You have created an event, but there is limited capacity. You want people to sign up but you don’t want anyone to show up just to realize the event is already fully booked. Group scheduling is the perfect way to control your event participation and using the Nylas Java SDK makes it possible.
You will need just to create an event, specify its capacity and let participants know how many spots are left for them to join.
If you already have the Nylas Java SDK installed and your Java environment is configured, then continue along with the blog.
Otherwise, I would recommend that you read the post How to Send Emails with the Nylas Java SDK where the basic setup is clearly explained.
Before going any further, let’s see what our application will look like:
We have the title, date and time of the event. Also, we have the number of available spots and we can enter our name and email address.
When we press submit, we’re going to get registered and receive a confirmation message:
Also, we will receive an invitation in our mailbox:
When registering, it’s important to fill out all fields:
When all available spots are taken, registration will fail:
With a confirmation message:
As we need an event where people can register, let’s create a project called EventGenerator. We need to create a folder called EventGenerator and modify the pom.xml file like this:
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Newsroom<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<groupId>EventGenerator</groupId>
<artifactId>EventGenerator</artifactId>
<version>1.0-SNAPSHOT</version>
<properties>
<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
<maven.compiler.source>17</maven.compiler.source>
<maven.compiler.target>17</maven.compiler.target>
</properties>
<dependencies>
<dependency>
<groupId>org.slf4j</groupId>
<artifactId>slf4j-simple</artifactId>
<version>1.7.25</version>
</dependency>
<dependency>
<groupId>io.github.cdimascio</groupId>
<artifactId>dotenv-java</artifactId>
<version>2.2.4</version>
</dependency>
<dependency>
<groupId>com.nylas.sdk</groupId>
<artifactId>nylas-java-sdk</artifactId>
<version>1.18.0</version>
</dependency>
</dependencies>
<build>
<pluginManagement>
<plugins>
<plugin>
<groupId>org.codehaus.mojo</groupId>
<artifactId>exec-maven-plugin</artifactId>
<version>1.2.1</version>
<executions>
<execution>
<phase>package</phase>
<goals>
<goal>java</goal>
</goals>
</execution>
</executions>
<configuration>
<mainClass>EventGenerator</mainClass>
<cleanupDaemonThreads>false</cleanupDaemonThreads>
</configuration>
</plugin>
</plugins>
</pluginManagement>
</build>
</project>
Then create a class called EventGenerator.java:
//Import Java Utilities
import java.io.IOException;
import java.time.Instant;
import java.time.LocalDate;
import java.time.ZoneOffset;
import java.time.temporal.ChronoUnit;
import java.util.Arrays;
// Import Nylas Packages
import com.nylas.RequestFailedException;
import com.nylas.NylasAccount;
import com.nylas.NylasClient;
import com.nylas.Event;
import com.nylas.Participant;
//Import DotEnv to handle .env files
import io.github.cdimascio.dotenv.Dotenv;
import io.github.cdimascio.dotenv.DotenvException;
public class EventGenerator {
public static void main(String[] args) throws RequestFailedException, IOException {
Dotenv dotenv = Dotenv.load();
// Create the client object
NylasClient client = new NylasClient();
// Connect it to Nylas using the Access Token from the .env file
NylasAccount account = client.account(dotenv.get("ACCESS_TOKEN"));
// Get today's date
LocalDate today = LocalDate.now();
// Set time. As we're using UTC we need to add the hours
// in difference
// from our own Timezone
Instant sixPmUtc = today.atTime(16, 0).toInstant(ZoneOffset.UTC);
// Set the date and time for the event.
// We add 30 minutes to the starting time
Event event = new Event(dotenv.get("CALENDAR_ID"),
new Event.Timespan(sixPmUtc,
sixPmUtc.plus(30, ChronoUnit.MINUTES)));
// Set Title, Location and Description
event.setTitle("Zumba Class with Nyla");
event.setLocation("Nylas' Office");
event.setCapacity(3);
Event event_created = account.events().create(event, true);
if(event_created.getId() != null){
System.out.println("Event created successfully");
System.out.println(“Id: “ + event_created.getId());
}else{
System.out.println("There was an error creating the event");
}
}
}
In order to run our application, we need to compile it by typing the following on the terminal window:
$ mvn package
To actually run the application, we need to type the following:
$ mvn exec:java -Dexec.mainClass="EventGenerator"
First, we’re going to create a folder called GroupScheduling that will include a folder called resources. Inside resources, we need to create a folder called templates and another folder called public. Inside the public folder, we need to create a new folder called images.
