Jackson 在反序列化 POJO 时坚持抛出令人困惑的异常

Question

即使一切正常，我也找不到为什么我从 Jacksoin 收到异常。

我有以下 Json：

      {
        "id": "8a599509-994a-4cff-ad6d-c3f770e8d159",
        "action": "0",
        "code": "13",
        "device_id": "0BC813D9-37FE-4FAB-9FA0-05F85CBAE777",
        "branch_id": "0BC813D9-37FE-4FAB-9FA0-05F85CBAE999",
        "description": "Sergio sei uno stra-figo",
        "date": "2021-11-09T10:22:45",
        "severity": 1
      }

我需要将 Json 反序列化为的类：

@JsonIgnorePropenter code hereerties(ignoreUnknown = true)
public class LogMdto {

private String id;

public String getId() {
    return id;
}

@JsonProperty(value = "object_id")
private String objectId;

@Size(max = Log.objectNameSize, message = "size may not by bigger than " + Log.objectNameSize)
@JsonProperty(value = "object_name")
private String objectName;

@JsonProperty("device_id")
private String deviceId;

@NotNull(message = "may not be null")
private String description;

@NotNull(message = "may not be null")
@Size(max = Log.codeSize, 
        message = "size may not by bigger than " + Log.codeSize)
private String code;

private Integer action;

private String id;

private int severity;

@JsonFormat(shape = JsonFormat.Shape.STRING, pattern="yyyy-MM-dd'T'HH:mm:ss")
private Timestamp date;


public Timestamp getDate() {
    return date;
}

public void setDate(String date) {
    DateTimeFormatter dft = DateTimeFormatter.ISO_LOCAL_DATE_TIME;
    this.date = Timestamp.valueOf(LocalDateTime.from(dft.parse(date)));
}

public String getObjectId() {
    return objectId;
}

public void setObjectId(String objectId) {
    this.objectId = objectId;
}

public String getObjectName() {
    return objectName;
}

public void setObjectName(String objectName) {
    this.objectName = objectName;
}

public String getDeviceId() {
    return deviceId;
}

public void setDeviceId(String deviceId) {
    this.deviceId = deviceId;
}

public String getDescription() {
    return description;
}

public void setDescription(String description) {
    this.description = description;
}

public String getCode() {
    return code;
}

public void setCode(String code) {
    this.code = code;
}

public Integer getAction() {
    return action;
}

public void setAction(Integer action) {
    this.action = action;
}

public void setId(String id) {
    this.id = id;
}

public int getSeverity() {
    return severity;
}

public void setSeverity(int severity) {
    this.severity = severity;
}

}

当我打电话给ObjectMapper().readValue(json, LogMdto.class) 时，我得到以下异常；

无法识别的字段“device_id”（com.plintech.LorikeetNestSpring.models.dto.mobile.LogMdto 类），未标记为可忽略

我不明白为什么会出现这个异常。 deviceId 字段是用@JsonProperty("device_id") 映射的，我有setter 和getter 但还是报错。

更新

我做了以下改动：

//Removed the annotation
private String deviceId;

.... ....

改变了setter和getter如下：

@JsonProperty(value = "device_id")
public String getDeviceId() {
    return deviceId;
}

@JsonProperty(value = "device_id")
public void setDeviceId(String deviceId) {
    this.deviceId = deviceId;
}

但结果总是相同的异常，我不明白我的代码有什么问题，我想不出还有什么可以尝试确保没有其他隐藏问题。

Answer 1

好的，谢谢大家的帮助，但答案有点微妙。代码没有问题，问题是mapper不对，是误导入了

org.codehaus.jackson

版本而不是

更快的xml

....更改了导入指令...一切都很好了。

Answer 2

苏珊的回答是正确的。

您必须将 @JsonProperty("device_id") 添加到您的 getter 和 setter。

为避免此类错误，您始终可以使用AnySetter 来保留无法正确映射的数据。

例如：

public class LogMdto {
....

    private Map<String, Object> additionalProperties = new HashMap<>(); // This Map holds all the properties that were not found.
    // You could check what is wrong with the names that this POJO receives from your JSON

    @JsonAnyGetter
    public Map<String, Object> getAdditionalProperties() {
        return this.additionalProperties;
    }

    @JsonAnySetter
    public void setAdditionalProperty(String name, Object value) {
        this.additionalProperties.put(name, value);
    }

....

Answer 3

如果我没记错的话，既然是私有字段，那么就不用Field@JsonProperty注解本身，而是用Getter/Setter。

Getter/Setter 将用于序列化/反序列化，在这两种情况下它们都不匹配 device_id 名称；

修复它：将 @JsonProperty 添加到您的 Getter/Setter。

另一方面，如果它是一个公共变量，那么下面没有 Getter/Setter 的情况就可以正常工作：

@JsonProperty("device_id")
public String deviceId;

=== 测试代码 ===

@JsonIgnoreProperties(ignoreUnknown = true)
public class LogMdto {

    private String id;

    @JsonProperty(value = "object_id")
    private String objectId;

    @JsonProperty(value = "object_name")
    private String objectName;

    private String deviceId;

    @NotNull(message = "may not be null")
    private String description;

    @NotNull(message = "may not be null")
    private String code;

    private Integer action;

    private int severity;

    @JsonFormat(shape = JsonFormat.Shape.STRING, pattern = "yyyy-MM-dd'T'HH:mm:ss")
    private Timestamp date;


    public String getId() {
        return id;
    }

    public Timestamp getDate() {
        return date;
    }

    public void setDate(String date) {
        DateTimeFormatter dft = DateTimeFormatter.ISO_LOCAL_DATE_TIME;
        this.date = Timestamp.valueOf(LocalDateTime.from(dft.parse(date)));
    }

    public String getObjectId() {
        return objectId;
    }

    public void setObjectId(String objectId) {
        this.objectId = objectId;
    }

    public String getObjectName() {
        return objectName;
    }

    public void setObjectName(String objectName) {
        this.objectName = objectName;
    }
    @JsonProperty("device_id")
    public String getDeviceId() {
        return deviceId;
    }
    @JsonProperty("device_id")
    public void setDeviceId(String deviceId) {
        this.deviceId = deviceId;
    }

    public String getDescription() {
        return description;
    }

    public void setDescription(String description) {
        this.description = description;
    }

    public String getCode() {
        return code;
    }

    public void setCode(String code) {
        this.code = code;
    }

    public Integer getAction() {
        return action;
    }

    public void setAction(Integer action) {
        this.action = action;
    }

    public void setId(String id) {
        this.id = id;
    }

    public int getSeverity() {
        return severity;
    }

    public void setSeverity(int severity) {
        this.severity = severity;
    }
}

---

public static void main(String[] args) throws Exception{
    String jsonTest = "{\n" +
            "        \"id\": \"8a599509-994a-4cff-ad6d-c3f770e8d159\",\n" +
            "        \"action\": \"0\",\n" +
            "        \"code\": \"13\",\n" +
            "        \"device_id\": \"0BC813D9-37FE-4FAB-9FA0-05F85CBAE777\",\n" +
            "        \"branch_id\": \"0BC813D9-37FE-4FAB-9FA0-05F85CBAE999\",\n" +
            "        \"description\": \"Sergio sei uno stra-figo\",\n" +
            "        \"date\": \"2021-11-09T10:22:45\",\n" +
            "        \"severity\": 1\n" +
            "      }";

    LogMdto logMdto = new ObjectMapper().readValue(jsonTest, LogMdto.class);

    System.out.println(logMdto.getDeviceId());
}

---

日志：

0BC813D9-37FE-4FAB-9FA0-05F85CBAE777