template-microservice

This serves as a template for the microservices

Package structure

This package structure is based on multiple sources of best practices in Spring Boot, using roughly the "Package by layer" approach.

• root
  • config
  • controller
  • dapr
  • dto
  • exception
  • persistence
    • entity
    • repository
    • mapper
  • service
  • util (optional, if needed)
  • validation

Detailed description of the packages:

Root package

This should be named after the microservice itself. This is the root package for the microservice. It contains the Application.java file (or of similar name), which is the entry point for the microservice. Usually, this is the only class in this package.

Config package

This package should contain any classes that are used to configure the application. This includes Sprint Boot configuration classes but might also contain anything else related to configuration the microservice. The classes that are in this package should not be deleted in the actual microservice as they provide useful functionality.

Controller package

Location:src/main/java/de/unistuttgart/iste/meitrex/{service_name}/controller

This package contains the GraphQL controllers (and other types of controllers if needed). The GraphQL controllers are annotated with the @Controller annotation. Controllers contain no business logic, but only delegate the requests to the service layer. They handle the "technical stuff" of the request.

In some services, there is also a class called SubscriptionController which handles all dapr event subscriptions.

More information can be found in the Controller package.

Dapr package

Location:src/main/java/de/unistuttgart/iste/meitrex/{service_name}/dapr

This package should contain all classes that are used to communicate with Dapr, e.g. using pub sub.

DTO package

This package will not be located in the src/main/java folder, but in the build/generated folder.

This package contains the generated DTOs (data transfer objects) from the GraphQL schema. The DTOs are generated when building the project with gradle.

If not necessary, no other files should be added manually to this package.

Why both DTOs and Entities?

The DTOs are used to transfer data between the GraphQL controller and the service layer. The entities are used to persist data in the database. This is done to separate the data transfer from the data persistence. This is a common approach in Spring Boot applications as it can happen that we want to store more data in the database than we want to transfer to the client or vice versa.

Exception package

Location:src/main/java/de/unistuttgart/iste/meitrex/{service_name}/exception

This package is used for exception handling. Note that with GraphQL, the exceptions are not thrown directly, but are wrapped in a GraphQLException, which is different that from the usual Spring Boot approach.

More information can be found in the Exception package.

Persistence package

Location:src/main/java/de/unistuttgart/iste/meitrex/{service_name}/persistence

This package contains all classes that are used to persist data in the database. This includes the entities, the mapping logic between entities and DTOs, as well as the repositories.

This package handles the calls to the database and defines the database entities. It is structured into three sub-packages:

1. entity

This package contains the database entities.

2. repository

This package contains the interfaces to the database, also known as Data Access Objects (DAOs), used to perform various database operations. Note that these interfaces may sometimes be empty, especially when the default methods provided by the Spring Framework are sufficient for the required operations.

3. mapper

The 'mapper' package is responsible for the mapping logic between the database entities and the data types defined in the GraphQL schema. Specifically, it maps the database entity classes to the corresponding classes generated from the GraphQL schema.

This structure helps organize the database-related components of the project, making it easier to manage and maintain.

More information can be found in the Entity package and the Repository package.

Service package

Location:src/main/java/de/unistuttgart/iste/meitrex/{service_name}/service

This package contains all classes that are used to handle the business logic of the microservice. Services are annotated with the @Service annotation. Services contain only business logic and delegate the data access to the persistence layer (repositories).

More information can be found in the Service package.

Validation package

Location:src/main/java/de/unistuttgart/iste/meitrex/{service_name}/validation

This package should contain the class-level validation logic, i.e. the validation logic that is not directly related to a specific field, e.g. validation if an end date is after a start date.

Field-level validation logic should not be placed in this package, but in the graphql schema, via directives. If these directives are not sufficient, the validation logic can also be placed in this package.

Getting Started

Todos

Follow the guide in the wiki: https://github.com/MEITREX/wiki/blob/main/dev-manuals/backend/new-service.md

Addtionally, after cloning the repository, you need to do the following steps:

• Setup the gradle files correctly. This means
  • Change the project name in the settings.gradle file
  • Change the package name in the build.gradle file (there is a TODO comment)
  • Change the sonar project key in the build.gradle file (should be MEITREX_repository_name)
  • Add/Remove dependencies in the build.gradle file
• Rename the package in the src/main/java folder to a more suitable name (should be the same as the package name in the build.gradle file)
• Remove the package-info.java files in the src/main/java folder (or update with the microservice specific information)
• Update the application.properties file in the src/main/resources folder (check the TODOS in the file)
• Change the ports and name of the database in the docker-compose.yml (see wiki on how to)
• Define the GraphQL schema in the src/main/resources/schema.graphqls file

After creating a new service you need to do the following:

• Add the repository to sonarcloud, follow the instructions for extra configuration, unselect automatic analysis and choose github actions, only the first step needs to be completed
• Add SONAR_TOKEN to the service repository secrets on Github (this requires you to have admin permissions on sonarcloud)

Pull new changes from this template

If this template changes and you want to pull the changes to the actual microservice, you can run the following commands:

git remote add template https://github.com/MEITREX/template_microservice # only necessary once
git fetch --all
git checkout [branch] # replace [branch] with the branch name you want the changes to be merged into (preferably not main)
git merge template/main --allow-unrelated-histories
# you will probably need to commit afterwars

Guides

The following guides illustrate how to use some features concretely:

• Building a GraphQL service
• Accessing Data with JPA
• Validation with GraphQL directives
• Error handling

Reference Documentation

For further reference, please consider the following sections:

• Official Gradle documentation
• Spring Boot Gradle Plugin Reference Guide
• Spring Configuration Processor
• Spring Boot DevTools
• Spring for GraphQL
• Spring Data JPA
• Validation
• Generating Sonarqube Token
• Adding secrets on Github