How to Serialise a JSON String to a JAVA Object using Jackson

I am having trouble in deserialising the below JSON String to a Java Object.

{
    "action": {
               "onWarning":{
                   "alert":{
                          "isEnabled": true,
                          "name": ""
                           }
                   },
               "onError":{
                 "alert":{
                        "isEnabled": true,
                        "name": ""
                        }
                   },
                "onSuccess":{
                 "alert":{
                        "isEnabled": true,
                        "name": ""
                        }
                   }
             }
}

The code below should work but i think my issue is with the mapper i am passing with it –

ObjectMapper mapper = new ObjectMapper();
JobConfig lib = mapper.readValue(jsonString, JobConfig.class);
System.out.println(lib.action.onWarning.alert.isEnabled);

The mapper i pass with it is like below :

Alert.java

public class Alert{
    @JsonProperty("isEnabled")
    public boolean isEnabled;

    @JsonProperty("name")
    public String name;
}

AlertConfig.java

public class AlertConfig {
    
    @JsonProperty("onSuccess")
    public Alert onSuccess;

    @JsonProperty("onWarning")
    public Alert onWarning;

    @JsonProperty("onError")
    public Alert onError;
}

JobConfig.java

public class JobConfig {
    @JsonProperty("action")
    public AlertConfig action;
}

Error i get is :

com.fasterxml.jackson.databind.exc.UnrecognizedPropertyException: Unrecognized field "alert" (class com.test.dv.service.domain.Alert), not marked as ignorable (2 known properties: "name", "isEnabled"])

I am nor sure how to name the content of alert JSON as alert but it already has been named as Alert.

Answer

You should create an AlertWrapper Class like below –

public class AlertWrapper {

    @JsonProperty("alert")
    public Alert alert;
}

And your AlertConfig class should contain AlertWrapper like below –

public class AlertConfig {

    @JsonProperty("onSuccess")
    public AlertWrapper onSuccess;

    @JsonProperty("onWarning")
    public AlertWrapper onWarning;

    @JsonProperty("onError")
    public AlertWrapper onError;
}

Doing this you will complete your DTO(s)