我们有个PO，长这样：
public class MyPO<T> implements java.io.Serializable{
private List<T> data = new ArrayList<T>();
｝
结果用RestTemplate.getForObject 后，不管这个T是什么，接收到都被转化为LinkedHashMap，造成ClassCastException。
上网查，在这篇找到关键信息（这是百度快照）：
You can refactor the code above to use exchange instead of postForObject, and use ParameterizedTypeReference to get a List<MyModelClass>
.
For example:
ParameterizedTypeReference<List<MyModelClass>> typeRef = new ParameterizedTypeReference<List<MyModelClass>>() {
};
ResponseEntity<List<MyModelClass>> responseEntity = restTemplate.exchange(url, HttpMethod.POST, new HttpEntity<>(mvm), typeRef);
List<MyModelClass> myModelClasses = responseEntity.getBody();