Table of Contents
A migration scenario from a legacy MVC php web application towards a modern RESTful web application with AJAX UI. The goals of the design of the migration path and the underlying architecture:
- Transform to a maintainable non-legacy application.
- Maximize development speed. The legacy application should be modified only where it is absolutely necessary.
- Separation of duties. There are more teams working on the application. It should be clear that who is responsible for what.
- Possibility to migrate to mobile app. All the new and overhauled functionalities are built with clear separation of the UI and the backend, with the backend having a REST interface.
- Possibility to migrate to distributed data architecture. Some or all of the data is envisioned to reside in a personal device cloud, using technologies like blockchain and torrent.
- Overhaul the UI, to provide similar but slightly different functionality than the legacy. This is done by the legacy development team. They also provide data interface for new functionalities. (green)
- Develop new functionalities. (blue)
The legacy application.
- Controller
-
Controller is a Component.
Appears in:
as the MVC model describes
connections:
- Controller provides API exposure
- Controller is contained by Legacy application
- Model
-
Model is a Component.
Appears in:
As the MVC model says. It is conceptually broken down to data access (just access to the data, no business rules, no provisions for data consistency), and business implementation (business rules and logic).
connections:
- Model provides API exposure
- Model uses SQL
- Model contains Data access
- Model contains Business implementation
- Model is contained by Legacy application
- Legacy application
-
Legacy application is a Component.
Appears in: Migration.
The legacy application. Written in php.
connections:
- Legacy application provides API exposure
- Legacy application contains Model
- Legacy application contains Controller
- Legacy application contains View
- View
-
View is a Component.
Appears in:
As the MVC model describes. It generates dynamic html. Ancient greek technology.
connections:
- View provides Web interface
- View is contained by Legacy application
- Web interface
-
Web interface is an Interface.
Appears in:
Legacy web interface for the legacy web UI.
connections:
- Web UI
-
Web UI is a Component.
Appears in: Migration.
The legacy web ui uses server generated html pages, and static content. The new web UI components are placed as static content in this.
connections:
- Web UI uses Web interface
- Web UI contains New features ajax Web UI
- Web UI contains UI overhaul
- Business implementation
-
Business implementation is a Component.
Appears in:
The business logic and rules: everything what is model and not data access
connections:
- Business implementation is contained by Model
- Data access
-
Data access is a Component.
Appears in:
A thin layer between the SQL api and the REST data interface. Its purpose is to provide a stable data model abstracting out SQL implementation details. No business logic or rules here. The responsibility for data consistency lies to the consumer. Governing design principle is development speed: expose on the REST API only whatever is asked. Do as few things with the data as possible.
connections:
- Data access provides REST data interface
- Data access is contained by Model
- Legacy database
-
Legacy database is a Component.
Appears in: Migration.
The database containing the legacy data model
connections:
- Legacy database provides SQL
- REST data interface
-
REST data interface is an Interface.
Appears in:
REST/json interface providing access to data for the new logic implementation. Can alsobe used by the UI overhaul logic.
connections:
- REST data interface provided by Data access
- REST data interface used by data access
- REST data interface used by Logic for UI overhaul
- SQL
-
SQL is an Interface.
Appears in:
SQL interface of the legacy database
connections:
- SQL provided by Legacy database
- SQL used by Model
- API exposure
-
API exposure is an Interface.
Appears in:
A REST interface exposing internal APIs of the legacy application. The governing design principle is development speed: Whatever is already implemented in the legacy application can be exposed here.
connections:
- API exposure provided by Legacy application
- API exposure provided by Model
- API exposure provided by Controller
- API exposure used by Logic for UI overhaul
- UI overhaul
-
UI overhaul is a Component.
Appears in:
Those parts of the UI which are rewritten. Ajax based. It contains static HTML pages (no server generated HTML) with JavaScript logic. Uses the REST API of the Logic for the overhaul, and can use the REST API for the new features.
connections:
- UI overhaul uses overhaul REST
- UI overhaul uses new REST
- UI overhaul is contained by Web UI
- Business implementation
-
Business implementation is a Component.
Appears in:
Implementation of busness rules and logic
connections:
- Business implementation uses Event interface
- Business implementation is contained by REST backend
- Controller
-
Controller is a Component.
Appears in:
Responsible for access control and orchestration of business logic.
connections:
- Controller provides new REST
- Controller is contained by REST backend
- Controller is contained by REST backend
- data access
-
Data access is a Component.
Appears in:
Abstracts out the physical data model. Its programmatic API is designed in a way which makes it possible to easily change the data access layer and database to an implementation employing distributed technologies (blockchain, tor, torrent).
connections:
- data access uses REST data interface
- data access uses SQL
- data access is contained by REST backend
- Greenfield database
-
Greenfield database is a Component.
Appears in: Migration.
The database for the new functionalities.
connections:
- Greenfield database provides SQL
- new REST
-
New REST is an Interface.
Appears in:
REST/json interface for new features.
connections:
- new REST provided by Controller
- new REST used by New features ajax Web UI
- new REST used by UI overhaul
- overhaul REST
-
Overhaul REST is an Interface.
Appears in:
REST/json interface for the UI overhaul logic
connections:
- overhaul REST provided by Logic for UI overhaul
- overhaul REST used by UI overhaul
- Logic for UI overhaul
-
Logic for UI overhaul is a Component.
Appears in:
The implementation of NEW business logic needed for the UI overhaul. This provides a rest API for the overhauled UI. Responsible for access control, orchestration of calls to the API exposure/REST data interfaces, and implementation of that business logic which changes due to overhaul of the UI.
connections:
- Logic for UI overhaul provides Event interface
- Logic for UI overhaul provides overhaul REST
- Logic for UI overhaul uses API exposure
- Logic for UI overhaul uses REST data interface
- Logic for UI overhaul is contained by REST backend
- New features ajax Web UI
-
New features ajax Web UI is a Component.
Appears in:
Static html+javascript web ui for the new features. Calls the new REST api.
connections:
- REST backend
-
REST backend is a Component.
Appears in: Migration.
New backend for greenfield components. Written in node.js All code have extensive unit test coverage (use TDD!)
connections:
- REST backend contains data access
- REST backend contains Controller
- REST backend contains Business implementation
- REST backend contains Controller
- REST backend contains Logic for UI overhaul
- SQL
-
SQL is an Interface.
Appears in:
SQl interface of the database
connections:
- SQL provided by Greenfield database
- SQL used by data access
- Event interface
-
Event interface is an Interface.
Appears in:
The interface where new business logic implementation can notify the legacy application about events, so it can consistently integrate them in the UI. An example is: "new vote is available"
connections:
- Event interface provided by Logic for UI overhaul
- Event interface used by Business implementation
