8. What is the difference between inner join and outer join queries?
inner join
Get the intersection of two tables
outer join
Get all the data of a table and the intersection data of two tables
9. The role of transaction management, four major characteristics
effect
Ensure that multiple addition, deletion and modification operations either succeed at the same time or fail at the same time
Four characteristics
1.Atomicity
Transactions are the smallest units of atoms, and they both succeed and fail together.
2. Consistency
Understanding 1: Data changes and is saved consistently. For example, if you deposit 500 in the bank, you will get 500.
Understanding 2: The expected value is consistent with the actual value
3. Isolation
Do not affect multiple transactions
4.Persistence
The operation will eventually be persisted to the database
10. Function and composition of JWT token
Used as a mark for login verification to prevent tampering
3 parts
Header, payload, signature Signature
Header
Algorithms and models
Payload
Store data about users
Signature
Combining the first two parts and a key generation
11. How to implement Spring transaction management
Add @Transactional annotation
Scope that can be added : methods, classes, interfaces
Automatically handle runtime exceptions
If you encounter a compile-time exception and need to roll back, add rollbackFor=Exception class.class
To call transactions to each other, you need to use transaction propagation behavior, add propagation=Propagation enumeration, and use SUPPORTS and NOT_SUPPORT.
12. What is transaction communication behavior?
Transactions call each other and propagate behaviors to each other.
There are two, SUPPORTS and NOT_SUPPORT.
For example, Teacher Xiaofeng invites you to dinner.
13. What is AOP and what is it used for? What are the core concepts
what is
Aspect-oriented programming is a programming method that enhances small aspects and aspects of the code, that is, methods.
effect
Methods can be enhanced, such as monitoring the method's running time to make improvements.
Core idea
JoinPoint
The methods that can be controlled by AOP are all methods
NotifyAdvice
Specific actions to strengthen it
Pointcut
Reinforced, specific methods of operation, sentences matching connection points
Aspect
Correspondence between notifications and entry points
Target objectTarget
Write the notification class