Spring Boot

Prerequisites

• One of the Java versions
  • Java SE 8
  • Java SE 11
• IntelliJ
• Postman
• Depending on your database, use one of the following
  • MySQL: https://www.apachefriends.org/download.html
  • MongoDB: https://www.mongodb.com/try/download/enterprise
• NOTE: This repository is for SQL-based projects. For MongoDB related projects, go to https://github.com/alanngo/SpringBoot-Mongo

Getting Started

1. Go to https://start.spring.io/

   • Apply the following settings
     • Project: Maven
     • Language: Java
     • Group: com.{project name}
     • Artifact: {NAME}
     • Name: {NAME}
     • Description: Spring Project (Doesn't matter)
     • Package name: com.{project name}
     • Packaging: Jar
     • Java: {Your version of Java installed}
   • Add the following Dependencies:
     • Lombok
     • Spring Web
     • Spring Data JPA

2. Click "Generate"

3. Unzip the download to your working directory

4. Manually add the following dependencies in pom.xml

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-validation</artifactId>
    <version>2.3.3.RELEASE</version>
</dependency>

<dependency>
    <groupId>mysql</groupId>
    <artifactId>mysql-connector-java</artifactId>
    <scope>runtime</scope>
</dependency>

File Structure

com/example/api
com/example/dto
com/example/entity
com/example/repository
com/example/service
com/example/utility

Integrating Lombok

IntelliJ:

https://www.youtube.com/watch?v=RwX1x7_k1b0

1. Depending on your OS
   • Windows/ Linux: File -> Settings -> Plugins (Ctrl + Alt + S)
   • Mac: IntelliJ Idea -> Preferences -> Plugins
2. Click on 'Marketplace tab' and search 'lombok'
3. Click Install
4. Click Apply and restart IntelliJ

Errors and Solutions :

If you are getting You aren't using a compiler supported by lombok, so lombok will not work and has been disabled error, follow the steps below.

1. Open Settings/Preferences -> Compiler
2. Add -Djps.track.ap.dependencies=false to 'Shared build process VM options'
3. Apply and OK
4. Rerun your program

https://i.stack.imgur.com/jwTAw.png

Important Annotations

API

// Class Based
@RestController // allows the class to have API routes
@CrossOrigin // allows other programs to consume SpringBoot app
@RequestMapping // root url mapping

// Field Based
@Autowired // dependency injection

// Method Based
@GetMapping("/URL") // allows a method to be called when GET request is made w/ '/URL'
@PostMapping("/URL") // allows a method to be called when POST request is made w/ '/URL'
@PutMapping("/URL") // allows a method to be called when PUT request is made w/ '/URL'
@DeleteMapping("/URL") // allows a method to be called when DELETE request is made w/ '/URL'

// Method Parameter Based
@RequestBody // allows POJO to be parsed as JSON request body
@PathVariable // used for url patterns of *./{pathVar}, method arg name must also be the same
@QueryParam // used for url patterns of ?key=value

DTO

// Class Based
@Data // constructor, getters, setters, equals, hashCode, toString 

Entity

// Class Based
@Data // constructor, getters, setters, equals, hashCode, toString 
@Table("TABLE_NAME") // binds class to SQL table if class/table name is different
@Entity // represents class as SQL table

// Field Based
@Id // primary key
@GeneratedValue(strategy = GenerationType.IDENTITY) // auto increment PK
@Column("COL_NAME") // binds field to DB column if field/column name is different

Repository

• none

Service

// Class Based
@Service // denotes service layer
@Transactional // allows the class to update DB fields

// Field Based
@Autowired // dependency injection

Utility

ErrorInfo

// Class Based
@Data // constructor, getters, setters, equals, hashCode, toString 

ExceptionControllerAdvice

// Class Based
@RestControllerAdvice // allows the app to output errors to user in a useful manner
@Slf4j // creates a logger variable automatically

// Field Based
@Autowired // dependency injection

// Method Based
@ExceptionHandler(value = Exception.class) // allows method to be called when exception is raised

LoggingAspect

// Class Based
@Component // denotes spring bean
@Aspect // used for crosscutting concern
@Slf4j // creates a logger variable automatically

// Method Based
@AfterThrowing(pointcut = "execution(CLASS_NAME)") // will execute after throwing exception

Repository Layer

public interface ExampleRepository extends CrudRepository<ENTITY, ID> 
{
    // SQL based programs use CrudRepository
}