OpenSource REST API URL and Retrieving Data From it By Using Spring MVC

Last Updated : 02 May, 2022

In this internet era, a lot of helper services are available in the form of REST API and mostly REST API provides us the details in the form of JSON/XML. We can use them in our applications and render the data as we like. Here is the list of a few opensource REST API URLs:

API Name	Description	URL
CoinGecko	Exchange rates	https://api.coingecko.com/api/v3/exchange_rates
ExchangeRate-API	Exchange rates	https://open.er-api.com/v6/latest/INR
Genderize.io	Prediction of gender based on name	https://api.genderize.io?name=rachel
WeatherDB	To know about the weather	https://weatherdbi.herokuapp.com/data/weather/london
Zippopotamus	Zipcode information	https://api.zippopotam.us/IN/600028

There are still more open-source APIs available. Here we will be learning how to extract the zip code details using Spring MVC:

REST API: http://api.zippopotam.us/IN/<Required Pincode>

Example:

http://api.zippopotam.us/IN/600028

Output: JSON

{   "post code": "600028",   "country": "India",   "country abbreviation": "IN",   "places": [     {       "place name": "Fore Shore Estate",       "longitude": "80.2417",       "state": "Tamil Nadu",       "state abbreviation": "TN",       "latitude": "13.0206"     },     {       "place name": "Ramakrishnanagar",       "longitude": "80.2417",       "state": "Tamil Nadu",       "state abbreviation": "TN",       "latitude": "13.0206"     },     {       "place name": "R A Puram Colony",       "longitude": "80.2417",       "state": "Tamil Nadu",       "state abbreviation": "TN",       "latitude": "13.0206"     }   ] }

Now using Spring MVC Framework, let us try to render the REST API details on the screen

Implementation:

It is as depicted Step by Step below where initially let us do see the project structure which is as follows:

A. File: pom.xml

XML

<project xmlns="http://maven.apache.org/POM/4.0.0"     xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"     xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/maven-v4_0_0.xsd">     <modelVersion>4.0.0</modelVersion>     <groupId>com.zipCode.zipCode_RestAPI</groupId>     <artifactId>zipCode_RestAPI</artifactId>     <packaging>war</packaging>     <version>0.0.1-SNAPSHOT</version>     <name>profileGenerator</name>     <url>http://maven.apache.org</url>     <properties>         <failOnMissingWebXml>false</failOnMissingWebXml>         <spring-version>5.1.0.RELEASE</spring-version>     </properties>     <dependencies>         <!-- https://mvnrepository.com/artifact/org.springframework/spring-webmvc -->         <dependency>             <groupId>org.springframework</groupId>             <artifactId>spring-webmvc</artifactId>             <version>${spring-version}</version>         </dependency>         <dependency>             <groupId>org.springframework</groupId>             <artifactId>spring-test</artifactId>             <version>${spring-version}</version>         </dependency>          <!-- JSTL Dependency -->         <dependency>             <groupId>javax.servlet.jsp.jstl</groupId>             <artifactId>javax.servlet.jsp.jstl-api</artifactId>             <version>1.2.1</version>         </dependency>         <dependency>             <groupId>taglibs</groupId>             <artifactId>standard</artifactId>             <version>1.1.2</version>         </dependency>          <!-- Servlet Dependency -->         <dependency>             <groupId>javax.servlet</groupId>             <artifactId>javax.servlet-api</artifactId>             <version>3.1.0</version>             <scope>provided</scope>         </dependency>          <!-- JSP Dependency -->         <dependency>             <groupId>javax.servlet.jsp</groupId>             <artifactId>javax.servlet.jsp-api</artifactId>             <version>2.3.1</version>             <scope>provided</scope>         </dependency>         <dependency>             <groupId>com.google.code.gson</groupId>             <artifactId>gson</artifactId>             <version>2.8.6</version>         </dependency>         <dependency>             <groupId>commons-io</groupId>             <artifactId>commons-io</artifactId>             <version>2.5</version>         </dependency>         <dependency>             <groupId>junit</groupId>             <artifactId>junit</artifactId>             <version>4.12</version>             <scope>test</scope>         </dependency>     </dependencies>     <build>         <finalName>Zipcode</finalName>         <sourceDirectory>src/main/java</sourceDirectory>         <plugins>             <plugin>                 <artifactId>maven-compiler-plugin</artifactId>                 <version>3.5.1</version>                 <configuration>                     <source>1.8</source>                     <target>1.8</target>                 </configuration>             </plugin>             <plugin>   <groupId>org.apache.maven.plugins</groupId>   <artifactId>maven-war-plugin</artifactId>   <version>3.3.2</version> </plugin>        <plugin>         <groupId>org.codehaus.mojo</groupId>         <artifactId>tomcat-maven-plugin</artifactId>         <version>1.0-beta-1</version>       </plugin>         </plugins>     </build> </project>

