On this page

Workflow Automation with Java and Servlets

One of the more abstract concepts you'll handle when building your business is what the workflow will look like.

At its core, setting up a standardized workflow is about enabling your service providers (agents, hosts, customer service reps, administrators, and the rest of the gang) to better serve your customers.

To illustrate a very real-world example, today we'll build a Java and Servlets webapp for finding and booking vacation properties — tentatively called Airtng.

Here's how it'll work:

A host creates a vacation property listing
A guest requests a reservation for a property
The host receives an SMS notifying them of the reservation request. The host can either Accept or Reject the reservation
The guest is notified whether a request was rejected or accepted

Learn how Airbnb used Twilio SMS to streamline the rental experience for 60M+ travelers around the world.

Workflow Building Blocks

We'll be using the Twilio REST API to send our users messages at important junctures. Here's a bit more on our API:

Sending Messages with Twilio API

User and Session Management

For this workflow to work, we need to have a user model and allow logins.

User and Session Management

src/main/java/org/twilio/airtng/models/User.java


_116package org.twilio.airtng.models;
_116
_116import javax.persistence.*;
_116import java.util.ArrayList;
_116import java.util.List;
_116
_116@Entity
_116@Table(name = "users")
_116public class User {
_116    @Id
_116    @GeneratedValue(strategy = GenerationType.IDENTITY)
_116    @Column(name = "id")
_116    private long id;
_116
_116    @Column(name = "name")
_116    private String name;
_116
_116    @Column(name = "email")
_116    private String email;
_116
_116    @Column(name = "password")
_116    private String password;
_116
_116    @Column(name = "phone_number")
_116    private String phoneNumber;
_116
_116    @OneToMany(mappedBy="user")
_116    private List<Reservation> reservations;
_116
_116    @OneToMany(mappedBy="user")
_116    private List<VacationProperty> vacationProperties;
_116
_116    public User() {
_116        this.reservations = new ArrayList<>();
_116        this.vacationProperties = new ArrayList<>();
_116    }
_116
_116    public User(
_116            String name,
_116            String email,
_116            String password,
_116            String phoneNumber) {
_116        this();
_116        this.name = name;
_116        this.email = email;
_116        this.password = password;
_116        this.phoneNumber = phoneNumber;
_116    }
_116
_116    public long getId() {
_116        return id;
_116    }
_116
_116    public void setId(long id) {
_116        this.id = id;
_116    }
_116
_116    public String getName() {
_116        return name;
_116    }
_116
_116    public void setName(String name) {
_116        this.name = name;
_116    }
_116
_116    public String getEmail() {
_116        return email;
_116    }
_116
_116    public void setEmail(String email) {
_116        this.email = email;
_116    }
_116
_116    public String getPassword() {
_116        return password;
_116    }
_116
_116    public void setPassword(String password) {
_116        this.password = password;
_116    }
_116
_116    public String getPhoneNumber() {
_116        return phoneNumber;
_116    }
_116
_116    public void setPhoneNumber(String phoneNumber) {
_116        this.phoneNumber = phoneNumber;
_116    }
_116
_116    public void addReservation(Reservation reservation) {
_116
_116        if (this.reservations.add(reservation) && reservation.getUser() != this) {
_116            reservation.setUser(this);
_116        }
_116    }
_116
_116    public void removeReservation(Reservation reservation) {
_116        if (this.reservations.remove(reservation) && reservation.getUser() == this) {
_116            reservation.setUser(null);
_116        }
_116    }
_116
_116    public void addVacationProperty(VacationProperty vacationProperty) {
_116
_116        if (this.vacationProperties.add(vacationProperty) && vacationProperty.getUser() != this) {
_116            vacationProperty.setUser(this);
_116        }
_116    }
_116
_116    public void removeVacationProperty(VacationProperty vacationProperty) {
_116        if (this.reservations.remove(vacationProperty) && vacationProperty.getUser() == this) {
_116            vacationProperty.setUser(null);
_116        }
_116    }
_116
_116}

Next, let's look at the Vacation Property model.

Vacation Property Model

In order to build a true vacation rental company we'll need a way to create a property rental listing.

The VacationProperty model belongs to the User who created it (we'll call this user the host moving forward) and contains only two properties: a description and an imageUrl.

The model has two associations implemented: there are many reservations in it and many users can make those reservations.

