Welcome To Fusebes - Dev & Programming Blog

Intro to Spring Boot Starters

Intro to Spring Boot Starters

1. Overview

Dependency management is a critical aspects of any complex project. And doing this manually is less than ideal; the more time you spent on it the less time you have on the other important aspects of the project.

Spring Boot starters were built to address exactly this problem. Starter POMs are a set of convenient dependency descriptors that you can include in your application. You get a one-stop-shop for all the Spring and related technology that you need, without having to hunt through sample code and copy-paste loads of dependency descriptors.

We have more than 30 Boot starters available – let’s see some of them in the following section

2. The Web Starter

First, let’s look at developing the REST service; we can use libraries like Spring MVC, Tomcat and Jackson – a lot of dependencies for a single application.

Spring Boot starters can help to reduce the number of manually added dependencies just by adding one dependency. So instead of manually specifying the dependencies just add one starter as in the following example:


Now we can create a REST controller. For the sake of simplicity we won’t use the database and focus on the REST controller:

public class GenericEntityController {
    private List<GenericEntity> entityList = new ArrayList<>();

    public List<GenericEntity> findAll() {
        return entityList;

    @RequestMapping(value = "/entity", method = RequestMethod.POST)
    public GenericEntity addEntity(GenericEntity entity) {
        return entity;

    public GenericEntity findById(@PathVariable Long id) {
        return entityList.stream().
                 filter(entity -> entity.getId().equals(id)).

The GenericEntity is a simple bean with id of type Long and value of type String.

That’s it – with the application running, you can access http://localhost:8080/entity/all and check the controller is working.

We have created a REST application with quite a minimal configuration.

3. The Test Starter

For testing we usually use the following set of libraries: Spring Test, JUnit, Hamcrest, and Mockito. We can include all of these libraries manually, but Spring Boot starter can be used to automatically include these libraries in the following way:


Notice that you don’t need to specify the version number of an artifact. Spring Boot will figure out what version to use – all you need to specify is the version of spring-boot-starter-parent artifact. If later on you need to upgrade the Boot library and dependencies, just upgrade the Boot version in one place and it will take care of the rest.

Let’s actually test the controller we created in the previous example.

There are two ways to test the controller:

  • Using the mock environment
  • Using the embedded Servlet container (like Tomcat or Jetty)

In this example we’ll use a mock environment:

@SpringApplicationConfiguration(classes = Application.class)
public class SpringBootApplicationIntegrationTest {
    private WebApplicationContext webApplicationContext;
    private MockMvc mockMvc;

    public void setupMockMvc() {
        mockMvc = MockMvcBuilders.webAppContextSetup(webApplicationContext).build();

    public void givenRequestHasBeenMade_whenMeetsAllOfGivenConditions_thenCorrect()
      throws Exception { 
        MediaType contentType = new MediaType(MediaType.APPLICATION_JSON.getType(),
        MediaType.APPLICATION_JSON.getSubtype(), Charset.forName("utf8"));
        andExpect(jsonPath("$", hasSize(4))); 

The above test calls the /entity/all endpoint and verifies that the JSON response contains 4 elements. For this test to pass, we also have to initialize our list in the controller class:

public class GenericEntityController {
    private List<GenericEntity> entityList = new ArrayList<>();

        entityList.add(new GenericEntity(1l, "entity_1"));
        entityList.add(new GenericEntity(2l, "entity_2"));
        entityList.add(new GenericEntity(3l, "entity_3"));
        entityList.add(new GenericEntity(4l, "entity_4"));

What is important here is that @WebAppConfiguration annotation and MockMVC are part of the spring-test module, hasSize is a Hamcrest matcher, and @Before is a JUnit annotation. These are all available by importing one this one starter dependency.

4. The Data JPA Starter

Most web applications have some sort of persistence – and that’s quite often JPA.

Instead of defining all of the associated dependencies manually – let’s go with the starter instead:


Notice that out of the box we have automatic support for at least the following databases: H2, Derby and Hsqldb. In our example, we’ll use H2.

Now let’s create the repository for our entity:

public interface GenericEntityRepository extends JpaRepository<GenericEntity, Long> {}

Time to test the code. Here is the JUnit test:

@SpringApplicationConfiguration(classes = Application.class)
public class SpringBootJPATest {
    private GenericEntityRepository genericEntityRepository;

    public void givenGenericEntityRepository_whenSaveAndRetreiveEntity_thenOK() {
        GenericEntity genericEntity = 
          genericEntityRepository.save(new GenericEntity("test"));
        GenericEntity foundedEntity = 
        assertEquals(genericEntity.getValue(), foundedEntity.getValue());

We didn’t spend time on specifying the database vendor, URL connection, and credentials. No extra configuration is necessary as we’re benefiting from the solid Boot defaults; but of course all of these details can still be configured if necessary.

5. The Mail Starter

A very common task in enterprise development is sending email, and dealing directly with Java Mail API usually can be difficult.

Spring Boot starter hides this complexity – mail dependencies can be specified in the following way:


Now we can directly use the JavaMailSender, so let’s write some tests.

For the testing purpose, we need a simple SMTP server. In this example, we’ll use Wiser. This is how we can include it in our POM:


Here is the source code for the test:

@SpringApplicationConfiguration(classes = Application.class)
public class SpringBootMailTest {
    private JavaMailSender javaMailSender;

    private Wiser wiser;

    private String userTo = "user2@localhost";
    private String userFrom = "user1@localhost";
    private String subject = "Test subject";
    private String textMail = "Text subject mail";

    public void setUp() throws Exception {
        final int TEST_PORT = 25;
        wiser = new Wiser(TEST_PORT);

    public void tearDown() throws Exception {

    public void givenMail_whenSendAndReceived_thenCorrect() throws Exception {
        SimpleMailMessage message = composeEmailMessage();
        List<WiserMessage> messages = wiser.getMessages();

        assertThat(messages, hasSize(1));
        WiserMessage wiserMessage = messages.get(0);
        assertEquals(userFrom, wiserMessage.getEnvelopeSender());
        assertEquals(userTo, wiserMessage.getEnvelopeReceiver());
        assertEquals(subject, getSubject(wiserMessage));
        assertEquals(textMail, getMessage(wiserMessage));

    private String getMessage(WiserMessage wiserMessage)
      throws MessagingException, IOException {
        return wiserMessage.getMimeMessage().getContent().toString().trim();

    private String getSubject(WiserMessage wiserMessage) throws MessagingException {
        return wiserMessage.getMimeMessage().getSubject();

    private SimpleMailMessage composeEmailMessage() {
        SimpleMailMessage mailMessage = new SimpleMailMessage();
        return mailMessage;

In the test, the @Before and @After methods are in charge of starting and stopping the mail server.

