SendGrid Hello World Email

Spring Boot integrates with SendGrid to send mail.
below is the minimum code needed to send an email with the SendGrid.

package org.wesome.sendgrid;

import com.sendgrid.SendGrid;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.annotation.Bean;
import org.springframework.web.bind.annotation.RestController;

@SpringBootApplication
@RestController
public class SendGridApplication {
    @Value("${send.grid.api.key}")
    private String sendGridApiKey;

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

    @Bean
    public SendGrid sendGrid() {
        SendGrid sendGrid = new SendGrid(sendGridApiKey);
        return sendGrid;
    }
}

package org.wesome.sendgrid.controller;

import com.sendgrid.Method;
import com.sendgrid.Request;
import com.sendgrid.Response;
import com.sendgrid.SendGrid;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.http.HttpStatus;
import org.springframework.http.ResponseEntity;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;

import java.io.IOException;

@RestController
public class SendGridController {
    @Autowired
    private SendGrid sendGrid;

    @GetMapping("/send")
    public ResponseEntity sendMail() throws IOException {
        Request request = new Request();
        request.setBody("{\"personalizations\":[{\"to\":[{\"email\":\"[email protected]\"}],\"subject\":\"WeSome.Org\"}],\"from\":{\"email\":\"[email protected]\"},\"content\":[{\"type\":\"text/plain\",\"value\": \"I am learning SendGrid from WeSome.Org because its fun\"}]}");
        Response response;
        try {
            request.setMethod(Method.POST);
            request.setEndpoint("mail/send");
            response = sendGrid.api(request);
            System.out.println("Headers := \n" + response.getHeaders());
            System.out.println("Body := \n" + response.getBody());
            System.out.println("StatusCode := \n" + response.getStatusCode());
        } catch (IOException ex) {
            throw ex;
        }
        return new ResponseEntity(HttpStatus.valueOf(response.getStatusCode()).getReasonPhrase(), HttpStatus.valueOf(response.getStatusCode()));
    }
}

plugins {
    id 'io.spring.dependency-management' version '1.0.11.RELEASE'
    id 'org.springframework.boot' version '2.5.5'
    id 'java'
}

group = 'org.wesome'
version = '0.0.1-SNAPSHOT'
sourceCompatibility = JavaVersion.VERSION_1_8

repositories {
    mavenCentral()
}
dependencies {
    implementation 'com.sendgrid:sendgrid-java:4.4.5'
    implementation 'commons-logging:commons-logging:1.2'
    implementation('org.springframework.boot:spring-boot-starter-web')
}

test {
    useJUnitPlatform()
}

send.grid.api.key=Your SendGrid Api Key

curl --location --request GET 'localhost:8080/send/'

SendGrid V3 API internally calls https://api.sendgrid.com/v3/mail/send

Creating the Mail body in JSON format is error-prone, to avoid this use SendGrid provides Mail class which internally creates a personalization object.