Clean Architecture with Spring

Clean Architecture with multimodules written in Java and the web layer build with the help of Spring.

Image source by Clean Architecture Website (Unlce Bob)

Clean Architecture main directory contains all the modules which realize the working of application.

• webapplication, inmemorydb and applicationdi modules are part of the Framework and Drivers layer.
• interfaceadpters module is part of Interface Adapters layer.
• usecases module is part of Application Business Rules layer.
• entities module is part of Enterprise Business Rules layer.

Dependency direction of the modules from the outermost to the center.

Outside layer depends on the layer below it. The inner layer has no dependency on the layer above and no information for any class or method from it. Changes on the outer layer should not cause changes to the inner layer .

applicationdi module (application dependency injection module)

applicationdi module uses:

• inmemorydb
• usecases
• interfaceadpters

modules to inject the dependencies that are needed in this application.

webapplication module

webapplication module is part of framework and drivers layer.

Framework and drivers layer is the outermost layer.

• webapplication module depends on the layer below it: interface adapters.
• webapplication module uses Spring framework. The endpoints which are in this layer with help of Spring annotations build together the entrypoints for the input.

Example schema of one case of Gauss elimination for linear equations with Clean Architecture.

This schema shows the interaction between weabapplication module and interfaceadapters module.

Class diagram shows the dependencies of GetGaussSolutionsEndpoint.class in webapplication module from the interfaceadapters module.

GetGaussSolutionsEndpoint.class uses two interfaces from interfaceadapters module to cross the boundary between layers.

• GetGaussSolutionsControllerInputBoundary interface that is implemented by GetGaussSolutionsController class which gets the input (GetSolutionsControllerRequest). GetGaussSolutionsController will send the input to the usecase layer to be processed, explained later in details.
• The second interface GaussSolutionsPresenterOutputBoundary that is implemented by GaussSolutionsPresenter class will be used by GetGaussSolutionsEndpoint.class to get the output (GaussSolutionsViewModel) and present to the web. GaussSolutionsPresenter receives the processed output from usecase layer, explained later in details.

code snippets

@RestController()
@RequestMapping("/api/v1/gausssolver")
public class GetGaussSolutionsEndpoint implements BaseEndpoint {

    private final GetGaussSolutionsControllerInputBoundary controller;
    private final GaussSolutionsPresenterOutputBoundary presenter;

    public GetGaussSolutionsEndpoint(
            GetGaussSolutionsControllerInputBoundary controller,
            GaussSolutionsPresenterOutputBoundary presenter) {
        this.controller = controller;
        this.presenter = presenter;
    }

    @GetMapping
    @ApiOperation(value = "Get solutions", response = GaussSolutionsViewModel.class)
    public ResponseEntity execute() {
        controller.execute(new GetSolutionsControllerRequest());

        return ResponseEntity.ok(presenter.getViewModel());
    }
}
public interface GetGaussSolutionsControllerInputBoundary {
    void execute(GetSolutionsControllerRequest getSolutionsControllerRequest);
}
public interface GaussSolutionsPresenterOutputBoundary {
    GaussSolutionsViewModel getViewModel();
}

interfaceadapters module

interfaceadapters module depends on the the layer below it concretely on usecases module.

The schema below shows the interaction between interfaceadapters module and usecases.

Class diagram below shows the dependencies of classes in interfaceadapters module on the layer above in usecase module.

Both the presenter and controller communicate with the usecase using the interfaces, which helps to pass the boundary and don’t break the dependency rules.

GetGaussSolutionsController.class in the interfaceadapters module uses the interface GetGaussSolutionsInputBoundary which is in the usecase module to send the request to the GetGaussSolutions.class.

GetGaussSolutions.class is the usecase of getting the gauss solutions. GetGaussSolutions.class implements GetGaussSolutionsInputBoundary interface and get the request from GetGaussSolutionsController.class.

On the same time GetGaussSolutions.class uses GaussSolutionsOutputBoundary interface.