B. File: index.jsp

This is the page that gets rendered when the project is deployed in tomcat

HTML

<!DOCTYPE html> <html lang="en"> <head>     <meta charset="utf-8">     <meta http-equiv="X-UA-Compatible" content="IE=edge">     <meta name="viewport" content="width=device-width, initial-scale=1">     <title>ZipCode</title>     <link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/4.5.0/css/bootstrap.min.css">     <script src="https://ajax.googleapis.com/ajax/libs/jquery/1.12.4/jquery.min.js"></script>     <script src="https://maxcdn.bootstrapcdn.com/bootstrap/4.5.0/js/bootstrap.min.js"></script>     <style type="text/css">         .main-form, .profile-area {             width: 500px;             background: #FF5733;                      }         .main-form {             margin: 50px auto 0px;         }         .profile-area {             margin: 10px auto;         }         .main-form section, .profile-area section {             margin-bottom: 15px;             background: #f7f7f7;             box-shadow: 0px 2px 2px rgba(0, 0, 0, 0.3);         }         .main-form section {             padding: 30px;         }         .profile-area section {             padding: 30px 30px 30px;         }         .profile-area section > div {             text-align: center;         }         .main-form h3 {             margin: 0 0 15px;         }         .form-control, .btn {             min-height: 38px;             border-radius: 2px;         }         .btn {             font-size: 15px;             font-weight: bold;         }         .hideElement {             display: none;         }     </style> </head> <body> <div class="main-form" id="main-form">     <section>         <h5 class="text-center">Enter your zipcode</h5>         <div class="form-group">             <input id="zipcode" type="text" class="form-control" placeholder="Enter zipcode here..." required="required">         </div>         <div class="form-group">             <button onclick="loadData()" class="btn btn-primary btn-block">Find Area Details</button>         </div>     </section> </div> <div class="profile-area hideElement" id="profile-area">     <section>         <div id="loader" class="hideElement">             <div class="spinner-border" role="status">                 <span class="sr-only">Loading...</span>             </div>         </div>         <div id="profile" class="hideElement">             <br><br>               <p><strong>Country : </strong><span id="country"></span></p>                 <p><strong>State    : </strong><span id="statename"></span></p>                 <p><strong>Localities : </strong><span id="associatedplaces"></span></p>                 <p><strong>Latitude    : </strong><span id="associatedlatitude"></span></p>                 <p><strong>Longitude : </strong><span id="associatedlongitude"></span></p>           </div>     </section> </div> </body> <script>     function loadData() {         document.getElementById("profile-area").classList.remove("hideElement");         document.getElementById("loader").classList.remove("hideElement");         document.getElementById("profile").classList.add("hideElement");          var zipCode = document.getElementById("zipcode").value;          if(zipCode != "" && zipCode != null) {             var xhttp = new XMLHttpRequest();             xhttp.onreadystatechange = function() {                 if (this.readyState == 4 && this.status == 200) {                     var jsonResponse = JSON.parse(this.responseText);                     document.getElementById("country").innerHTML = jsonResponse.country;                     document.getElementById("statename").innerHTML = jsonResponse.statename;                     document.getElementById("associatedplaces").innerHTML = jsonResponse.associatedplaces;                     document.getElementById("associatedlatitude").innerHTML = jsonResponse.associatedlatitude;                     document.getElementById("associatedlongitude").innerHTML = jsonResponse.associatedlongitude;                     document.getElementById("loader").classList.add("hideElement");                     document.getElementById("profile").classList.remove("hideElement");                 }             };             xhttp.open("GET", "getLocalityDetailsByZipCode?zipCode=" + zipCode, true);             xhttp.send();             console.log("done");         } else {             console.log("Enter zipcode...")         }     } </script> </html>

Output:

On entering any valid zip code. For example 600028, name in the input box, we will get the below details.

