没有String-argument构造函数/工厂方法从String值反序列化（''）

时间：2017-07-14 19:29:48

标签： java json spring

我在使用ObjectMapper包中的com.fasterxml.jackson.databind类时遇到了json解析问题，而我得到的错误是：

com.fasterxml.jackson.databind.JsonMappingException: Can not construct instance of com.graybar.utilities.ups.beans.Address: no String-argument constructor/factory method to deserialize from String value ('')

发生此问题的Web应用程序是使用AngularJS前端的Spring MVC应用程序，但我可以使用更小的全java程序复制该问题。这是我的豆子：

Shipment.java 

@JsonIgnoreProperties(ignoreUnknown = true)
public class Shipment {
    @JsonProperty("Activity")
    private ArrayList<Activity> activity;
    public ArrayList<Activity> getActivity() {
        return activity;
    }
    public void setActivity(ArrayList<Activity> activity) {
        this.activity = activity;
    }
}

Activity.java 

@JsonIgnoreProperties(ignoreUnknown = true)
public class Activity {
    @JsonProperty("ActivityLocation")
    private ArrayList<ActivityLocation> activityLocation;
    public ArrayList<ActivityLocation> getActivityLocation() {
        return activityLocation;
    }
    public void setActivityLocation(ArrayList<ActivityLocation> activityLocation) {
        this.activityLocation = activityLocation;
    }
}

ActivityLocation.java 

@JsonIgnoreProperties(ignoreUnknown = true)
public class ActivityLocation {
    @JsonProperty("Address")
    private Address address;
    public Address getAddress() {
        return address;
    }
    public void setAddress(Address address) {
        this.address = address;
    }
}

Address.java 

@JsonIgnoreProperties(ignoreUnknown = true)
public class Address {
    @JsonProperty("City")
    private String city;
    @JsonProperty("StateProvinceCode")
    private String stateProvinceCode;
    @JsonProperty("CountryCode")
    private String countryCode;
    public String getCity() {
        return city;
    }
    public void setCity(String city) {
        this.city = city;
    }
    public String getCountryCode() {
        return countryCode;
    }
    public void setCountryCode(String countryCode) {
        this.countryCode = countryCode;
    }
    public String getStateProvinceCode() {
        return stateProvinceCode;
    }
    public void setStateProvinceCode(String stateProvinceCode) {
        this.stateProvinceCode = stateProvinceCode;
    }
}

以下是我可以正确映射json的代码：

public static void main(String[] args) {
    String jsonMessage = "" +
        "{" + 
        "   \"Activity\": [{ " +
        "       \"ActivityLocation\": { " +
        "           \"Address\": { " +
        "               \"City\": \"Hana\", " +
        "               \"StateProvinceCode\": \"Hi\", " +
        "               \"CountryCode\": \"US\" " +
        "           } " +
        "       } " +
        "   }, " +
        "   { " +
        "       \"ActivityLocation\": { " +
        "           \"Address\": { " +
        "               \"City\": \"Honolulu\", " +
        "               \"StateProvinceCode\": \"Hi\", " +
        "               \"CountryCode\": \"US\" " +
        "           } " +
        "       } " +
        "   }] " +
    "} ";

    try {
        ObjectMapper mapper = new ObjectMapper();
        mapper.enable(DeserializationFeature.ACCEPT_SINGLE_VALUE_AS_ARRAY);

        Shipment shipment = mapper.readValue(jsonMessage, Shipment.class);
        System.out.println("shipment.toString = " + shipment.toString());
    } catch (Exception e) {
        e.printStackTrace();
    }
}

调整jsonMessage var中的数据时，我遇到上面提到的错误：

    "{" + 
    "   \"Activity\": [{ " +
    "       \"ActivityLocation\": { " +
    "           \"Address\": { " +
    "               \"City\": \"Hana\", " +
    "               \"StateProvinceCode\": \"Hi\", " +
    "               \"CountryCode\": \"US\" " +
    "           } " +
    "       } " +
    "   }, " +
    "   { " +
    "       \"ActivityLocation\": { " +
    "           \"Address\": \"\" " +
    "           } " +
    "       } " +
    "   }] " +
    "} ";

因此，从此更改json时会出现问题：

{
    "ActivityLocation": { 
        "Address": {
            "City": "Honolulu", 
            "StateProvinceCode": "Hi", 
            "CountryCode": "US"
        }
    }
}]

到此：

{
"ActivityLocation": {
     "Address": ""
    }
}

我没有为我的Address bean发送值，而只是一个空字符串。不幸的是，我从第三方接收数据，无法控制收到的数据。

是否需要添加注释才能处理此问题？

6 个答案:

答案 0 :(得分：27)

尝试设置mapper.configure(DeserializationConfig.Feature.ACCEPT_EMPTY_STRING_AS_NULL_OBJECT, true)

或

mapper.enable(DeserializationFeature.ACCEPT_EMPTY_STRING_AS_NULL_OBJECT);

取决于您的杰克逊版本。

答案 1 :(得分：0)

当我不小心打电话给

mapper.convertValue(...)

