java - JAXB:删除父节点并保留其子节点

Question

我知道这没有多大意义，但我必须从没有某些元素的父节点的 Java 对象生成 XML，如下所述。

这是 XML 的 Java 类模型示例:

@XmlRootElement(name = "person")
public class PersonXml {

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

    @XmlElement(name = "car")
    private List<CarXml> cars;

.

@XmlRootElement(name = "car")
public class CarXml {

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

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

默认情况下，如果我从 PersonXml 的对象生成 XML像这样:

StringWriter writer = new StringWriter();

JAXBContext ctx = JAXBContext.newInstance(PersonXml.class);
Marshaller marshaller = ctx.createMarshaller();
marshaller.marshal(xml, writer);

我会得到:

<person>
    <name>Pedro</name>
    <car>
        <model>Logan</model>
        <brand>Renault</brand>
    </car>
    <car>
        <model>Duster</model>
        <brand>Renault</brand>
    </car>
</person>

我需要删除 <car>标记，甚至完全阻止其生成。

我需要这样的 XML:

<person>
    <name>Pedro</name>
    <model>Logan</model>
    <brand>Renault</brand>
    <model>Duster</model>
    <brand>Renault</brand>
</person>

当然，我可以将 XML 转换为字符串并使用 replaceAll 删除标签。或类似的东西，但我想知道是否有更好的方法来实现这一点。

Answer 1

如果需要生成此输出，可以按如下方式使用 JAXB:

1) 创建一个新的 Person 类:

import java.util.ArrayList;
import java.util.List;
import javax.xml.bind.JAXBElement;
import javax.xml.bind.annotation.XmlAccessType;
import javax.xml.bind.annotation.XmlAccessorType;
import javax.xml.bind.annotation.XmlElementRef;
import javax.xml.bind.annotation.XmlElementRefs;
import javax.xml.bind.annotation.XmlRootElement;
import javax.xml.bind.annotation.XmlType;


@XmlAccessorType(XmlAccessType.FIELD)
@XmlType(name = "", propOrder = {
    "field"
})
@XmlRootElement(name = "person")
public class Person {

    @XmlElementRefs({
        @XmlElementRef(name = "name", type = JAXBElement.class, required = false),
        @XmlElementRef(name = "model", type = JAXBElement.class, required = false),
        @XmlElementRef(name = "brand", type = JAXBElement.class, required = false)
    })
    protected List<JAXBElement<String>> field;

    public List<JAXBElement<String>> getNameOrModelOrBrand() {
        if (field == null) {
            field = new ArrayList<>();
        }
        return this.field;
    }

}

2) 创建一个ObjectFactory以方便使用person类:

import javax.xml.bind.JAXBElement;
import javax.xml.bind.annotation.XmlElementDecl;
import javax.xml.bind.annotation.XmlRegistry;
import javax.xml.namespace.QName;

@XmlRegistry
public class ObjectFactory {

    private final static QName _PersonName_QNAME = new QName("", "name");
    private final static QName _PersonModel_QNAME = new QName("", "model");
    private final static QName _PersonBrand_QNAME = new QName("", "brand");

    public ObjectFactory() {
    }

    public Person createPerson() {
        return new Person();
    }

    @XmlElementDecl(namespace = "", name = "name", scope = Person.class)
    public JAXBElement<String> createPersonName(String value) {
        return new JAXBElement<>(_PersonName_QNAME, String.class, Person.class, value);
    }

    @XmlElementDecl(namespace = "", name = "model", scope = Person.class)
    public JAXBElement<String> createPersonModel(String value) {
        return new JAXBElement<>(_PersonModel_QNAME, String.class, Person.class, value);
    }

    @XmlElementDecl(namespace = "", name = "brand", scope = Person.class)
    public JAXBElement<String> createPersonBrand(String value) {
        return new JAXBElement<>(_PersonBrand_QNAME, String.class, Person.class, value);
    }

}

按如下方式使用工厂:

import javax.xml.bind.JAXBContext;
import javax.xml.bind.JAXBException;
import javax.xml.bind.JAXBElement;
import javax.xml.bind.Marshaller;
import java.io.StringWriter;
import java.util.List;

...

ObjectFactory factory = new ObjectFactory();

Person person = factory.createPerson();
List<JAXBElement<String>> list = person.getNameOrModelOrBrand();
list.add(factory.createPersonName("Pedro"));
list.add(factory.createPersonModel("Logan"));
list.add(factory.createPersonBrand("Renault"));
list.add(factory.createPersonModel("Duster"));
list.add(factory.createPersonBrand("Renault"));

JAXBContext ctx = JAXBContext.newInstance(Person.class);
Marshaller marshaller = ctx.createMarshaller();
marshaller.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT, Boolean.TRUE);
StringWriter writer = new StringWriter();
marshaller.marshal(person, writer);
System.out.println(writer.toString());

最终结果是 XML 如下:

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<person>
    <name>Pedro</name>
    <model>Logan</model>
    <brand>Renault</brand>
    <model>Duster</model>
    <brand>Renault</brand>
</person>

据我所知，以这种方式创建元素是获得所需最终结果的唯一方法。

您可能可以采取多种措施来重构上述代码，以简化元素列表的创建 - 但这向您展示了基本方法。

正如您所知 - 这远非理想。最终结果不是我想要接收的任何类型的 XML。