What It Is

1. Explanation of IoC

Inversion of Control.

Before IoC, when we wanted to use an object, we first had to create it ourselves with new.

With Spring, Spring creates it for us and puts it into the container. We obtain the object directly from the container and use it.

2. Implementation Principle

Factory pattern + reflection + XML parsing.

Scan all XML files, parse them with dom4j, then create Beans and put them into a map in the factory. When we call getBean, the Bean is obtained from that map.

3. Benefits of IoC

Everything is for decoupling.

If A uses B and directly creates B with new, A and B are highly coupled.

After introducing a factory, the factory and B become highly coupled.

After introducing XML parsing, the factory class uses dom4j to parse XML and then uses reflection to create objects.