Upgrade A Spring Boot Project from 2.0 to 2.1

Upgrade Java, Spring Boot, Gradle, Flyway, etc.

Why upgrade

• Faster
• Security
• Eliminate risks of upgrading to a higher version

Processes

1. Before the upgrade, run all unit tests
2. Upgrade Gradle, Spring Boot, Java
3. Implement fix to make it builds
4. Run Unit tests or implements fix

Details

Update Gradle wrapper from 4.7 to 5.6

1. Update local Gradle to the latest version (5.6)

    sdk list gradle
    sdk use gradle 5.6.2
   

2. Generate lastest Gradle Wrapper

    gradle wrapper
   

3. Check gradle/wrapper/gradle-wrapper.properties file

      distributionUrl=https\://services.gradle.org/distributions/gradle-5.6.2-bin.zip
   

Upgrade Spring Boot from 2.0 to 2.1.8

1. Generate new build.gradle

   Go to Spring Initializr, regenerate your dependencies. It uses a new default format of build.gradle and latest version. Tick Java 11, we’ll talk it later.

2. Allow bean definition override

    spring.main.allow-bean-definition-overriding=true
   

   1. We customized Flyway bean to run with dynamic databases.
   2. We override bean in unit tests because we don’t want the real instance to load.

3. Lombok changes

   Spring Boot 2.1 has upgraded to Lombok 1.18.x from 1.16.x. In 1.18, Lombok will no longer generate a private, no-args constructor by default. It can be enabled by setting lombok.noArgsConstructor.extraPrivate=true in a lombok.config configuration file.

4. Flyway changes

   //todo

5. Junit from v4 to v5

   //todo

Oracle Java 8 to OpenJDK Java 11

There is a Java 9 introduced bug, please see this interesting blog.

// todo a workaround

References

1. Spring Boot 2.1 Release Notes
2. Java 11 date parsing? Locale, locale, locale