Notice that we’re wiring in the JavaMailSender bean – the bean was automatically created by Spring Boot.

Just like any other defaults in Boot, the email settings for the JavaMailSender can be customized in application.properties:


So we configured the mail server on localhost:25 and we didn’t require authentication.

6. Conclusion

In this article we have given an overview of Starters, explained why we need them and provided examples on how to use them in your projects.

Let’s recap the benefits of using Spring Boot starters:

  • increase pom manageability
  • production-ready, tested & supported dependency configurations
  • decrease the overall configuration time for the project
@Scope – How to get Scope of Bean

@Scope – How to get Scope of Bean

@Scope – How to get Scope of Bean from Code

When we create a Bean we are creating  actual instances of the class defined by that bean definition. We can also control the scope of the objects created from a particular bean definition.

There are 5 types of scopes in bean,

  • singleton (default scope)
  • prototype
  • request
  • session
  • global-session

Single instance per spring IoC container

Single bean definition to any number of object instances.

Bean definition for each request. Only valid web-aware Spring ApplicationContext.

Bean definition for a session. Only valid web-aware Spring ApplicationContext.

Similar to session but the only makes sense in the context of portlet-based web applications. Only valid web-aware Spring ApplicationContext.

Deploying a stateless Go app with Redis on Kubernetes

Deploying a stateless Go app with Redis on Kubernetes

In this article, we’ll go a step further and deploy a stateless Go web app with Redis on Kubernetes. You’ll get to understand how the deployment of multiple distinct Pods work and how two Pods can communicate with each other in the cluster.

Building a sample Go app that uses Redis

We’ll create a simple web application in Go that contains an API to display the “Quote of the day”.

The app fetches the quote of the day from a public API hosted at http://quotes.rest/, then it caches the result in Redis until the end of the day. For subsequent API calls, the app will return the result from Redis cache instead of fetching it from the public API.

Open your terminal and type the following commands to create the project and initialize Go modules

$ mkdir go-redis-kubernetes
$ cd go-redis-kubernetes
$ go mod init github.com/username/go-redis-kubernetes # Change `username` to your Github username

Next, create a file called main.go with the following code:

package main

import (


func indexHandler(w http.ResponseWriter, r *http.Request) {
	w.Write([]byte("Welcome! Please hit the `/qod` API to get the quote of the day."))

func quoteOfTheDayHandler(client *redis.Client) http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {
		currentTime := time.Now()
		date := currentTime.Format("2006-01-02")

		val, err := client.Get(date).Result()
		if err == redis.Nil {
			log.Println("Cache miss for date ", date)
			quoteResp, err := getQuoteFromAPI()
			if err != nil {
				w.Write([]byte("Sorry! We could not get the Quote of the Day. Please try again."))
			quote := quoteResp.Contents.Quotes[0].Quote
			client.Set(date, quote, 24*time.Hour)
		} else {
			log.Println("Cache Hit for date ", date)

func main() {
	// Create Redis Client
	var (
		host     = getEnv("REDIS_HOST", "localhost")
		port     = string(getEnv("REDIS_PORT", "6379"))
		password = getEnv("REDIS_PASSWORD", "")

	client := redis.NewClient(&redis.Options{
		Addr:     host + ":" + port,
		Password: password,
		DB:       0,

	_, err := client.Ping().Result()
	if err != nil {

	// Create Server and Route Handlers
	r := mux.NewRouter()

	r.HandleFunc("/", indexHandler)
	r.HandleFunc("/qod", quoteOfTheDayHandler(client))

	srv := &http.Server{
		Handler:      r,
		Addr:         ":8080",
		ReadTimeout:  10 * time.Second,
		WriteTimeout: 10 * time.Second,

	// Start Server
	go func() {
		log.Println("Starting Server")
		if err := srv.ListenAndServe(); err != nil {

	// Graceful Shutdown

func waitForShutdown(srv *http.Server) {
	interruptChan := make(chan os.Signal, 1)
	signal.Notify(interruptChan, os.Interrupt, syscall.SIGINT, syscall.SIGTERM)

	// Block until we receive our signal.

	// Create a deadline to wait for.
	ctx, cancel := context.WithTimeout(context.Background(), time.Second*10)
	defer cancel()

	log.Println("Shutting down")

func getQuoteFromAPI() (*QuoteResponse, error) {
	API_URL := "http://quotes.rest/qod.json"
	resp, err := http.Get(API_URL)
	if err != nil {
		return nil, err
	defer resp.Body.Close()
	log.Println("Quote API Returned: ", resp.StatusCode, http.StatusText(resp.StatusCode))

	if resp.StatusCode >= 200 && resp.StatusCode <= 299 {
		quoteResp := &QuoteResponse{}
		return quoteResp, nil
	} else {
		return nil, errors.New("Could not get quote from API")


func getEnv(key, defaultValue string) string {
	value := os.Getenv(key)
	if value == "" {
		return defaultValue
	return value

Also, create the following structs in a file named quote.go to parse the JSON response returned from http://quotes.rest/ API.

package main

type QuoteData struct {
	Id         string   `json:"id"`
	Quote      string   `json:"quote"`
	Length     string   `json:"length"`
	Author     string   `json:"author"`
	Tags       []string `json:"tags"`
	Category   string   `json:"category"`
	Date       string   `json:"date"`
	Permalink  string   `json:"parmalink"`
	Title      string   `json:"title"`
	Background string   `json:"Background"`

type QuoteResponse struct {
	Success  APISuccess   `json:"success"`
	Contents QuoteContent `json:"contents"`

type QuoteContent struct {
	Quotes    []QuoteData `json:"quotes"`
	Copyright string      `json:"copyright"`

type APISuccess struct {
	Total string `json:"total"`

Let’s now build and run the app locally:

$ go build
$ ./go-redis-kubernetes
2019/07/28 13:32:05 Starting Server
$ curl localhost:8080
Welcome! Please hit the `/qod` API to get the quote of the day.

$ curl localhost:8080/qod
I’ve missed more than 9000 shots in my career. I’ve lost almost 300 games. 26 times, I’ve been trusted to take the game winning shot and missed. I’ve failed over and over and over again in my life. And that is why I succeed.

