Cómo Leer Una API con Spring Framework

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En alguna ocasión necesitamos leer los datos de una API con Spring Framework o Spring Boot.

Hacerlo es muy fácil, solo debes seguir ciertos pasos que te compartiré a continuación.

En este tutorial te enseñaré a Cómo Leer Una API con Spring Framework, vamos con ello.

Creación de Nuevo Proyecto

Ejecutamos el siguiente comando para crear un nuevo proyecto, le daré el nombre miapp (tu le puedes colocar el nombre que desees):


spring boot new miapp 

Getting project from https://github.com/rd-1-2022/rest-service
Created project in directory 'miapp'

spring boot new miapp

Getting project from https://github.com/rd-1-2022/rest-service

Created project in directory 'miapp'

Luego de ejecutar el comando anterior, Spring Framework me ha creado la siguiente estructura de directorios y archivos para el proyecto:


/miapp
  ├── /.mvn
  ├── /.vscode
  ├── /src
  ├── /target
  ├── .gitignore
  ├── LICENSE
  ├── mvnw
  ├── mvnw.cmd 
  ├── porn.xml
  ├── README.adoc

/miapp

├── /.mvn

├── /.vscode

├── /src

├── /target

├── .gitignore

├── LICENSE

├── mvnw

├── mvnw.cmd

├── porn.xml

├── README.adoc

Abrimos el archivo GreetingController.java que se encuentra en miapp > src > main > java > com > example > restservice > greeting > GreetingController.java:


/miapp 
  ├── /.mvn
  ├── /src
      ├── /main
          ├── /java  
              ├── /com 
                  ├── /example 
                      ├── /greeting 
                          ├── Greeting.java   
                          ├── GreetingController.java // Abre este Archivo  
                      ├── /Application.java 
          ├── /test
  ├── /target
  ├── .gitignore
  ├── HELP.md
  ├── mvnw
  ├── mvnw.cmd 
  ├── porn.xml

/miapp

├── /.mvn

├── /src

├── /main

├── /java

├── /com

├── /example

├── /greeting

├── Greeting.java

├── GreetingController.java // Abre este Archivo

├── /Application.java

├── /test

├── /target

├── .gitignore

├── HELP.md

├── mvnw

├── mvnw.cmd

├── porn.xml

Dentro del archivo GreetingController.java creamos sobre el final un nueva ruta llamada /api y nueva función para leer la API.

A mi función le daré el nombre leerAPI(), tu le puedes colocar el nombre que desees (He colocado comentarios para explicar que hace cada línea del código):


package com.example.restservice.greeting;

import java.util.concurrent.atomic.AtomicLong;

import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.bind.annotation.RestController;
import org.springframework.web.client.RestTemplate;

@RestController
public class GreetingController {

	private static final String template = "Hello, %s!";
	private final AtomicLong counter = new AtomicLong();

	@GetMapping("/greeting")
	public Greeting greeting(@RequestParam(value = "name", defaultValue = "World") String name) {
		return new Greeting(counter.incrementAndGet(), String.format(template, name));
	}

	// Ruta y función para leer la API
	@GetMapping("/api") // Ruta para la API	
	private String leerAPI() {

		// Colocamos la URL de la API 
		String url = "https://nubecolectiva.com/api/v1/postres";

		// Usamos 'RestTemplate', un cliente síncrono para realizar solicitudes HTTP
		RestTemplate restTemplate = new RestTemplate();

		// Obtenemos la respuesta de la API
		String respuesta = restTemplate.getForObject(url, String.class);

		// Imprimimos los datos de la API en la vista HTML
		return respuesta;

	}

}

package com.example.restservice.greeting;

import java.util.concurrent.atomic.AtomicLong;

import org.springframework.web.bind.annotation.GetMapping;

import org.springframework.web.bind.annotation.RequestParam;

import org.springframework.web.bind.annotation.RestController;

import org.springframework.web.client.RestTemplate;

@RestController

public class GreetingController {

private static final String template = "Hello, %s!";

private final AtomicLong counter = new AtomicLong();

@GetMapping("/greeting")

public Greeting greeting(@RequestParam(value = "name", defaultValue = "World") String name) {

return new Greeting(counter.incrementAndGet(), String.format(template, name));

}

// Ruta y función para leer la API

@GetMapping("/api") // Ruta para la API

private String leerAPI() {

// Colocamos la URL de la API

String url = "https://nubecolectiva.com/api/v1/postres";

// Usamos 'RestTemplate', un cliente síncrono para realizar solicitudes HTTP

RestTemplate restTemplate = new RestTemplate();

// Obtenemos la respuesta de la API

String respuesta = restTemplate.getForObject(url, String.class);

// Imprimimos los datos de la API en la vista HTML

return respuesta;

}

Este tutorial también te sirve para Spring Boot.

