JSON - 无法使用Jackson在Object中序列化JSONObject

Question

我有以下课程:

class A{    
    String abc;
    String def;
    // appropriate getters and setters with JsonProperty Annotation 
}

我打电话给Jacksons objectMapper.writeValueAsString(A)哪个工作正常.

现在我需要添加另一个实例成员:

class A{    
    String abc;
    String def;
    JSONObject newMember; // No, I cannot Stringify it, it needs to be JSONObject
    // appropriate getters and setters with JsonProperty Annotation 
}

但是当我序列化时,我会遇到异常:

org.codehaus.jackson.map.JsonMappingException: No serializer found for class org.json.JSONObject and no properties discovered to create BeanSerializer

我尝试了JSONNode,但它将Output作为{outerjson:" {innerjson} " }而不是{outerjson:{innerjson}}.

是否可以使用Jackson实现上述输出,即JSONObject中的JSONObject？

Answer 1

要用什么东西jackson-datatype-json-org

// import com.fasterxml.jackson.datatype.jsonorg.JsonOrgModule;

ObjectMapper mapper = new ObjectMapper();
mapper.registerModule(new JsonOrgModule());

请参阅https://github.com/FasterXML/jackson-datatype-json-org

Answer 2

好吧，如果您无法替换 POJO 或 Map 上的 JSONObject，那么您可以编写自定义序列化程序。这是一个例子：

public class JacksonJSONObject {

    public static class MyObject {
        public final String string;
        public final JSONObject object;

        @JsonCreator
        public MyObject(@JsonProperty("string") String string, @JsonProperty("object") JSONObject object) {
            this.string = string;
            this.object = object;
        }

        @Override
        public String toString() {
            return "MyObject{" +
                    "string='" + string + '\'' +
                    ", object=" + object +
                    '}';
        }
    }

    public static void main(String[] args) throws IOException {
        ObjectMapper mapper = new ObjectMapper();
        SimpleModule module = new SimpleModule("org.json");
        module.addSerializer(JSONObject.class, new JsonSerializer<JSONObject>() {
            @Override
            public void serialize(JSONObject value, JsonGenerator jgen, SerializerProvider provider) throws IOException {
            jgen.writeRawValue(value.toString());
            }
        });
        module.addDeserializer(JSONObject.class, new JsonDeserializer<JSONObject>() {
            @Override
            public JSONObject deserialize(JsonParser jp, DeserializationContext ctxt) throws IOException {
                Map<String, Object> bean = jp.readValueAs(new TypeReference<Map<String, Object>>() {});
                return new JSONObject(bean);
            }
        });
        mapper.registerModule(module);
        JSONObject object = new JSONObject(Collections.singletonMap("key", "value"));
        String json = mapper.writerWithDefaultPrettyPrinter().writeValueAsString(new MyObject("string", object));

        System.out.println("JSON: " + json);
        System.out.println("Object: " + mapper.readValue(json, MyObject.class));
    }
}

输出：

JSON: {
  "string" : "string",
  "object" : {"key":"value"}
}
Object: MyObject{string='string', object={"key":"value"}}