从 MODS 模式生成的 JAXB 不获取元素的值

Question

我在 xjc 的帮助下从 xsd 中生成了 classes（http://www.loc.gov/standards/mods/mods.xsd). Now I want to read values of elements for example xml file (https://www.loc.gov/standards/mods/v3/mods-userguide-examples.html - 第二个示例：数字化书籍）。我正在动态获取 classes 和此 classes 的方法，其中 returns 列出或字符串（getter 方法）。我得到的是属性值而不是元素值。

我的 classes：解组

import java.io.File;
import java.util.List;
import javax.xml.bind.JAXBContext;
import javax.xml.bind.JAXBException;
import javax.xml.bind.Unmarshaller;

public class XMLToObject {

    /**
     *
     * @return List of mods definitions from xml file
     */
    public static List convert() {
        try {
            JAXBContext jaxbContext = JAXBContext.newInstance(ModsCollectionDefinition.class);
            Unmarshaller u = jaxbContext.createUnmarshaller();

            File f = new File("test.xml");
            ModsCollectionDefinition test = (ModsCollectionDefinition)((javax.xml.bind.JAXBElement) u.unmarshal(f)).getValue();
            return test.getMods();
        } catch (JAXBException e) {
            e.printStackTrace();
        }
        return null;
    }
}

Class 用于处理 xml 数据

import java.lang.reflect.*;
import java.util.List;
import org.example.mods.XMLToObject;
/**
 * Operations on XML data
 */
public class MODS {
    private static List xmlData = XMLToObject.convert();
    public static StringBuilder stringBuilder = new StringBuilder();

    /**
     *
     * Get the whole content of the xml file
     *
     * @return String
     */
    public String getXML() {
        if(xmlData != null) {
            processClass(xmlData);
            xmlData = null;
        } else {
            stringBuilder.append("No file imported!");
        }
        return stringBuilder.toString();
    }

    /**
     *
     * @param list from which will be derived class type
     */
    private void processClass(List list) {
        for (int i = 0; i < list.size(); i++) {
            Class current = castDynamic(list.get(i));
            try {
                Method[] methods = current.getMethods();
                if (methods.length > 0) {
                    for (int j = 0; j < methods.length; j++) {
                        if (checkIfMethodReturnsString(methods[j]) && !methods[j].getName().contains("toString")) {
                            callMethodWhichReturnsString(methods[j], list.get(i));
                        } else if (checkIfMethodReturnsList(methods[j])) {
                            callMethodWhichReturnsList(methods[j], list.get(i));
                        }
                    }
                }
            } catch (NullPointerException e) {
                stringBuilder.append("No methods in this class!");
            }
        }
    }

    /**
     *
     * @param object from which will be derived class
     * @return Class
     */
    private Class castDynamic(Object object) {
        String className = object.getClass().getName();
        try {
            Class cls = Class.forName(className);
            cls.cast(object);
            return cls;
        } catch (ClassNotFoundException e) {
            return null;
        }
    }

    /**
     *
     * @param method of the class
     * @return String
     */
    private String getMethodType(Method method) {
        return method.getReturnType().getName();
    }

    /**
     *
     * @param method which will be checked according to return type
     * @return boolean
     */
    private boolean checkIfMethodReturnsString(Method method) {
        if(getMethodType(method).contains("String")) {
            return true;
        } else {
            return false;
        }
    }

    /**
     *
     * @param method which will be checked according to return type
     * @return boolean
     */
    private boolean checkIfMethodReturnsList(Method method) {
        if(getMethodType(method).contains("List")) {
            return true;
        } else {
            return false;
       }
    }

    /**
     *
     *
     * @param method which is invoked
     * @param obj on which method is invoked
     */
    private void callMethodWhichReturnsList(Method method, Object obj) {
        try {
            List list = (List) method.invoke(obj);
            processClass(list);
        } catch (IllegalAccessException | InvocationTargetException ex) {
            stringBuilder.append("Invoke exception!");
        }
    }

    /**
     * Method returns strings which are attributes but doesn't return values of the elements!
     *
     * @param method which is invoked
     * @param obj on which method is invoked
     */
    private void callMethodWhichReturnsString(Method method, Object obj) {
        try {
            stringBuilder.append(obj.getClass().getSimpleName().replace("Definition", ""));
            stringBuilder.append(" - ");
            stringBuilder.append(method.getName().replace("get", ""));
            stringBuilder.append(": ");
            stringBuilder.append(method.invoke(obj));
        } catch (IllegalAccessException | InvocationTargetException | IllegalArgumentException ex) {
            stringBuilder.append("Invoke exception!");
        }
    }
}

