# Spring Boot — Production-Grade Java Apps with Minimum Fuss

> Spring Boot makes it easy to create stand-alone, production-grade Spring-based applications. Auto-configuration, embedded servers, actuator endpoints, and a massive starter ecosystem. The dominant framework for enterprise Java backends.

## Install

Save in your project root:

## Quick Use

```bash
# Use Spring Initializr
curl https://start.spring.io/starter.zip \
  -d type=maven-project -d language=java -d javaVersion=21 \
  -d dependencies=web,data-jpa,h2 \
  -d name=demo -o demo.zip
unzip demo.zip && cd demo
./mvnw spring-boot:run
# Visit http://localhost:8080
```

Or use https://start.spring.io web UI.

Minimal REST controller:
```java
@RestController
@RequestMapping("/api/assets")
public class AssetController {

    @Autowired
    private AssetRepository repo;

    @GetMapping
    public List<Asset> list() {
        return repo.findAll(Sort.by("stars").descending());
    }

    @PostMapping
    public Asset create(@RequestBody Asset asset) {
        return repo.save(asset);
    }
}

@Entity
public class Asset {
    @Id @GeneratedValue
    private Long id;
    private String name;
    private int stars;
    // getters, setters
}

public interface AssetRepository extends JpaRepository<Asset, Long> {}
```

## Intro

Spring Boot is a project by VMware (now Broadcom) that simplifies building production-grade Spring-based applications. Auto-configuration, embedded servers (Tomcat/Jetty/Undertow), actuator monitoring endpoints, and a massive starter dependency ecosystem. The dominant framework for enterprise Java and Kotlin backends.

- **Repo**: https://github.com/spring-projects/spring-boot
- **Stars**: 80K+
- **Language**: Java
- **License**: Apache 2.0

## What Spring Boot Does

- **Auto-configuration** — detect classpath and wire beans automatically
- **Embedded server** — Tomcat, Jetty, or Undertow built in (no WAR deploy)
- **Starters** — spring-boot-starter-web, -data-jpa, -security, -actuator
- **Actuator** — health, metrics, info, env, configprops endpoints
- **Spring Data JPA** — repository interfaces auto-implement CRUD
- **Spring Security** — auth, authorization, OAuth2, CORS, CSRF
- **Spring MVC** — annotation-driven REST controllers
- **Spring WebFlux** — reactive non-blocking stack
- **Profiles** — dev/test/prod environment configuration
- **GraalVM native** — compile to native binary (Spring AOT)

## Architecture

Spring IoC container manages beans. Auto-configuration inspects the classpath and conditionally registers beans. Starters bring in curated dependency sets. Actuator exposes operational endpoints. Configuration via `application.yml` / `application.properties` with profiles.

## Self-Hosting

```bash
# Build executable JAR
./mvnw package -DskipTests
java -jar target/demo-0.0.1-SNAPSHOT.jar

# Docker
FROM eclipse-temurin:21-jre
COPY target/*.jar app.jar
ENTRYPOINT ["java", "-jar", "app.jar"]

# Native image
./mvnw -Pnative native:compile
./target/demo    # ~30ms startup
```

## Key Features

- Auto-configuration
- Embedded server
- 80+ official starters
- Spring Data (JPA, MongoDB, Redis, Elasticsearch)
- Spring Security
- Spring Actuator
- Spring WebFlux (reactive)
- GraalVM native compilation
- Profiles for environment config
- Excellent documentation and guides

## Comparison

| Framework | Language | Config | Best For |
|---|---|---|---|
| Spring Boot | Java/Kotlin | Auto-config | Enterprise |
| Quarkus | Java/Kotlin | CDI | Cloud-native |
| Micronaut | Java/Kotlin | Compile-time DI | Serverless |
| NestJS | TypeScript | Decorators + DI | Node enterprise |
| Django | Python | settings.py | Full stack |
| Rails | Ruby | Convention | Full stack |

## 常见问题 FAQ

**Q: Spring Boot vs Spring Framework？**
A: Spring Framework 是底层 IoC + AOP + MVC。Spring Boot 是上面一层：自动配置、starter、embedded server，让你不用写 XML 和复杂 bean 配置。

**Q: 启动慢？**
A: JVM 启动确实慢（1-5s）。解决方案：Spring AOT + GraalVM Native Image 可以把启动时间降到 30-50ms。

**Q: 和 Quarkus 比？**
A: Quarkus 专为云原生优化（更快启动、更小 RSS）；Spring Boot 生态最大、企业经验最多。中大型团队多数仍选 Spring Boot。

## 来源与致谢 Sources

- Docs: https://docs.spring.io/spring-boot/docs
- GitHub: https://github.com/spring-projects/spring-boot
- License: Apache 2.0

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Source: https://tokrepo.com/en/workflows/cc16509a-362e-11f1-9bc6-00163e2b0d79
Author: AI Open Source