• GaussSolutionsOutputBoundary interface is implemented by GaussSolutionsPresenter.class in interfaceadapters module.
• GetGaussSolutions.class presents the response to GaussSolutionsPresenter.class with the help of GaussSolutionsOutputBoundary interface.

public class GetGaussSolutionsController implements GetGaussSolutionsControllerInputBoundary {
    private final GetGaussSolutionsInputBoundary useCase;

    public GetGaussSolutionsController(GetGaussSolutionsInputBoundary useCase) {
        this.useCase = useCase;
    }

    @Override
    public void execute(GetSolutionsControllerRequest getSolutionsControllerRequest) {
        useCase.execute(new GetSolutionsDataRequest());
    }
}
public class GaussSolutionsPresenter extends BaseGaussSolutionPresenter
        implements GaussSolutionsOutputBoundary, GaussSolutionsPresenterOutputBoundary {

    private GaussSolutionsViewModel viewModel;

    @Override
    public GaussSolutionsViewModel getViewModel() {
        return viewModel;
    }

    @Override
    public void present(GaussSolutionsResponse responseModel) {
        GaussSolutionsViewModel.GaussSolutionsViewModelBuilder gaussSolutionsViewModelBuilder = GaussSolutionsViewModel.builder();
        responseModel.getSolutions()
                .stream()
              .map(BaseGaussSolutionPresenter::mapToGaussSolutionsViewModel)
                .forEach(gaussSolutionsViewModelBuilder::showSolutionsDataViewModel);
        viewModel = gaussSolutionsViewModelBuilder.build();
    }
}
public interface GetGaussSolutionsInputBoundary {
    void execute(GetSolutionsDataRequest request);
}
public interface GaussSolutionsOutputBoundary {

    void present(GaussSolutionsResponse responseModel);
}
public class GaussSolutionsPresenter extends BaseGaussSolutionPresenter
        implements GaussSolutionsOutputBoundary, GaussSolutionsPresenterOutputBoundary {

    private GaussSolutionsViewModel viewModel;

    @Override
    public GaussSolutionsViewModel getViewModel() {
        return viewModel;
    }

    @Override
    public void present(GaussSolutionsResponse responseModel) {
        GaussSolutionsViewModel.GaussSolutionsViewModelBuilder gaussSolutionsViewModelBuilder = GaussSolutionsViewModel.builder();
        responseModel.getSolutions()
                .stream()
                .map(BaseGaussSolutionPresenter::mapToGaussSolutionsViewModel)
                .forEach(gaussSolutionsViewModelBuilder::showSolutionsDataViewModel);
        viewModel = gaussSolutionsViewModelBuilder.build();
    }
}

In this way the direction of the dependency stays from interfaceadapters layer to usecase layer without breaking any depency rules and without creating any dependency from the higher level module to the lower level module.

usecases module

usecases module schema which shows the only dependency to entities module.

Class diagram of the usecase.

public class GetGaussSolutions extends GetGaussSolutionBase implements GetGaussSolutionsInputBoundary {
    private final GaussSolutionsOutputBoundary presenter;
    private final GaussSolutionGateway gaussSolutionGateway;

    public GetGaussSolutions(GaussSolutionsOutputBoundary presenter, GaussSolutionGateway gaussSolutionGateway) {
        this.presenter = presenter;
        this.gaussSolutionGateway = gaussSolutionGateway;
    }

    @Override
    public void execute(GetSolutionsDataRequest request) {
        GaussSolutionsResponse.GaussSolutionsResponseBuilder result = GaussSolutionsResponse.builder();
        gaussSolutionGateway.getAllGaussSolutionsData().forEach(solution -> result.addSolution(makeGaussSolutionResponse(solution)));

        presenter.present(result.build());
    }
}

Api calls

Api call to solve linear equations with gausssolver

POST
http://localhost:8080/gausssolver-service/api/v1/gausssolver
body 
{
    "a": [[2.0,4.0],[5.0, -6.0]],
    "b": [8.0,4.0]
}

Response of the call: 

{
    "solution": [
        2.0,
        1.0
    ]
}

Api call to get the solutions

GET
http://localhost:8080/gausssolver-service/api/v1/gausssolver

Response of the call:

{
    "solutionsData": [
        {
            "id": 1,
            "date": "2020-11-11",
            "document": "{\"a\":[[2.0,4.0],[5.0,-6.0]],\"b\"[8.0,4.0]}",
            "result": "[2.0,1.0]"
        }
    ]
}

Swagger documentation:

http://localhost:8080/gausssolver-service/swagger-ui.html#/gausssolver

Thank you for reading :)

My repository link:

rildikondi/CleanArchitectureSpring

References:

Clean Coder Blog