Recap: Wiring Beans Together

Constructor injection, stereotypes, ambiguous beans and @Bean methods, with where each was.

Wiring beans together comes down to the five ideas below, each listed with the card that covers it.

What the topic established, and which card it was on
The idea	Where
Constructor injection is the default: no half-built objects, every dependency in one place	Constructor Injection: Why It Is Spring's Default
A class's only constructor needs no `@Autowired`	Constructor Injection Example: One Constructor, No @Autowired
The four stereotypes register beans identically; `@Repository` also translates exceptions	@Component, @Service, @Repository and @Controller Compared
Two candidates for one parameter stop startup; `@Primary` sets a default, `@Qualifier` picks one	Ambiguous Beans: Two Implementations of One Interface
A class you cannot annotate becomes a bean through a `@Bean` method	@Bean Methods Example: Registering a Class You Cannot Annotate

Most startup failures in a Spring application are one of these: a missing bean, two candidates for one parameter, or a class nobody told the container about.

Dependency Injection

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