Probando la API

Iniciamos el servidor de Spring Framework ejecutando el siguiente comando:


./mvnw spring-boot:run

[INFO] Scanning for projects...
[INFO]
[INFO] -------------------------< com.example:miapp >--------------------------
[INFO] Building miapp 0.0.1-SNAPSHOT
[INFO] --------------------------------[ jar ]---------------------------------
[INFO]
[INFO] >>> spring-boot-maven-plugin:3.2.3:run (default-cli) > test-compile @ miapp >>>
[INFO]
[INFO] --- maven-resources-plugin:3.3.1:resources (default-resources) @ miapp ---
[INFO] skip non existing resourceDirectory D:\contenidos\nc\tutoriales\blog\miapp\src\main\resources
[INFO] skip non existing resourceDirectory D:\contenidos\nc\tutoriales\blog\miapp\src\main\resources
[INFO]
[INFO] --- maven-compiler-plugin:3.11.0:compile (default-compile) @ miapp ---
[INFO] Nothing to compile - all classes are up to date
[INFO]
[INFO] --- maven-resources-plugin:3.3.1:testResources (default-testResources) @ miapp ---
[INFO] skip non existing resourceDirectory D:\contenidos\nc\tutoriales\blog\miapp\src\test\resources
[INFO]
[INFO] --- maven-compiler-plugin:3.11.0:testCompile (default-testCompile) @ miapp ---
[INFO] Nothing to compile - all classes are up to date
[INFO]
[INFO] <<< spring-boot-maven-plugin:3.2.3:run (default-cli) < test-compile @ miapp <<<
[INFO]
[INFO]
[INFO] --- spring-boot-maven-plugin:3.2.3:run (default-cli) @ miapp ---
[INFO] Attaching agents: []

  .   ____          _            __ _ _
 /\\ / ___'_ __ _ _(_)_ __  __ _ \ \ \ \
( ( )\___ | '_ | '_| | '_ \/ _` | \ \ \ \
 \\/  ___)| |_)| | | | | || (_| |  ) ) ) )
  '  |____| .__|_| |_|_| |_\__, | / / / /
 =========|_|==============|___/=/_/_/_/
 :: Spring Boot ::                (v3.2.3)

2024-08-15T20:35:51.294-05:00  INFO 22072 --- [           main] com.example.restservice.Application      : Starting Application using Java 17.0.10 with PID 22072 (D:\contenidos\nc\tutoriales\blog\miapp\target\classes started by jrclu in D:\contenidos\nc\tutoriales\blog\miapp)
2024-08-15T20:35:51.297-05:00  INFO 22072 --- [           main] com.example.restservice.Application      : No active profile set, falling back to 1 default profile: "default"
2024-08-15T20:35:52.015-05:00  INFO 22072 --- [           main] o.s.b.w.embedded.tomcat.TomcatWebServer  : Tomcat initialized with port 8080 (http)
2024-08-15T20:35:52.023-05:00  INFO 22072 --- [           main] o.apache.catalina.core.StandardService   : Starting service [Tomcat]
2024-08-15T20:35:52.024-05:00  INFO 22072 --- [           main] o.apache.catalina.core.StandardEngine    : Starting Servlet engine: [Apache Tomcat/10.1.19]
2024-08-15T20:35:52.063-05:00  INFO 22072 --- [           main] o.a.c.c.C.[Tomcat].[localhost].[/]       : Initializing Spring embedded WebApplicationContext
2024-08-15T20:35:52.064-05:00  INFO 22072 --- [           main] w.s.c.ServletWebServerApplicationContext : Root WebApplicationContext: initialization completed in 736 ms
2024-08-15T20:35:52.364-05:00  INFO 22072 --- [           main] o.s.b.a.e.web.EndpointLinksResolver      : Exposing 1 endpoint(s) beneath base path '/actuator'
2024-08-15T20:35:52.400-05:00  INFO 22072 --- [           main] o.s.b.w.embedded.tomcat.TomcatWebServer  : Tomcat started on port 8080 (http) with context path ''
2024-08-15T20:35:52.411-05:00  INFO 22072 --- [           main] com.example.restservice.Application      : Started Application in 1.351 seconds (process running for 1.567)

./mvnw spring-boot:run

[INFO] Scanning for projects...

