JAXB：泛型的多態性

Question

我正在嘗試使用JAXB（在澤西島內）與泛型的多態性：

@XmlRootElement
public class Performance<M extends IMeasurement> {

    @XmlAnyElement
    private List<M> measurement;   
}

@XmlJavaTypeAdapter(MeasurementAbstract.Adapter.class)
public interface IMeasurement<D extends Serializable, V extends Number>
        extends Serializable {

    D getDate();    
    void setDate(D date);    
    V getValue();    
    void setValue(V value);
}

@XmlTransient
@XmlAccessorType(XmlAccessType.FIELD)
@XmlSeeAlso({MeasurementStringDouble.class, MeasurementStringInteger.class})
public abstract class MeasurementAbstract<D extends Serializable, V extends Number> implements IMeasurement<D, V> {

    @XmlElement
    protected D date;
    @XmlElement
    protected V value;

    static class Adapter extends XmlAdapter<MeasurementAbstract, IMeasurement> {
        public IMeasurement unmarshal(MeasurementAbstract m) { return m; }
        public MeasurementAbstract marshal(IMeasurement v) { return (MeasurementAbstract) v; }
    }
}

@XmlRootElement
public class MeasurementStringDouble extends MeasurementAbstract<String, Double> {}

@XmlRootElement
public class MeasurementStringInteger extends MeasurementAbstract<String, Integer> {}

我有這個錯誤：

GRAVE：響應的映射異常：500（內部服務器錯誤）javax.ws.rs.WebApplicationException：javax.xml.bind.MarshalException - 包含鏈接異常：[javax.xml.bind.JAXBException：class org.test.jaxb.MeasurementStringDouble在這種情況下，也不知道它的任何超類。]

Answer 1

我找到了解決這個問題的解決方案：

@XmlRootElement
public class Performance<M extends IMeasurement> {

    @XmlElementWrapper(name = "measurementsPerformance")
    @XmlElements({
        @XmlElement(name = "measurement", type = MeasurementStringDouble.class),
        @XmlElement(name = "measurement", type = MeasurementStringInteger.class)})
    private List<M> measurement;   
}

public interface IMeasurement<D extends Serializable, V extends Number> extends Serializable {

    D getDate();    
    void setDate(D date);    
    V getValue();    
    void setValue(V value);
}

@XmlTransient
public abstract class MeasurementAbstract<D extends Serializable, V extends Number> implements IMeasurement<D, V>, Serializable {

    protected D date;
    protected V value;
}

@XmlRootElement
@XmlAccessorType(XmlAccessType.PROPERTY)
public class MeasurementStringDouble extends MeasurementAbstract<String, Double> {

    @XmlElement
    @Override
    public String getDate() {
        return date;
    }

    @XmlElement
    @Override
    public Double getValue() {
        return value;
    }
}

@XmlRootElement
@XmlAccessorType(XmlAccessType.PROPERTY)
public class MeasurementStringInteger extends MeasurementAbstract<String, Integer> {

    @XmlElement
    @Override
    public String getDate() {
        return date;
    }

    @XmlElement
    @Override
    public Integer getValue() {
        return value;
    }
}

此解決方案的缺點是重復子類中的getter / setter。