Spring Boot Demo Projects

This repository contains small Spring Boot projects that demonstrate different Spring Boot concepts. Each project is stored in its own numbered folder and includes its own README with project-specific instructions.

Projects

01profileDemo

Demonstrates Spring Boot profiles and shows how the same application variables can have different values in the default, dev, test, and prod environments.

The application provides a /profile endpoint that displays the active profile and its resolved configuration values.

See 01profileDemo/README.md for the complete example and profile values.

02interceptors

Demonstrates a custom Spring MVC interceptor, how to register it for selected URL patterns, and how to exclude other endpoints from interception.

See 02interceptors/README.md for details.

03filters

Demonstrates a custom servlet filter that runs once per request, generates a request ID, adds response headers, and logs before and after controller execution.

See 03filters/README.md for details.

04interceptorAndFilter

Combines two custom interceptors and three custom filters. Its response displays their execution order so the difference between filters and interceptors is easy to understand.

See 04interceptorAndFilter/README.md for details.

05exceptionHandling

Demonstrates comprehensive Spring Boot exception handling, including global advice (@RestControllerAdvice), standard error response models, Jakarta bean validation handling (@Valid), custom domain exceptions, controller-scoped handlers, and @ResponseStatus.

See 05exceptionHandling/README.md for details.

Prerequisites

Install the following before running the projects:

Java 17 or later
Apache Maven

Confirm that they are available:

java -version
mvn -version

Running a project

From the repository folder, enter the project you want to run:

cd .\01profileDemo\

Replace 01profileDemo with 02interceptors, 03filters, 04interceptorAndFilter, or 05exceptionHandling to run another demo.

Run it with its default configuration:

mvn spring-boot:run

Run it with a specific Spring profile in PowerShell:

mvn spring-boot:run "-Dspring-boot.run.profiles=dev"
mvn spring-boot:run "-Dspring-boot.run.profiles=test"
mvn spring-boot:run "-Dspring-boot.run.profiles=prod"

Keep the complete -D argument inside quotes in PowerShell. The selected profile tells Spring Boot which application-{profile}.properties file to load in addition to the base application.properties file.

After the application starts, open http://localhost:8080/profile to view the active profile and configuration values.

Command explanations

Command	Explanation
`cd .\01profileDemo\`	Moves the terminal into the selected project folder.
`mvn spring-boot:run`	Compiles and starts the Spring Boot application using Maven.
`"-Dspring-boot.run.profiles=dev"`	Passes `dev` to Spring Boot as the active profile. Replace `dev` with `test` or `prod` when needed.
`mvn test`	Compiles the project and runs its automated tests.
`mvn clean package`	Deletes old build output, runs the tests, and creates an executable JAR inside the `target` folder.
`java -jar target/profile-demo-0.0.1-SNAPSHOT.jar --spring.profiles.active=dev`	Runs the packaged JAR with the `dev` profile.

Stop a running application by pressing Ctrl+C in its terminal.

mohit2978/Springboot_code

README