🍃 Spring Boot

This repository is aimed at providing a comprehensive introduction to Spring Boot, particularly focusing on three main aspects: basic Spring Boot concepts, building REST APIs, and integrating with a database using Spring Data JPA.

📝 Explanation of Spring Concepts

• Spring Beans:

  • Objects managed by Spring IoC container.
  • Core building blocks of a Spring application.
  • Configured with metadata supplied to the container.
  • Typically Java objects.

• Spring Profiles:

  • Segregate parts of application configuration.
  • Available only in specific environments.
  • Enable different configurations for development, testing, production, etc.
  • Control which beans are loaded and which configurations are applied.

• Qualifiers:

  • Resolve ambiguity when multiple beans of the same type are available.
  • Used with @Qualifier annotation.
  • Specify which bean should be autowired into a particular field or parameter.
  • Useful when multiple beans implement the same interface or are of the same type.

📂 Folder Structure

project/
│
├── demo/
│   ├── src/
│   │   ├── main/
│   │   │   ├── java/
│   │   │   │   ├── com.example.demo/
│   │   │   │   │   └── ...
│   │   │   └── resources/
│   │   │       └── ...
│   │   └── test/
│   │       └── ...
│   └── pom.xml
│
├── rest/
│   ├── src/
│   │   ├── main/
│   │   │   ├── java/
│   │   │   │   ├── com.example.rest/
│   │   │   │   │   └── ...
│   │   │   └── resources/
│   │   │       └── ...
│   │   └── test/
│   │       └── ...
│   └── pom.xml
│
└── rest_database/
    ├── src/
    │   ├── main/
    │   │   ├── java/
    │   │   │   ├── com.example.rest_database/
    │   │   │   │   ├── students/
    │   │   │   │   │   ├── controller/
    │   │   │   │   │   ├── mapper/
    │   │   │   │   │   ├── response/
    │   │   │   │   │   ├── dto/
    │   │   │   │   │   ├── repository/
    │   │   │   │   │   └── service/
    │   │   │   │   ├── studentProfile/
    │   │   │   │   │   ├── controller/
    │   │   │   │   │   ├── mapper/
    │   │   │   │   │   ├── response/
    │   │   │   │   │   ├── dto/
    │   │   │   │   │   ├── repository/
    │   │   │   │   │   └── service/
    │   │   │   │   ├── School/
    │   │   │   │       ├── controller/
    │   │   │   │       ├── mapper/
    │   │   │   │       ├── response/
    │   │   │   │       ├── dto/
    │   │   │   │       ├── repository/
    │   │   │   │       └── service/
    │   │   │   └── ...
    │   │   └── resources/
    │   │       └── ...
    │   └── test/
    │       └── ...
    └── pom.xml

The project is organized into three main folders:

1. 📁 demo: Basic Spring Boot concepts are covered in this folder including Spring Beans, Qualifier, Spring Profiles, Dependency Injection, and creating the first class and service.

2. 📁 rest: This folder covers the basics of building REST APIs with Spring Boot. It includes creating the first controller using @RestController, and utilizing @GetMapping, @PostMapping, @PutMapping, and @DeleteMapping. Path variables and request parameters are also demonstrated, along with creating the first record.

3. 📁 rest_database: This folder focuses on integrating Spring Boot with a database using Spring Data JPA. Notably, the application.properties file is updated to application.yaml to configure the database connection. Below is the configuration explained:

spring:
  datasource:
    url: jdbc:postgresql://localhost:5432/postgres
    username: postgres
    password: qwerty123
    driver-class-name: org.postgresql.Driver
  jpa:
    hibernate:
      ddl-auto: update
    show-sql: true
    properties:
      hibernate:
        dialect: org.hibernate.dialect.PostgreSQLDialect
        format_sql: true
    database: postgresql
    database-platform: org.hibernate.dialect.PostgresSQLDialect

Explanation of Configuration

• Datasource Configuration: Specifies the URL, username, password, and driver class for connecting to the PostgreSQL database.
• JPA Configuration: Configures Hibernate behavior, including DDL auto, SQL logging, and database dialect.

📁 Package Structure for rest_database

In each of the students, studentProfile, and School packages within the rest_database folder, the following components are created:

• Controller: Defines endpoints for handling HTTP requests.
• Mapper: Converts between DTOs (Data Transfer Objects) and domain objects.
• Response: Defines response structures for API endpoints.
• DTO: Data Transfer Objects representing the data exchanged between the client and server.
• Repository: Interfaces defining methods for interacting with the database.
• Service: Implements business logic and interacts with repositories.

This structure helps in maintaining a clean and organized codebase, following the principles of separation of concerns and modularity.

❌ Exception Handling & Validation

In the rest_database module, exception handling and validation are implemented to enhance the robustness and reliability of the REST API endpoints.

Exception Handling

• Exception handling is crucial for handling errors and exceptions gracefully in a Spring Boot application.
• In the controller layer, exception handling is implemented using @ControllerAdvice and @ExceptionHandler annotations.
• Custom exception classes can be created to represent different types of errors that may occur during the execution of API endpoints.
• Global exception handlers catch exceptions thrown during request processing and return appropriate HTTP responses with error details.
• This ensures consistent error responses across all endpoints and improves the overall user experience.

Validation

• Input validation is important for ensuring that the data sent to the API endpoints is valid and meets the required criteria.
• In the studentDTO layer, input validation is performed using annotations such as @Valid and @Validated.
• Bean validation annotations like @NotBlank, @NotNull, @Size, etc., are used to define validation rules for request parameters, request bodies, and path variables.
• If the incoming data fails validation, Spring Boot automatically detects the validation errors and returns appropriate error responses with details about the validation failures.
• This helps in preventing invalid data from being processed further, improving data integrity and API reliability.