Containerizing the Go app

Let’s now containerize our Go app by creating a Dockerfile with the following configurations:

# Dockerfile References: https://docs.docker.com/engine/reference/builder/

# Start from the latest golang base image
FROM golang:latest as builder

# Add Maintainer Info
LABEL maintainer="Rajeev Singh <rajeevhub@gmail.com>"

# Set the Current Working Directory inside the container

# Copy go mod and sum files
COPY go.mod go.sum ./

# Download all dependencies. Dependencies will be cached if the go.mod and go.sum files are not changed
RUN go mod download

# Copy the source from the current directory to the Working Directory inside the container
COPY . .

# Build the Go app
RUN CGO_ENABLED=0 GOOS=linux go build -a -installsuffix cgo -o main .

######## Start a new stage from scratch #######
FROM alpine:latest  

RUN apk --no-cache add ca-certificates

WORKDIR /root/

# Copy the Pre-built binary file from the previous stage
COPY --from=builder /app/main .

# Expose port 8080 to the outside world

# Command to run the executable
CMD ["./main"] 

Check out the article Building Docker Containers for Go Applications to learn more about how to containerize a Go app.

I’ve already built and published the docker image for our app on docker hub. You can use the following commands to do so –

# Build the image
$ docker build -t go-redis-kubernetes .

# Tag the image
$ docker tag go-redis-kubernetes username/go-redis-app:1.0.0

# Login to docker with your docker Id
$ docker login
Login with your Docker ID to push and pull images from Docker Hub. If you don\'t have a Docker ID, head over to https://hub.docker.com to create one.
Username (username): username
Login Succeeded

# Push the image to docker hub
$ docker push project/go-redis-app:1.0.0

Creating the Kubernetes deployment and service manifest for Redis

Let’s now create the configuration for deploying our Redis app on Kubernetes. We’ll need to create a deployment for managing the Redis instance and a Service to proxy traffic from our Go app to the Redis Pod.

Create a folder called deployments inside the project’s root directoy to store all the deployment manifests. And then, create a file called redis-master.yml with the following configurations:

apiVersion: apps/v1  # API version
kind: Deployment
  name: redis-master # Unique name for the deployment
    app: redis       # Labels to be applied to this deployment
    matchLabels:     # This deployment applies to the Pods matching these labels
      app: redis
      role: master
      tier: backend
  replicas: 1        # Run a single pod in the deployment
  template:          # Template for the pods that will be created by this deployment
      labels:        # Labels to be applied to the Pods in this deployment
        app: redis
        role: master
        tier: backend
    spec:            # Spec for the container which will be run inside the Pod.
      - name: master
        image: redis
            cpu: 100m
            memory: 100Mi
        - containerPort: 6379
apiVersion: v1
kind: Service        # Type of Kubernetes resource
  name: redis-master # Name of the Kubernetes resource
  labels:            # Labels that will be applied to this resource
    app: redis
    role: master
    tier: backend
  - port: 6379       # Map incoming connections on port 6379 to the target port 6379 of the Pod
    targetPort: 6379
  selector:          # Map any Pod with the specified labels to this service
    app: redis
    role: master
    tier: backend

The redis-master Service is only accessible within the container cluster because the default type for a Service is ClusterIP. ClusterIP provides a single IP address for the set of Pods the Service is pointing to. This IP address is accessible only within the cluster.

Kubernetes deployment manifest for the Go app

Let’s now create a deployment and a service for our Go app. We’ll run 3 Pods for the Go app and the Pods will be exposed via a Service to the outside world:

apiVersion: apps/v1
kind: Deployment                 # Type of Kubernetes resource
  name: go-redis-app             # Unique name of the Kubernetes resource
  replicas: 3                    # Number of pods to run at any given time
      app: go-redis-app          # This deployment applies to any Pods matching the specified label
  template:                      # This deployment will create a set of pods using the configurations in this template
      labels:                    # The labels that will be applied to all of the pods in this deployment
        app: go-redis-app 
      - name: go-redis-app
        image: project/go-redis-app:1.0.0 
        imagePullPolicy: IfNotPresent
            cpu: 100m
            memory: 100Mi
          - containerPort: 8080  # Should match the port number that the Go application listens on    
        env:                     # Environment variables passed to the container
          - name: REDIS_HOST
            value: redis-master
          - name: REDIS_PORT
            value: "6379"    
apiVersion: v1
kind: Service                    # Type of kubernetes resource
  name: go-redis-app-service     # Unique name of the resource
  type: NodePort                 # Expose the Pods by opening a port on each Node and proxying it to the service.
  ports:                         # Take incoming HTTP requests on port 9090 and forward them to the targetPort of 8080
  - name: http
    port: 9090
    targetPort: 8080
    app: go-redis-app            # Map any pod with label `app=go-redis-app` to this service

The Golang app can communicate with Redis using the hostname redis-master. This is automatically resolved by Kubernetes to point to the IP address of the service redis-master.

Deploying the Go app and Redis on Kubernetes

We’ll deploy the Go web app and Redis on a local kubernetes cluster created using Minikube.

Please install Minikube and Kubectl if you haven’t installed them already. Check out the Kubernetes official documentation for instructions.

Start a Kubernetes cluster using minikube

$ minikube start

Deploy Redis

$ kubectl apply -f deployments/redis-master.yml
deployment.apps/redis-master created
service/redis-master created
$ kubectl get pods
NAME                            READY   STATUS    RESTARTS   AGE
redis-master-7b44998456-pl8h9   1/1     Running   0          34s

Deploy the Go app

$ kubectl apply -f deployments/go-redis-app.yml
deployment.apps/go-redis-app created
service/go-redis-app-service created
$ kubectl get pods
NAME                            READY   STATUS    RESTARTS   AGE
go-redis-app-57b7d4d4cd-fkddw   1/1     Running   0          27s
go-redis-app-57b7d4d4cd-l9wg9   1/1     Running   0          27s
go-redis-app-57b7d4d4cd-m9t8b   1/1     Running   0          27s
redis-master-7b44998456-pl8h9   1/1     Running   0          82s

Accessing the application

The Go app is exposed as NodePort via the service. You can get the service URL using minikube like this –

$ minikube service go-redis-app-service --url

You can use the above endpoint to access the application:

$ curl
Welcome! Please hit the `/qod` API to get the quote of the day.

$  curl
I’ve missed more than 9000 shots in my career. I’ve lost almost 300 games. 26 times, I’ve been trusted to take the game winning shot and missed. I’ve failed over and over and over again in my life. And that is why I succeed.


In this article, you learned how to deploy a stateless Go web app with Redis on a local Kubernetes cluster created using Minikube.

