SendGrid Email API integration with Spring Boot REST Application

SendGrid is a popular cloud-based email delivery service. A few months ago, I had an opportunity to work with this technology along with Spring Boot application to send email to subscribers. Today I am going to develop a very simple Spring Boot REST application to integrate SendGrid email API to send an email to a valid email address.

Spring Boot REST API - Convert English Number into Words

Spring is one of the most popular Java EE application framework. Today we will develop a very simple Spring Boot REST API which receives a number as a request and in response, we will get the corresponding English words.

Please note that, this is not a tutorial to learn about Spring Boot REST API. I assumed you already familiar with this technology.

Spring Boot REST API - Spring Bean Scope illustration

We already know that Spring defines 5 types of bean scopes:

a) singleton
b) prototype
c) request
d) session
e) globalSession

Last three scopes are only available on web-aware application. Singleton and prototype are spring’s core scope and singleton is the default scope.

Eclipse Paho Java Client (MQTT client) integration with Spring Boot REST API

MQTT is an open, lightweight, simple client-server (publish / subscriber) messaging transport protocol. It is designed with a minimal protocol overhead. On the other hand Eclipse Paho is one of the most popular client library implementations. In the following example, I will show how to integrate Spring Boot with Eclipse Paho.

Tested with the following environment and technologies:

a) JDK 1.8
b) Eclipse
c) Maven
d) Spring Boot
e) Eclipse Paho as MQTT client library.
f) Postman as REST API client (Google Chrome extension)
g) MQTTLens as client tool for MQTT (Google Chrome extension)