java JAXB列表中的不同元素

Question

我有一些XML文件具有以下结构：

<?xml version="1.0" encoding="iso-8859-1"?>
<ROOT xmlns="http://www.XXX.com/YYY"
    xmlns:xs="http://www.w3.org/2001/XMLSchema-instance">
    <DOCUMENT>
        <title>Doc 1</title>
    </DOCUMENT>
    <DOCUMENT>
        <title>Doc 2</title>
    </DOCUMENT>
    <TEXT>
        <content>Text 1</content>
    </TEXT>
    <TEXT>
        <content>Text 2</content>
    </TEXT>
    <ITEM>
        <id>1</id>
    </ITEM>
    <ITEM>
        <id>2</id>
    </ITEM>
</ROOT>

我想使用JAXB解析文件，因此我必须为所有元素创建模型。但是ROOT元素的模型是什么？XML中是否允许将不同的数据类型放在一个列表中

我调用了我的模型DocumentList，但我的列表的通用类型是什么？我可以用一个列表吗，还是必须创建不同的列表

@XmlRootElement(name = "ROOT")
public class DocumentList {

    private List elements;

}

提前谢谢

更新

我的模型课是这样的：

@XmlRootElement(name = "ROOT")
@XmlAccessorType(XmlAccessType.FIELD)
public class Root {

    @XmlElement(name = "DOCUMENT")
    private List<Document> documents;

    @XmlElement(name = "TEXT")
    private List<Text> texts;

    @XmlElement(name = "ITEM")
    private List<Item> items;

}

@XmlRootElement(name = "DOCUMENT")
@XmlAccessorType(XmlAccessType.FIELD)
public class Document {

    @XmlElement(name = "title")
    private String title;

}

@XmlRootElement(name = "TEXT")
@XmlAccessorType(XmlAccessType.FIELD)
public class Text {

    @XmlElement(name = "content")
    private String content;

}

@XmlRootElement(name = "ITEM")
@XmlAccessorType(XmlAccessType.FIELD)
public class Item {

    @XmlElement(name = "id")
    private String id;

}

也实现了getter和setter

现在我得到了以下异常：

javax.xml.bind.UnmarshalException: unexpected element (uri:"http://www.XXX.com/YYY", local:"ROOT"). Expected elements are <{}DOCUMENT>,<{}TEXT>,<{}ITEM>,<{}ROOT>
    at com.sun.xml.internal.bind.v2.runtime.unmarshaller.UnmarshallingContext.handleEvent(Unknown Source)
    at com.sun.xml.internal.bind.v2.runtime.unmarshaller.Loader.reportError(Unknown Source)
    at com.sun.xml.internal.bind.v2.runtime.unmarshaller.Loader.reportError(Unknown Source)
    at com.sun.xml.internal.bind.v2.runtime.unmarshaller.Loader.reportUnexpectedChildElement(Unknown Source)
    at com.sun.xml.internal.bind.v2.runtime.unmarshaller.UnmarshallingContext$DefaultRootLoader.childElement(Unknown Source)
    at com.sun.xml.internal.bind.v2.runtime.unmarshaller.UnmarshallingContext._startElement(Unknown Source)
    at com.sun.xml.internal.bind.v2.runtime.unmarshaller.UnmarshallingContext.startElement(Unknown Source)
    at com.sun.xml.internal.bind.v2.runtime.unmarshaller.SAXConnector.startElement(Unknown Source)
    at com.sun.org.apache.xerces.internal.parsers.AbstractSAXParser.startElement(Unknown Source)
    at com.sun.org.apache.xerces.internal.impl.XMLNSDocumentScannerImpl.scanStartElement(Unknown Source)
    at com.sun.org.apache.xerces.internal.impl.XMLNSDocumentScannerImpl$NSContentDriver.scanRootElementHook(Unknown Source)
    at com.sun.org.apache.xerces.internal.impl.XMLDocumentFragmentScannerImpl$FragmentContentDriver.next(Unknown Source)
    at com.sun.org.apache.xerces.internal.impl.XMLDocumentScannerImpl$PrologDriver.next(Unknown Source)
    at com.sun.org.apache.xerces.internal.impl.XMLDocumentScannerImpl.next(Unknown Source)
    at com.sun.org.apache.xerces.internal.impl.XMLNSDocumentScannerImpl.next(Unknown Source)
    at com.sun.org.apache.xerces.internal.impl.XMLDocumentFragmentScannerImpl.scanDocument(Unknown Source)
    at com.sun.org.apache.xerces.internal.parsers.XML11Configuration.parse(Unknown Source)
    at com.sun.org.apache.xerces.internal.parsers.XML11Configuration.parse(Unknown Source)
    at com.sun.org.apache.xerces.internal.parsers.XMLParser.parse(Unknown Source)
    at com.sun.org.apache.xerces.internal.parsers.AbstractSAXParser.parse(Unknown Source)
    at com.sun.org.apache.xerces.internal.jaxp.SAXParserImpl$JAXPSAXParser.parse(Unknown Source)
    at com.sun.xml.internal.bind.v2.runtime.unmarshaller.UnmarshallerImpl.unmarshal0(Unknown Source)
    at com.sun.xml.internal.bind.v2.runtime.unmarshaller.UnmarshallerImpl.unmarshal(Unknown Source)
    at javax.xml.bind.helpers.AbstractUnmarshallerImpl.unmarshal(Unknown Source)
    at javax.xml.bind.helpers.AbstractUnmarshallerImpl.unmarshal(Unknown Source)
    at com.siemens.xmlmerger.Test.main(Test.java:53)

