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Modernize Java apps by using GitHub Copilot modernization in the Copilot CLI

This article provides an overview of how Java developers can modernize their applications by using the GitHub Copilot modernization plugin in Copilot CLI. By using this approach, developers can modernize applications wherever they code. The plugin delivers a seamless, end-to-end experience - from upgrade and migration to deployment - helping teams accelerate transformation, boost productivity, and confidently move their applications to modern platforms.

Screenshot of the GitHub Copilot CLI that shows a GitHub Copilot modernization prompt.

Note

GitHub Copilot CLI is available with the GitHub Copilot Pro, GitHub Copilot Pro+, GitHub Copilot Business, and GitHub Copilot Enterprise plans. If you receive Copilot from an organization, the Copilot CLI policy must be enabled in the organization's settings.

By using Copilot CLI for modernization, you can run modernization tasks directly from the terminal, with no need to switch to an IDE. This approach supports both interactive - human-in-the-loop - and batch workflows.

What you can do

Capability Description
Java upgrade Upgrade Java version (8 → 11 → 17 → 21 → 25), migrate Spring Boot 2.x to 3.x, javax to jakarta, and deprecated APIs
Azure migration Assess and migrate Java applications to Azure services (Azure Service Bus, Azure SQL, Redis, Azure Key Vault, Application Insights, Managed Identity)
CVE and vulnerability fixing Scan and fix CVE vulnerabilities in Maven dependencies, including Log4j, Spring, Jackson, and OWASP dependency analysis
Application rearchitecture Structural rewrites such as monolith-to-microservices decomposition, legacy UI modernization, and module extraction
Deploy to Azure Deploy upgraded or migrated Java applications directly to Azure

Prerequisites

Note

An Azure account is required only for deploying resources to Azure, and isn't needed when using GitHub Copilot modernization to make code changes.

Install the plugin

  1. Add the marketplace and install the plugin:

    copilot plugin marketplace add microsoft/github-copilot-modernization
copilot plugin install github-copilot-modernization@github-copilot-modernization

  2. Verify the plugin is installed by listing installed plugins:

    /plugin list

    You should see github-copilot-modernization@github-copilot-modernization in the list.

Tip

To update the plugin when a new version is available, run:

copilot plugin update github-copilot-modernization@github-copilot-modernization

Start a modernization task

Option 1: Start with the agent directly

Navigate to your Java project folder and start Copilot CLI with the modernization agent:

cd /path/to/your/java-app
copilot --agent=github-copilot-modernization:modernize

Option 2: Select the agent from inside Copilot CLI

If you're already in a Copilot CLI session, use the /agent command to switch to the modernization agent:

/agent

Select modernize from the list.

Important

You must select the github-copilot-modernization:modernize agent before running any modernization prompts. Without selecting the agent, Copilot CLI uses the default agent, which can't use the full multi-agent orchestration and specialized migration capabilities provided by the plugin.

Run a modernization prompt

Once the agent is active, describe what you want in natural language:

modernize my application

Or be more specific:

upgrade this app to Java 21 and Spring Boot 3.2

migrate this Spring Boot app to Azure

fix CVE vulnerabilities in my project

For unattended execution, use the --allow-all flag:

copilot --agent=github-copilot-modernization:modernize --allow-all

How the workflow works

The plugin uses a three-phase workflow that runs automatically. You don't need to invoke each phase manually - the orchestrator handles routing based on your request.

Phase 1: Assessment

  • Discovers Java applications in the specified path.
  • Analyzes dependencies, frameworks, and Java version.
  • Identifies modernization opportunities and risks.
  • Saves results to .github/modernize/assessment/.

Phase 2: Planning

  • Loads assessment results.
  • Generates an executable task plan.
  • Saves the plan to .github/modernize/<app>/plan.md and tasks.json.

Phase 3: Execution

  • Routes tasks to specialized executor agents based on task type.
  • Each executor queries a knowledge base for migration patterns.
  • Monitors progress with automatic retry on failure.
  • Creates detailed per-task commits for review.

The orchestrator supports multiple entry points depending on your intent:

Workflow When it activates What happens
Broad intent "modernize my application" Full assess → plan → execute pipeline
Specific task "upgrade to Java 21" Skips assessment, goes straight to plan → execute
Execute existing plan "execute the plan" Skips assessment and planning, runs an existing plan
Headless Unattended execution with --allow-all Same as broad intent with no user prompts

Common scenarios

Upgrade your Java application

To upgrade your Java application to a newer runtime or framework version, use the following example:

copilot --agent=github-copilot-modernization:modernize

upgrade this project to JDK 21 and Spring Boot 3.2

The modernization task then executes, including generating the upgrade plan, performing code remediation, building the project, and checking for vulnerabilities as shown in the following screenshot:

Screenshot of GitHub Copilot CLI that shows running tasks in Java upgrade scenarios.

The project is successfully upgraded to JDK 21 and Spring Boot 3.2, and an upgrade summary is displayed.

Screenshot of GitHub Copilot CLI that shows the Java upgrade summary.

Migrate your Java application to Azure

To migrate your Java application to Azure, describe your migration scenario, as shown in the following example. For more information on predefined migration tasks, see Predefined tasks for GitHub Copilot modernization for Java developers.

copilot --agent=github-copilot-modernization:modernize

migrate this application from S3 to Azure Blob Storage

With this prompt, the migration task is executed and shows progress in Copilot CLI.

Screenshot of GitHub Copilot CLI that shows running tasks in Java migration scenarios.

When the project is successfully migrated to Microsoft Azure Blob Storage, a migration summary is displayed.

Screenshot of GitHub Copilot CLI that shows the Java migration summary.

Deploy your Java application to Azure

After upgrading or migrating your application, you can deploy it directly from Copilot CLI by using the following example:

copilot --agent=github-copilot-modernization:modernize

Scan my project and help me plan how to containerize my application using the #appmod-get-containerization-plan tool. Execute the plan. The end goal is to have Dockerfiles that are able to be built.

By using this prompt, the deployment task runs and shows progress in Copilot CLI.

Screenshot of GitHub Copilot CLI that shows the Java deployment details.

When the project is successfully deployed, a deployment summary is displayed.

Screenshot of GitHub Copilot CLI that shows the Java deployment summary.

Troubleshooting

Plugin not found

# Verify marketplace is added
copilot plugin marketplace list

# Re-add the marketplace if needed
copilot plugin marketplace add microsoft/github-copilot-modernization

# Reinstall
copilot plugin install github-copilot-modernization@github-copilot-modernization

Assessment fails: no Java application found

  • Verify pom.xml or build.gradle exists in your project root.
  • Ensure you're in the correct directory before starting Copilot CLI.

MCP server issues

The plugin uses the MCP server defined in its configuration. If you encounter problems, try reinstalling the plugin to reset the MCP configuration.

Provide feedback

If you have any feedback about the GitHub Copilot modernization plugin, create an issue at the github-copilot-appmod repository.

Next step

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