Vacation Property Model

src/main/java/org/twilio/airtng/models/VacationProperty.java


_83package org.twilio.airtng.models;
_83
_83import javax.persistence.*;
_83import java.util.ArrayList;
_83import java.util.List;
_83
_83@Entity
_83@Table(name = "vacation_properties")
_83public class VacationProperty {
_83
_83    @javax.persistence.Id
_83    @GeneratedValue(strategy = GenerationType.IDENTITY)
_83    @Column(name = "id")
_83    private long id;
_83
_83    @Column(name = "description")
_83    private String description;
_83
_83    @Column(name = "image_url")
_83    private String imageUrl;
_83
_83    @OneToMany(mappedBy = "vacationProperty")
_83    private List<Reservation> reservations;
_83
_83    @ManyToOne(fetch = FetchType.LAZY)
_83    @JoinColumn(name = "user_id")
_83    private User user;
_83
_83    public VacationProperty() {
_83        this.reservations = new ArrayList<Reservation>();
_83    }
_83
_83    public VacationProperty(String description, String imageUrl, User user) {
_83        this.description = description;
_83        this.imageUrl = imageUrl;
_83        this.user = user;
_83    }
_83
_83    public long getId() {
_83        return id;
_83    }
_83
_83    public void setId(long id) {
_83        this.id = id;
_83    }
_83
_83    public String getDescription() {
_83        return description;
_83    }
_83
_83    public void setDescription(String description) {
_83        this.description = description;
_83    }
_83
_83    public String getImageUrl() {
_83        return imageUrl;
_83    }
_83
_83    public void setImageUrl(String imageUrl) {
_83        this.imageUrl = imageUrl;
_83    }
_83
_83    public User getUser() {
_83        return this.user;
_83    }
_83
_83    public void setUser(User user) {
_83        this.user = user;
_83    }
_83
_83    public void addReservation(Reservation reservation) {
_83
_83        if (this.reservations.add(reservation) && reservation.getVacationProperty() != this) {
_83            reservation.setVacationProperty(this);
_83        }
_83    }
_83
_83    public void removeReservation(Reservation reservation) {
_83        if (this.reservations.remove(reservation) && reservation.getVacationProperty() == this) {
_83            reservation.setVacationProperty(null);
_83        }
_83    }
_83}

Next, let's look at the all-important Reservation model.

The Reservation Model

The Reservation model is at the center of the workflow for this application. It is responsible for keeping track of:

The guest who performed the reservation
The vacation property the guest is requesting (and associated host )
The status of the reservation: pending , confirmed , or rejected

The Reservation Model

src/main/java/org/twilio/airtng/models/Reservation.java


_133package org.twilio.airtng.models;
_133
_133import javax.persistence.*;
_133
_133@Entity
_133@Table(name = "reservations")
_133public class Reservation {
_133
_133    @javax.persistence.Id
_133    @GeneratedValue(strategy = GenerationType.IDENTITY)
_133    @Column(name = "id")
_133    private long id;
_133
_133    @Column(name = "message")
_133    private String message;
_133
_133    @Column(name = "status")
_133    private Integer status;
_133
_133    @ManyToOne(fetch = FetchType.LAZY)
_133    @JoinColumn(name = "user_id")
_133    private User user;
_133
_133    @ManyToOne(fetch = FetchType.LAZY)
_133    @JoinColumn(name = "vacation_property_id")
_133    private VacationProperty vacationProperty;
_133
_133    public Reservation() {
_133    }
_133
_133    public Reservation(String message, VacationProperty vacationProperty, User user) {
_133        this();
_133        this.message = message;
_133        this.vacationProperty = vacationProperty;
_133        this.user = user;
_133        this.setStatus(Status.Pending);
_133    }
_133
_133    public long getId() {
_133        return id;
_133    }
_133
_133    public void setId(long id) {
_133        this.id = id;
_133    }
_133
_133    public String getMessage() {
_133        return message;
_133    }
_133
_133    public void setMessage(String message) {
_133        this.message = message;
_133    }
_133
_133    public Status getStatus() {
_133        return Status.getType(this.status);
_133    }
_133
_133    public void setStatus(Status status) {
_133        if (status == null) {
_133            this.status = null;
_133        } else {
_133            this.status = status.getValue();
_133        }
_133    }
_133
_133    public VacationProperty getVacationProperty() {
_133        return vacationProperty;
_133    }
_133
_133    public void setVacationProperty(VacationProperty vacationProperty) {
_133        this.vacationProperty = vacationProperty;
_133    }
_133
_133    public User getUser() {
_133        return this.user;
_133    }
_133
_133    public void setUser(User user) {
_133        this.user = user;
_133    }
_133
_133    public void reject() {
_133        this.setStatus(Status.Rejected);
_133    }
_133
_133    public void confirm() {
_133        this.setStatus(Status.Confirmed);
_133    }
_133
_133    public enum Status {
_133
_133        Pending(0), Confirmed(1), Rejected(2);
_133
_133        private int value;
_133
_133        Status(int value) {
_133            this.value = value;
_133        }
_133
_133        public int getValue() {
_133            return value;
_133        }
_133
_133        @Override
_133        public String toString() {
_133            switch (value) {
_133                case 0:
_133                    return "pending";
_133                case 1:
_133                    return "confirmed";
_133                case 2:
_133                    return "rejected";
_133            }
_133            return "Value out of range";
_133        }
_133
_133
_133        public static Status getType(Integer id) {
_133
_133            if (id == null) {
_133                return null;
_133            }
_133
_133            for (Status status : Status.values()) {
_133                if (id.equals(status.getValue())) {
_133                    return status;
_133                }
_133            }
_133            throw new IllegalArgumentException("No matching type for value " + id);
_133        }
_133    }
_133}

