On March 1st, Spring Boot reached GA on its second major version. To celebrate this, we invited Spring Boot legend Stéphane Nicoll to give us an in-depth view on what’s new in Spring Boot 2. He talked about the new features while migrating a Spring Boot 1.x application to Spring Boot 2.0.

Spring Boot 2.0

Stéphane gave us an overview of the new features in Spring Boot 2.0. It was kind of a summary of Phil Webb’s announcement post Spring Boot 2.0 goes GA.

Code says more than a thousand words. And like every talk I attended from Stéphane, he started live coding quite quickly. We migrated a Spring Boot 1.x application to Spring Boot 2.0.

The migration process is very simple. In short, these are the steps you have to follow:

  1. Change Spring Boot parent version number in your pom.xml
  2. Replace deprecated property keys with the help of the spring-boot-properties-migrator module
  3. If you’re working with passwords, define a PasswordEncoder

When you use a lot of hookpoints and Spring Boot classes directly, eg. SpringBootServletInitializer, migrating is slightly more work. The reason behind this is that a lot of the Spring Boot API’s have changed.

Change version number

Change the Spring Boot Starter Parent version number in your pom.xml to the new Spring Boot version.

<parent>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-parent</artifactId>
    <version>2.0.1.RELEASE</version>
</parent>

As from April 5th, this is the 2.0.1.RELEASE. Stéphane released it on the train to the Ordina HQ in Mechelen.


Property keys and the properties migrator

Property key changes

When you upgrade, you will get compilation errors saying there are unknown properties in your properties files. Some property keys have been deprecated and won’t work anymore.

Old property New property
spring.datasource.initialize spring.datasource.initialization-mode
endpoints.health.path management.endpoints.web.path-mapping

All major IDEs, eg. IntelliJ, Netbeans and STS, will inform you about the newer property key.

Properties migrator

You can add the spring-boot-properties-migrator module to your Maven project.

<dependency>
  <groupId>org.springframework.boot</groupId>
  <artifactId>spring-boot-properties-migrator</artifactId>
  <scope>runtime</scope>
</dependency>

The Spring Boot Properties Migrator looks for configuration properties it can replace and provides the programmer with feedback. For example, endpoints.health.path will automatically be replaced by the new management.endpoints.web.path-mapping property.

Spring Boot 2.0 will also tell you you’re using an old key when you provide old keys as environment variable. It will not tell you the line on which you defined the property, but it will give an appropriate message.

Some properties cannot be fixed automatically:

  • The security auto-configuration is no longer customizable
  • Replacement key 'spring.datasource.initialization-mode' uses an incompatible target type — String was replaced by an enumeration

Spring Security changes

As from Spring Security 5.x, a lot of security features were redesigned. Some features are made more strict.

Since Spring Boot 2.x now uses Spring Security 5.x under the hood, the Spring Security autoconfiguration has been redesigned as well.

Previously with Spring Boot 1.x, you could have Spring Security configuration spread accross your application. With Spring Boot 2.0, if you want to know what the security configuration of your application is, you only have to look at one file, your SecurityConfiguration class.

No password encoder

When you haven’t defined a PasswordEncoder bean, Spring will throw the There is no PasswordEncoder mapped for the id "null" error when creating your application context.

As from Spring Security 5.x, Spring Security enforces you to use a password encoder. Spring Security enforces this by activating the default DelegatingPasswordEncoder, which looks for PasswordEncoder beans. By adding a BCryptPasswordEncoder, the DelegatingPasswordEncoder will return that instance to encrypt passwords.

@Bean
public BCryptPasswordEncoder passwordEncoder() {
    return new BCryptPasswordEncoder();
}

If you really want to, you can override password encoding by adding {noop} to the password value. This will treat the password by activating the NoOpPasswordEncoder instead of the default DelegatingPasswordEncoder and will treat your password as plain text.

Please note that this is not recommended if you deploy your app to a production environment!

Actuator endpoints

Some Actuator security endpoint settings aren’t modifyable by properties anymore. For example, management.security.roles=HERO won’t be picked up anymore.

Only two endpoints are being exposed by default, /info and /health. You can include or exclude management endpoints by using the new property management.endpoints.web.exposure.include.

Old property New property
endpoints.health.path management.endpoints.web.path-mapping

Other enhancements

Configuration processor

When you add the spring-boot-configuration-processor Maven module to your project, your IDE will be able to interpret your @ConfigurationProperties class and autocomplete the properties files.

There were some other enhancements too. You can now use the Duration type for properties directly.

private Duration delay = Duration.ofSeconds(3)

The hello.delay autocompletion now also shows the unit behind the value, eg. hello.delay=3s.

Spring Boot Dev Tools enhancements

DevTools is a feature in Spring Boot which adds nice development features.

