What is Spring PetClinic?

The Spring PetClinic application is a widely used reference project demonstrating how to build a simple, full-stack web application using Spring Boot, Spring Data, Thymeleaf, and other components from the Spring ecosystem.

Spring PetClinic Sample Application

Understanding the Spring Petclinic application with a few diagrams

See the presentation here

Run Petclinic locally

Spring Petclinic is a Spring Boot application built using Maven or Gradle. You can build a jar file and run it from the command line (it should work just as well with Java 17 or newer):

git clone https://github.com/spring-projects/spring-petclinic.git
cd spring-petclinic
./mvnw package
java -jar target/*.jar

You can then access the Petclinic at http://localhost:8080/.

Or you can run it from Maven directly using the Spring Boot Maven plugin. If you do this, it will pick up changes that you make in the project immediately (changes to Java source files require a compile as well - most people use an IDE for this):

./mvnw spring-boot:run

NOTE: If you prefer to use Gradle, you can build the app using ./gradlew build and look for the jar file in build/libs.

Terminology

Spring-Boot: It is a web-based framework. It allows us to make business based apps efficiently.

SQL: Stands for Structured Query Language. It is used to communicate with the database. SQL statements can be used to update, delete, and more within a database.

API: Stands for Application Programming Interface. API's sre HTTP services that can be accessed from any client. It is an ideal platform for building CRUD applications with the ASP.NET framework

CRUD: Stands for Create, Read, Update, Delete. These are the 4 basic database operations.

MVC: Stands for model-view-controller. MVC is a pattern for developing applications that are testable and easy to maintain.

Models: These are classes that represent the data of the application and that use validation logic to enforce business rules for that data.

Views: Consist of template files that the application uses in order to dynamically generate HTML responses.

Controllers: This project contains controllers that handle HTTP requests and responses. Each controller is responsible for a specific resource or entity. Controllers use HTTP methods (GET, POST, PUT, DELETE) that map to specific actions for CRUD loperations.

Routing: This maps incoming HTTP requests to the appropriate controller and action method based on the URL. RESTful APIs typically use a resource-based URL pattern.

HTTP Methods: RESTful APIs use standard HTTP methods (GET, POST, PUT, DELETE) to perform CRUD operations on resources. Each HTTP method corresponds to a specific action on the API.

Status Codes: RESTful APIs use standard HTTP status codes to indicate the success or failure of an API request. For example, 200 (OK) for successful GET requests, 201 (Created) for successful POST requests, 204 (No Content) for successful DELETE requests, etc.

Building a Container

There is no Dockerfile in this project. You can build a container image (if you have a docker daemon) using the Spring Boot build plugin:

./mvnw spring-boot:build-image

In case you find a bug/suggested improvement for Spring Petclinic

Our issue tracker is available here.

Database configuration

By default, Spring PetClinic uses an in-memory H2 database that gets populated with sample data during startup. The H2 console can be accessed at http://localhost:8080/h2-console. You can inspect the database using the following JDBC URL: jdbc:h2:mem: where the UUID is printed at startup.

If you need a persistent database, MySQL and PostgreSQL configurations are also supported. When switching databases, you'll need to activate the appropriate profile by setting spring.profiles.active=mysql or spring.profiles.active=postgres.

Here’s how to start MySQL or PostgreSQL with Docker:

MySQL

docker run -e MYSQL_USER=petclinic -e MYSQL_PASSWORD=petclinic -e MYSQL_ROOT_PASSWORD=root -e MYSQL_DATABASE=petclinic -p 3306:3306 mysql:8.4

or

PostgreSQL

docker run -e POSTGRES_USER=petclinic -e POSTGRES_PASSWORD=petclinic -e POSTGRES_DB=petclinic -p 5432:5432 postgres:16.3

Further documentation is provided for MySQL and PostgreSQL.

Alternatively, use the provided docker-compose.yml file for a more streamlined setup:

docker-compose --profile mysql up

or

docker-compose --profile postgres up

Test Applications

MySqlTestApplication

We recommend running the test applications configured in the following classes for faster feedback during development:

PetClinicIntegrationTests(using the default H2 database and Spring Boot DevTools) MySqlTestApplication (for MySQL) PostgresIntegrationTests (for PostgreSQL) These classes are designed to help you test the application easily in your IDE and can also be run as integration tests. MySQL tests use Testcontainers to manage the database, while PostgreSQL tests rely on Docker Compose.

Compiling the CSS

There is a petclinic.css in src/main/resources/static/resources/css. It was generated from the petclinic.scss source, combined with the Bootstrap library. If you make changes to the scss, or upgrade Bootstrap, you will need to re-compile the CSS resources using the Maven profile "css", i.e. ./mvnw package -P css. There is no build profile for Gradle to compile the CSS.

Working with Petclinic in your IDE

Prerequisites

The following items should be installed in your system:

• Java 17 or newer (full JDK, not a JRE)
• Git command line tool
• Your preferred IDE
  • Eclipse with the m2e plugin. Note: when m2e is available, there is an m2 icon in Help -> About dialog. If m2e is not there, follow the install process here
  • Spring Tools Suite (STS)
  • IntelliJ IDEA
  • VS Code

Steps

1. On the command line run:

   git clone https://github.com/spring-projects/spring-petclinic.git
   

2. Inside Eclipse or STS:

   Open the project via File -> Import -> Maven -> Existing Maven project, then select the root directory of the cloned repo.

   Then either build on the command line ./mvnw generate-resources or use the Eclipse launcher (right-click on project and Run As -> Maven install) to generate the CSS. Run the application's main method by right-clicking on it and choosing Run As -> Java Application.

3. Inside IntelliJ IDEA:

   In the main menu, choose File -> Open and select the Petclinic pom.xml. Click on the Open button.

   • CSS files are generated from the Maven build. You can build them on the command line ./mvnw generate-resources or right-click on the spring-petclinic project then Maven -> Generates sources and Update Folders.

   • A run configuration named PetClinicApplication should have been created for you if you're using a recent Ultimate version. Otherwise, run the application by right-clicking on the PetClinicApplication main class and choosing Run 'PetClinicApplication'.

4. Navigate to the Petclinic

   Visit http://localhost:8080 in your browser.

Looking for something in particular?

Spring Boot Configuration	Class or Java property files
The Main Class	PetClinicApplication
Properties Files	application.properties
Caching	CacheConfiguration

Explore Other Forks and Branches

The Spring Petclinic "main" branch in the spring-projects repository is the "canonical" implementation based on Spring Boot and Thymeleaf. There are quite a few forks in the GitHub org spring-petclinic. If you are interested in using a different technology stack to implement the Pet Clinic, please join the community there.

Interaction with other open-source projects

One of the best parts about working on the Spring Petclinic application is that we have the opportunity to work in direct contact with many Open Source projects. We found bugs/suggested improvements on various topics such as Spring, Spring Data, Bean Validation and even Eclipse! In many cases, they've been fixed/implemented in just a few days. Here is a list of them:

Name	Issue
Spring JDBC: simplify usage of NamedParameterJdbcTemplate	SPR-10256 and SPR-10257
Bean Validation / Hibernate Validator: simplify Maven dependencies and backward compatibility	HV-790 and HV-792
Spring Data: provide more flexibility when working with JPQL queries	DATAJPA-292

Contributing

The issue tracker is the preferred channel for bug reports, feature requests and submitting pull requests.

For pull requests, editor preferences are available in the editor config for easy use in common text editors. Read more and download plugins at https://editorconfig.org. If you have not previously done so, please fill out and submit the Contributor License Agreement.

License

The Spring PetClinic sample application is released under version 2.0 of the Apache License.