no string-argument constructor/factory method to deserialize from string value

SyntaxFix
3 min readMar 4, 2022

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What is the problem ?

I’m running into a json parsing issue when using the ObjectMapper class from the com.fasterxml.jackson.databind package, and the error that I'm getting is:

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 ('')

The web application where this problem is occurring is a Spring MVC application using an AngularJS front end, but I can duplicate the issue with a much smaller, all java program. Here are my beans:

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;
}
}

Here is the code where I can properly map the json:

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();
}
}

When adjusting the data in the jsonMessage var is when I run into the error that I mentioned above:

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

So, the problem happens when changing the json from this:

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

to this:

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

Instead of sending values for my Address bean, I'm getting just an empty string. Unfortunately, I'm receiving my data from a third party and have no control over the data I receive.

Is there an annotation that needs to be added to be able to handle this?

The Solution is…

Try setting mapper.configure(DeserializationConfig.Feature.ACCEPT_EMPTY_STRING_AS_NULL_OBJECT, true)

or

mapper.enable(DeserializationFeature.ACCEPT_EMPTY_STRING_AS_NULL_OBJECT);

depending on your Jackson version.

For more solutions on this problem check them on syntaxfix

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