demo-forum-backend

The purpose of this demo is to give a quick overview to how to build a modern backend using Java and Spring Framework. The application that we build is a simple discussion forum. The application allows user to view topics and message chains under a specific topic. The user is also able to create new topics and post new messages to existing topics.

The demo is split into following sections in different GIT branches:

develop

This is the starting point of the demo. The branch contains a simple "Hello World!!" -application that can be compiled using Gradle: gradlew clean build. If you intend to follow the demo as a hands-on exercise on your own computer you are required to do the following steps before the demo.

1. Install and configure Java 1.8
2. Run command gradlew clean build. This will bootsrap Gradle to you computer
3. Install Java IDE (recommended Eclipse) and import the project to the IDE
4. Install Gradle plugin to your IDE. For Eclipse the plugin is called Gradle IDE Pack

version_1

This step adds Spring Boot to the project. After this step the project can already be run the from IDE or from command line: java -jar build/libs/demo-forum-backend.jar The web server can be accessed with URL http://localhost:8080. The web server still responds with error page because no content is available yet.

1. Update build.gradle with Spring Boot dependencies
2. Update App.class to be main function for Spring Boot application

version_2

This step adds the frontend as a dependency jar. After this step the UI of the application can be accessed using URL http://localhost:8080/webjars/forum/index.html The REST API is still missing so expect to get JavaScript errors when using the application.

1. Update build.gradle with dependency to libs directory

version_3

This step adds database to the application. The used database is a light-weight H2 embedded database that does not require installation. The data of the database is written to the demo-demo-forum-backend/db directory. The database can be reset at any time by deleting the directory and restarting the application.

1. Update build.gradle with JPA and H2 dependencies
2. Add database configuration to application.properties file

version_4

This step add SQL script that can be used to create the schema and add some initial data. Also uses Flyway to automatically update the database schema.

1. Update build.gradle with Flyway dependency
2. Add SQL migration scripts to project

version_5

This step adds Controller, Service and Model layers to the project.

1. Add code in controller, service and model packages to the project

version_6

This step adds DAO layer to the project. The DAOs are created using Spring JpaRepository-mechanism. After this step we have a fully working backend implementation.

1. Uncomment code in the service classes (TopicService, MessageService) and create the missing DAO interfaces (TopicDao, MessageDao) to dao package.

References

• http://www.oracle.com/technetwork/java/index.html
• https://eclipse.org/
• http://gradle.org/
• http://mvnrepository.com/
• http://projects.spring.io/spring-boot/
• http://docs.spring.io/spring-boot/docs/current/reference/html/common-application-properties.html
• http://tomcat.apache.org/
• http://docs.spring.io/spring-data/data-commons/docs/1.6.1.RELEASE/reference/html/repositories.html
• http://hibernate.org/orm/
• https://flywaydb.org/
• http://www.h2database.com/html/main.html