Spring MVC - Get Exchange Rate Values using REST API

import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Configuration;
import org.springframework.web.servlet.config.annotation.EnableWebMvc;
import org.springframework.web.servlet.view.InternalResourceViewResolver;
import org.springframework.web.servlet.view.JstlView;

@Configuration
@EnableWebMvc
@ComponentScan(basePackages = { "com.exchangeRate.exchangeRate_Rest_API" })
public class AppConfig {
    @Bean
    public InternalResourceViewResolver resolver() {
        InternalResourceViewResolver resolver = new InternalResourceViewResolver();
        resolver.setViewClass(JstlView.class);
        resolver.setPrefix("/");
        resolver.setSuffix(".jsp");
        return resolver;
    }
}

import org.springframework.web.servlet.support.AbstractAnnotationConfigDispatcherServletInitializer;

public class SpringMvcDispatcherServletInitializer 
          extends AbstractAnnotationConfigDispatcherServletInitializer {
    
    @Override
    protected Class<?>[] getRootConfigClasses() {
        return null;
    }
 
    @Override
    protected Class<?>[] getServletConfigClasses() {
        return new Class[] { AppConfig.class };
    }
 
    @Override
    protected String[] getServletMappings() {
        return new String[] { "/" };
    } 
  
}

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.net.URL;
import java.util.ArrayList;
import java.util.StringTokenizer;
import org.springframework.stereotype.Controller;
import org.springframework.util.StringUtils;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.ResponseBody;
import com.google.gson.Gson;
import com.google.gson.JsonObject;

@Controller
public class ExchangeRateController {

    @RequestMapping("/getExchangeRateDetailsByCurrency")
    public @ResponseBody
    JsonObject getExchangeRateDetails(String  currency) throws IOException {

        JsonObject jsonObject = new JsonObject();
        String data = getExchangeRateData(currency);
        data = data.replaceAll("^\"|\"$", "");
        StringTokenizer jsonTokenizer = new StringTokenizer(data,",");
        String internalData[];
        String expectedExchangeRateOutput = null;
        ArrayList otherCurrencies = new ArrayList();
        
        // Here given provisions to get the 
        // value of GBP and EUR for INR
        if (currency.equalsIgnoreCase("INR")) {
            otherCurrencies.add("GBP");
            otherCurrencies.add("EUR");
        }
      
        // Here given provisions to get the 
        // value of INR and EUR for GBP
        if (currency.equalsIgnoreCase("GBP")) {
            otherCurrencies.add("INR");
            otherCurrencies.add("EUR");
        }
      
        // Here given provisions to get the value
        // of GBP and INR for EUR
        if (currency.equalsIgnoreCase("EUR")) {
            otherCurrencies.add("INR");
            otherCurrencies.add("GBP");
        }
        while (jsonTokenizer.hasMoreTokens()) {  
            expectedExchangeRateOutput = jsonTokenizer.nextToken();
            internalData = StringUtils.split(expectedExchangeRateOutput,":");
            System.out.println(internalData[0]+internalData[1]);
            if (internalData[0].substring(2,internalData[0].length()-1).equalsIgnoreCase(currency)) {
                jsonObject.addProperty(currency, internalData[1]);                
            }
            if (internalData[0].substring(1,internalData[0].length()-1).equalsIgnoreCase(otherCurrencies.get(0).toString())) {
                jsonObject.addProperty(otherCurrencies.get(0).toString(), internalData[1]);
            }
            if (internalData[0].substring(1,internalData[0].length()-1).equalsIgnoreCase(otherCurrencies.get(1).toString())) {
                jsonObject.addProperty(otherCurrencies.get(1).toString(), internalData[1]);
            }
        } 

        return jsonObject;
    }

    private String getExchangeRateData(String currency) throws IOException {
        String data = null;
        StringBuilder responseData = new StringBuilder();
        JsonObject jsonObject = null;
        URL url = null;
        url = new URL("https://api.exchangerate-api.com/v4/latest/" + currency);        
        HttpURLConnection con = (HttpURLConnection) url.openConnection();
        con.setRequestMethod("GET");
        con.setRequestProperty("User-Agent", "Mozilla/5.0");
        int responseCode = con.getResponseCode();
        System.out.println("\nSending 'GET' request to URL : " + url);
        // System.out.println("Response Code : " + responseCode);
        try (BufferedReader in = new BufferedReader(
                new InputStreamReader(con.getInputStream()))) {
            String line;
            while ((line = in.readLine()) != null) {
                responseData.append(line);
            }
            jsonObject = new Gson().fromJson(responseData.toString(), JsonObject.class);
            
            data = jsonObject.get("rates").toString();

        }
        // System.out.println(data);
        return data;
    }
}