Project structure walkthrough in Spring Boot - Step-by-Step Execution

Concept Flow - Project structure walkthrough

Start: Spring Boot Project Creation

↓

Create src/main/java folder

↓

Add Application class with @SpringBootApplication

↓

Create packages: controller, service, repository

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Add classes in each package

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Create src/main/resources folder

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Add application.properties or application.yml

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Create src/test/java for tests

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Build & Run Project

This flow shows the main steps to build a Spring Boot project structure from creation to running.

Execution Sample

Spring Boot

src/
  main/
    java/
      com/example/demo/
        DemoApplication.java
        controller/
          HelloController.java
        service/
          HelloService.java
    resources/
      application.properties

This shows the typical folder and file layout of a Spring Boot project.

Execution Table

Step	Action	Folder/File Created	Purpose
1	Create project root folder	demo/	Base folder for project
2	Create source folder	src/main/java	Java source code location
3	Create main package	com/example/demo	Namespace for code
4	Add main class	DemoApplication.java	Entry point with @SpringBootApplication
5	Create controller package	controller/	Handles web requests
6	Add controller class	HelloController.java	Defines REST endpoints
7	Create service package	service/	Business logic layer
8	Add service class	HelloService.java	Implements logic
9	Create resources folder	src/main/resources	Static resources and config
10	Add config file	application.properties	App configuration
11	Create test folder	src/test/java	Unit and integration tests
12	Build and run project	N/A	Compile and start Spring Boot app

💡 All main folders and files created, project ready to build and run

Variable Tracker

Folder/File	Before	After Step 1	After Step 2	After Step 3	After Step 4	After Step 5	After Step 6	After Step 7	After Step 8	After Step 9	After Step 10	After Step 11	Final
demo/	Not exist	Exists	Exists	Exists	Exists	Exists	Exists	Exists	Exists	Exists	Exists	Exists	Exists
src/main/java	Not exist	Not exist	Exists	Exists	Exists	Exists	Exists	Exists	Exists	Exists	Exists	Exists	Exists
com/example/demo	Not exist	Not exist	Not exist	Exists	Exists	Exists	Exists	Exists	Exists	Exists	Exists	Exists	Exists
DemoApplication.java	Not exist	Not exist	Not exist	Not exist	Exists	Exists	Exists	Exists	Exists	Exists	Exists	Exists	Exists
controller/	Not exist	Not exist	Not exist	Not exist	Not exist	Exists	Exists	Exists	Exists	Exists	Exists	Exists	Exists
HelloController.java	Not exist	Not exist	Not exist	Not exist	Not exist	Not exist	Exists	Exists	Exists	Exists	Exists	Exists	Exists
service/	Not exist	Not exist	Not exist	Not exist	Not exist	Not exist	Not exist	Exists	Exists	Exists	Exists	Exists	Exists
HelloService.java	Not exist	Not exist	Not exist	Not exist	Not exist	Not exist	Not exist	Not exist	Exists	Exists	Exists	Exists	Exists
src/main/resources	Not exist	Not exist	Not exist	Not exist	Not exist	Not exist	Not exist	Not exist	Not exist	Exists	Exists	Exists	Exists
application.properties	Not exist	Not exist	Not exist	Not exist	Not exist	Not exist	Not exist	Not exist	Not exist	Not exist	Exists	Exists	Exists
src/test/java	Not exist	Not exist	Not exist	Not exist	Not exist	Not exist	Not exist	Not exist	Not exist	Not exist	Not exist	Exists	Exists

Key Moments - 3 Insights

Why do we create separate packages like controller, service, and repository?

Separating code into packages helps organize by role: controller handles web requests, service contains business logic, and repository manages data access. This is shown in steps 5-8 in the execution_table.

What is the purpose of the DemoApplication.java class?

DemoApplication.java is the main entry point annotated with @SpringBootApplication. It starts the Spring Boot app. This is created at step 4 in the execution_table.

Why do we have src/main/resources folder?

src/main/resources holds configuration files and static resources like application.properties. This folder is created at step 9 and config file added at step 10.

Visual Quiz - 3 Questions

Look at the execution_table, at which step is the main application class created?

A Step 6

B Step 4

C Step 9

D Step 11

💡 Hint

Check the 'Folder/File Created' column for DemoApplication.java in execution_table

According to variable_tracker, when does the 'controller/' package first exist?

A After Step 5

B After Step 7

C After Step 3

D After Step 9

💡 Hint

Look at the 'controller/' row in variable_tracker and find when it changes from 'Not exist' to 'Exists'

If we skip creating src/test/java, which step in execution_table would be missing?

A Step 10

B Step 7

C Step 11

D Step 12

💡 Hint

Step 11 in execution_table is about creating the test folder src/test/java

Concept Snapshot

Spring Boot project structure:
- src/main/java: Java code
- Main class with @SpringBootApplication
- Packages: controller (web), service (logic), repository (data)
- src/main/resources: config files
- src/test/java: tests
Organizing code this way keeps project clean and manageable.

Full Transcript

This visual execution shows how a Spring Boot project is structured step-by-step. We start by creating the main source folder and package. Then we add the main application class with the @SpringBootApplication annotation. Next, we create separate packages for controller, service, and repository to organize code by responsibility. We add classes in each package accordingly. The resources folder holds configuration files like application.properties. Finally, we create a test folder for unit and integration tests. This structure helps keep the project clean and easy to maintain. The execution table and variable tracker show when each folder and file is created. Key moments clarify why we separate packages and the role of the main class. The quiz tests understanding of these steps.