I don’t actually think that DI/IoC are that uncommon in Python. What is uncommon, however, are DI/IoC frameworks/containers. Think about it: what does a DI container do? It allows you to wire together independent components into a complete application … … at runtime. We have names for “wiring together” and “at runtime”: scripting dynamic So, … Read more
Both @Autowired (or @Inject) and @Resource work equally well. But there is a conceptual difference or a difference in the meaning @Resource means get me a known resource by name. The name is extracted from the name of the annotated setter or field, or it is taken from the name-Parameter. @Inject or @Autowired try to … Read more
NOTE: This answer talks about the Entity Framework’s DbContext, but it is applicable to any sort of Unit of Work implementation, such as LINQ to SQL’s DataContext, and NHibernate’s ISession. Let start by echoing Ian: Having a single DbContext for the whole application is a Bad Idea. The only situation where this makes sense is … Read more
Import it from the file where it is declared directly instead of the barrel. I don’t know what exactly causes the issue but I saw it mentioned several times (probably some kind of circular dependency). It should also be fixable by changing the order of the exports in the barrel (don’t know details, but was … Read more
The IServiceCollection interface is used for building a dependency injection container. After it’s fully built, it gets composed to an IServiceProvider instance which you can use to resolve services. You can inject an IServiceProvider into any class. The IApplicationBuilder and HttpContext classes can provide the service provider as well, via their ApplicationServices or RequestServices properties … Read more
When using a factory your code is still actually responsible for creating objects. By DI you outsource that responsibility to another class or a framework, which is separate from your code.
Wow, can’t believe that Joel would favor this: var svc = new ShippingService(new ProductLocator(), new PricingService(), new InventoryService(), new TrackingRepository(new ConfigProvider()), new Logger(new EmailLogger(new ConfigProvider()))); over this: var svc = IoC.Resolve<IShippingService>(); Many folks don’t realize that your dependencies chain can become nested, and it quickly becomes unwieldy to wire them up manually. Even with factories, … Read more
First, I want to explain an assumption that I make for this answer. It is not always true, but quite often: Interfaces are adjectives; classes are nouns. (Actually, there are interfaces that are nouns as well, but I want to generalize here.) So, e.g. an interface may be something such as IDisposable, IEnumerable or IPrintable. … Read more
The Inversion-of-Control (IoC) pattern, is about providing any kind of callback (which “implements” and/or controls reaction), instead of acting ourselves directly (in other words, inversion and/or redirecting control to the external handler/controller). For example, rather than having the application call the implementations provided by a library (also known as toolkit), a framework calls the implementations provided by the application. The Dependency-Injection (DI) pattern is a … Read more
Assuming here you’re referring to the javax.inject.Inject annotation. @Inject is part of the Java CDI (Contexts and Dependency Injection) standard introduced in Java EE 6 (JSR-299), read more. Spring has chosen to support using the @Inject annotation synonymously with their own @Autowired annotation. So, to answer your question, @Autowired is Spring’s own annotation. @Inject is … Read more