1. What is Spring IOC?
The translation of IOC into Chinese is inversion of control . In layman's terms, it means transferring the work of creating objects and managing object relationships from programmers to Spring.
2. What is the purpose?
Reduce coupling between classes.
3. If there is a UserSevice class and a UserDao class now, if you want to call a method of UserDao in the UserSevice class, how to do it?
3.1. Traditional way:
Create a new UserDao object in the UserSevice class, and then call its method.
3.2. Factory mode:
Design a factory class, create a new object in the factory class and return it, UserSecieve only needs to call this method of the factory class.
3.3.IOC (using xml + factory mode + reflection)
write an xml file, configure the information of the class to be created, then design a factory class, parse the class name configured in the xml file in the factory class, and then use the reflection mechanism , create an object with the class name, and return it.
Compare the three methods: the first method has a high degree of coupling, although the second method uses the factory mode, it is actually a new object in the factory class, with a high degree of coupling, and the third method uses the reflection mechanism. The degree of coupling is minimal.
The first one: If the class path of the latter changes, the former needs to modify the code, and the coupling degree is very high. The third way: If you modify the path of the latter class, you only need to change the path information of the configuration file. The degree of coupling is low.
