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;