AEM 6.3 Sling Models Error: Cannot be correctly instantiated by the Use API.

I am working on a AEM 6.1 to 6.3 Migration project. After replacing all the deprecated methods/api's like admin resource resolver and WCMUse with getServiceResourceResolver and WCMUsePojo respectively, my application is throwing an error on sling models (as below). Basically it's not getting instantiated -

Error Says:

Code is written like:

import java.io.UnsupportedEncodingException;

import java.net.URLDecoder;

import java.util.List;

import java.util.Locale;

import java.util.Map;

import javax.annotation.PostConstruct;

import javax.inject.Inject;

import org.apache.commons.lang3.BooleanUtils;

import org.apache.commons.lang3.StringUtils;

import org.apache.felix.scr.annotations.Reference;

import org.apache.sling.api.SlingHttpServletRequest;

import org.apache.sling.api.resource.Resource;

import org.apache.sling.api.resource.ResourceResolver;

import org.apache.sling.api.resource.ValueMap;

import org.apache.sling.commons.json.JSONException;

import org.apache.sling.commons.json.JSONObject;

import org.apache.sling.models.annotations.Model;

import org.apache.sling.models.annotations.injectorspecific.Self;

import org.slf4j.Logger;

import org.slf4j.LoggerFactory;

import com.day.cq.wcm.api.Page;

import com.google.gson.Gson;

/**

* Sling Model for getting selectValue.

*/

@Model(adaptables = SlingHttpServletRequest.class)

public class SelectValue {

    private static final Logger LOG = LoggerFactory.getLogger(SelectValue.class);

    @Inject

    private Page currentPage;

    @Inject @Self

    private SlingHttpServletRequest request;

    private String localCode;

    @PostConstruct

    public void init() {     

        localCode = LanguagesUtil.getLanguageLocaleCode(currentPage.getPath());

..........

Is there any issue with the code written?

Has anyone encountered this type of issue while migrating aem 6.1 to 6.3?