java - jackson 对象映射器 : readValue returns null

Question

我需要解析这个json:

{
   "id":"cpd4-b39c4b2a-b5cb-4581-b519-6034aaa7fe4e",
   "transactionId":"768a9be4-b5b3-452f-9bd3-9fff2e9ace5c",
   "status":"PUBLIC",
   "confidential":true,
   "expiringAt":1231231,
   "locked":true,
   "metadata":[
      {
         "user":"admin",
         "creationTimestamp":1538578453285,
         "value":"metadata"
      }
   ],
   "security":"read",
   "timestampCreation":1538578453285,
   "userCreation":"admin",
   "appCreation":"app",
   "document":{
      "id":null,
      "transactionId":"768a9be4-b5b3-452f-9bd3-9fff2e9ace5c",
      "docId":"68aab3799a9380fe82ed43ff2d46a5b07da1b270-1282",
      "size":1282,
      "name":"pom.xml",
      "alias":"alias",
      "hash":"68aab3799a9380fe82ed43ff2d46a5b07da1b270",
      "title":"title",
      "encoding":"UTF-8",
      "mimeType":"application/xml"
   }
}

对象引用类:

public class Reference {

    private String id;
    private String transactionId;

    private DocumentStatus status;
    private Boolean confidential;
    private Integer expiringAt;
    private Boolean locked;

    private List<Metadata> metadata;
    private String security;

    // IDReferenciaAlta
    private Date timestampCreation;
    private String userCreation;
    private String appCreation;

    private Date timestampModified;
    private String userModified;
    private String appModified;

    private Date timestampDeletion;
    private String userDeletion;
    private String appDeletion;

    //getters and setters...
}

其中元数据是:

public class Metadata {

    private String user;
    private Date creationTimestamp;
    private String value;

    //getters an setters
}

目前，我正在使用此代码:

Reference reference = null;
try {
    reference = this.mapper.readValue(jsonDocument, Reference.class);
} catch (IOException e1) {
    // TODO: Throw domain exception...
    e1.printStackTrace();
}

问题是 this.mapper.readValue(...) 返回 null。

我知道 json 架构和 Reference 类属性并不完全相同，但我希望获得具有“常见”json 属性的引用

Answer 1

如果没有堆栈跟踪，我们几乎不知道错误是什么。然而，从这个问题中可以看出，document属性没有映射到Reference类的任何字段。

所以你可以:

• 将 document 属性映射到字段。
  
  

• 使用@JsonIgnoreProperties("document")在 Reference 类中忽略 document 属性。或者您可以使用@JsonIgnoreProperties(ignoreUnknown = true)忽略任何未知属性。
  
  

• 配置您的 ObjectMapper通过禁用DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES来忽略未知属性。见下文:
  
  

  ObjectMapper mapper = new ObjectMapper();
  mapper.disable(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES);
  Reference reference = mapper.readValue(jsonDocument, Reference.class);