Next up, we'll show how our new application will create a new reservation.

Create a Reservation

The reservation creation form holds only one field: the message that will be sent to the host when reserving one of her properties.

The rest of the information necessary to create a reservation is taken from the logged in user and the relationship between a property and its owner. Our base generic Repository is in charge of handling entity insertion.

A reservation is created with a default status pending. This lets our application easily react to a host rejecting or accepting a reservation request.

Create a new reservation

src/main/java/org/twilio/airtng/servlets/ReservationServlet.java


_81package org.twilio.airtng.servlets;
_81
_81import org.twilio.airtng.lib.notifications.SmsNotifier;
_81import org.twilio.airtng.lib.servlets.WebAppServlet;
_81import org.twilio.airtng.lib.web.request.validators.RequestParametersValidator;
_81import org.twilio.airtng.models.Reservation;
_81import org.twilio.airtng.models.User;
_81import org.twilio.airtng.models.VacationProperty;
_81import org.twilio.airtng.repositories.ReservationRepository;
_81import org.twilio.airtng.repositories.UserRepository;
_81import org.twilio.airtng.repositories.VacationPropertiesRepository;
_81
_81import javax.servlet.ServletException;
_81import javax.servlet.http.HttpServletRequest;
_81import javax.servlet.http.HttpServletResponse;
_81import java.io.IOException;
_81
_81public class ReservationServlet extends WebAppServlet {
_81
_81    private final VacationPropertiesRepository vacationPropertiesRepository;
_81    private final ReservationRepository reservationRepository;
_81    private UserRepository userRepository;
_81    private SmsNotifier smsNotifier;
_81
_81    public ReservationServlet() {
_81        this(new VacationPropertiesRepository(), new ReservationRepository(), new UserRepository(), new SmsNotifier());
_81    }
_81
_81    public ReservationServlet(VacationPropertiesRepository vacationPropertiesRepository, ReservationRepository reservationRepository, UserRepository userRepository, SmsNotifier smsNotifier) {
_81        super();
_81        this.vacationPropertiesRepository = vacationPropertiesRepository;
_81        this.reservationRepository = reservationRepository;
_81        this.userRepository = userRepository;
_81        this.smsNotifier = smsNotifier;
_81    }
_81
_81    @Override
_81    public void doGet(HttpServletRequest request, HttpServletResponse response)
_81            throws ServletException, IOException {
_81
_81        VacationProperty vacationProperty = vacationPropertiesRepository.find(Long.parseLong(request.getParameter("id")));
_81        request.setAttribute("vacationProperty", vacationProperty);
_81        request.getRequestDispatcher("/reservation.jsp").forward(request, response);
_81    }
_81
_81    @Override
_81    public void doPost(HttpServletRequest request, HttpServletResponse response)
_81            throws ServletException, IOException {
_81
_81        super.doPost(request, response);
_81
_81        String message = null;
_81        VacationProperty vacationProperty = null;
_81
_81        if (isValidRequest()) {
_81            message = request.getParameter("message");
_81            String propertyId = request.getParameter("propertyId");
_81            vacationProperty = vacationPropertiesRepository.find(Long.parseLong(propertyId));
_81
_81            User currentUser = userRepository.find(sessionManager.get().getLoggedUserId(request));
_81            Reservation reservation = reservationRepository.create(new Reservation(message, vacationProperty, currentUser));
_81            smsNotifier.notifyHost(reservation);
_81            response.sendRedirect("/properties");
_81        }
_81        preserveStatusRequest(request, message, vacationProperty);
_81        request.getRequestDispatcher("/reservation.jsp").forward(request, response);
_81    }
_81
_81    @Override
_81    protected boolean isValidRequest(RequestParametersValidator validator) {
_81
_81        return validator.validatePresence("message");
_81    }
_81
_81    private void preserveStatusRequest(
_81            HttpServletRequest request,
_81            String message, Object vacationProperty) {
_81        request.setAttribute("message", message);
_81        request.setAttribute("vacationProperty", vacationProperty);
_81    }
_81}

Now let's look at how the system will notify a host when a new reservation request is submitted.