属性输出：

<mods version="3.3">

模组 - 版本：3.3

元素的输出：

<titleInfo>
    <title>At Gettysburg, or, What a Girl Saw and Heard of the Battle: A True Narrative</title>
</titleInfo>

TitleInfo - 类型：空 TitleInfo - 权限：null TitleInfo - ID：空 TitleInfo - 脚本：空 TitleInfo - ContentType：空 TitleInfo - 角色：空 TitleInfo - 用法：主要 TitleInfo - 标题：空 TitleInfo - 其他类型：空 TitleInfo - 提供：是 TitleInfo - 音译：空 TitleInfo - NameTitleGroup：空 TitleInfo - AltRepGroup：空 TitleInfo - TypeBinded：简单 TitleInfo - AltFormat：空标题信息 - 显示标签：空 TitleInfo - Href：空 TitleInfo - Arcrole: 空 TitleInfo - 显示：空 TitleInfo - 启动：空 TitleInfo - 语言：空 TitleInfo - LangBinded: 空 TitleInfo - AuthorityURI: 空 TitleInfo - ValueURI: null

已生成 class TitleInfoDefinition：

@XmlAccessorType(XmlAccessType.FIELD)
@XmlType(name = "titleInfoDefinition", propOrder = {
    "titleOrSubTitleOrPartNumber"
})
public class TitleInfoDefinition {

    @XmlElementRefs({
        .......
        @XmlElementRef(name = "title", namespace = "http://www.loc.gov/mods/v3", type = JAXBElement.class, required = false),
        ......
    })
    protected List<Object> titleOrSubTitleOrPartNumber;
    ......
    @XmlAttribute(name = "title", namespace = "http://www.w3.org/1999/xlink")
    protected String title;
    .....

     * <p>
     * Objects of the following type(s) are allowed in the list
     * {@link JAXBElement }{@code <}{@link StringPlusLanguage }{@code >}
     * {@link JAXBElement }{@code <}{@link StringPlusLanguage }{@code >}
     * {@link JAXBElement }{@code <}{@link StringPlusLanguage }{@code >}
     * {@link JAXBElement }{@code <}{@link StringPlusLanguage }{@code >}
     * {@link NonSort }
     * 
     * 
     */
    public List<Object> getTitleOrSubTitleOrPartNumber() {
        if (titleOrSubTitleOrPartNumber == null) {
            titleOrSubTitleOrPartNumber = new ArrayList<Object>();
        }
        return this.titleOrSubTitleOrPartNumber;
    }

   ......

    /**
     * Ruft den Wert der title-Eigenschaft ab.
     * 
     * @return
     *     possible object is
     *     {@link String }
     *     
     */
    public String getTitle() {
        return title;
    }
    .......
}

我试过直接获取这个值：

((JAXBElement)((TitleInfoDefinition)test).getTitleOrSubTitleOrPartNumber().get(0)).getValue();

输出： gov.loc.mods.v3.StringPlusLanguage@2986fc10

((JAXBElement)((TitleInfoDefinition)test).getTitleOrSubTitleOrPartNumber().get(0)).getName()

输出： {http://www.loc.gov/mods/v3}标题

如何获取 title 元素的值？

Answer 1

当您获得 StringPlusLanguage class 实例时，它对应于您的 title 元素。这是一个复杂的类型，架构中的内容很简单：

<xs:complexType name="stringPlusLanguage">
    <xs:simpleContent>
        <xs:extension base="xs:string">
            <xs:attributeGroup ref="languageAttributeGroup"/>
        </xs:extension>
    </xs:simpleContent>
</xs:complexType>

所以您可能有一个属性，例如 content 或 value，检查 class 并访问此属性。这将包含元素的文本值。

title 不只是字符串的原因恰恰是因为它在模式中被建模为复杂类型。如果它本来是 xs:string，那么你会得到一个字符串值属性。

从 MODS 模式生成的 JAXB 不获取元素的值

JAXB generated from MODS schema doesn't get values of elements

java

xml

xsd

jaxb

xjc