spring-014: mvn spring-boot:run-lifecycle-phases

When you start your Spring Boot app using mvn spring-boot:run, Maven executes the necessary lifecycle phases in order. Here’s what happens at each phase:

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1️⃣ validate Phase

🔹 What happens?

• Maven checks the project structure and pom.xml configuration.
• Ensures all required properties are defined.
• Verifies that all dependencies are resolved (if any are missing, Maven will try to download them).

🔹 Key tasks:

• Ensures all necessary files exist (e.g., src/main/java, pom.xml).
• Validates if groupId, artifactId, and version are correctly defined.

📌 If an issue is found (e.g., missing dependencies), Maven stops here with an error.

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2️⃣ compile Phase

🔹 What happens?

• Compiles Java source code (.java → .class files).
• Stores compiled .class files inside target/classes/.

🔹 Key tasks:

• Uses the Maven Compiler Plugin to compile source files.
• If annotation processing (e.g., Lombok) is enabled, it processes those annotations.

📌 If compilation fails due to syntax errors, Maven stops here.

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3️⃣ package Phase

🔹 What happens?

• Creates a JAR/WAR file containing the compiled classes and resources.
• Moves the packaged file to target/your-app.jar (for Spring Boot, a fat JAR is created).

🔹 Key tasks:

• Runs spring-boot-maven-plugin (for Spring Boot apps) to package dependencies into the JAR.
• Includes META-INF/MANIFEST.MF (defines the main class to run).
• Copies src/main/resources/ files into the JAR.

📌 If packaging fails (e.g., missing files), Maven stops here.

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4️⃣ spring-boot:run (Runs the App)

• JVM starts and loads Demo1Application.main().
• Spring Boot initializes the app, loads dependencies, and starts an embedded web server (if applicable).
• The app is now running and ready to serve requests.

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🔄 Summary of Lifecycle Execution Before spring-boot:run

Phase	Action Taken
validate	Checks project structure, dependencies, and configuration.
compile	Compiles .java files into .class files inside target/classes/.
package	Bundles everything into a .jar/.war file in target/.
spring-boot:run	Runs the packaged app using an embedded JVM.

📌 These phases ensure that when your app starts, everything is correctly compiled and packaged, preventing runtime errors. 🚀