Java / JAXB：基于属性将XML解组到特定子类

JAXB是一个规范，特定的实现将提供扩展点来执行此类操作。如果使用的是Eclipselink
JAXB（MOXy）
，则可以如下修改Shape类：

import javax.xml.bind.annotation.XmlAttribute;import org.eclipse.persistence.oxm.annotations.XmlCustomizer;@XmlCustomizer(ShapeCustomizer.class)public abstract class Shape {    int points;    @XmlAttribute    public int getPoints() {        return points;    }    public void setPoints(int points) {        this.points = points;    }}

然后使用MOXy @XMLCustomizer，您可以访问InheritancePolicy，并将类指示符字段从“ @xsi：type”更改为“
type”：

import org.eclipse.persistence.config.DescriptorCustomizer;import org.eclipse.persistence.descriptors.ClassDescriptor;public class ShapeCustomizer implements DescriptorCustomizer {    @Override    public void customize(ClassDescriptor descriptor) throws Exception {        descriptor.getInheritancePolicy().setClassIndicatorFieldName("@type");    }}

您将需要确保在模型类（Shape，Square等）的模型类中包含一个jaxb.properties文件，并使用以下条目指定Eclipselink MOXy
JAXB实现：

javax.xml.bind.context.factory=org.eclipse.persistence.jaxb.JAXBContextFactory

下面是其余的模型类：

形状

import java.util.ArrayList;import java.util.List;import javax.xml.bind.annotation.XmlRootElement;@XmlRootElementpublic class Shapes {    private List<Shape> shape = new ArrayList<Shape>();;    public List<Shape> getShape() {        return shape;    }    public void setShape(List<Shape> shape) {        this.shape = shape;    }}

广场

import javax.xml.bind.annotation.XmlAttribute;public class Square extends Shape {    private String squareSpecificAttribute;    @XmlAttribute(name="square-specific-attribute")    public String getSquareSpecificAttribute() {        return squareSpecificAttribute;    }    public void setSquareSpecificAttribute(String s) {        this.squareSpecificAttribute = s;    }}

三角形

import javax.xml.bind.annotation.XmlAttribute;public class Triangle extends Shape {    private String triangleSpecificAttribute;    @XmlAttribute(name="triangle-specific-attribute")    public String getTriangleSpecificAttribute() {        return triangleSpecificAttribute;    }    public void setTriangleSpecificAttribute(String t) {        this.triangleSpecificAttribute = t;    }}

下面是一个演示程序，用于检查一切是否正常：

import java.io.StringReader;import javax.xml.bind.JAXBContext;import javax.xml.bind.Marshaller;import javax.xml.bind.Unmarshaller;public class Demo {    public static void main(String[] args) throws Exception {        JAXBContext jaxbContext = JAXBContext.newInstance(Shapes.class, Triangle.class, Square.class);        StringReader xml = new StringReader("<shapes><shape square-specific-attribute='square stuff' type='square'><points>4</points></shape><shape triangle-specific-attribute='triangle stuff' type='triangle'><points>3</points></shape></shapes>");        Unmarshaller unmarshaller = jaxbContext.createUnmarshaller();        Shapes root = (Shapes) unmarshaller.unmarshal(xml);        Marshaller marshaller = jaxbContext.createMarshaller();        marshaller.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT, true);        marshaller.marshal(root, System.out);    }}

我希望这有帮助。

有关Eclipselink MOXy的更多信息，请参见：

• http://www.eclipse.org/eclipselink/moxy.php

编辑

在Eclipselink 2.2中，我们使它更易于配置，请查看以下文章以获取更多信息：

• http://bdoughan.blogspot.com/2010/11/jaxb-and-inheritance-moxy-extension.html