我想使用反射获取泛型的实例:
this.wrapperInstance = ((Class<WRAPPER>) ((ParameterizedType) (getClass().getGenericSuperclass())).getActualTypeArguments()[1]).newInstance();
但我得到了异常(exception):
java.lang.ClassCastException: java.lang.Class cannot be cast to java.lang.reflect.ParameterizedType
不知道问题出在哪里,也许有人可以帮助我?有完整的类代码:
public class XMLUtils<MODEL extends AbstractModel, WRAPPER extends WraperInterface<MODEL>> {
private WRAPPER wrapperInstance;
@SuppressWarnings("unchecked")
public XMLUtils() throws InstantiationException, IllegalAccessException {
this.wrapperInstance = ((Class<WRAPPER>) ((ParameterizedType) (getClass().getGenericSuperclass())).getActualTypeArguments()[1]).newInstance();
}
@SuppressWarnings("unchecked")
public List<MODEL> loadDataFromXML(String fileName) {
try {
File pajamuFile = new File(
UserDataLoader.INSTANCE.getCurrentUserFolder() + fileName);
JAXBContext context = JAXBContext.newInstance(wrapperInstance.getClass());
Unmarshaller um = context.createUnmarshaller();
WRAPPER wrapper = (WRAPPER) um.unmarshal(pajamuFile);
return wrapper.getDataList();
} catch (JAXBException e) {
e.printStackTrace();
return new ArrayList<MODEL>();
}
}
public void saveDataToXML(List<MODEL> dataList, String fileName) {
try {
File pajamuFile = new File(
UserDataLoader.INSTANCE.getCurrentUserFolder() + fileName);
JAXBContext context = JAXBContext.newInstance(wrapperInstance.getClass());
Marshaller m = context.createMarshaller();
WRAPPER wrapper = wrapperInstance;
wrapper.setDataList(dataList);
m.marshal(wrapper, pajamuFile);
} catch (JAXBException e) {
e.printStackTrace();
}
}
}
在谷歌中,我发现大多数类似的情况,但是对于 spring,这里我没有使用 spring,所以也许有任何明确的解决方案来解决我想要做的事情。
最佳答案
Do not know where is problem, maybe someaone can help me
错误消息是不言自明的。以下语句返回一个 Class
:
(getClass().getGenericSuperclass())
并且您正尝试将其转换为ParameterizedType
((ParameterizedType) (getClass().getGenericSuperclass()))
Class
和 ParameterizedType
是 sibling 。兄弟不是姐妹,所以试图将他们强加给彼此是残酷的。
话虽如此,问题的快速解决方案是要求客户端代码将 Class
类型传递给您的 XmlUtils
类。
public class XMLUtils<MODEL extends AbstractModel, WRAPPER extends WraperInterface<MODEL>> {
private WRAPPER wrapperInstance;
public XMLUtils(Class<WRAPPER> wrapperInstance) throws InstantiationException, IllegalAccessException {
this.wrapperInstance = wrapperInstance
}
//more code follows
}
关于java - 尝试获取泛型类型参数时出现 ClassCastException,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/30557421/