为什么它期望<{}ROOT>？我做错了什么

Answer 1

我会使用三个不同的列表（每种类型一个）

@XmlRootElement(name = "ROOT")
public class DocumentList {

    @XmlElement(name="DOCUMENT")
    private List documents;

    @XmlElement(name="TEXT")
    private List texts;

    @XmlElement(name="ITEMS")
    private List items;

}

Answer 2

xml中的元素将映射到绑定类的属性中

所以

@XmlRootElement(name = "ROOT")
public class DocumentList {

    @XmlElement(name="DOCUMENT")
    private List documents;

    @XmlElement(name="TEXT")
    private List texts;

    @XmlElement(name="ITEMS")
    private List items;

在上面的类中，属性与xml中的元素列表映射

我希望你能理解

Answer 3

如果您想将这个用例表示为一个列表，有两种不同的方法来支持它（见下文）。也可以将其表示为单独的列表

选项#1-每个元素对应一个唯一的类

如果列表中的每个元素名称对应一个不同的类，那么可以通过利用@XmlElements并执行以下操作来使用一个List：

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

@XmlRootElement(name = "ROOT")
@XmlAccessorType(XmlAccessType.FIELD)
public class DocumentList {

    @XmlElements({
       @XmlElement(name="DOCUMENT", type=Document.class),
       @XmlElement(name="TEXT", type=Text.class),
       @XmlElement(name="ITEM", type=Item.class)
    })
    private List elements;

}

选项#2-多个元素对应于同一类

如果List中条目的Class不足以唯一地将其映射到元素，则需要利用JAXBElement来维护元素信息。请注意，我们已经删除了@XmlElements注释，并将其替换为@XmlElementRefs

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

@XmlRootElement(name = "ROOT")
@XmlAccessorType(XmlAccessType.FIELD)
public class DocumentList {

    @XmlElementRefs({
       @XmlElementRef(name="DOCUMENT", type=JAXBElement.class),
       @XmlElementRef(name="TEXT", type=JAXBElement.class),
       @XmlElementRef(name="ITEM", type=JAXBElement.class)
    })
    private List elements;

}

除了@XmlElementRefs/@XmlElementRef注释之外，我们还需要在用^{注释的类上提供@XmlElementDecl注释

import javax.xml.bind.JAXBElement;
import javax.xml.bind.annotation.*;
import javax.xml.namespace.QName;

@XmlRegistry
public class ObjectFactory {

    @XmlElementDecl(name="DOCUMENT")
    public JAXBElement<String> createDocument(String value) {
        return new JAXBElement<String>(new QName("DOCUMENT"), String.class, value);
    }

    @XmlElementDecl(name="TEXT")
    public JAXBElement<String> createText(String value) {
        return new JAXBElement<String>(new QName("TEXT"), String.class, value);
    }

    @XmlElementDecl(name="ITEM")
    public JAXBElement<String> createItem(String value) {
        return new JAXBElement<String>(new QName("ITEM"), String.class, value);
    }

}