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

The error message “no string-argument constructor/factory method to deserialize from string value” typically occurs when you are trying to deserialize an object from a string value, but the object does not have a suitable constructor or factory method that takes a string argument.

When deserializing an object from a string value, the deserialization process relies on a constructor or factory method to create an instance of the object using the provided string value. However, if the object does not have a constructor or factory method that accepts a string argument, the deserialization process fails and throws the mentioned error.

Here is an example to illustrate the issue:

    
public class Person {
    private String name;
  
    public Person() {
        // Default constructor without any arguments
    }
  
    public Person(String name) {
        this.name = name;
    }
  
    public String getName() {
        return name;
    }
}
  
String jsonString = "{\"name\":\"John\"}";
ObjectMapper objectMapper = new ObjectMapper();
Person person = objectMapper.readValue(jsonString, Person.class);
    
  

In the above example, the Person class does not have a constructor or factory method that accepts a string argument. When trying to deserialize the JSON string into a Person object using readValue(jsonString, Person.class), the deserialization process fails and throws the “no string-argument constructor/factory method” error.

To resolve this issue, you have a few options:

• Add a constructor or factory method to the object that accepts a string argument:

      
public class Person {
    private String name;

    public Person() {
        // Default constructor without any arguments
    }

    public Person(String name) {
        this.name = name;
    }

    public String getName() {
        return name;
    }

    public static Person fromString(String jsonString) {
        // Create a new Person object from the provided string value
        // Parse the jsonString and set the necessary fields
        return new Person(parsedName);
    }
}

String jsonString = "{\"name\":\"John\"}";
ObjectMapper objectMapper = new ObjectMapper();
Person person = objectMapper.readValue(jsonString, Person.class);
      
    

• If modifying the object is not an option, you can create a custom deserializer:

      
public class PersonDeserializer extends StdDeserializer<Person> {

    public PersonDeserializer() {
        this(null);
    }

    public PersonDeserializer(Class<?> vc) {
        super(vc);
    }

    @Override
    public Person deserialize(JsonParser jp, DeserializationContext ctxt)
            throws IOException, JsonProcessingException {
        // Parse the jsonString and set the necessary fields
        return new Person(parsedName);
    }
}

String jsonString = "{\"name\":\"John\"}";
ObjectMapper objectMapper = new ObjectMapper();
SimpleModule module = new SimpleModule();
module.addDeserializer(Person.class, new PersonDeserializer());
objectMapper.registerModule(module);
Person person = objectMapper.readValue(jsonString, Person.class);
      
    

Both of the above options provide a way to deserialize the object from the string value by either adding a suitable constructor or factory method, or by creating a custom deserializer to handle the deserialization process.