ioc is that we need a new target before we go now we are the objects we need to directly to the spring.
aop is to add new services without modifying the source code based on, such as logging performance testing
di is an object that needs to access a database before we write the code needed to create a connction object to the connection object, and now we just need to get @autowrite connection object, the system is running, spring will go to create this at the right time object, the object does not have to be concerned about a connection is how to create, when created, this completes the control of each object relationships