Call another rest api from my server in Spring-Boot

Question

I want to call another web-api from my backend on a specific request of user  For example  I want to call Google FCM send message api to send a message to a specific user on an event    Does Retrofit have any method to achieve this  If not  how I can do that

User · Answer

Create Bean for Rest Template to auto wiring the Rest Template object.

@SpringBootApplication
public class ChatAppApplication {

    @Bean
    public RestTemplate getRestTemplate(){
        return new RestTemplate();
    }

    public static void main(String[] args) {
        SpringApplication.run(ChatAppApplication.class, args);
    }

}

Consume the GET/POST API by using RestTemplate - exchange() method. Below is for the post api which is defined in the controller.

@RequestMapping(value = "/postdata",method = RequestMethod.POST)
    public String PostData(){

       return "{\n" +
               "   \"value\":\"4\",\n" +
               "   \"name\":\"David\"\n" +
               "}";
    }

    @RequestMapping(value = "/post")
    public String getPostResponse(){
        HttpHeaders headers=new HttpHeaders();
        headers.setAccept(Arrays.asList(MediaType.APPLICATION_JSON));
        HttpEntity<String> entity=new HttpEntity<String>(headers);
        return restTemplate.exchange("http://localhost:8080/postdata",HttpMethod.POST,entity,String.class).getBody();
    }

Refer this tutorial[1]

[1] https://www.tutorialspoint.com/spring_boot/spring_boot_rest_template.htm

User · Answer

Modern Spring 5  answer using WebClient instead of RestTemplate  Configure WebClient for a specific web-service or resource as a bean  additional properties can be configured    Bean public WebClient localApiClient         return WebClient create  quot http   localhost 8080 api v3 quot       Inject and use the bean from your service s    Service public class UserService        private static final Duration REQUEST TIMEOUT   Duration ofSeconds 3        private final WebClient localApiClient        Autowired     public UserService WebClient localApiClient            this localApiClient   localApiClient             public User getUser long id            return localApiClient                  get                    uri  quot  users  quot    id                   retrieve                    bodyToMono User class                   block REQUEST TIMEOUT

User · Answer

Instead of String you are trying to get custom POJO object details as output  by calling another API URI  try the this solution  I hope it will be clear and helpful for how to use RestTemplate also   In Spring Boot  first we need to create Bean for RestTemplate under the  Configuration annotated class  You can even write a separate class and annotate with  Configuration like below    Configuration public class RestTemplateConfig         Bean     public RestTemplate restTemplate RestTemplateBuilder builder           return builder build              Then  you have to define RestTemplate with  Autowired or  Injected under your service Controller  whereever you are trying to use RestTemplate  Use the below code    Autowired private RestTemplate restTemplate    Now  will see the part of how to call another api from my application using above created RestTemplate  For this we can use multiple methods like execute    getForEntity    getForObject   and etc  Here I am placing the code with example of execute    I have even tried other two  I faced problem of converting returned LinkedHashMap into expected POJO object  The below  execute   method solved my problem   ResponseEntity lt List lt POJO gt  gt  responseEntity   restTemplate exchange      URL       HttpMethod GET       null       new ParameterizedTypeReference lt List lt POJO gt  gt              List lt POJO gt  pojoObjList   responseEntity getBody      Happy Coding

User · Answer

Does Retrofit have any method to achieve this  If not  how I can do that    YES  Retrofit is type-safe REST client for Android and Java  Retrofit turns your HTTP API into a Java interface   For more information refer the following link  https   howtodoinjava com retrofit2 retrofit2-beginner-tutorial

User · Answer

This website has some nice examples for using spring s RestTemplate  Here is a code example of how it can work to get a simple object   private static void getEmployees         final String uri    http   localhost 8080 springrestexample employees xml        RestTemplate restTemplate   new RestTemplate        String result   restTemplate getForObject uri  String class        System out println result

[api] Call another rest api from my server in Spring-Boot

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