Java Jackson反序列化-空对象引用上的JsonMappingException

我有一个Note类型的object newNote。我正在通过向newNote添加值来合成对象（使用Jackson库），这没关系，但当我尝试这样做时：

String bodyRequest = mapper.writeValueAsString(newNote);

我有一个空对象引用的JsonMappingException

我正在尝试撰写一个POST请求的正文，以便在此处插入：

URL url = new URL("http://myUrl");

            HttpURLConnection connection = (HttpURLConnection)url.openConnection();
            connection.setRequestMethod("POST");
            connection.setRequestProperty("Content-Type", "application/json");
            connection.setRequestProperty("Authorization", mAuth);
            connection.setDoOutput(true);

            //here I try to set up the body
            String bodyRequest = mapper.writeValueAsString(newNote);



            DataOutputStream dStream = new DataOutputStream(connection.getOutputStream());

            //here I have the other problem
            dStream.writeBytes(bodyRequest);
            dStream.flush();
            dStream.close();

但是，当我试图：

dStream.writeBytes(bodyRequest);

我将ObjectMapper配置为：

mapper = new ObjectMapper();
                mapper.registerModule(new ThreeTenModule());
                mapper.configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false);
                mapper.enable(SerializationFeature.USE_EQUALITY_FOR_OBJECT_ID);
                mapper.configure(DeserializationFeature.FAIL_ON_INVALID_SUBTYPE, false);
                mapper.configure(DeserializationFeature.FAIL_ON_IGNORED_PROPERTIES, false);
                mapper.configure(DeserializationFeature.FAIL_ON_MISSING_CREATOR_PROPERTIES, false);
                mapper.configure(DeserializationFeature.FAIL_ON_NULL_FOR_PRIMITIVES, false);
                mapper.configure(DeserializationFeature.FAIL_ON_NUMBERS_FOR_ENUMS, false);
                mapper.configure(DeserializationFeature.FAIL_ON_READING_DUP_TREE_KEY, false);
                mapper.configure(DeserializationFeature.FAIL_ON_UNRESOLVED_OBJECT_IDS, false);

我的笔记课是：

@Entity
@JsonIdentityInfo(generator = IdentityGenerator.class)
@JsonIgnoreProperties(ignoreUnknown = true)

public class Note {

@Id
private Long id;
private User author;
private ZonedDateTime created;
private String content;
private Status status;
private User assignee;
private Activity activity;
private List<File> attachments = new ArrayList<>();
private Boolean restricted;  
private Status NextStatus;
private User NextAssignee;

...
//setters and getters
//hashcode and equals methods
...
}

使用者

mapper.setSerializationInclusion(Include.NON_NULL);

或

---

Jackson还允许在ObjectMapper上全局配置此行为：

提供stackstrace

mapper.setSerializationInclusion(Include.NON_NULL);

 mapper.setSerializationInclusion(JsonSerialize.Inclusion.NON_NULL);