Interview Focused : What is Autowiring in Spring Framework? In 10 Points.

1. In Spring Framework wiring of beans means configuring a bean along with its dependencies using an xml configuration file.Spring framework provides autowiring to wire beans and we don’t need to provide bean configuration explicitly.
2. Autowiring is disabled in spring framework by default, If autowiring is enabled then spring container will take care of injecting the dependencies.
3. @Autowired annotation is used to perform Dependency Injection in Spring.
4. If @Autowired is applied to
   field: then the dependency is stored in this field
   setter: then the setter in invoked, with the parameter that is determined by the same algorithm like for the field dependency injection
   constructor: then the constructor in invoked with the parameters determined by the same algorithm like for the field dependency injection
5. @Autowired is to spring framework similarly @Inject is used in java , these annotation tell the context to try to set an object into that field.The javax.annotation/javax.inject is supported by spring so you don’t have to have the code dependency on Spring.
6. @Autowired indicates Spring to find a bean of the declared type and wire in that bean,not requiring explicit lookup by bean name. It can sometimes make configuring applications easier if you only have one implementation of your types in a given Spring context.
7. <context:annotation-config /> in the config file is used to ask spring to find all the beans in the java classes which are @Autowired.
8. Bootstrapping time might increase with using Autowiring, as autowiring scanner loads all classes from autowiring search classpath, so, lots of classes are loaded eagerly during Spring initialization.
9. Example of @Autowired
   1. @Autowired
   2. public void setAnimal( Animal animal){
   3. this.animal= animal;
   4. }
10. @Qualifier Annotation
    It is used to avoid conflicts that occur with @Autowired annotation. If we have more than one bean of same type to autowire with @Autowired annotation, to avoid conflict we use @Qualifier annotation with some name. We need to use this annotation with @Autowired annotation. @Autowired annotation uses ““Bean Type”” to resolve dependencies, @Qualifier annotation uses “Bean Name”” to do the same.
    @Qualifier annotation uses “byName” autowiring mode.
11. Pros and Cons
    Pro:
    Lean XML
    Easy debugging , you just go through java code
    Quicker Development
    Cons:
    Framework Dependency
    XML is good for configuration which does not change frequently, concern can be separated using XML.