Retrieving Data from an Open Source REST API Using Spring MVC

// Java Program to Illustrate Application 
// configuration Class

// Importing required classes
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;

// Annotations
@Configuration
@EnableWebMvc
@ComponentScan(basePackages
               = { "com.zipCode.zipCode_RestAPI" })

// Class
public class AppConfig {

    @Bean public InternalResourceViewResolver resolver()
    {

        InternalResourceViewResolver resolver
            = new InternalResourceViewResolver();
        resolver.setViewClass(JstlView.class);
        resolver.setPrefix("/");
        resolver.setSuffix(".jsp");

        return resolver;
    }
}

// Java Program to Illustrate
// SpringMvcDispatcherServletInitializer Class

// Importing required classes
import org.springframework.web.servlet.support.AbstractAnnotationConfigDispatcherServletInitializer;

// Class
public class SpringMvcDispatcherServletInitializer
    extends AbstractAnnotationConfigDispatcherServletInitializer {

    // Method 1
    @Override protected Class<?>[] getRootConfigClasses()
    {
        return null;
    }

    // Method 2
    @Override protected Class<?>[] getServletConfigClasses()
    {
        return new Class[] { AppConfig.class };
    }

    // Method 3
    @Override protected String[] getServletMappings()
    {
        return new String[] { "/" };
    }
}

package com.zipCode.zipCode_RestAPI;

import com.google.gson.Gson;
import com.google.gson.JsonArray;
import com.google.gson.JsonElement;
import com.google.gson.JsonObject;

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.Iterator;

import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.ResponseBody;

@Controller
public class ZipCodeController {

    @RequestMapping("/getLocalityDetailsByZipCode")
    public @ResponseBody JsonObject getLocalityDetailsByZipCode(String zipCode)
            throws IOException {

        JsonObject jsonObject = getLocalityDetailsByZip(zipCode);

        JsonObject finalJsonObject = new JsonObject();

        String country =
                jsonObject.get("country").toString()
                        .replaceAll("^\"|\"$", "");

        JsonArray jsonPlacesArray =
                jsonObject.get("places").getAsJsonArray();

        ArrayList<String> placesList = new ArrayList<>();
        ArrayList<String> stateList = new ArrayList<>();
        ArrayList<String> latitudeList = new ArrayList<>();
        ArrayList<String> longitudeList = new ArrayList<>();

        Iterator<JsonElement> objectIterator =
                jsonPlacesArray.iterator();

        while (objectIterator.hasNext()) {

            JsonObject jObj =
                    objectIterator.next().getAsJsonObject();

            placesList.add(
                    jObj.get("place name")
                            .toString()
                            .replaceAll("^\"|\"$", ""));

            stateList.add(
                    jObj.get("state")
                            .toString()
                            .replaceAll("^\"|\"$", ""));

            latitudeList.add(
                    jObj.get("latitude")
                            .toString()
                            .replaceAll("^\"|\"$", ""));

            longitudeList.add(
                    jObj.get("longitude")
                            .toString()
                            .replaceAll("^\"|\"$", ""));
        }

        finalJsonObject.addProperty("country", country);
        finalJsonObject.addProperty(
                "statename", stateList.get(0));
        finalJsonObject.addProperty(
                "associatedplaces", placesList.toString());
        finalJsonObject.addProperty(
                "associatedlatitude",
                latitudeList.toString());
        finalJsonObject.addProperty(
                "associatedlongitude",
                longitudeList.toString());

        return finalJsonObject;
    }

    private JsonObject getLocalityDetailsByZip(String zipCode)
            throws IOException {

        URL url =
                new URL("http://api.zippopotam.us/IN/" + zipCode);

        HttpURLConnection con =
                (HttpURLConnection) url.openConnection();

        con.setRequestMethod("GET");

        StringBuilder responseData = new StringBuilder();

        try (BufferedReader in =
                     new BufferedReader(
                             new InputStreamReader(
                                     con.getInputStream()))) {

            String line;

            while ((line = in.readLine()) != null) {
                responseData.append(line);
            }
        }

        return new Gson().fromJson(
                responseData.toString(),
                JsonObject.class);
    }
}