URL de la API REST de código abierto y recuperación de datos mediante el uso de Spring MVC

En esta era de Internet, muchos servicios auxiliares están disponibles en forma de API REST y, en su mayoría, la API REST nos proporciona los detalles en forma de JSON/XML. Podemos usarlos en nuestras aplicaciones y renderizar los datos como queramos. Aquí está la lista de algunas URL de API REST de código abierto:

Todavía hay más API de código abierto disponibles. Aquí aprenderemos cómo extraer los detalles del código postal usando Spring MVC:

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

Ejemplo:

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

Salida: 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"
    }
  ]
}

Ahora, usando Spring MVC Framework , intentemos representar los detalles de la API REST en la pantalla

Implementación:

Es como se muestra paso a paso a continuación, donde inicialmente nos permite ver la estructura del proyecto, que es la siguiente:

 

A. Archivo: pom.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. Archivo: index.jsp

Esta es la página que se representa cuando el proyecto se implementa en tomcat

<!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>

Producción:

 

Al ingresar cualquier código postal válido. Por ejemplo, 600028, nombre en el cuadro de entrada, obtendremos los detalles a continuación.

Proceso de ejecución: desde la página JSP, se invoca un método «GET» con la string de búsqueda y se redirige a la clase Spring Controller, donde se encuentra la URL de la API REST, <a target=»_blank» rel=»noopener noreferrer nofollow» href =»http://api.zippopotam.us/IN/http://api.zippopotam.us/IN/<código postal válido> se invoca y creará el objeto JSON como se indicó anteriormente. De eso, estamos tomando « valores  de país”, “estado”, “latitud”, “longitud” y “localidades” .

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]

Salida: Pantalla 

 

El código requerido para recuperar los datos y analizar la salida JSON es el siguiente. Importantes archivos necesarios para lograr el flujo

Archivo: AppConfig.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;
    }
}

Archivo: SpringMvcDispatcherServletInitializer.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[] { "/" };
    }
}

Archivo: ZipCodeController.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;
    }
}

Conclusión: este proceso de código es necesario para recuperar cualquier llamada a la API REST. Necesitamos saber si la API REST proporciona JSONObject/JSONArray y, en consecuencia, tenemos que analizar los datos.