Execution Process: From the JSP page, a "GET" method is invoked with the search string and it is redirected to the Spring Controller class, where the REST API URL, <a target="_blank" rel="noopener noreferrer nofollow" href="http://api.zippopotam.us/IN/http://api.zippopotam.us/IN/<valid zipcode> is invoked and it will create the JSON object as given above, From that, we are taking "country", "state","latitude","longitude" and "localities" values.

Country : India  State : Tamil Nadu  Localities : [Fore Shore Estate, Ramakrishnanagar, R A Puram Colony]  Latitude : [13.0206, 13.0206, 13.0206]  Longitude : [80.2417, 80.2417, 80.2417]

Output: Screen

Required code for retrieving the data and parsing the JSON output is as follows. Important necessary files to achieve the flow

File: AppConfig.java

Java

// 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;     } }

File: SpringMvcDispatcherServletInitializer.java

Java

// 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[] { "/" };     } }

File: ZipCodeController.java

Java

// Java Program to Illustrate ZipCodeController Class  // Importing required classes 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;  // Annotation @Controller // Class public class ZipCodeController {      // Method 1     @RequestMapping("/getLocalityDetailsByZipCode")     public @ResponseBody     JsonObject getLocalityDetailsByZipCode(String zipCode)         throws IOException     {          JsonObject jsonObject = new JsonObject();         jsonObject = getLocalityDetailsByZip(zipCode);          // Parsing the JSONObject         JsonObject finalJsonObject = new JsonObject();          String country             = jsonObject.get("country").toString();         country = country.replaceAll("^\"|\"$", "");         JsonArray jsonPlacesArray = null;          ArrayList placesList = new ArrayList();         ArrayList stateList = new ArrayList();         ArrayList latitudeList = new ArrayList();         ArrayList longitudeList = new ArrayList();          // Places data is available as JSONArray         jsonPlacesArray             = jsonObject.get("places").getAsJsonArray();         // It is iterated         Iterator<JsonElement> objectIterator             = jsonPlacesArray.iterator();          while (objectIterator.hasNext()) {             JsonElement object = objectIterator.next();             JsonObject jObj = object.getAsJsonObject();             System.out.println(                 jObj.get("place name").toString()                 + jObj.get("state").toString());             placesList.add(jObj.get("place name")                                .toString()                                .replaceAll("^\"|\"$", ""));             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("associatedplaces",                                     placesList.toString());         finalJsonObject.addProperty("associatedplacessize",                                     placesList.size());         finalJsonObject.addProperty("state",                                     stateList.toString());         finalJsonObject.addProperty(             "statename", stateList.get(0).toString());         finalJsonObject.addProperty(             "associatedlatitude", latitudeList.toString());         finalJsonObject.addProperty(             "associatedlatitudesize", latitudeList.size());         finalJsonObject.addProperty(             "associatedlongitude",             longitudeList.toString());         finalJsonObject.addProperty(             "associatedlongitudesize",             longitudeList.size());          return finalJsonObject;     }      // Method 2     private JsonObject     getLocalityDetailsByZip(String zipCode)         throws IOException     {          String data = null;         StringBuilder responseData = new StringBuilder();         JsonObject jsonObject = null;          URL url = null;         url = new URL("http://api.zippopotam.us/IN/"                       + zipCode);          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 block to check for exceptions         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);         }          // System.out.println(data);         return jsonObject;     } }

Conclusion: This process of code is required for retrieving any REST API call. We need to know whether REST API provides either JSONObject/JSONArray and accordingly we have to parse the data.

OpenSource REST API URL and Retrieving Data From it By Using Spring MVC

priyarajtt

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Article Tags :

Practice Tags :

Java

OpenSource REST API URL and Retrieving Data From it By Using Spring MVC

A. File: pom.xml

B. File: index.jsp

File: AppConfig.java

File: SpringMvcDispatcherServletInitializer.java

File: ZipCodeController.java

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