Spring Boot Tutorial

Spring Boot Tutorial

Spring Boot is a Spring framework module which provides RAD (Rapid Application Development) feature to the Spring framework. It is highly dependent on the starter templates feature which is very powerful and works flawlessly.

Spring boot modules
Spring boot modules

1. What is starter template?

Spring Boot starters are templates that contain a collection of all the relevant transitive dependencies that are needed to start a particular functionality. For example, If you want to create a Spring WebMVC application then in a traditional setup, you would have included all required dependencies yourself. It leaves the chances of version conflict which ultimately result in more runtime exceptions.

With Spring boot, to create MVC application all you need to import is spring-boot-starter-web dependency.

<!-- Parent pom is mandatory to control versions of child dependencies --><parent><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-parent</artifactId><version>2.1.6.RELEASE</version><relativePath /></parent> <!-- Spring web brings all required dependencies to build web application. --><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-web</artifactId></dependency>

Above spring-boot-starter-web dependency, internally imports all given dependencies and add to your project. Notice how some dependencies are direct, and some dependencies further refer to other starter templates which transitively downloads more dependencies.

Also, notice that you do not need to provide version information into child dependencies. All versions are resolved in relation to version of parent starter (in our example it’s 2.0.4.RELEASE).


Read More : Spring boot starter templates list

2. Spring boot autoconfiguration

Autoconfiguration is enabled with @EnableAutoConfiguration annotation. Spring boot auto configuration scans the classpath, finds the libraries in the classpath and then attempt to guess the best configuration for them, and finally configure all such beans.

Auto-configuration tries to be as intelligent as possible and will back-away as you define more of your own configuration.

Auto-configuration is always applied after user-defined beans have been registered.

Spring boot auto-configuration logic is implemented in spring-boot-autoconfigure.jar. Yoy can verify the list of packages here.

Spring boot autoconfiguration packages
Spring boot autoconfiguration packages

For example, look at auto-configuration for Spring AOP. It does the followings-

  1. Scan classpath to see if EnableAspectJAutoProxyAspectAdvice and AnnotatedElement classes are present.
  2. If classes are not present, no autoconfiguration will be made for Spring AOP.
  3. If classes are found then AOP is configured with Java config annotation @EnableAspectJAutoProxy.
  4. It checks for property spring.aop which value can be true or false.
  5. Based on the value of property, proxyTargetClass attribute is set.
@Configuration@ConditionalOnClass({ EnableAspectJAutoProxy.class, Aspect.class, Advice.class,AnnotatedElement.class })@ConditionalOnProperty(prefix = "spring.aop", name = "auto", havingValue = "true", matchIfMissing = true)public class AopAutoConfiguration { @Configuration@EnableAspectJAutoProxy(proxyTargetClass = false)@ConditionalOnProperty(prefix = "spring.aop", name = "proxy-target-class", havingValue = "false", matchIfMissing = false)public static class JdkDynamicAutoProxyConfiguration { } @Configuration@EnableAspectJAutoProxy(proxyTargetClass = true)@ConditionalOnProperty(prefix = "spring.aop", name = "proxy-target-class", havingValue = "true", matchIfMissing = true)public static class CglibAutoProxyConfiguration { } }

3. Embedded server

Spring boot applications always include tomcat as embedded server dependency. It means you can run the Spring boot applications from the command prompt without needling complex server infrastructure.

You can exclude tomcat and include any other embedded server if you want. Or you can make exclude server environment altogether. It’s all configuration based.

For example, below configuration exclude tomcat and include jetty as embedded server.

<dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-web</artifactId><exclusions><exclusion><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-tomcat</artifactId></exclusion></exclusions></dependency> <dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-jetty</artifactId></dependency>

4. Bootstrap the application

To run the application, we need to use @SpringBootApplication annotation. Behind the scenes, that’s equivalent to @Configuration@EnableAutoConfiguration, and @ComponentScan together.

It enables the scanning of config classes, files and load them into spring context. In below example, execution start with main() method. It start loading all the config files, configure them and bootstrap the application based on application properties in application.properties file in /resources folder.

@SpringBootApplicationpublic class MyApplication {public static void main(String[] args) {SpringApplication.run(Application.class, args);}}
### Server port #########server.port=8080 ### Context root ########server.contextPath=/home

To execute the application, you can run the main() method from IDE such eclipse, or you can build the jar file and execute from command prompt.

$ java -jar spring-boot-demo.jar

5. Advantages of Spring boot

  • Spring boot helps in resolving dependency conflict. It identifies required dependencies and import them for you.
  • It has information of compatible version for all dependencies. It minimizes the runtime classloader issues.
  • It’s “opinionated defaults configuration” approach helps you in configuring most important pieces behind the scene. Override them only when you need. Otherwise everything just works, perfectly. It helps in avoiding boilerplate code, annotations and XML configurations.
  • It provides embedded HTTP server Tomcat so that you can develop and test quickly.
  • It has excellent integration with IDEs like eclipse and intelliJ idea.
Spring Boot JSP View Resolver Example

Spring Boot JSP View Resolver Example

Learn to create and configure spring boot jsp view resolver which uses JSP template files to render view layer. This example uses embedded Tomcat server to run the application.

Maven dependencies – pom.xml

This application uses given below dependencies.

<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/maven-v4_0_0.xsd"><modelVersion>4.0.0</modelVersion><groupId>com.fusebes</groupId><artifactId>spring-boot-demo</artifactId><packaging>war</packaging><version>0.0.1-SNAPSHOT</version><name>spring-boot-demo Maven Webapp</name><url>http://maven.apache.org</url><parent><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-parent</artifactId><version>1.5.1.RELEASE</version></parent><properties><java.version>1.8</java.version></properties><dependencies><!-- Web --><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-web</artifactId></dependency><!-- Tomcat Embed --><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-tomcat</artifactId><scope>provided</scope></dependency><!-- JSTL --><dependency><groupId>javax.servlet</groupId><artifactId>jstl</artifactId></dependency><!-- To compile JSP files --><dependency><groupId>org.apache.tomcat.embed</groupId><artifactId>tomcat-embed-jasper</artifactId><scope>provided</scope></dependency></dependencies></project>

Spring Boot Application Initializer

The first step in producing a deployable war file is to provide a SpringBootServletInitializer subclass and override its configure() method. This makes use of Spring Framework’s Servlet 3.0 support and allows you to configure your application when it’s launched by the servlet container.