Spring created its own small LiveReload server, with a reload function. The communication protocol of LiveReload is open source. When you start the app, it also starts the LiveReload server. Something in your application watches the classpath for changes. If you change a template or a configuration property, Spring Boot will pick up the change, restart the Spring context and notify LiveReload. The restart only takes about 1 to 3 seconds, because the JVM is still hot.

Spring Boot Dev Tools is not a new feature from Spring Boot 2, but the Spring developers have added some enhancements. One of those new features is that you get a delta of what changed and what triggered the LiveReload functionality.

Micrometer

In Spring Boot 1.x, there was a metrics system with which you could register gauges etc. There’s an Actuator endpoint with which you could view those metrics. You could export those metrics to Prometheus or some other system.

Micrometer is comparable to what SLF4J is for logging. You get an API for metrics that is independent of any vendor. You can record values and expose those values with a registry system to the outside world.

<dependency>
    <groupId>io.micrometer</groupId>
    <artifactId>micrometer-registry-prometheus</artifactId>
    <version>1.0.2</version>
</dependency>

For all projects that are supported by Micrometer, the metrics are exposed, eg. HikariCP. Spring Boot detects that you use HikariCP and automatically exposes those metrics to the different registries.

To get more into detail we recommend you to check out this post, which covers Micrometer more in-depth.

Q&A

How should I convince my manager to upgrade?

Because of some security issues in previous versions, Pivotal will stop providing support for those version. Another reason to upgrade is if you’re going to add new features to an application, eg. add metrics.

When will Spring Cloud be ready to support Spring Boot 2?

You can check http://start.spring.io/actuator/info in the spring-cloud section to see whether there are Spring Cloud versions which use Spring Boot 2.

{
  "Angel.SR6": "Spring Boot >=1.2.3.RELEASE and <1.3.0.RELEASE",
  "Brixton.SR7": "Spring Boot >=1.3.0.RELEASE and <1.4.0.RELEASE",
  "Camden.SR7": "Spring Boot >=1.4.0.RELEASE and <=1.4.999.RELEASE",
  "Edgware.SR3": "Spring Boot >=1.5.0.RELEASE and <=1.5.11.RELEASE",
  "Edgware.BUILD-SNAPSHOT": "Spring Boot >=1.5.12.BUILD-SNAPSHOT and <2.0.0.M1",
  "Finchley.M2": "Spring Boot >=2.0.0.M3 and <2.0.0.M5",
  "Finchley.M3": "Spring Boot >=2.0.0.M5 and <=2.0.0.M5",
  "Finchley.M4": "Spring Boot >=2.0.0.M6 and <=2.0.0.M6",
  "Finchley.M5": "Spring Boot >=2.0.0.M7 and <=2.0.0.M7",
  "Finchley.M6": "Spring Boot >=2.0.0.RC1 and <=2.0.0.RC1",
  "Finchley.M7": "Spring Boot >=2.0.0.RC2 and <=2.0.0.RC2",
  "Finchley.M9": "Spring Boot >=2.0.0.RELEASE and <=2.0.0.RELEASE",
  "Finchley.BUILD-SNAPSHOT": "Spring Boot >=2.0.0.BUILD-SNAPSHOT"
}

Does Spring Boot 2 support Java 10?

Yes. However, the Java 10 build step for Spring Boot 2.0.1 failed after Stéphane released it on the train to Mechelen. Eric De Witte posted a tweet about it during the meetup.

Stéphane tweets the day after that the Java 10 build was fixed.

The meetup

The Spring Boot 2.0 Anniversary Meetup event started at 18h at the Ordina headquarters in Mechelen. Since you cannot learn on an empty stomach, we started off with Belgian French fries.

Stéphane’s presentation started at 19h. He took us on a two hour ride through the Spring Boot landscape.

After the presentation, a huge celebration cake was carried in. Our bakery had done its best to transform the Spring Boot logo into an immense nice looking cake. We think he did a good job! Check out Stéphane’s tweet.


A professional photographer took some atmospheric photos of the event. You can see all pictures on Elke.photos.

Spring Boot 2.0 Anniversary Meetup

Useful links

The event was streamed live on YouTube. Subscribe to our channel for more Java- and JavaScript related videos.

You can also consult the Spring Boot 2.0 Migration Guide for more information.

Ken is a Principal Java Consultant at Ordina, passionate about all Java- and JavaScript related technologies. Aside from his day-to-day occupation as a consultant, he is also Backend Practice Manager of the Ordina JWorks unit. In this capacity, he narrows the gap between consultants and potential innovative customer projects. He does this by organizing workshops, talks and courses about the newest technologies, whereby people can grow in their role as a software consultant.