如何使用JAXB将含diffgr标签的XML字符串反序列化为Java POJO

问题核心原因 #

你的代码存在两处核心错误导致匹配失败：

• 层级结构不匹配：XML为嵌套结构，<Result>下仅包含<diffgr:diffgram>子节点，<NewDataSet>是diffgram的子节点，<DT1>又是NewDataSet的子节点，你将三个属性都定义在Response同一层级，自然无法匹配到节点。
• 命名空间处理错误：diffgr是命名空间前缀，对应的完整命名空间为urn:schemas-microsoft-com:xml-diffgram-v1，不能直接将前缀写在@XmlElement的name属性中，需要单独指定namespace参数。

正确实现代码 #

1. 按XML嵌套结构定义POJO

import javax.xml.bind.annotation.*;
import java.util.ArrayList;
import java.util.List;

// 根节点Result
@XmlAccessorType(XmlAccessType.FIELD)
@XmlRootElement(name = "Result")
public class Response {

    @XmlElement(name = "diffgram", namespace = "urn:schemas-microsoft-com:xml-diffgram-v1")
    private Diffgram diffgram;

    public Diffgram getDiffgram() {
        return diffgram;
    }

    public void setDiffgram(Diffgram diffgram) {
        this.diffgram = diffgram;
    }

    // Diffgram节点类
    @XmlAccessorType(XmlAccessType.FIELD)
    public static class Diffgram {
        @XmlElement(name = "NewDataSet")
        private NewDataSet newDataSet;

        public NewDataSet getNewDataSet() {
            return newDataSet;
        }

        public void setNewDataSet(NewDataSet newDataSet) {
            this.newDataSet = newDataSet;
        }
    }

    // NewDataSet节点类
    @XmlAccessorType(XmlAccessType.FIELD)
    public static class NewDataSet {
        @XmlElement(name = "DT1")
        private List<DT> dtList;

        public List<DT> getDtList() {
            if (dtList == null) {
                dtList = new ArrayList<>();
            }
            return dtList;
        }

        public void setDtList(List<DT> dtList) {
            this.dtList = dtList;
        }
    }

    // DT1节点类
    @XmlAccessorType(XmlAccessType.FIELD)
    public static class DT {
        @XmlElement(name = "TEST_NO")
        private String testNo;
        @XmlElement(name = "TEST_DESC")
        private String testDesc;

        public String getTestNo() {
            return testNo;
        }

        public void setTestNo(String testNo) {
            this.testNo = testNo;
        }

        public String getTestDesc() {
            return testDesc;
        }

        public void setTestDesc(String testDesc) {
            this.testDesc = testDesc;
        }

        @Override
        public String toString() {
            return "DT{" +
                    "testNo='" + testNo + '\'' +
                    ", testDesc='" + testDesc + '\'' +
                    '}';
        }
    }
}

2. 反序列化测试代码

JAXBContext jaxbContext = JAXBContext.newInstance(Response.class);
Unmarshaller jaxbUnMarshaller = jaxbContext.createUnmarshaller();
Response response = (Response)jaxbUnMarshaller.unmarshal(new StringReader(xml));
// 直接获取DT列表
List<Response.DT> dtList = response.getDiffgram().getNewDataSet().getDtList();
// 输出验证
dtList.forEach(System.out::println);

如果不需要保留diffgram、NewDataSet两层冗余包装，也可以在反序列化前通过StAX解析器过滤外层节点，直接从<NewDataSet>节点开始反序列化，减少不必要的类定义。

内容的提问来源于stack exchange，提问作者Ye.s