package com.fusebes.app.controller; import org.springframework.boot.SpringApplication;import org.springframework.boot.autoconfigure.SpringBootApplication;import org.springframework.boot.builder.SpringApplicationBuilder;import org.springframework.boot.web.support.SpringBootServletInitializer; @SpringBootApplicationpublic class SpringBootWebApplication extends SpringBootServletInitializer { @Overrideprotected SpringApplicationBuilder configure(SpringApplicationBuilder application) {return application.sources(SpringBootWebApplication.class);} public static void main(String[] args) throws Exception {SpringApplication.run(SpringBootWebApplication.class, args);}}

Spring Controller

Controller classes can have methods mapped to specific URLs in the application. In given application, it has two views i.e. “/” and “/next”.

package com.fusebes.app.controller; import java.util.Map; import org.springframework.stereotype.Controller;import org.springframework.web.bind.annotation.RequestMapping; @Controllerpublic class IndexController { @RequestMapping("/")public String home(Map<String, Object> model) {model.put("message", "Fusebes Reader !!");return "index";} @RequestMapping("/next")public String next(Map<String, Object> model) {model.put("message", "You are in new page !!");return "next";} }

Spring Boot JSP ViewResolver Configuration

To resolve JSP files location, you can have two approaches.

1) Add entries in application.properties

spring.mvc.view.prefix=/WEB-INF/view/spring.mvc.view.suffix=.jsp //For detailed logging during development logging.level.org.springframework=TRACElogging.level.com=TRACE

2) Configure InternalResourceViewResolver to serve JSP pages

package com.fusebes.app.controller; import org.springframework.context.annotation.ComponentScan;import org.springframework.context.annotation.Configuration;import org.springframework.web.servlet.config.annotation.EnableWebMvc;import org.springframework.web.servlet.config.annotation.ViewResolverRegistry;import org.springframework.web.servlet.config.annotation.WebMvcConfigurerAdapter;import org.springframework.web.servlet.view.InternalResourceViewResolver;import org.springframework.web.servlet.view.JstlView; @Configuration@EnableWebMvc@ComponentScanpublic class MvcConfiguration extends WebMvcConfigurerAdapter{@Overridepublic void configureViewResolvers(ViewResolverRegistry registry) {InternalResourceViewResolver resolver = new InternalResourceViewResolver();resolver.setPrefix("/WEB-INF/view/");resolver.setSuffix(".jsp");resolver.setViewClass(JstlView.class);registry.viewResolver(resolver);}}

JSP Files

Two used JSP files in this spring boot jsp example – are below.


<!DOCTYPE html><%@ taglib prefix="spring" uri="http://www.springframework.org/tags"%><html lang="en"><body><div><div><h1>Spring Boot JSP Example</h1><h2>Hello ${message}</h2> Click on this <strong><a href="next">link</a></strong> to visit another page.</div></div></body></html>


<!DOCTYPE html><%@ taglib prefix="spring" uri="http://www.springframework.org/tags"%><html lang="en"><body><div><div><h1>Another page</h1><h2>Hello ${message}</h2> Click on this <strong><a href="/">link</a></strong> to visit previous page.</div></div></body></html>


After whole code is written and placed inside folders, run the application by executing main() method in SpringBootWebApplication class.

Now hit the URL: http://localhost:8080/

And Click next link

Microservices vs Monolithic Architecture: Which is Right for Startups?

Microservices vs Monolithic Architecture: Which is Right for Startups?

Microservices architecture has become a hot topic in the software backend development world. The ecosystem carries a profound impact on not just the enterprises’ IT function but also in the digital transformation of an entire app business. 

The debate of Microservices vs monolithic architecture defines a revolutionary shift in how an IT  team approaches their software development cycle: Whether they go with the approach that brands like Google, Amazon, and Netflix chose or do they go with the simplicity quotient that a startup which is at the development stage demands.

In this article, we are going to get startups an answer to which backend architecture they should choose when they are starting their journey to become a startup. 

Table Of Content:

  1. What are Microservices Architecture?
  2. What is Monolithic Architecture?
  3. Microservices vs Monolithic Architecture: Advantages and Disadvantages
  4. How to Choose Between Monolithic and Microservice Architecture?
  5. Migrating from a Monolithic Architecture to a Microservice Ecosystem
  6. Conclusion

What are Microservices Architecture?

Microservices architecture contains a mix of small and autonomous services where every service is self-contained and must be implemented as a single business ability. It is a distinct approach used for development of software systems which focus on developing several single-function modules with clearly-defined operations and interfaces. The approach has become a popular trend in the past several years as more and more Enterprises are looking to become Agile and make a shift towards DevOps. 

Components of Microservices architecture that makes it one of the best enterprise architecture:

  • The services are independent, small, and loosely coupled
  • Encapsulates a business or customer scenario
  • Every service is different codebase
  • Services can be independently deployed 
  • Services interact with each other using APIs

With the question of what are microservices architecture now answered, let us move on to look into what is monolithic architecture.

What is Monolithic Architecture? 

Monolithic application has a single codebase having multiple modules. The modules, in turn, are divided into either technical features or business features. The architecture comes with a single build system that helps build complete application. It also comes with a single deployable or executable binary.

Now that we have looked into what is monolithic architecture and microservices architecture, let us look into the disadvantages and benefits that both the backend system offers to get an understanding of what separates them from each other. 

Microservices vs Monolithic Architecture: Advantages and Disadvantages

Microservices vs Monolithic Architecture Advantages and Disadvantages

Advantages of Monolithic Architecture

A. Zero Deployment Dependencies

An organized and well-documented Monolith architecture makes it possible for Backend developers to not worry about which version would be compatible with which service, how to find which services are present and what they do, etc. 

B. Error Tracing

One of the biggest benefits of monolithic is that all the transactions are logged into one place, making error tracing task a breeze. 

C. No Silos

The one factor that works in the favour of monolithic in the microservices vs monolithic architecture debate is absence of silos. It becomes very easy for the developers to work on multiple parts of the app for they are all structured similarly, using the same tools, which makes it okay to have no prior distributed computing knowledge. 

D. Cross-cutting concerns:

 Spending time in defining the services which do not bleed in each other’s time is the time that you can actually spend in developing things that help the customers. 

E. Shared Code: 

No shared libraries where the complete scope needed for services to operate is sent along each request. 

Limitations of Monolithic Architecture

A. Lack of Flexibility:

Monolithic architectures are not flexible. You cannot use different technologies when you have incorporated Monolithic. The technology stack which have been decided at the beginning have to be followed throughout the project, making upgrades a next to impossible task. 

