JsonMappingException when reading the response from RestTemplate

Seeing the exception when I call the GET method in RestTemplate

com.fasterxml.jackson.databind.JsonMappingException: N/A at [Source: (StringReader); line: 1, column: 13700] (through reference chain: com.homedepot.merch.meter.model.ResultSet[“issues”]->java.util.ArrayList[0]->com.homedepot.merch.meter.model.Issue[“fields”])

the sample java code is

ResponseEntity<String> response = restTemplate.exchange(JIRA_URL, HttpMethod.GET, entity, String.class);
            ObjectMapper jsonMapper = new ObjectMapper().configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false);
            if(response != null && response.getStatusCode() == HttpStatus.OK) {
                ResultSet resultSet = jsonMapper.readValue(response.getBody(), ResultSet.class);
                List<Issue> issues = resultSet.getIssues();
            }

java classses are

@Data
public class ResultSet {
    private int startAt;
    private int maxResults;
    private int total;
    private List<Issue> issues;
}

and the Issue class definition is

@Data
public class Issue {
    private String teamid;
    private String jiraboardid;
    @JsonAlias("id")
    private int id;
    @JsonAlias("key")
    private String issueid;
    private String issuetype;
    //private Sprint sprint;
    private int sprintId;
    private String sprintname;
    private Timestamp sprintstartdate;
    private Timestamp sprintenddate;
    private String state;
    private String status;
    private String createddate;
    private String creator_emailAddress;
    private String creator_displayName;
    private String creator_accountId;
    private boolean creator_isActive;
    private String inprogressdate;
    private String developmentdate;
    private String completeddate;
    private double developmentleadtime;
    private double leadtime;
    private String statuscategorychangeddate;
    private String lastupdateduser;
    private String lastupdateddate;
    private Double issuepoints;
    private ChangeLog changelog;
    
    @JsonProperty("fields")
    private void unpackNameFromNestedObject(Map<String, Object> brand) throws ParseException, JSONException, InterruptedException {
        createddate = brand.get("created").toString();
        statuscategorychangeddate = brand.get("statuscategorychangedate").toString();
        lastupdateddate = brand.get("updated").toString();
        issuetype = objectToString(brand.get("issuetype"), "issuetype");
        status = objectToString(brand.get("status"), "status");
        lastupdateduser = objectToString(brand.get("assignee"), "assignee");
        developmentdate = getIssueDevelopmentDoneTime(getChangelog().getHistories());

        if (brand.get("resolutiondate") != null) {
            completeddate = brand.get("resolutiondate").toString();
        }else
            completeddate = getIssueDoneTime(getChangelog().getHistories());

        if (brand.get("customfield_10025") != null)
            issuepoints = Double.parseDouble(brand.get("customfield_10025").toString());
        else
            issuepoints = 0.0;
        inprogressdate = getIssueInProgressTime(getChangelog().getHistories());
        if (inprogressdate != null && completeddate != null)
            leadtime = findDifference(inprogressdate, completeddate);
        if (inprogressdate != null && developmentdate != null)
            developmentleadtime = findDifference(inprogressdate, developmentdate);
        else
            developmentleadtime = leadtime;

        //If there's no Done status, assign developmentleadtime for leadtime
        if (developmentdate != null && completeddate == null)
            leadtime = developmentleadtime;
        try{
            creator_emailAddress = objectToCreator(brand.get("creator"), "emailAddress");
        }catch (Exception ex){
            System.out.println(issueid+ " Exception :"+ex);
        }
        creator_displayName = objectToCreator(brand.get("creator"), "displayName");
        creator_accountId = objectToCreator(brand.get("creator"), "accountId");
        creator_isActive = Boolean.parseBoolean(objectToCreator(brand.get("creator"), "isActive"));
    }
}

How do I fix this JsonMappingException?

Answer

You are trying to serialize the result of a method that returns void. Also, I am not sure if private access methods can be serialized. I think that serialization methods are not supposed to get parameters, typically they are getters.