Consuming RESTful API services using Rest Template

One of most important and basic operations in Java Backend is Consuming Rest api. In this blog I use REST Template to demonstrate the task.

GET Method

You have to create 2 projects, from one demo we use other's get endpoint.

For 1st Project, which only has the name[Your name].

1. 
   

   You have to add spring-web dependency for web services.
   
   

   
   

   <dependency>
   
   <groupId>org.springframework.boot</groupId>
   
   <artifactId>spring-boot-starter-webmvc</artifactId>
   
   </dependency>
   
   

   
   

   
   
   java

   
   



2. Create a MainController class in the controller package.




3. Add @RestController annotation to make it RESTful web services and instruct it to return the data instead of view.




4. Add a Get endpoint return your name.
   
   

 package com.example.demo.controller;

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

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



 @RestController

 public class MainController {



    @GetMapping("/name")

    public String myName() {

        return "Ayush Singh";

    }

  }

1. Add a variable in application.properties to change the server port, server.port = 9090.

For 2nd Project, do the same for dependencies and controller.

1. Create a Rest Template bean OR initialize it in the MainController class.
   
   
private RestTemplate rest;
public MainController() {
rest = new RestTemplate();
}

   
   java


2. Create a hello() method for showing the greeting and annotate it with @GetMapping("/hello")
   


3. In the application.properties create a variable to store the url like name.service.url = http://localhost:9090. This will be the url from where we fetch the name of the user.


4. 
   

   Add a field in the MainController name baseUrl to inject the value of the url of another server.
   
   

   
   

   @Value("${name.service.url}")
   
   private String baseUrl;
   
   

   
   
   



5. Create a full URI by adding base url and resource name.



6. 
   

   Now implement the getForObject() method to get the data from the another server.
   
   

   
   

   String response = rest.getForObject(url, String.class);
   
   

   
   
   
   
   
   
   • 
     url is the full url.
   
   
   • 
     String.class is the response type.
   
   
   
   


7. 
   

   At last return the response variable add with Hello.
   
   

   
   

   return "Hello " + response;