B. Development Speed:

Microservices speed development process is famous when you compare microservices architecture vs monolithic architecture. Development is very slow in monolithic architecture. It can be very difficult for team members to understand and then modify the code of large monolithic applications. Additionally, as the size of codebase increases, the IDE gets overloaded and gets slower. All of this results in a slowed down app development speed.  

C. Difficult Scalability:

Scaling monolithic applications becomes difficult when the apps becomes large. While developers can develop new instances of monolith and load balancer to distribute the traffic to new instances, monolithic architecture cannot scale with the increasing load. 

Benefits of Microservices Architecture

  1. The biggest factor in favor of microservices in the difference between microservices and monolithic architecture is that it handles complexity issues by decomposing the app into manageable service set that are faster to develop and easier to maintain and understand. 
  2. It enables independent service development through a team which is focused on the particular service, which makes the ideal choice of businesses that work with an Agile development approach. 
  3. It lowers the barrier of adopting newer technologies as the developers have the freedom to choose whatever technology that makes sense to their project. 
  4. It makes it possible for every microservice to be deployed individually. The result of which is that continuous deployment of complex application becomes possible. 

Drawbacks of Microservices Architecture

  1. Microservices add a complexity to project simply by the fact that the microservices application is distributed system. To solve the complexities, developers have to select and implement inter-process communication that is based on either RPC or messaging. 
  2. They work with partitioned database architecture. The business transactions which update multiple business entities inside the microservices application also have to update different databases that are owned by multiple services. 
  3. It is a lot more difficult to implement changes which span across multiple services. While in case of Monolithic architecture, an app development agency only have to change the corresponding modules, integrate all the changes, and then deploy them all in one go. 
  4. Deployment of a microservice application is very complex. It consists of a number of services, which individually have multiple runtime instances. In contrast, a monolithic application is deployed on set of identical servers behind load balancer. 

The benefits and limitations are prevalent in both monolithic and microservices architecture. This makes it extremely difficult for a startup to gauge which backend architecture to incorporate in their journey. 

Let us help you. 

How to Choose Between Monolithic and Microservice Architecture? 

The fact that both the approaches come with their own set of pros and cons are a sign that there is no one size fits all methodology when it comes to choosing a backend architecture. But there are a few questions that can help you decide which is the right direction to head into. 

Are You Working in a Familiar Sector?

When you work in an industry where you know the veins of the sector and you know the demands and the needs of the customers, it becomes easier to enter into the system with a definite structure. The same, however, is not possible with a business that is very new in the industry, for the amount of looming doubts are much greater. 

So, the use of microservice architecture in app development is best suited in cases where you know the industry inside out. If that is not the case, go with monolithic approach to develop your app. 

How Prepared is Your Team?

Is your team aware with the best practices for implementing microservices? Or are they more comfortable with working around the simplicity of monolithic? Will your team and your business offering expand in the coming time? You will have to find answers to all these questions to gauge whether the people who have to work on a project are even ready to migrate. 

What is Your Infrastructure Like?

Everything from the development to the deployment of a monolithic web application would require a cloud-based infrastructure. You will have to make use of Amazon AWS and Google Cloud for deploying even tiny elements. While the cloud technologies make the process easier, The idea of setting up database server for every other microservice and then scaling out is something that startup entrepreneur might not be comfortable with. 

Have you Evaluated the Business Risk?

More often than not, businesses take microservices’ side in the Microservices vs Monolithic Architecture thinking it is the right thing for their business. What they forget to factor in is the chance that their application might not become as scalable as they are optimistically expecting and they might have to suffer the risks of adding a highly scalable system in their process. 

Here is a short list of pointers that would help you make the decision of choosing to opt for software development processes with microservices vs monolithic architecture:

When to Choose Monolithic Architecture?

  • When your team is at a founding stage
  • When you are developing a proof of concept
  • When you have no experience in microservices
  • When you have experience in the development on solid frameworks, like the Ruby on Rails, Laravel, etc.

When to Choose Microservices Architecture?

  • You need independent, quick delivery service
  • You need to extend your team
  • Your platform need to be extremely efficient
  • You don’t have a tight deadline to work with

Migrating from a Monolithic Architecture to a Microservice Ecosystem 

Migrating from a Monolithic Architecture to a Microservice Ecosystem

The right approach for migrating a monolithic architecture to a microservice ecosystem is to divide the monolith processes and turn them into microservices. The result of this is a two-factor plan:

  1. Identification of existing monolithic elements which can get decoupled
  2. A validation that the new functionality can be developed as microservice

One of the main challenges that can emerge when initiating the migration from a monolithic architecture to a microservice architecture is to design and create an integration between existing system and a new microservice. A solution for this can be to add a glue code which allows them to connect later, something like an API. 

API gateway can also help in combining multiple individual service calls in one coarse-grained service, and this in turn would help reduce the integration cost with monolithic system.


When you compare microservices architecture vs monolithic architecture, you will find the former being a hot trend. Every entrepreneur wants to say that their app is based on this architecture. But the temptation to focus only on the problems of monolithic architecture and abandon the architecture should be measured against the actual value of microservice architecture. 

The right approach would be to develop new apps using a monolithic approach and move to microservices only when the justification of the move is backed by proper metrics like performance monitoring.

For established businesses, microservices tend to be avenues for continuous deployment, team based development, and an agility to shift to new technologies. But for startups, or companies that are just starting, adopting microservices can impact the software project success very negatively. 

FAQs About Microservices vs Monolithic Architecture

Q. What is the Purpose of Microservices?

The Microservice architectures allow you to divide the application in separate independent services, where each of them are managed by different groups in the software development agency. This way, the responsibility gets divided and the application is developed and deployed at a much faster rate. 

Q. Does moving from a monolith to a Microservice architecture help with resilience?

Yes. Since microservices enable developers to handle multiple parts of the project at the same time in a streamlined manner, it becomes much easier to identify issues and solve them within time. Something that is next to impossible in case of Monolithic architecture where it is impossible to add new technologies or change the process, mid project. 

Q. What is the difference between Microservices vs Monolithic approach?

The difference in microservices and monolithic architecture is the difference of approaches. While in case of Monolithic architecture, there is a single build system, Microservices come with multiple build systems, which makes development and deployment of an application faster. 

Q. When To Choose Microservices Over Monolithic Architecture

The choice of going with microservices over monolithic architecture can be decided upon these factors:

  • When you require an independent delivery service
  • When you have to extend the team
  • When you have to make an efficient platform
  • When you do not have a tight deadline 
How to create and bootstrap a simple boot application

How to Create and Bootstrap a Simple Boot Application?

