conversion empty map fail with jackson

Question

I use spring boot 2, In a dto have

@JsonInclude(value=Include.NON_EMPTY, content=Include.NON_NULL)
private Map<String, String> settings;

I get this error

org.springframework.http.converter.HttpMessageNotReadableException: JSON parse error: Cannot construct instance of java.util.LinkedHashMap (although at least one Creator exists): no String-argument constructor/factory method to deserialize from String value (''); nested exception is com.fasterxml.jackson.databind.exc.MismatchedInputException: Cannot construct instance of java.util.LinkedHashMap (although at least one Creator exists): no String-argument constructor/factory method to deserialize from String value ('')

from the client when i check what is sent, i see

settings: ""

why i get this error?

Edit

public Map<String, String> getSettings() {
    settings = settings == null ? new LinkedHashMap<>() : settings;
    return settings;
}

public void setSettings(Map<String, String> settings) {
    this.settings = new LinkedHashMap<>(settings);
}

web part

transfort come from: https://github.com/dominicbarnes/form-serialize

var form = transForm.serialize('#form'); form = JSON.stringify(form);

Tried to add on the field

@JsonInclude(value=JsonInclude.Include.CUSTOM, valueFilter=FilterMap.class)

My class

public class FilterMap {

   @Override
   public boolean equals(Object other) {
     return true;
   }
}

same problem