我们可以通过传递类类型作为参数来使用 Java 泛型创建不同的类实例吗

Question

I am trying to create object from a xml file. Currently I am providing the Class type to be parsed in the method signature. For instance TestRequest as you see in the below code. Due to this I cannot use the same method to create another object type. Is it possible to write a method, probably using generics, to return different class instance by passing class type as parameter.

Current Code:

  private static JAXBElement<TestRequest> createRequestObject(String xmlFile) {

    JAXBElement<VerifyRequest> result;
    try {
      JAXBContext ctx = JAXBContext.newInstance(TestRequest.class);
      Unmarshaller unmarshaller = ctx.createUnmarshaller();
      String xmlString = loadFile(xmlFile);
      result = unmarshaller.unmarshal(new StreamSource(new ByteArrayInputStream(xmlString.getBytes())), VerifyRequest.class);
    } catch (JAXBException | IOException e) {
      throw new RuntimeException(e);
    }
    return result;
  }

Expecting something like

private static <T> JAXBElement<T> createRequestObject(String xmlFile, Class objectType) {

Answer 1

private static <T> JAXBElement<T> 
createRequestObject (String xmlFile, Class<T> type)

That should be enough.

If you call createRequestObject(file, TestRequest.class) , T is resolved to be TestRequest and thus the return type would be JAXBElement<TestRequest> . Similar for other types.