📦 Spring Boot: Packaging and Deployment

The Lunchbox Story 🍱

Imagine you made the most delicious lunch ever. Now you need to:

1. Pack it in a lunchbox (Packaging)
2. Take it to school or work (Deployment)
3. Leave a note about what’s inside (Logging)

That’s exactly what Spring Boot does with your application!

🎯 What You’ll Learn

• Packaging Options - Different lunchboxes for different needs
• Executable JAR - The magic all-in-one lunchbox
• Container Deployment - Shipping your lunch in a truck
• Logging Configuration - Writing notes about your lunch

📦 Packaging Options

What is Packaging?

When you build a Spring Boot app, you need to bundle everything together. Just like packing a suitcase for a trip!

Two Main Lunchbox Types

graph TD
    A[Your App] --> B{Choose Package}
    B --> C[JAR File]
    B --> D[WAR File]
    C --> E[Runs Anywhere]
    D --> F[Needs App Server]

Simple Example

In your pom.xml:

<packaging>jar</packaging>

That’s it! Maven knows to make a JAR.

🚀 Executable JAR (Fat JAR)

The Magic Lunchbox

An executable JAR is special. It contains:

• Your code ✅
• All libraries ✅
• A web server ✅
• Everything to run ✅

One file. That’s all you need.

Why “Fat” JAR?

Regular JAR:    Your code only (small)
Fat JAR:        Your code + ALL dependencies (big)

Think of it like:

• Regular JAR = Empty lunchbox
• Fat JAR = Lunchbox with food, napkin, fork, and drink!

How Spring Boot Does It

Spring Boot uses a special plugin to create fat JARs:

<build>
  <plugins>
    <plugin>
      <groupId>
        org.springframework.boot
      </groupId>
      <artifactId>
        spring-boot-maven-plugin
      </artifactId>
    </plugin>
  </plugins>
</build>

Building Your JAR

Run this command:

mvn clean package

You’ll find your JAR in the target/ folder:

target/
  └── myapp-0.0.1.jar  ← Your app!

Running Your JAR

Just one command:

java -jar myapp-0.0.1.jar

🎉 That’s it! Your app is running!

Inside the Fat JAR

graph TD
    A[myapp.jar] --> B[Your Classes]
    A --> C[BOOT-INF/lib]
    A --> D[Embedded Tomcat]
    C --> E[spring-core.jar]
    C --> F[jackson.jar]
    C --> G[other libs...]

🐳 Container Deployment

What’s a Container?

Imagine shipping your lunchbox in a protective box that has:

• Perfect temperature
• Right humidity
• Same conditions everywhere

That’s a Docker container!

Why Use Containers?

Creating a Dockerfile

A Dockerfile is like a recipe for your container:

FROM eclipse-temurin:17-jre
COPY target/myapp.jar app.jar
ENTRYPOINT ["java","-jar","/app.jar"]

Line by line:

1. Start with Java 17
2. Copy your JAR file
3. Tell it how to run

Building the Container

docker build -t myapp .

Running the Container

docker run -p 8080:8080 myapp

Your app runs inside its own little world!

Better Dockerfile (Layered)

Spring Boot 2.3+ supports layered JARs:

FROM eclipse-temurin:17-jre
WORKDIR /app
COPY target/myapp.jar app.jar
RUN java -Djarmode=layertools \
    -jar app.jar extract
FROM eclipse-temurin:17-jre
COPY --from=0 /app/dependencies/ ./
COPY --from=0 /app/application/ ./
ENTRYPOINT ["java", "org...."]

Why layers? Faster rebuilds! Only changed layers update.

graph TD
    A[Layered JAR] --> B[dependencies]
    A --> C[spring-boot-loader]
    A --> D[snapshot-deps]
    A --> E[application]
    B --> F[Changes rarely]
    E --> G[Changes often]

📝 Logging Configuration

Why Logs Matter

Logs are like a diary for your app. They tell you:

• What happened ✅
• When it happened ✅
• What went wrong ❌

Default Logging

Spring Boot uses Logback by default. No setup needed!

2024-01-15 10:30:45 INFO  Starting MyApp
2024-01-15 10:30:46 INFO  Tomcat started on port 8080

Log Levels

graph TD
    A[TRACE] --> B[DEBUG]
    B --> C[INFO]
    C --> D[WARN]
    D --> E[ERROR]
    style A fill:#e8f5e9
    style B fill:#e3f2fd
    style C fill:#fff3e0
    style D fill:#ffecb3
    style E fill:#ffcdd2

Setting Log Levels

In application.properties:

# Root level (all logs)
logging.level.root=INFO

# Your package (more detailed)
logging.level.com.myapp=DEBUG

# Spring (less noise)
logging.level.org.springframework=WARN

Logging to a File

# Log file location
logging.file.name=app.log

# Or use a path
logging.file.path=/var/logs

Log Format

Customize how logs look:

logging.pattern.console=\
%d{HH:mm:ss} %-5level %msg%n

Output:

10:30:45 INFO  Starting MyApp
10:30:46 INFO  Tomcat started

Using Logs in Code

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

public class MyService {
  private static final Logger log =
    LoggerFactory.getLogger(MyService.class);

  public void doSomething() {
    log.info("Starting task");
    log.debug("Details: {}", data);
    log.error("Oops!", exception);
  }
}

Environment-Specific Logging

Use profiles for different settings:

application-dev.properties:

logging.level.root=DEBUG

application-prod.properties:

logging.level.root=WARN
logging.file.name=/var/log/app.log

Run with profile:

java -jar app.jar --spring.profiles.active=prod

🎯 Quick Summary

🚀 Real-World Flow

graph LR
    A[Write Code] --> B[mvn package]
    B --> C[JAR Created]
    C --> D{Deploy Where?}
    D --> E[java -jar]
    D --> F[Docker Container]
    D --> G[Cloud Platform]

💡 Remember

1. JAR = Your whole app in one file
2. Docker = Ship your app safely anywhere
3. Logs = Your app’s diary

You’re now ready to package and deploy like a pro! 🎉