Java:泛型继承

Question

我有一个marshaller的以下界面,它将Object一个DataNode对象和一个对象组合在一起:

public interface DataMarshaller<T> {

    /**
     * returns the actual class that this marshaller is capable of marshalling.
     * @return 
     */
    Class<T> getDataClass();

    /**
     * marshalls the object to a DataNode
     * 
     * @param object
     * @return 
     */
    DataNode marshal(T object);

    /**
     * unmarshalls the object from a DataNode
     * 
     * @param node
     * @return 
     */
    T unMarshal(DataNode node);

}

为了确保我能够为对象获取正确的编组器,我还有Class<T> getDataClass()返回其类的方法(由于类型擦除而在编译后会丢失).

现在我想在一个能够编组类型对象的类中实现这个接口Octree<T>:

public class OctreeMarshaller<T> implements DataMarshaller<Octree<T>> {

    @Override
    public Class<Octree<T>> getDataClass() {
        return Octree.class; //<- compiletime error
    }

    @Override
    public DataNode marshal(Octree<T> object) {
        //...
    }

    @Override
    public Octree<T> unMarshal(DataNode node) {
        //...
    }


}

我的问题是,(当然)Octree.class不是类型Class<Octree<T>>,而是非泛型类型Class<Octree>,Java不允许我将其转换为Class<Octree<T>>.

现在的问题是:有没有比我已经考虑过的两种解决方案更优雅的方法:

• 将界面中的返回值更改Class<T>为Class<?>
• 将类签名更改OctreeMarshaller为public class OctreeMarshaller implements DataMarshaller<Octree>

Answer 1

如果没有 的实例，Octree<T>则无法构造类型 的类对象Class<Octree<T>>。但由于我们知道（由于类型擦除）在运行时只有一个类Octree，因此可以安全地编写

public class OctreeMarshaller<T> implements DataMarshaller<Octree<T>> {

    @Override
    @SuppressWarnings("unchecked")
    public Class<Octree<T>> getDataClass() {
        return (Class<Octree<T>>)(Class<?>)Octree.class;
    }

    [...]
}