On the images folder, we will have this image:
We want to use a web framework, and a very light and fast option is Spark. For the template engine, Mustache is more than enough.
Now, let’s create our pom.xml file:
<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<groupId>GroupScheduling</groupId>
<artifactId>GroupScheduling</artifactId>
<version>1.0-SNAPSHOT</version>
<properties>
<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
<maven.compiler.source>17</maven.compiler.source>
<maven.compiler.target>17</maven.compiler.target>
</properties>
<dependencies>
<dependency>
<groupId>org.slf4j</groupId>
<artifactId>slf4j-simple</artifactId>
<version>1.7.25</version>
</dependency>
<dependency>
<groupId>com.sparkjava</groupId>
<artifactId>spark-core</artifactId>
<version>2.9.4</version>
</dependency>
<dependency>
<groupId>io.github.cdimascio</groupId>
<artifactId>dotenv-java</artifactId>
<version>2.2.4</version>
</dependency>
<dependency>
<groupId>com.sparkjava</groupId>
<artifactId>spark-template-mustache</artifactId>
<version>2.7.1</version>
</dependency>
<dependency>
<groupId>com.nylas.sdk</groupId>
<artifactId>nylas-java-sdk</artifactId>
<version>1.18.0</version>
</dependency>
</dependencies>
</project>
Our main class will be called GroupScheduling.java:
// Import Java Utilities
import java.io.IOException;
import java.lang.Exception;
import java.text.DateFormat;
import java.text.SimpleDateFormat;
import java.time.LocalDateTime;
import java.time.ZoneId;
import java.time.ZoneOffset;
import java.util.ArrayList;
import java.util.Date;
import java.util.HashMap;
import java.util.Map;
import java.time.temporal.ChronoUnit;
// Import Spark and Mustache libraries
import spark.ModelAndView;
import static spark.Spark.*;
import spark.template.mustache.MustacheTemplateEngine;
//Import Nylas Packages
import com.nylas.RequestFailedException;
import com.nylas.NylasAccount;
import com.nylas.NylasClient;
import com.nylas.Event;
import com.nylas.Participant;
//Import DotEnv to handle .env files
import io.github.cdimascio.dotenv.Dotenv;
public class GroupScheduling {
public static void main(String[] args) throws RequestFailedException, IOException {
staticFiles.location("/public");
// Load the .env file
Dotenv dotenv = Dotenv.load();
// Create the client object
NylasClient client = new NylasClient();
// Connect it to Nylas using the Access Token from the .env file
NylasAccount account = client.account(dotenv.get("ACCESS_TOKEN"));
// Get an event using its Id
Event event = account.events().get(dotenv.get("EVENT_ID"));
// Read the event details
String title = event.getTitle();
Event.Timespan _day = (Event.Timespan) event.getWhen();
LocalDateTime ldt = LocalDateTime.ofInstant(_day.getStartTime(), ZoneOffset.UTC);
LocalDateTime ldt_to = LocalDateTime.ofInstant(_day.getEndTime(), ZoneOffset.UTC);
String day_name = ldt.getDayOfWeek().toString().toLowerCase();
String day = day_name.substring(0, 1).toUpperCase() + day_name.substring(1) + " " + ldt.getDayOfMonth() + ", " + ldt.getYear();
DateFormat dateFormat = new SimpleDateFormat("hh:mm aa");
Date _from_date = Date.from(ldt.minus(5, ChronoUnit.HOURS).atZone(ZoneId.systemDefault()).toInstant());
Date _to_date = Date.from(ldt_to.minus(5, ChronoUnit.HOURS).atZone(ZoneId.systemDefault()).toInstant());
String _from = dateFormat.format(_from_date).toString().toUpperCase();
String _to = dateFormat.format(_to_date).toString().toUpperCase();
// Default path when we load our web application
get("/", (request, response) -> {
// Update capacity
Integer capacity = event.getCapacity() - event.getParticipants().size();
if (capacity < 0){
capacity = 0;
}
// Create a model to pass information to the mustache template
Map<String, Object> model = new HashMap<>();
model.put("title", title);
model.put("day", day);
model.put("_from", _from);
model.put("_to", _to);
model.put("capacity", capacity.toString());
model.put("name", "");
model.put("email", "");
// Call the mustache template
return new ModelAndView(model, "main.mustache");
}, new MustacheTemplateEngine());
// When we submit the form, we're posting data
post("/", (request, response) -> {
