>\n" +
                "  </book>\n" +
                "</books>";

        XmlMapper xmlMapper = new XmlMapper();
        // 将XML解析为包含books键的Map，再提取book列表
        Map<String, List<Map<String, String>>> resultMap = xmlMapper.readValue(xmlContent, Map.class);
        List<Map<String, String>> bookList = resultMap.get("book");

        // 输出结果
        System.out.println(bookList);
    }
}

3. 使用Apache Commons Digester（需引入依赖） #

Apache Commons Digester可以通过配置规则将XML解析为Map列表：

添加Maven依赖：

<dependency>
    <groupId>commons-digester</groupId>
    <artifactId>commons-digester</artifactId>
    <version>2.1</version>
</dependency>

实现代码：

import org.apache.commons.digester3.Digester;
import java.io.ByteArrayInputStream;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

public class DigesterXmlToMapList {
    public static void main(String[] args) throws Exception {
        String xmlContent = "<?xml version=\"1.0\" encoding=\"UTF-8\" standalone=\"yes\"?>\n" +
                "<books>\n" +
                "  <book>\n" +
                "    <name>SCJP</name>\n" +
                "    <author>Kathy Sierra</author>\n" +
                "    <publisher>Tata McGraw Hill</publisher>\n" +
                "    <isbn>856-545456736</isbn>\n" +
                "  </book>\n" +
                "  <book>\n" +
                "    <name>Java Persistence with Hibernate</name>\n" +
                "    <author>Christian Bauer</author>\n" +
                "    <publisher>Manning</publisher>\n" +
                "    <isbn>978-3832180577</isbn>\n" +
                "  </book>\n" +
                "</books>";

        Digester digester = new Digester();
        digester.setValidating(false);

        // 根节点books对应一个List
        digester.addObjectCreate("books", ArrayList.class);
        // 每个book节点创建一个HashMap，加入List
        digester.addObjectCreate("books/book", HashMap.class);
        digester.addSetNext("books/book", "add");
        // 将book的子节点作为键值对存入HashMap
        digester.addBeanPropertySetter("books/book/*");

        List<Map<String, String>> bookList = digester.parse(new ByteArrayInputStream(xmlContent.getBytes()));

        // 输出结果
        System.out.println(bookList);
    }
}

内容的提问来源于stack exchange，提问作者user3608694