Tagged: Spring Cache

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
How to Change the Default Port in Spring Boot

How to Change the Default Port in Spring Boot

Spring Boot provides sensible defaults for many configuration properties. But we sometimes need to customize these with our case-specific values.

And a common use case is changing the default port for the embedded server.

In this quick tutorial, we’ll cover several ways to achieve this.

2. Using Property Files

The fastest and easiest way to customize Spring Boot is by overriding the values of the default properties.

For the server port, the property we want to change is server.port.

By default, the embedded server starts on port 8080.

So, let’s see how to provide a different value in an application.properties file:


Now the server will start on port 8081.

And we can do the same if we’re using an application.yml file:

  port : 8081

Both files are loaded automatically by Spring Boot if placed in the src/main/resources directory of a Maven application.

2.1. Environment-Specific Ports

If we have an application deployed in different environments, we may want it to run on different ports on each system.

We can easily achieve this by combining the property files approach with Spring profiles. Specifically, we can create a property file for each environment.

For example, we’ll have an application-dev.properties file with this content:


Then we’ll add another application-qa.properties file with a different port:


Now, the property files configuration should be sufficient for most cases. However, there are other options for this goal, so let’s explore them as well.

3. Programmatic Configuration

We can configure the port programmatically either by setting the specific property when starting the application or by customizing the embedded server configuration.

First, let’s see how to set the property in the main @SpringBootApplication class:

public class CustomApplication {
    public static void main(String[] args) {
        SpringApplication app = new SpringApplication(CustomApplication.class);
          .singletonMap("server.port", "8083"));

Next, to customize the server configuration, we have to implement the WebServerFactoryCustomizer interface:

public class ServerPortCustomizer 
  implements WebServerFactoryCustomizer<ConfigurableWebServerFactory> {
    public void customize(ConfigurableWebServerFactory factory) {

Note that this applies to the Spring Boot 2.x version.

For Spring Boot 1.x, we can similarly implement the EmbeddedServletContainerCustomizer interface.

4. Using Command-Line Arguments

When packaging and running our application as a jar, we can set the server.port argument with the java command:

java -jar spring-5.jar --server.port=8083

or by using the equivalent syntax:

java -jar -Dserver.port=8083 spring-5.jar

5. Order of Evaluation

As a final note, let’s look at the order in which these approaches are evaluated by Spring Boot.

Basically, the configurations priority is

  • embedded server configuration
  • command-line arguments
  • property files
  • main @SpringBootApplication configuration

6. Conclusion

In this article, we saw how to configure the server port in a Spring Boot application.

Configuring Spring Boot's Server, GZip compression, HTTP/2, caching and much more

Configuring Spring Boot’s Server, GZip compression, HTTP/2, caching and much more

Spring Boot is powerful yet flexible. It tries to auto-configure most of the stuff for you so that you can get up and running quickly with your application.

It uses sensible defaults during auto-configuration but also gives you the flexibility to change those defaults by just tweaking a few things.

In this article, you’ll learn about the most common configuration tweaks that might need to do in your application.

Changing the embedded server in Spring Boot

Spring Boot uses Tomcat as the default embedded server. If you wanna use some other popular server like Jetty or Undertow then you just need to exclude tomcat dependency and add the other server dependency.

1. Using Jetty as the embedded server in Spring Boot

<!-- Exclude tomcat dependency -->
<!-- Include jetty dependency -->

2. Using undertow as the embedded server in Spring Boot

<!-- Exclude tomcat dependency -->
<!-- Include undertow dependency -->

Changing the default server port and context path in Spring Boot

By default, Spring Boot runs your application on port 8080 with the context path /.

If you wanna change the default port and context path, then it’s just a matter of specifying the corresponding values in the application.properties file –

# HTTP Server port

# Make the application accessible on the given context path (http://localhost:8080/myapp)

Enabling GZip compression in Spring Boot

GZip compression is a very simple and effective way to save bandwidth and improve the speed of your website.

It reduces the response time of your website by compressing the resources and then sending it over to the clients. It saves bandwidth by at least 50%.

GZip compression is disabled by default in Spring Boot. To enable it, add the following properties to your application.properties file –

# Enable response compression

# The comma-separated list of mime types that should be compressed

# Compress the response only if the response size is at least 1KB

Note that, GZip compression has a small overhead. Therefore I’ve added a min-response-size property to tell spring boot server to compress the response only if the size is more than the given value.

Enabling HTTP/2 support in Spring Boot

HTTP/2 is an improvement over the HTTP1 protocol. It improves the page load speed of your website by employing several mechanisms like data compression, server push, multiplexing of multiple requests over a single TCP connection etc.

You can enable HTTP2 in spring boot with the following property, if the server has support for it –

# Enable HTTP/2 support, if the current environment supports it

Enabling browser caching of static resources in Spring Boot

Browser caching is another way to improve the page load speed of your website. You can set cache-control headers to tell browsers to cache static resources until a certain period of time.

Browser caching is disabled by default in Spring Boot. You can enable caching by setting the following properties in the application.properties file.

# Maximum time the response should be cached (in seconds) 

# The cache must re-validate stale resources with the server. Any expired resources must not be used without re-validating.

Following are few other cache related properties that you should be aware of –

# The resources are private and intended for a single user. They must not be stored by a shared cache (e.g CDN).
spring.resources.cache.cachecontrol.cache-private= # set a boolean value true/false

# The resources are public and any cache may store the response.
spring.resources.cache.cachecontrol.cache-public= # set a boolean value true/false

Configuring multipart file uploads in Spring Boot

Multipart file uploads are enabled by default in Spring Boot with the following property –


But there are few other default multipart properties that you might need to change.

By default, Spring Boot allows you to upload a file with a maximum size of 1MB. You might need to change this to the desired value as per your requirements.

Following is the complete set of properties –

# Write files to disk if the file size is more than 2KB.

# The intermediate disk location where the uploaded files are written

# Maximum file size that can be uploaded

# Maximum allowed multipart request size


In this short article, you learned how to tweak Spring Boot’s default configurations as per your needs. You can find a full index of common application properties on the following official Spring Boot page –

Spring Boot Common application properties

Whenever you need to configure anything in your spring boot application, the first thing you should do is – check the above common application properties page. Most probably, you’ll find a property for configuring the stuff that you’re looking for.

I hope you enjoyed this article. As always, Thanks for reading.