Take the modification as an example:
First,
1. Write the method in the Dao layer interface
2. Use the Dao.xml file to implement the execution of the sql statement
3. Service layer injection modification method
4. Implement this method in the Service implementation class (this is actually calling the sql method in the second step Dao.xml file)
5. The Controller layer calls and returns the corresponding results to the front page
specific process:
