Spring Boot Firebase CRUD

In this article, we show How to build a CRUD application using Firebase and Spring boot.

Create a Firebase project in the Firebase console:


Hit the https://console.firebase.google.com and sign up for an account.

Click the “Add Project” button from the project overview page.

Type “Firebase DB for Spring Boot” in the “Project name” field.

Click the “CREATE PROJECT” button.

Now we have created a project on Firebase, now let us add firebase to our spring boot app.

Add Firebase to your web app:

You can find your Realtime Database URL in the Database tab (DEVELOP → Database → Realtime Database → Start in test Mode ) in the Firebase console. It will be in the form of https://<databaseName>.firebaseio.com.

Create Firebase in test mode this is not useful for Prod development but for our this article we will use it in test mode which is available publicly. 

Your Database URL should look like this https://<Projectname XYZ>.firebaseio.com/

Our data is ready but still, we need a service account 

Go and click on Project settings → Service Accounts → Choose Language as Java. to copy code snippet

and Download JSON file as well by clicking on “Generate new private key”

We will also grab the admin SDK configuration snippet for java.

Then go to https://start.spring.io/ and create a project, Once the project added then open the pom.xml file and add below dependency.


Now everything is ready to Let us initialize Firebase Database.

import com.google.auth.oauth2.GoogleCredentials;
import com.google.firebase.FirebaseApp;
import com.google.firebase.FirebaseOptions;
import org.springframework.stereotype.Service;

import javax.annotation.PostConstruct;
import java.io.FileInputStream;

public class FBInitialize {

    public void initialize() {
        try {
            FileInputStream serviceAccount =
                    new FileInputStream("./serviceaccount.json");

            FirebaseOptions options = new FirebaseOptions.Builder()

        } catch (Exception e) {


I am using the existing Firebase Database.

@Service and @PostConstruct these are the two annotations from Spring Boot. 

First-line reads the configurations from the JSON file and then initializes the connection for the specified database. 

Now firebase connection is initialized then let us create CRUD operations.

Create a POJO class as a Patient

public class Patient {

    private String name;

    private int age;

    private String city;

    public Patient(String name, int age, String city) {

    public String getName() {
        return name;

    public void setName(String name) {
        this.name = name;

    public int getAge() {
        return age;

    public void setAge(int age) {
        this.age = age;

    public String getCity() {
        return city;

    public void setCity(String city) {
        this.city = city;

Create Service class

import com.google.api.core.ApiFuture;
import com.google.cloud.firestore.DocumentReference;
import com.google.cloud.firestore.DocumentSnapshot;
import com.google.cloud.firestore.Firestore;
import com.google.cloud.firestore.WriteResult;
import com.google.firebase.cloud.FirestoreClient;
import org.springframework.stereotype.Service;

import java.util.concurrent.ExecutionException;

//CRUD operations
public class PatientService {

    public static final String COL_NAME="users";

    public String savePatientDetails(Patient patient) throws InterruptedException, ExecutionException {
        Firestore dbFirestore = FirestoreClient.getFirestore();
        ApiFuture<WriteResult> collectionsApiFuture = dbFirestore.collection(COL_NAME).document(patient.getName()).set(patient);
        return collectionsApiFuture.get().getUpdateTime().toString();

    public Patient getPatientDetails(String name) throws InterruptedException, ExecutionException {
        Firestore dbFirestore = FirestoreClient.getFirestore();
        DocumentReference documentReference = dbFirestore.collection(COL_NAME).document(name);
        ApiFuture<DocumentSnapshot> future = documentReference.get();

        DocumentSnapshot document = future.get();

        Patient patient = null;

        if(document.exists()) {
            patient = document.toObject(Patient.class);
            return patient;
        }else {
            return null;

    public String updatePatientDetails(Patient person) throws InterruptedException, ExecutionException {
        Firestore dbFirestore = FirestoreClient.getFirestore();
        ApiFuture<WriteResult> collectionsApiFuture = dbFirestore.collection(COL_NAME).document(person.getName()).set(person);
        return collectionsApiFuture.get().getUpdateTime().toString();

    public String deletePatient(String name) {
        Firestore dbFirestore = FirestoreClient.getFirestore();
        ApiFuture<WriteResult> writeResult = dbFirestore.collection(COL_NAME).document(name).delete();
        return "Document with Patient ID "+name+" has been deleted";


Now we are ready with CRUD operation let us develop the REST Controller which will help us in interaction with this service layer.

Note:- You have to enable Cloud FireStore API.

Now we just need to create Controller which can handle REST request.

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.*;

import java.util.concurrent.ExecutionException;

public class PatientController {

    PatientService patientService;

    public Patient getPatient(@RequestParam String name ) throws InterruptedException, ExecutionException{
        return patientService.getPatientDetails(name);

    public String createPatient(@RequestBody Patient patient ) throws InterruptedException, ExecutionException {
        return patientService.savePatientDetails(patient);

    public String updatePatient(@RequestBody Patient patient  ) throws InterruptedException, ExecutionException {
        return patientService.updatePatientDetails(patient);

    public String deletePatient(@RequestParam String name){
        return patientService.deletePatient(name);

Now coding is done try by yourself and let’s know.

Spring Cloud function Helloworld on AWS and local!!

In this article, we’ll learn how to use Spring Cloud Function. Serverless function using spring cloud function.

A serverless function is a modern industry buzzword and the reason behind that is boost in cloud computing.

credit goes to gitconnected

As part of this article, We’ll build and run a simple Spring Cloud Function locally and then deploy it to the AWS cloud platform.

