java - 具有对象类型的 Jackson JSON 列表

Question

我必须从对象列表中序列化 JSON。生成的 JSON 必须如下所示:

{
    "status": "success",
    "models": [
        {
            "model": {
                "id": 23,
                "color": "red"
            }
        },
        {
            "model": {
                "id": 24,
                "color": "green"
            }
        }
    ]
}

当我简单地序列化它时，我缺少类型/键“模型”:

List<Model> list = new ArrayList<Model>(); // add some new Model(...)
Response r = new Response("success", list); // Response has field "models"

相反，我只是得到这个:

{
    "status": "success",
    "models": [
        {
            "id": 23,
            "color": "red"
        },
        {
            "id": 24,
            "color": "green"
        }
    ]
}

如何为每个对象添加“模型”，而不必编写带有属性“模型”的愚蠢包装类？

我的类(class)是这样的:

public class Response {
    private String status;
    private List<Model> models;
    // getters / setters
}

public class Model {
    private Integer id;
    private String color;
    // getters / setters
}

Answer 1

没有内置的方法可以做到这一点。您必须编写自己的 JsonSerializer。有点像

class ModelSerializer extends JsonSerializer<List<Model>> {

    @Override
    public void serialize(List<Model> value, JsonGenerator jgen,
            SerializerProvider provider) throws IOException {
        jgen.writeStartArray();
        for (Model model : value) {
            jgen.writeStartObject();
            jgen.writeObjectField("model", model);
            jgen.writeEndObject();    
        }
        jgen.writeEndArray();
    }

}

然后注释 models 字段以便它使用它

@JsonSerialize(using = ModelSerializer.class)
private List<Model> models;

这将序列化为

{
    "status": "success",
    "models": [
        {
            "model": {
                "id": 1,
                "color": "red"
            }
        },
        {
            "model": {
                "id": 2,
                "color": "green"
            }
        }
    ]
}

如果您同时对此进行序列化和反序列化，您还需要一个自定义反序列化器。