代替

mapper.readValue(...)

因此，只需确保调用正确的方法，因为参数相同并且IDE可以找到很多东西

答案 2 :(得分：0)

此异常表明您正在尝试从字符串“ \” \“”反序列化对象“ Address”，而不是诸如“ {…}”之类的对象描述。解串器找不到带有String参数的Address的构造函数。您必须用{}替换“”，以避免出现此错误。

答案 3 :(得分：0)

我找到了另一种方法来处理此错误。 （变量根据原始问题）

   JsonNode parsedNodes = mapper.readValue(jsonMessage , JsonNode.class);
        Response response = xmlMapper.enable(ACCEPT_EMPTY_STRING_AS_NULL_OBJECT,ACCEPT_SINGLE_VALUE_AS_ARRAY )
                .disable(FAIL_ON_UNKNOWN_PROPERTIES, FAIL_ON_IGNORED_PROPERTIES)
                .convertValue(parsedNodes, Response.class);

答案 4 :(得分：0)

使用以下代码段对我有用

ObjectMapper objectMapper = new ObjectMapper();
String jsonString = "{\"symbol\":\"ABCD\}";
objectMapper.configure(DeserializationFeature.ACCEPT_EMPTY_STRING_AS_NULL_OBJECT, true);
Trade trade = objectMapper.readValue(jsonString, new TypeReference<Symbol>() {});

模型类

@JsonIgnoreProperties    public class Symbol {
    @JsonProperty("symbol")
    private String symbol;
}

答案 5 :(得分：-3)

mapper.enable(DeserializationFeature.ACCEPT_EMPTY_STRING_AS_NULL_OBJECT);

我的代码与上面的答案一样运行良好。 原因是来自jackson的json与从控制器发送的json不同。

String test1= mapper.writeValueAsString(result1);

和json一样（可以正常反序列化）：

{"code":200,"message":"god","data":[{"nics":null,"status":null,"desktopOperatorType":null,"marker":null,"user_name":null,"user_group":null,"user_email":null,"product_id":null,"image_id":null,"computer_name":"AAAA","desktop_id":null,"created":null,"ip_address":null,"security_groups":null,"root_volume":null,"data_volumes":null,"availability_zone":null,"ou_name":null,"login_status":null,"desktop_ip":null,"ad_id":null},{"nics":null,"status":null,"desktopOperatorType":null,"marker":null,"user_name":null,"user_group":null,"user_email":null,"product_id":null,"image_id":null,"computer_name":"BBBB","desktop_id":null,"created":null,"ip_address":null,"security_groups":null,"root_volume":null,"data_volumes":null,"availability_zone":null,"ou_name":null,"login_status":null,"desktop_ip":null,"ad_id":null}]}

但是json从另一个服务发送，就像：

{"code":200,"message":"查询桌面列表成功","data":[{"nics":"","status":"","metadata":"","desktopOperatorType":"","marker":"","user_name":"csrgzbsjy","user_group":"ADMINISTRATORS","user_email":"","product_id":"","image_id":"","computer_name":"B-jiegou-all-15","desktop_id":"6360ee29-eb82-416b-aab8-18ded887e8ff","created":"2018-11-12T07:45:15.000Z","ip_address":"192.168.2.215","security_groups":"","root_volume":"","data_volumes":"","availability_zone":"","ou_name":"","login_status":"","desktop_ip":"","ad_id":""},{"nics":"","status":"","metadata":"","desktopOperatorType":"","marker":"","user_name":"glory_2147","user_group":"ADMINISTRATORS","user_email":"","product_id":"","image_id":"","computer_name":"H-pkpm-all-357","desktop_id":"709164e4-d3e6-495d-9c1e-a7b82e30bc83","created":"2018-11-09T09:54:09.000Z","ip_address":"192.168.2.235","security_groups":"","root_volume":"","data_volumes":"","availability_zone":"","ou_name":"","login_status":"","desktop_ip":"","ad_id":""}]}

在不启动参数的情况下，您会注意到差异。 小心

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