RestController - Simple Calculator - Service and Client

This simple Calculator demonstrates the usage of Spring Boot Rest service and Rest Client

Service Steps involved:
1) Maven Dependencies
2) Implement model class
3) Implement service class
4) Injecting resources into service class
5) Service class Configuration
6) Running Service and port settings

Client Steps involved:
1) Maven dependencies
2) RestTemplate instantiation
3) Creating Headers
4) Creating Request Parameters
5) Dealing with requests and responses


Service Steps involved:
1) Maven Dependencies and package structure

Spring Boot dependency:

               <dependency>

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

Spring Rest dependency:

              <dependency>

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

Package Structure:

2) Implement model class

package com.calculator.app.calculatorapp.model;

import org.springframework.stereotype.Component;

import java.math.BigDecimal;

@Componentpublic class CalculatorModel {
    public BigDecimal add(BigDecimal number1 , BigDecimal number2){
        return new BigDecimal(number1.intValue() + 

                              number2.intValue());
    }
}

3) Implement service class
4) Injecting resources into service class
5) Service class Configuration

import com.calculator.app.calculatorapp.model.CalculatorModel;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.context.annotation.Bean;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.bind.annotation.RestController;

@RestController
public class CalculatorService {
    @Autowired    private CalculatorModel calculatorModel;
    @GetMapping(value = "/add")
    public BigDecimal addNumbers(@RequestParam(name = "number1") 

BigDecimal number1, @RequestParam(name = "number2") 

BigDecimal number2){
        return calculatorModel.add(number1,number2);
    }
}

6) Running Service and Port settings

application.properties

server.port=7070

package com.calculator.app.calculatorapp;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

@SpringBootApplicationpublic class CalculatorAppApplication {

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

The service starts on Port number 7070 and can be accessed via Http url

http://localhost:7070/add?number1=34&number2=44

Client Steps involved:

1) Maven dependencies

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

2) RestTemplate instantiation

3) Creating Headers

4) Creating Request Parameters

5) Dealing with requests and responses


public static void main(String[] args) {
      RestTemplate restTemplate = new RestTemplate();
      HttpHeaders headers = new HttpHeaders();
      headers.set("Accept", MediaType.APPLICATION_JSON_VALUE);
      UriComponentsBuilder uriComponentsBuilder = 
UriComponentsBuilder.fromHttpUrl("http://localhost:7070/add").
queryParam("number1",344334).
            queryParam("number2",434343433);
      HttpEntity<?> entity = new HttpEntity<>(headers);
      HttpEntity<BigDecimal> sum = restTemplate.exchange
(uriComponentsBuilder.toUriString(), 
HttpMethod.GET,entity,BigDecimal.class);
      System.out.println(sum.getBody());
   }