// Grab the form fields
String name = request.queryParams("name");
String email = request.queryParams("email");
String message = "";
String explanation = "";
// Validate that they are all filled
// Otherwise halt execution and display an error message
if(name.equals("") || email.equals("")){
String halt_msg = "<html>\n" +
"<head>\n" +
" <script src=\"https://cdn.tailwindcss.com\"></script>\n" +
" <title>Zumba Class with Nyla</title>\n" +
"</head>\n" +
"<body>\n" +
"<div class=\"bg-red-300 border-green-600 border-b p-4 m-4 rounded grid place-items-center\">\n" +
"<p class=\"font-semibold\">You must specify all fields</p>\n" +
"</div>\n" +
"</body>\n" +
"</html>";
halt(halt_msg);
}
// Create an array of participants
ArrayList<Participant> participants = new ArrayList<Participant>();
// Add existing participants
for(Participant participant : event.getParticipants()){
participants.add(new Participant(participant.getEmail()).name(participant.getName()));
}
// Add new participant
participants.add(new Participant(email).name(name));
// Set the participants list
event.setParticipants(participants);
try{
// Update the event
account.events().update(event, true);
message = "Thanks " + name + " - " + email;
explanation = "You have successfully registered for " + title;
} catch(Exception e){
message = "Sorry " + name + " - " + email;
explanation = "Sadly, there's not space left for you to join " + title;
} finally {
// Create a model to pass information to the mustache template
Map<String, Object> model = new HashMap<>();
model.put("message", message);
model.put("explanation", explanation);
return new ModelAndView(model, "confirmation.mustache");
}
}, new MustacheTemplateEngine());
}
}
We’re going to need two mustache template files, main.mustache and confirmation.mustache:
Let’s start with main.mustache:
<html>
<head>
<script src="https://cdn.tailwindcss.com"></script>
<title>Zumba Class with Nyla</title>
</head>
<body>
<div class="bg-[#315acb] border-green-600 border-b p-4 m-4 rounded grid place-items-center">
<p class="text-6xl text-center">{{title}}</p><br>
<p class="text-4xl text-center">{{day}}</p><br>
<p class="text-4xl text-center">from {{_from}} to {{_to}}</p><br>
<img src="images/Nyla.png">
<br>
<p class="text-2xl text-center">Currently we have <b>{{capacity}}</b> available spots.</p>
<br>
<form method="post">
<label for="name"><b>Name</b></label>
<input type="text" name="name"
placeholder="Your name"
value="{{name}}"></input>
<br><br>
<label for="email"><b>Email</b></label>
<input type="email" name="email"
placeholder="Your email"
value="{{email}}"></input>
<br><br>
<button type="submit" class="block bg-blue-500 hover:bg-blue-700 text-white text-lg mx-auto py-2 px-4 rounded-full">Submit</button>
</form>
</div>
</body>
</html>
And then confirmation.mustache:
<html>
<head>
<script src="https://cdn.tailwindcss.com"></script>
<title>Zumba Class with Nyla</title>
</head>
<body>
<div class="bg-[#315acb] border-green-600 border-b p-4 m-4 rounded grid place-items-center">
<h1 class="text-3xl">{{message}}</h1>
<p class="font-semibold">{{explanation}}</p>
<p class="font-semibold">You can now go <a href="/" class="text-green-600">back</a></p>
</div>
</body>
</html>
In order to run our application, we need to compile it by typing the following on the terminal window:
$ mvn package
To run our Group Scheduling application using Java, we need to type the following:
$ mvn exec:java -Dexec.mainClass="GroupScheduling"
Our application will be running on port 4567 of localhost, so we just need to open our favourite browser and go to the following address:
http://localhost:4567
If you want to learn more about our Calendar APIs, please go to our documentation Calendar API Overview.
You can sign up Nylas for free and start building!
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Blag aka Alvaro Tejada Galindo is a Senior Developer Advocate at Nylas. He loves learning about programming and sharing knowledge with the community. When he’s not coding, he’s spending time with his wife, daughter and son. He loves Punk Music and reading all sorts of books.