Jackson序列化:忽略空值(或null)
我目前正在使用杰克逊2.1.4,并且在将对象转换为JSON字符串时忽略字段时遇到了一些麻烦。
这是我的类,它充当要转换的对象:
public class JsonOperation {public static class Request {
@JsonInclude(Include.NON_EMPTY)
String requestType;
Data data = new Data();
public static class Data {
@JsonInclude(Include.NON_EMPTY)
String username;
String email;
String password;
String birthday;
String coinsPackage;
String coins;
String transactionId;
boolean isLoggedIn;
}
}
public static class Response {
@JsonInclude(Include.NON_EMPTY)
String requestType = null;
Data data = new Data();
public static class Data {
@JsonInclude(Include.NON_EMPTY)
enum ErrorCode { ERROR_INVALID_LOGIN, ERROR_USERNAME_ALREADY_TAKEN, ERROR_EMAIL_ALREADY_TAKEN };
enum Status { ok, error };
Status status;
ErrorCode errorCode;
String expiry;
int coins;
String email;
String birthday;
String pictureUrl;
ArrayList <Performer> performer;
}
}
}
这是我如何转换它:
ObjectMapper mapper = new ObjectMapper();mapper.setVisibility(PropertyAccessor.FIELD, Visibility.ANY);
JsonOperation subscribe = new JsonOperation();
subscribe.request.requestType = "login";
subscribe.request.data.username = "Vincent";
subscribe.request.data.password = "test";
Writer strWriter = new StringWriter();
try {
mapper.writeValue(strWriter, subscribe.request);
} catch (JsonGenerationException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (JsonMappingException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
Log.d("JSON", strWriter.toString())
这是输出:
{"data":{"birthday":null,"coins":null,"coinsPackage":null,"email":null,"username":"Vincent","password":"test","transactionId":null,"isLoggedIn":false},"requestType":"login"}
如何避免这些空值?我只想获取“订阅”目的所需的信息!
这正是我要寻找的输出:
{"data":{"username":"Vincent","password":"test"},"requestType":"login"}
我还尝试了@JsonInclude(Include.NON_NULL)并将所有变量都设置为null,但是它也不起作用!感谢您的帮助!
回答:
你将注解放置在错误的位置-注解必须在类上,而不是在字段上。即:
@JsonInclude(Include.NON_NULL) //or Include.NON_EMPTY, if that fits your use case public static class Request {
// ...
}
如注释中所述,在2.x以下的版本中,此注释的语法为:
@JsonSerialize(include = JsonSerialize.Inclusion.NON_NULL) // or JsonSerialize.Inclusion.NON_EMPTY
另一种选择是ObjectMapper直接配置,只需调用 mapper.setSerializationInclusion(Include.NON_NULL);
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