Notify the Host

When a reservation is created for a property we want to notify the owner that someone has made a reservation.

We use an abstraction called SmsNotifier which under the hood uses another abstraction called Sender. Here is where we use Twilio's Rest API to send an SMS message to the host using your Twilio phone number. That's right - it's as simple as that to send a SMS with Twilio.

Notify the host

src/main/java/org/twilio/airtng/lib/sms/Sender.java


_28package org.twilio.airtng.lib.sms;
_28
_28import com.twilio.http.TwilioRestClient;
_28import com.twilio.rest.api.v2010.account.MessageCreator;
_28import com.twilio.type.PhoneNumber;
_28import org.twilio.airtng.lib.Config;
_28
_28public class Sender {
_28
_28    private final TwilioRestClient client;
_28
_28    public Sender() {
_28        client = new TwilioRestClient.Builder(Config.getAccountSid(), Config.getAuthToken()).build();
_28    }
_28
_28    public Sender(TwilioRestClient client) {
_28        this.client = client;
_28    }
_28
_28    public void send(String to, String message) {
_28        new MessageCreator(
_28                new PhoneNumber(to),
_28                new PhoneNumber(Config.getPhoneNumber()),
_28                message
_28        ).create(client);
_28    }
_28
_28}

The next step shows how to handle a host accepting or rejecting a request - let's continue.

Handle Incoming Messages

Let's take a closer look at the ReservationConfirmation servlet. This servlet handles our incoming Twilio request and does three things:

Check for a pending reservation from the incoming user.
Update the status of the reservation.
Respond to the host and send notification to the guest.

Incoming Twilio Requests

In the Twilio console, you should change the 'A Message Comes In' webhook to call your application's endpoint in the route /reservation-confirmation:

One way to expose your machine to the world during development is to use ngrok. Your URL for the SMS web hook on your phone number should look something like this:


_10http://<subdomain>.ngrok.io/reservation-confirmation

An incoming request from Twilio comes with some helpful parameters, including the From phone number and the message Body.

We'll use the From parameter to lookup the host and check if he/she has any pending reservations. If he/she does, we'll use the message body to check for an 'accept' or 'reject'.

Finally, we update the reservation status and use the SmsNotifier abstraction to send an SMS to the guest with the news.

Handle incoming messages

Webhook for handling Host's decision


_70package org.twilio.airtng.servlets;
_70
_70import com.twilio.twiml.MessagingResponse;
_70import com.twilio.twiml.TwiMLException;
_70import org.twilio.airtng.lib.helpers.TwiMLHelper;
_70import org.twilio.airtng.lib.notifications.SmsNotifier;
_70import org.twilio.airtng.lib.servlets.WebAppServlet;
_70import org.twilio.airtng.models.Reservation;
_70import org.twilio.airtng.models.User;
_70import org.twilio.airtng.repositories.ReservationRepository;
_70import org.twilio.airtng.repositories.UserRepository;
_70
_70import javax.servlet.ServletException;
_70import javax.servlet.http.HttpServletRequest;
_70import javax.servlet.http.HttpServletResponse;
_70import java.io.IOException;
_70
_70public class ReservationConfirmationServlet extends WebAppServlet {
_70
_70    private UserRepository userRepository;
_70    private ReservationRepository reservationRepository;
_70    private SmsNotifier smsNotifier;
_70
_70    public ReservationConfirmationServlet() {
_70        this(new UserRepository(), new ReservationRepository(), new SmsNotifier());
_70    }
_70
_70    public ReservationConfirmationServlet(UserRepository userRepository, ReservationRepository reservationRepository, SmsNotifier smsNotifier) {
_70        super();
_70        this.userRepository = userRepository;
_70        this.reservationRepository = reservationRepository;
_70        this.smsNotifier = smsNotifier;
_70    }
_70
_70    @Override
_70    public void doPost(HttpServletRequest request, HttpServletResponse response) throws IOException, ServletException {
_70
_70        String phone = request.getParameter("From");
_70        String smsContent = request.getParameter("Body");
_70
_70        String smsResponseText = "Sorry, it looks like you don't have any reservations to respond to.";
_70
_70        try {
_70            User user = userRepository.findByPhoneNumber(phone);
_70            Reservation reservation = reservationRepository.findFirstPendantReservationsByUser(user.getId());
_70            if (reservation != null) {
_70                if (smsContent.contains("yes") || smsContent.contains("accept"))
_70                    reservation.confirm();
_70                else
_70                    reservation.reject();
_70                reservationRepository.update(reservation);
_70
_70                smsResponseText = String.format("You have successfully %s the reservation", reservation.getStatus().toString());
_70                smsNotifier.notifyGuest(reservation);
_70            }
_70
_70        respondSms(response, smsResponseText);
_70
_70        } catch (Exception e) {
_70            throw new RuntimeException(e);
_70        }
_70    }
_70
_70    private void respondSms(HttpServletResponse response, String message)
_70            throws IOException, TwiMLException {
_70        MessagingResponse twiMLResponse = TwiMLHelper.buildSmsRespond(message);
_70        response.setContentType("text/xml");
_70        response.getWriter().write(twiMLResponse.toXml());
_70    }
_70}