[INFO]

[INFO] -------------------------< com.example:miapp >--------------------------

[INFO] Building miapp 0.0.1-SNAPSHOT

[INFO] --------------------------------[ jar ]---------------------------------

[INFO]

[INFO] >>> spring-boot-maven-plugin:3.2.3:run (default-cli) > test-compile @ miapp >>>

[INFO]

[INFO] --- maven-resources-plugin:3.3.1:resources (default-resources) @ miapp ---

[INFO] skip non existing resourceDirectory D:\contenidos\nc\tutoriales\blog\miapp\src\main\resources

[INFO]

[INFO] --- maven-compiler-plugin:3.11.0:compile (default-compile) @ miapp ---

[INFO] Nothing to compile - all classes are up to date

[INFO]

[INFO] --- maven-resources-plugin:3.3.1:testResources (default-testResources) @ miapp ---

[INFO] skip non existing resourceDirectory D:\contenidos\nc\tutoriales\blog\miapp\src\test\resources

[INFO]

[INFO] --- maven-compiler-plugin:3.11.0:testCompile (default-testCompile) @ miapp ---

[INFO] Nothing to compile - all classes are up to date

[INFO]

[INFO] <<< spring-boot-maven-plugin:3.2.3:run (default-cli) < test-compile @ miapp <<<

[INFO]

[INFO] --- spring-boot-maven-plugin:3.2.3:run (default-cli) @ miapp ---

[INFO] Attaching agents: []

. ____ _ __ _ _

/\\ / ___'_ __ _ _(_)_ __ __ _ \ \ \ \

( ( )\___ | '_ | '_| | '_ \/ _` | \ \ \ \

\\/ ___)| |_)| | | | | || (_| | ) ) ) )

' |____| .__|_| |_|_| |_\__, | / / / /

=========|_|==============|___/=/_/_/_/

:: Spring Boot :: (v3.2.3)

2024-08-15T20:35:51.294-05:00 INFO 22072 --- [ main] com.example.restservice.Application : Starting Application using Java 17.0.10 with PID 22072 (D:\contenidos\nc\tutoriales\blog\miapp\target\classes started by jrclu in D:\contenidos\nc\tutoriales\blog\miapp)

2024-08-15T20:35:51.297-05:00 INFO 22072 --- [ main] com.example.restservice.Application : No active profile set, falling back to 1 default profile: "default"

2024-08-15T20:35:52.015-05:00 INFO 22072 --- [ main] o.s.b.w.embedded.tomcat.TomcatWebServer : Tomcat initialized with port 8080 (http)

2024-08-15T20:35:52.023-05:00 INFO 22072 --- [ main] o.apache.catalina.core.StandardService : Starting service [Tomcat]

2024-08-15T20:35:52.024-05:00 INFO 22072 --- [ main] o.apache.catalina.core.StandardEngine : Starting Servlet engine: [Apache Tomcat/10.1.19]

2024-08-15T20:35:52.063-05:00 INFO 22072 --- [ main] o.a.c.c.C.[Tomcat].[localhost].[/] : Initializing Spring embedded WebApplicationContext

2024-08-15T20:35:52.064-05:00 INFO 22072 --- [ main] w.s.c.ServletWebServerApplicationContext : Root WebApplicationContext: initialization completed in 736 ms

2024-08-15T20:35:52.364-05:00 INFO 22072 --- [ main] o.s.b.a.e.web.EndpointLinksResolver : Exposing 1 endpoint(s) beneath base path '/actuator'

2024-08-15T20:35:52.400-05:00 INFO 22072 --- [ main] o.s.b.w.embedded.tomcat.TomcatWebServer : Tomcat started on port 8080 (http) with context path ''

2024-08-15T20:35:52.411-05:00 INFO 22072 --- [ main] com.example.restservice.Application : Started Application in 1.351 seconds (process running for 1.567)

Si vamos a la ruta local http://localhost:8080/api, podemos ver que Spring Framework lee la API correctamente: