Spring Boot Cheatsheet

Main Annotations

Annotation	Description
`@SpringBootApplication`	Entry point. Combines `@Configuration`, `@EnableAutoConfiguration`, and `@ComponentScan`
`@RestController`	Controller that returns data (not a view)
`@Controller`	Conventional controller (returns a view/template)
`@Service`	Mark a class as a service layer
`@Repository`	Mark a class as a data access layer
`@Component`	Mark a class as a Spring-managed bean
`@Configuration`	Mark a class as configuration
`@Bean`	Register a method's return value as a bean
`@Autowired`	Inject dependencies automatically
`@Qualifier`	Pick a specific bean when multiple beans exist

Web Annotations

Annotation	Description
`@RequestMapping`	Map an HTTP request to a method
`@GetMapping`	Handle a GET request
`@PostMapping`	Handle a POST request
`@PutMapping`	Handle a PUT request
`@DeleteMapping`	Handle a DELETE request
`@PathVariable`	Get a value from the URL path
`@RequestParam`	Get a query parameter
`@RequestBody`	Bind the request body to an object
`@Valid`	Validate input with Bean Validation

JPA Annotations

Annotation	Description
`@Entity`	Mark a class as a database table
`@Table`	Set the table name
`@Id`	Mark the primary key
`@GeneratedValue`	Auto-increment ID
`@Column`	Column configuration
`@ManyToOne`	Many-to-one relationship
`@OneToMany`	One-to-many relationship
`@ManyToMany`	Many-to-many relationship
`@JoinColumn`	Set the foreign key column

Testing Annotations

Annotation	Description
`@SpringBootTest`	Load the full Spring context
`@WebMvcTest`	Test the controller only (slice test)
`@DataJpaTest`	Test the repository with an embedded database
`@MockBean`	Create a mock bean in the Spring context
`@Autowired`	Inject a bean for testing
`@BeforeEach`	Setup before each test
`@Test`	Mark a method as a test
`@ActiveProfiles`	Activate a profile for the test

Security Annotations

Annotation	Description
`@EnableWebSecurity`	Enable Spring Security
`@EnableMethodSecurity`	Enable method-level security
`@PreAuthorize`	Check role/permission before executing the method
`@Secured`	Check roles with an annotation

Configuration Annotations

Annotation	Description
`@ConfigurationProperties`	Bind external configuration to an object
`@Value`	Get a single property value
`@Profile`	Activate a bean for a specific profile
`@ConditionalOnProperty`	Bean only if the property matches

HTTP Methods

Method	Description	Idempotent
`GET`	Fetch data	Yes
`POST`	Create new data	No
`PUT`	Update data (full replace)	Yes
`PATCH`	Update data (partial)	No
`DELETE`	Delete data	Yes

HTTP Status Codes

Code	Description
`200 OK`	Success
`201 Created`	Resource created successfully
`204 No Content`	Success, without a response body
`400 Bad Request`	Invalid request
`401 Unauthorized`	Not logged in
`403 Forbidden`	No access
`404 Not Found`	Resource not found
`500 Internal Server Error`	Server error

application.properties Common

# Server
server.port=8080
server.servlet.context-path=/api

# Database
spring.datasource.url=jdbc:postgresql://localhost:5432/myapp
spring.datasource.username=postgres
spring.datasource.password=secret
spring.jpa.hibernate.ddl-auto=validate

# JPA
spring.jpa.show-sql=true
spring.jpa.properties.hibernate.format_sql=true

# Actuator
management.endpoints.web.exposure.include=health,info,metrics

# Logging
logging.level.root=INFO
logging.level.com.example=DEBUG

# File upload
spring.servlet.multipart.max-file-size=10MB
spring.servlet.multipart.max-request-size=10MB

Key Dependencies

<!-- Web -->
<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-web</artifactId>
</dependency>

<!-- JPA -->
<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-data-jpa</artifactId>
</dependency>

<!-- Validation -->
<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-validation</artifactId>
</dependency>

<!-- Security -->
<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-security</artifactId>
</dependency>

<!-- Actuator -->
<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-actuator</artifactId>
</dependency>

<!-- H2 (Development) -->
<dependency>
    <groupId>com.h2database</groupId>
    <artifactId>h2</artifactId>
    <scope>runtime</scope>
</dependency>

<!-- PostgreSQL (Production) -->
<dependency>
    <groupId>org.postgresql</groupId>
    <artifactId>postgresql</artifactId>
    <scope>runtime</scope>
</dependency>

<!-- Swagger/OpenAPI -->
<dependency>
    <groupId>org.springdoc</groupId>
    <artifactId>springdoc-openapi-starter-webmvc-ui</artifactId>
    <version>2.3.0</version>
</dependency>

<!-- Lombok -->
<dependency>
    <groupId>org.projectlombok</groupId>
    <artifactId>lombok</artifactId>
    <optional>true</optional>
</dependency>

<!-- MapStruct -->
<dependency>
    <groupId>org.mapstruct</groupId>
    <artifactId>mapstruct</artifactId>
    <version>1.5.5.Final</version>
</dependency>

Key Commands

# Build
mvn clean package
mvn clean package -DskipTests

# Run
java -jar target/myapp-1.0.0.jar
mvn spring-boot:run

# Test
mvn test

# Docker
docker build -t myapp .
docker run -p 8080:8080 myapp

Project Structure

src/
├── main/
│   ├── java/com/example/myapp/
│   │   ├── MyApplication.java
│   │   ├── controller/
│   │   │   └── UserController.java
│   │   ├── service/
│   │   │   ├── UserService.java
│   │   │   └── UserServiceImpl.java
│   │   ├── repository/
│   │   │   └── UserRepository.java
│   │   ├── model/
│   │   │   ├── entity/
│   │   │   │   └── User.java
│   │   │   └── dto/
│   │   │       ├── UserRequestDTO.java
│   │   │       └── UserResponseDTO.java
│   │   ├── mapper/
│   │   │   └── UserMapper.java
│   │   ├── config/
│   │   │   └── SecurityConfig.java
│   │   └── exception/
│   │       └── GlobalExceptionHandler.java
│   └── resources/
│       ├── application.properties
│       ├── application-dev.properties
│       ├── application-prod.properties
│       └── data.sql
└── test/
    └── java/com/example/myapp/
        ├── controller/
        │   └── UserControllerTest.java
        ├── service/
        │   └── UserServiceTest.java
        └── repository/
            └── UserRepositoryTest.java

Closing

Congratulations! You've completed the Spring Boot tutorial from the basics all the way to deployment.

What you've learned:

Setting up and configuring Spring Boot
REST API with controllers
Data persistence with JPA & Repository
Service layer and DTO pattern
Development database (H2) and production database (MySQL/PostgreSQL)
Proper testing
Monitoring with Actuator
Security with Spring Security
API documentation with Swagger/OpenAPI
Deploying to production

Keep practicing, read the official Spring Boot documentation, and build your own projects to deepen your understanding.

Happy learning Spring Boot! 🚀