无法解析为某种类型？

I want to convert a json string to a List<Someclass> using jackson json library.

我想使用jackson json库将json字符串转换为List 。

public static List<T> toList(String json, Class<T> type, ObjectMapperProperties objectMapperProperties){

        ObjectMapper objectMapper = ObjectMapperFactory.getObjectMapper(objectMapperProperties);

        try {
            return objectMapper.readValue(json, objectMapper.getTypeFactory().constructCollectionType(List.class, type));
        } catch (JsonParseException e) {
            e.printStackTrace();
        } catch (JsonMappingException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

So if I pass Attribute.class as type, then it must return a List<Attribute>.

因此，如果我将Attribute.class作为类型传递，那么它必须返回List 。

However, this gives me a compile time error

但是，这给了我编译时错误

T cannot be resolved to a type

I guess generics part is not clear to me here. Any help is appreciated.

我想泛型部分在这里我不清楚。任何帮助表示赞赏。

1 个解决方案

#1

you need to declare T first in your generic method, In your case it would be :

你需要先在你的泛型方法中声明T，在你的情况下它将是：

public static <T> List<T> toList(String json, Class<T> type,  ObjectMapperProperties objectMapperProperties)

for more info please check oracle documentation for generic methods:

有关更多信息，请查看oracle文档以获取通用方法：

https://docs.oracle.com/javase/tutorial/extra/generics/methods.html

#1