Steps to Successfully Upgrade Spring Boot from Java 8 to Java 17

Source: Steps to Successfully Upgrade Spring Boot from Java 8 to Java 17

1. Analyze Current Application Compatibility

1.1 Assess Codebase Readiness

Before starting the upgrade, ensure your application is free from deprecated APIs and follows modern coding practices. Java 17 introduces stricter checks and removes several APIs that were deprecated in Java 8.

Example: Handling Removed java.util.Date Methods

In Java 17, several methods from java.util.Date have been removed or discouraged. If your code

Date today = new Date();
System.out.println(today.getYear());

You need to replace it with the modern java.time API:

LocalDate today = LocalDate.now();
System.out.println(today.getYear());

This ensures compatibility and adheres to best practices for date-time handling.

1.2 Verify Dependencies

Spring Boot applications rely heavily on dependencies. Some older libraries may not support Java 17. Use tools like mvn dependency:tree to audit your dependencies.

Action Plan:

Identify libraries and their supported Java versions.
Replace outdated libraries with actively maintained alternatives.

2. Upgrade Java Version and Dependencies

2.1 Update Java Version

Update the JDK in your build system. For Maven, modify the pom.xml file to specify Java 17:

<properties>
    <java.version>17</java.version>
</properties>

Ensure your local development environment and CI/CD pipelines are also updated to use JDK 17.

2.2 Upgrade Spring Boot

Spring Boot versions before 2.5.x are not compatible with Java 17. Upgrade to the latest compatible Spring Boot version by updating the spring-boot-starter-parent in your pom.xml:

<parent>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-parent</artifactId>
    <version>2.7.6</version>
</parent>

Run mvn clean install to verify the compatibility of your dependencies.

3. Address Code-Level Changes

3.1 Adapt to Java 17 Language Features

Java 17 introduces features like sealed classes, records, and switch expressions. While these features are optional, using them can modernize and simplify your code.

Example: Using Switch Expressions

Old-style switch:

String result;
switch (day) {
    case "MONDAY":
    case "FRIDAY":
        result = "Workday";
        break;
    default:
        result = "Weekend";
}

Modern switch in Java 17:

String result = switch (day) {
    case "MONDAY", "FRIDAY" -> "Workday";
    default -> "Weekend";
};

This reduces boilerplate and improves readability.

3.2 Handle Deprecated Features

Features deprecated in Java 8 may no longer be available in Java 17. Refactor your code to use recommended alternatives.

Example: Replace PermGen with Metaspace Java 8 removed the PermGen memory area, which was replaced by Metaspace. If your application’s configuration still references PermGen, update it:

# Old (Java 8)
-XX:PermSize=256m
-XX:MaxPermSize=512m

# New (Java 17)
-XX:MetaspaceSize=256m
-XX:MaxMetaspaceSize=512m

4. Update Build and Test Pipelines

4.1 Configure CI/CD for JDK 17

Ensure your CI/CD pipeline uses JDK 17. For example, in GitHub Actions:

jobs:
  build:
    runs-on: ubuntu-latest
    steps:
      - name: Set up JDK 17
        uses: actions/setup-java@v3
        with:
          java-version: '17'

4.2 Extensive Testing

Testing is critical after an upgrade. Focus on:

Unit tests: Validate core functionality.
Integration tests: Ensure dependencies interact correctly.
Performance tests: Measure the impact of the JDK upgrade.

5. Deploy and Monitor the Application

Gradual Rollout

Roll out the upgraded application to a staging environment first. Monitor logs and performance metrics for anomalies.

Monitor Production

After deployment, use tools like Spring Boot Actuator and distributed tracing systems (e.g., Zipkin, Jaeger) to monitor the application.

6. Conclusion

Upgrading from Java 8 to Java 17 is a critical step in modernizing your Spring Boot application. It ensures your application remains secure, performant, and future-proof. By following the steps outlined above, you can minimize risks and maximize the benefits of the upgrade.

Have questions or need further guidance? Feel free to comment below!