  • To create any simple spring boot application, we need to start by creating a pom.xml file. Add spring-boot-starter-parent as parent of the project which makes it a spring boot application.pom.xml<?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 https://maven.apache.org/xsd/maven-4.0.0.xsd"><modelVersion>4.0.0</modelVersion> <groupId>com.example</groupId><artifactId>myproject</artifactId><version>0.0.1-SNAPSHOT</version> <parent><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-parent</artifactId><version>2.2.1.RELEASE</version></parent></project>Above is simplest spring boot application which can be packaged as jar file. Now import the project in your IDE (optional).
  • Now we can start adding other starter dependencies that we are likely to need when developing a specific type of application. For example, for a web application, we add a spring-boot-starter-web dependency.pom.xml<dependencies><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-web</artifactId></dependency></dependencies>
  • Start adding application business logic, views and domain data at this step. By default, Maven compiles sources from src/main/java so create your application code inside this folder only.As the very initial package, add the application bootstrap class and add @SpringBootApplication annotation. This class will be used to run the application. It’s main() method acts as the application entry point.MyApplication.javaimport org.springframework.boot.SpringApplication;import org.springframework.boot.autoconfigure.SpringBootApplication; @SpringBootApplicationpublic class MyApplication {public static void main(String[] args) {SpringApplication.run(MyApplication.class, args);}}
  • The SpringApplication class provided in above main() method bootstraps our application, starting Spring, which, in turn, starts the auto-configured Tomcat web server. MyApplication (method argument) indicates the primary Spring component.
  • Since we used the spring-boot-starter-parent POM, we have a useful “run” goal that we can use to start the application. Type 'mvn spring-boot:run' from the root project directory to start the application.It will start the application which we can verify in console logs as well as in browser by hitting URL: localhost:8080.
A Guide to JPA with Spring

A Guide to JPA with Spring

This tutorial shows how to set up Spring with JPA, using Hibernate as a persistence provider.

For a step by step introduction about setting up the Spring context using Java-based configuration and the basic Maven pom for the project, see this article.

We’ll start by setting up JPA in a Spring Boot project, then we’ll look into the full configuration we need if we have a standard Spring project.

JPA in Spring Boot

The Spring Boot project is intended to make creating Spring applications much faster and easier. This is done with the use of starters and auto-configuration for various Spring functionalities, JPA among them.

2.1. Maven Dependencies

To enable JPA in a Spring Boot application, we need the spring-boot-starter and spring-boot-starter-data-jpa dependencies:


The spring-boot-starter contains the necessary auto-configuration for Spring JPA. Also, the spring-boot-starter-jpa project references all the necessary dependencies such as hibernate-core.

2.2. Configuration

Spring Boot configures Hibernate as the default JPA provider, so it’s no longer necessary to define the entityManagerFactory bean unless we want to customize it.

Spring Boot can also auto-configure the dataSource bean, depending on the database we’re using. In the case of an in-memory database of type H2HSQLDB, and Apache Derby, Boot automatically configures the DataSource if the corresponding database dependency is present on the classpath.

For example, if we want to use an in-memory H2 database in a Spring Boot JPA application, we only need to add the h2 dependency to the pom.xml file:


This way, we don’t need to define the dataSource bean, but we can do so if we want to customize it.

If we want to use JPA with MySQL database, then we need the mysql-connector-java dependency, as well as to define the DataSource configuration.

We can do this in a @Configuration class, or by using standard Spring Boot properties.

The Java configuration looks the same as it does in a standard Spring project:

public DataSource dataSource() {
    DriverManagerDataSource dataSource = new DriverManagerDataSource();

    return dataSource;

To configure the data source using a properties file, we have to set properties prefixed with spring.datasource:


Spring Boot will automatically configure a data source based on these properties.

Also in Spring Boot 1, the default connection pool was Tomcat, but with Spring Boot 2 it has been changed to HikariCP.

As we can see, the basic JPA configuration is fairly simple if we’re using Spring Boot.

However, if we have a standard Spring project, then we need more explicit configuration, using either Java or XML. That’s what we’ll focus on in the next sections.

3. The JPA Spring Configuration With Java – in a Non-Boot Project

To use JPA in a Spring project, we need to set up the EntityManager.

This is the main part of the configuration and we can do it via a Spring factory bean. This can be either the simpler LocalEntityManagerFactoryBean or the more flexible LocalContainerEntityManagerFactoryBean.

Let’s see how we can use the latter option:

public class PersistenceJPAConfig{

   public LocalContainerEntityManagerFactoryBean entityManagerFactory() {
      LocalContainerEntityManagerFactoryBean em 
        = new LocalContainerEntityManagerFactoryBean();
      em.setPackagesToScan(new String[] { "com.baeldung.persistence.model" });

      JpaVendorAdapter vendorAdapter = new HibernateJpaVendorAdapter();

      return em;
   // ...


We also need to explicitly define the DataSource bean we’ve used above:

public DataSource dataSource(){
    DriverManagerDataSource dataSource = new DriverManagerDataSource();
    dataSource.setUsername( "tutorialuser" );
    dataSource.setPassword( "tutorialmy5ql" );
    return dataSource;

The final part of the configuration are the additional Hibernate properties and the TransactionManager and exceptionTranslation beans:

public PlatformTransactionManager transactionManager() {
    JpaTransactionManager transactionManager = new JpaTransactionManager();

    return transactionManager;

public PersistenceExceptionTranslationPostProcessor exceptionTranslation(){
    return new PersistenceExceptionTranslationPostProcessor();

Properties additionalProperties() {
    Properties properties = new Properties();
    properties.setProperty("hibernate.hbm2ddl.auto", "create-drop");
    properties.setProperty("hibernate.dialect", "org.hibernate.dialect.MySQL5Dialect");
    return properties;

4. The JPA Spring Configuration With XML

Next, let’s see the same Spring Configuration with XML:

<bean id="myEmf" 
    <property name="dataSource" ref="dataSource" />
    <property name="packagesToScan" value="com.baeldung.persistence.model" />
    <property name="jpaVendorAdapter">
        <bean class="org.springframework.orm.jpa.vendor.HibernateJpaVendorAdapter" />
    <property name="jpaProperties">
            <prop key="hibernate.hbm2ddl.auto">create-drop</prop>
            <prop key="hibernate.dialect">org.hibernate.dialect.MySQL5Dialect</prop>

<bean id="dataSource" 
    <property name="driverClassName" value="com.mysql.cj.jdbc.Driver" />
    <property name="url" value="jdbc:mysql://localhost:3306/spring_jpa" />
    <property name="username" value="tutorialuser" />
    <property name="password" value="tutorialmy5ql" />

<bean id="transactionManager" class="org.springframework.orm.jpa.JpaTransactionManager">
    <property name="entityManagerFactory" ref="myEmf" />
<tx:annotation-driven />

<bean id="persistenceExceptionTranslationPostProcessor" class=
  "org.springframework.dao.annotation.PersistenceExceptionTranslationPostProcessor" />

There’s a relatively small difference between the XML and the new Java-based configuration. Namely, in XML, a reference to another bean can point to either the bean or a bean factory for that bean.