Spring Cloud Function is a project with the following high-level goals as per spring cloud official website:

  • Promote the implementation of business logic via functions.
  • Decouple the development lifecycle of business logic from any specific runtime target so that the same code can run as a web endpoint, a stream processor, or a task.
  • Support a uniform programming model across serverless providers, as well as the ability to run standalone (locally or in a PaaS).
  • Enable Spring Boot features (auto-configuration, dependency injection, metrics) on serverless providers.

If you could able to understand the above things you will be able to relate things this with any serverless technology by any cloud provider. The reason behind serverless is concentrating on business logic, not on infra and any other things.


There are below number features spring cloud function provides.

  • Choice of programming styles — reactive, imperative or hybrid.
  • Function composition and adaptation (e.g., composing imperative functions with reactive).
  • Support for reactive function with multiple inputs and outputs allowing merging, joining and other complex streaming operations to be handled by functions.
  • Transparent type conversion of inputs and outputs.
  • Packaging functions for deployments, specific to the target platform (e.g., Project Riff, AWS Lambda and more)
  • Adapters to expose a function to the outside world as HTTP endpoints etc.
  • Deploying a JAR file containing such an application context with an isolated classloader, so that you can pack them together in a single JVM.
  • Compiling strings which are Java function bodies into bytecode, and then turning them into @Beans that can be wrapped as above.
  • Adapters for AWS Lambda, Microsoft Azure, Apache OpenWhisk and possibly other “serverless” service providers.

Let us deep dive and do some coding.

We will take one simple example 

  • Convert a String to lower case, using a String method
  • And a HelloWorld greeting message using a dedicated class.

For this example, I am using Maven you can use Gradle as a build tool as well. 

#add spring cloud function dependency

First Spring Cloud Function:

We will expose @Bean of type function using spring cloud function. As part of this code, we are exposing toLowerCase functionality as a spring cloud function.

public class CloudFunctionApp {
public static void main(String[] args) {
SpringApplication.run(CloudFunctionApp.class, args);
public Function<String, String> lowerCaseString() {
return value -> new StringBuilder(value).toString().toLowerCase().toString();

Test this functionality in our local using curl command

curl localhost:8087/lowerCaseString -H "Content-Type: text/plain" -d "Spring cloud FUNCTION"

The endpoint is the name of the bean. here it is lowerCaseString.

Spring Cloud Function in Packages:

In the above we have exposed @Bean as method Apart from this, we could also write our software as classes that implement the functional interface Function<T, R>. We can specify the packages to scan for relevant beans in the application.properties file.

package com.techwasti.spring.cloudfunction.functions;

public class Hello implements Function<String, String> {
public String apply(String s) {
return "Hello " + s + ", and welcome to Server less world!!!";

Also as mentioned above add below line in application.properties file


We can also test this one in our local

curl localhost:8080/hello -H "Content-Type: text/plain" -d "Maheshwar"

The endpoint is the name of the class that implements the functional interface.

Spring Cloud Function on AWS:

The best thing about the spring ecosystem is seamless adoption and customization. The same applies to Spring Cloud Function, spring cloud function so powerful is that we can build Spring enabled functions that are cloud-agnostic. Spring cloud function provides abstraction API and adapter so that we can build function tests on local and deploy on any cloud provider such as AWS, Azure or Google Cloud platform without changing any of the business logic.

AWS is a popular one so for this exercise we choose AWS. 

Remember we have used above spring cloud function maven dependency we need the same one for this as 

##to handle AWS lambda we need below dependency 

We are going to upload the artifact generated by the maven build to AWS Lambda, we need to build an artifact that is shaded, which means, it has all the dependencies burst out as individual class files instead of jars.

We are adding spring-boot-thin-layout dependency that helps us to reduce the size of the artifact by excluding some dependencies that are not needed.


If we are shipping our spring cloud function such as lower case String converter to handle this over AWS we need Handler

public class MyHelloWorldHandlers extends SpringBootRequestHandler<String, String> {


Spring Cloud Function AWS also ships with SpringBootStreamHandler and FunctionInvokingS3EventHandler as well.

This is just an empty class but it plays a very important role in both acting as an entry point and also defines the input and output types.

How Does AWS lambda Know Which Spring Cloud Function to Invoke?

In our example, if we have more than one spring cloud function How AWS know which one we have to invoke,

Even if we have more than one Spring Cloud Function in our application, AWS can invoke only one of them.

We have to specify the cloud function name in an environment variable called FUNCTION_NAME on the AWS console.

Upload function over AWS and Test:

Now we are ready to upload spring cloud function over AWS.

On the AWS Lambda console page, in the Function code section, we can select a Java 8runtime and simply click Upload. As I mentioned we need to specify handler as well i.e MyHelloWorldHandlers.

And then specify FUNCTION_NAME in environment variable as lowerCaseString.

it’s time for us to test the Lambda spring cloud function by creating a test event and supplying a sample string such as “Spring CLOUD function”, then save it and, then click the Test button. Similar way we can test the “hello” spring cloud function by changing the value of FUNCTION_NAME parameter. 

Spring Cloud Function is a powerful tool for decoupling the business logic from any specific runtime environment.


Introducing Spring Cloud Function
Spring Cloud Function is a new project with the following high-level goals: Promote the implementation of business…spring.io

Spring Cloud Function
Spring Cloud Function features: Choice of programming styles – reactive, imperative or hybrid. Function composition and…spring.io