JSON序列化-如何不使用整个结构序列化一个类属性

Question

我想序列化一些字符串json（我用的是Spring Boot）：

{
  "commandId": "34d3a914-a3d7-112a-bs37-3452ac130002",
  "status": "SUCCESS",
  "response": {
    "prop1": "",
    "prop2": "",
    "prop3": "true",
    "prop4": ""
  }
}

我的映射器：

private static final ObjectMapper mapper = new ObjectMapper();

public static <T> T fromJson(String json, TypeReference<T> type) {
    T t;
    try {
      t = mapper.reader().forType(type).readValue(json);
    } catch (IOException e) {
      String message = "Error converting from json";
      log.error(message, e);
      throw new IllegalArgumentException(message);
    }

mapper的用法：

final Command command =
              JsonUtils.fromJson(json, new TypeReference<Command>() {});

命令类：

public class Command {
  private UUID commandId;
  private status status;
  private String response;
  private String error;
}

目前我收到错误：

com.fasterxml.jackson.databind.exc.MismatchedInputException: Cannot deserialize instance of `java.lang.String` out of START_OBJECT token

我想在 Mongo db response 字段中保存为字符串，稍后在从 DB 接收到该对象后，我可以反序列化整个对象。是否有任何注释告诉 Json 映射器不要序列化 ​​response 字段内的结构？

Answer 1

您可以为response 字段编写自定义反序列化程序，以将响应节点对象反序列化为字符串。并使用@JsonDeserialize 使用它一个reponnse 字段。

public class Command {
  ...
  @JsonDeserialize(using = RawJsonDeserializer.class)
  private String response;
  ...
}

public class RawJsonDeserializer extends JsonDeserializer<String> {
    @Override
    public String deserialize(JsonParser jp, DeserializationContext ctxt)
           throws IOException, JsonProcessingException {
        ObjectMapper mapper = (ObjectMapper) jp.getCodec();
        JsonNode node = mapper.readTree(jp);
        return mapper.writeValueAsString(node);
    }
}

Answer 2

除了反序列化器之外，另一种更简单的方法是在您的 Command 类中使用 @JsonProperty 注释。

public class Command {
  private UUID commandId;
  private String status;
  private String response;
  private String error;

  public UUID getCommandId() {
    return commandId;
  }

  @JsonProperty("commandId")
  public void setCommandId(String commandId) {
    this.commandId = UUID.fromString(commandId);
  }

  public String getStatus() {
    return status;
  }

  public void setStatus(String status) {
    this.status = status;
  }

  public String getResponse() {
    return response;
  }

  @JsonProperty("response")
  private void setResponse(Map<String, String> response) {
    this.response = response.toString();
  }

  public String getError() {
    return error;
  }

  public void setError(String error) {
    this.error = error;
  }
}