In Java, however, since the types are different, the compiler doesn’t allow it, and so the EntityManagerFactory is first retrieved from its bean factory and then passed to the transaction manager:


5. Going Full XML-less

Usually, JPA defines a persistence unit through the META-INF/persistence.xml file. Starting with Spring 3.1, the persistence.xml is no longer necessary. The LocalContainerEntityManagerFactoryBean now supports a packagesToScan property where the packages to scan for @Entity classes can be specified.

This file was the last piece of XML we need to remove. We can now set up JPA fully with no XML.

We would usually specify JPA properties in the persistence.xml file. Alternatively, we can add the properties directly to the entity manager factory bean:


As a side note, if Hibernate would be the persistence provider, then this would be the way to specify Hibernate specific properties as well.

6. The Maven Configuration

In addition to the Spring Core and persistence dependencies – show in detail in the Spring with Maven tutorial – we also need to define JPA and Hibernate in the project, as well as a MySQL connector:



Note that the MySQL dependency is included here as an example. We need a driver to configure the datasource, but any Hibernate-supported database will do.

7. Conclusion

This tutorial illustrated how to configure JPA with Hibernate in Spring in both a Spring Boot and a standard Spring application.

What is auto-configuration? How to enable or disable certain configuration?

What is Auto-Configuration? How to Enable or Disable Certain Configuration?

Spring boot auto configuration scans the classpath, finds the libraries in the classpath and then attempt to guess the best configuration for them, and finally configure all such beans.

Auto-configuration tries to be as intelligent as possible and will back-away as we define more of our own custom configuration. It is always applied after user-defined beans have been registered.

Auto-configuration works with help of @Conditional annotations such as @ConditionalOnBean and @ConditionalOnClass.

For example, look at AopAutoConfiguration class.

If class path scanning finds EnableAspectJAutoProxy, Aspect, Advice and AnnotatedElement classes and spring.aop.auto=false is not present in properties file then Spring boot will configure the Spring AOP module for us.

@Configuration @ConditionalOnClass({ EnableAspectJAutoProxy.class, Aspect.class, Advice.class, AnnotatedElement.class }) @ConditionalOnProperty(prefix = "spring.aop", name = "auto", havingValue = "true", matchIfMissing = true) public class AopAutoConfiguration {//code}
Understanding Regular Expressions

Understanding Regular Expressions

it’s time to get over your fears of regular expressions(regex)! If you’re like me, you’ve heard of regex but have always been confused by the cryptic syntax. Fear not, because in the next 5 minutes, you’ll have a basic understanding of what’s going on and how to use RegEx to make your life easier!

So what are Regular Expressions ?

Basically, regular expressions are patterns that you can use to find matching patterns in strings. This could be useful for password validation, or checking if the formatting of input fields is correct, or perhaps you want to parse a phone number, etc…

How do you use them?

There are a couple ways of creating a regex, you can either use the literal version( which I prefer) or you can use the constructor option. The literal version looks like so:

const regEx = /hello/;

When making a regular expression literal, you place the pattern between two forward slashes. Above, we would be searching for the word ‘hello’.

Using the constructor would look something like this:

 const regEx = new RegExp('hello');

I’m not the biggest fan of this, so moving forward I will only be using the literal version.

Testing Methods

How do you test your regex anyways? JavaScript provides us a couple of methods that are compatible with regular expressions:

  • test()
  • exec()
  • match()
  • matchAll()
  • replace()
  • search()
  • split()

For my examples I will primarily be using test() and match(). Test is a RegExp method used to search a string and return either true or false if your pattern is found, and match is a string method that can use regex and returns the instances found in an array.

How to Match Strings

As you saw in my example above, I created the regex /hello/. This pattern would be useful for finding the first case sensitive instance of ‘hello’. What if you want to find every instance of ‘hello’, case insensitive? This is where ‘flags’ come in.

Flags act as modifiers to your regular expression. They go after the closing slash and there are five native flags in JavaScript!

  • i : This makes your search case-insensitive!
  • g : This flag tells your search to look for all matches, not just the first one.
  • m : Multiline mode
  • s : This enables “dotall” mode. It allows ‘.’ to match newlines
  • u : Enables full unicode support
  • y : sticky; it matches only from the index indicated by the lastIndex property of the regex in the target string.

So if we wanted to find every instance of ‘hello’ case insensitive, in the string “Hello heLLO hellO HELLO!”, we would do something like this:

let regex = /hello/gi;
let string = “Hello heLLO hellO HELLO!”;
string.match(regex);//returns [ 'Hello', 'heLLO', 'hellO', 'HELLO' ]

See that’s not so bad! Let’s look at another tool that’s very useful: character classes.

Character Classes

Character classes let you match a group of characters by placing them inside square brackets! This lets you find multiple matches with different characters. For example: if you wanted to find the words ‘big’, ‘bag’, ‘bog’, ‘bug’ in the string “The big bug crawled out of my bag and went into the bog.” you could use a simple regular expression to do so!

let string = “The big bug crawled out of my bag and went into the bog.”;let regex = /b[aiou]g/gi;
string.match(regex);//returns [ 'big', 'bug', 'bag', 'bog' ]

That’s pretty cool. You can also search for a range of characters inside of a character set using a hyphen ‘-’! For example, if I wanted to find every number in a string for some reason, I could do something like this:

let string = "I want 6 chocolates, 5 pop tarts, and 3 pumpkin pies please."let regex = /[0-9]/g;
string.match(regex);//returns [ '6', '5', '3' ]

You can do the above and so, so much more using Regular Expressions. You’ll find it’s basically like another language! This is just the tip of the iceberg, and I hope at least I’ve made regex a little less scary. There is so much more to regular expressions than I can cover here, but there are plenty of great resources to continue learning.

Happy Coding!