A RESTful CRUD demo application with Delphi

Habari Web Components is a web application framework for small to medium size HTTP services, based on the Internet Direct (Indy) library.

A new demo application – included with full source code in demo/restful-crud – exposes a RESTful API which supports HTTP GET / POST / DELETE commands to read, create and delete data.

The source code below shows the configuration code for the RESTful API. Every request handler is bound to a resource address, document type (MIME type), and HTTP method.

Note that PUT is not yet implemented in the API because web browsers do not support HTTP PUT in HTML forms. For HTTP DELETE, the web interface uses a Javascript-based workaround to delete a resource.

procedure TMyRestfulComponent.Init(const Config:
            IWebComponentConfig);
begin
  inherited; // always call inherited.Init

  // GET http://localhost/rest/persons
  // list all persons
  &Path('persons');
  Produces('text/html');
  GET(procedure(Request: TRequest; Response: TResponse)
  begin
    Response.ContentText := CRUDModule.GetPersons;
    Response.CharSet := 'UTF-8';
  end);

  // POST http://localhost/rest/persons
  // add new person
  &Path('persons');
  Produces('text/html');
  POST(procedure(Request: TRequest; Response: TResponse)
  var
    Name: string;
    Person: TPerson;
  begin
    Name := UTF8Decode(Request.Params.Values['name']);
    Person := TPerson.Create(CRUDModule.NextID, Name);
    CRUDModule.SavePerson(Person);
    Response.Redirect(Request.Document);
  end);

  // PUT http://localhost/rest/persons/{id}
  // update person
  &Path('persons/{id}');
  Produces('text/html');
  PUT(procedure(Request: TRequest; Response: TResponse)
  var
    ID: string;
  begin
    ID := Request.Params.Values['id'];
    // TODO
  end);

  // DELETE http://localhost/rest/persons/{id}
  // delete person
  &Path('persons/{id}');
  Produces('text/html');
  DELETE(procedure(Request: TRequest; Response: TResponse)
  var
    ID: string;
  begin
    ID := Request.Params.Values['id'];
    CRUDModule.DeletePerson(StrToInt(ID));
  end);

  // GET http://localhost/rest/persons/{id}
  // get person information
  &Path('persons/{id}');
  Produces('text/html');
  GET(procedure(Request: TRequest; Response: TResponse)
  var
    ID: string;
  begin
    ID := Request.Params.Values['id'];
    Response.ContentText := CRUDModule.GetPerson(StrToInt(ID));
    Response.CharSet := 'UTF-8';
  end);
end;