如何将 Jackson 的 TypeReference 与泛型一起使用?

问题描述

对于 json 映射，我使用以下方法:

For json mapping I use the following method:

public static <T> T mapJsonToObject(String json, T dtoClass) throws Exception {
    ObjectMapper mapper = new ObjectMapper();
    return mapper.readValue(json, new TypeReference<RestResponse<UserDto>>() {
    });
}

UserDto 看起来像这样:

@JsonIgnoreProperties(ignoreUnknown = true)
public class UserDto {

    @JsonProperty("items")
    private List<User> userList;

    public List<User> getUserList() {
        return userList;
    }

    public void setUserList(List<User> userList) {
        this.userList = userList;
    }
}

我想改进这种映射方法，而不是附加到 UserDto 类，而是将其替换为泛型.

I want to improve this method of mapping without being attached to a UserDto class, and replacing it with a generic.

有可能吗?以及如何?

谢谢.

推荐答案

TypeReference 要求您静态指定参数，而不是动态指定参数，因此如果您需要进一步参数化类型，它不起作用.

TypeReference requires you to specify parameters statically, not dynamically, so it does not work if you need to further parameterize types.

我认为您需要的是 JavaType:您可以使用 TypeFactory 动态构建实例.您可以通过 ObjectMapper.getTypeFactory() 获得 TypeFactory 的实例.您还可以从简单的 Class 以及 TypeReference 构建 JavaType 实例.

What I think you need is JavaType: you can build instances dynamically by using TypeFactory. You get an instance of TypeFactory via ObjectMapper.getTypeFactory(). You can also construct JavaType instances from simple Class as well as TypeReference.

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