Blue-green deployment Classic deployment technique described in the Continuous Delivery book by Jez Humble and David Farley: The idea is to have two identical versions of your production environment, which we’ll call blue and green… Users of the system are routed to the green environment, which is the currently designated production. We want to release … Read more
If there is no diamond, then we have a simple association. If the diamond is left empty, it signifies it is an aggregation. This relation is stronger than a simple association. In this case a Customer aggregates Orders. If the diamond is black, this means it is a composition, which is even stronger than an … Read more
The Decorator Pattern is used for adding additional functionality to an existing object (i.e. already instantiated class at runtime), as opposed to object’s class and/or subclass. It is easy to add functionality to an entire class of objects by subclassing an object’s class, but it is impossible to extend a single object this way. With … Read more
Singletons can implement interfaces and inherit from other classes. Singletons can be lazy loaded. Only when it is actually needed. That’s very handy if the initialisation includes expensive resource loading or database connections. Singletons offer an actual object. Singletons can be extended into a factory. The object management behind the scenes is abstract so it’s … Read more
In an optimistic update the UI behaves as though a change was successfully completed before receiving confirmation from the server that it actually was – it is being optimistic that it will eventually get the confirmation rather than an error. This allows for a more responsive user experience.
Use the Replace Constructor with Builder refactoring. To use this function, click on the constructor’s signature in your code, then right click and select the “Refactor” menu, then click “Replace Constructor with Builder…” to bring up the dialog box to generate the code.
I prefer to create an interface for setting query, loading, and saving. By using dependency injection, I can inject this into each component that requires it. This allows flexibility in terms of replacing the configuration strategy, and gives a common base for everything to work from. I prefer this to a single, global “settings loader” … Read more
…most sites point out that the mediator “adds functionality”… The facade only exposes the existing functionality from a different perspective. The mediator “adds” functionality because it combines different existing functionality to create a new one. Take the following example: You have a logging system. From that logging system, you can either log to a file, … Read more
There are loads of different design patterns used, but there are a few obvious ones: Proxy – used heavily in AOP, and remoting. Singleton – beans defined in spring config files are singletons by default. Template method – used extensively to deal with boilerplate repeated code (such as closing connections cleanly, etc..). For example JdbcTemplate, … Read more
You might want to check the original paper describing it http://www.dre.vanderbilt.edu/~schmidt/PDF/reactor-siemens.pdf The Reactor design pattern handles service requests that are delivered concurrently to an application by one or more clients. Each service in an application may consist of serveral methods and is represented by a separate event handler that is responsible for dispatching service-specific requests. … Read more