Next up, let's see how we will respond to Twilio.

TwiML Response

Finally, we'll use Twilio's TwiML as a response to Twilio's server instructing it to send SMS notification message to the host.

We'll be using the Message verb to instruct Twilio's server that it should send the message.

Build a TwiML response

src/main/java/org/twilio/airtng/servlets/ReservationConfirmationServlet.java


_70package org.twilio.airtng.servlets;
_70
_70import com.twilio.twiml.MessagingResponse;
_70import com.twilio.twiml.TwiMLException;
_70import org.twilio.airtng.lib.helpers.TwiMLHelper;
_70import org.twilio.airtng.lib.notifications.SmsNotifier;
_70import org.twilio.airtng.lib.servlets.WebAppServlet;
_70import org.twilio.airtng.models.Reservation;
_70import org.twilio.airtng.models.User;
_70import org.twilio.airtng.repositories.ReservationRepository;
_70import org.twilio.airtng.repositories.UserRepository;
_70
_70import javax.servlet.ServletException;
_70import javax.servlet.http.HttpServletRequest;
_70import javax.servlet.http.HttpServletResponse;
_70import java.io.IOException;
_70
_70public class ReservationConfirmationServlet extends WebAppServlet {
_70
_70    private UserRepository userRepository;
_70    private ReservationRepository reservationRepository;
_70    private SmsNotifier smsNotifier;
_70
_70    public ReservationConfirmationServlet() {
_70        this(new UserRepository(), new ReservationRepository(), new SmsNotifier());
_70    }
_70
_70    public ReservationConfirmationServlet(UserRepository userRepository, ReservationRepository reservationRepository, SmsNotifier smsNotifier) {
_70        super();
_70        this.userRepository = userRepository;
_70        this.reservationRepository = reservationRepository;
_70        this.smsNotifier = smsNotifier;
_70    }
_70
_70    @Override
_70    public void doPost(HttpServletRequest request, HttpServletResponse response) throws IOException, ServletException {
_70
_70        String phone = request.getParameter("From");
_70        String smsContent = request.getParameter("Body");
_70
_70        String smsResponseText = "Sorry, it looks like you don't have any reservations to respond to.";
_70
_70        try {
_70            User user = userRepository.findByPhoneNumber(phone);
_70            Reservation reservation = reservationRepository.findFirstPendantReservationsByUser(user.getId());
_70            if (reservation != null) {
_70                if (smsContent.contains("yes") || smsContent.contains("accept"))
_70                    reservation.confirm();
_70                else
_70                    reservation.reject();
_70                reservationRepository.update(reservation);
_70
_70                smsResponseText = String.format("You have successfully %s the reservation", reservation.getStatus().toString());
_70                smsNotifier.notifyGuest(reservation);
_70            }
_70
_70        respondSms(response, smsResponseText);
_70
_70        } catch (Exception e) {
_70            throw new RuntimeException(e);
_70        }
_70    }
_70
_70    private void respondSms(HttpServletResponse response, String message)
_70            throws IOException, TwiMLException {
_70        MessagingResponse twiMLResponse = TwiMLHelper.buildSmsRespond(message);
_70        response.setContentType("text/xml");
_70        response.getWriter().write(twiMLResponse.toXml());
_70    }
_70}

Congrats! You've just learned how to automate your workflow with Twilio SMS.

Next, let's look at some other interesting features you might want to add to your application.

Where to Next?

Like Twilio? Like Java? You're in the right place. Here are a couple other excellent tutorials:

SMS and MMS notifications

Build a server notification system that will alert all administrators via SMS when a server outage occurs.

Click To Call

Convert web traffic into phone calls with the click of a button.

Did this help?

Thanks for checking this tutorial out! Tweet to us @twilio with what you're building!