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What happens when a transactional method invokes another transactional method?

What if a method without a transaction invokes a method with a transaction?

Answers to multi-transaction nesting problems

1. In the same class, a non-transactional method calls another method with transaction annotations (such as @ Async,@Transational), and annotated transactions will not take effect.

2. In the same class, one transactional method calls another method with transactional annotations (such as @ Async,@Transational). Only the outer transaction is valid, and the annotated transaction will not take effect.

3. In different classes, one non-transactional method calls another method with transaction annotations (such as @ Async,@Transational), and annotated transactions take effect.

4. In different classes, one method with transaction calls and the other method with transaction annotation (such as @ Async,@Transational). Both methods have transactions.

Code example:

@ Service

Public class PersonServiceImpl implements PersonService {

@ Autowired

PersonDao personDao

@ Override

@ Transactional

Public boolean addPerson (Person person) {

Boolean result = personDao.insertPerson (person) > 0? True: false

Return result

}

@ Override

@ Transactional

Public boolean updatePersonByPhoneNo (Person person) {

Boolean result = personDao.updatePersonByPhoneNo (person) > 0? True: false

AddPerson (person); / / Test whether @ Transactional works in the same class

Return result

}

}

In the above case, to put it bluntly, within an Service, nested calls between transaction methods, regardless of normal methods and transaction methods being called, will not open a new transaction! Which Zhengzhou abortion hospital has a good http://www.gz020zj.com/?

When spring scans the bean, it scans for @ Transactional annotations on the method. If so, spring dynamically generates a class (that is, the proxy class, proxy) for the bean, which inherits the original bean. At this point, when the annotated method is called, it is actually called by the proxy class, which starts the transaction before it is called. However, if the annotated method is called by another method in the same class, then the method is called not through the proxy class, but directly through the original bean, so the transaction will not be started, and what we see is that the @ Transactional annotation is invalid.

Summary: spring uses dynamic proxy mechanism to achieve transaction control, dynamic proxy will eventually call the original object, and the original object will not trigger the proxy when it invokes the method!

Important: you can also implement a transaction by yourself, which is based on the dynamic proxy in AOP.

The nested transaction solution is simple (two):

Separate the two methods into different classes and add comments to the class name

7 propagation attributes of Spring transaction:

REQUIRED (require) default level: create a transaction if there is no transaction

REQUIRES_NEW (requires_new): create a new transaction of your own, regardless of whether the current transaction exists or not, the existing transaction is suspended

NESTED (nested): if a transaction exists, it runs in a nested transaction, and a transaction is created whether the caller or callee does not exist

SUPPORTS (supports): join if there is a transaction, or you can join if it doesn't exist

NOT_SUPPORT (not_support): runs in a non-transactional manner, suspending the current transaction if there is a current transaction

MANDATORY (mandatory): if there is a transaction, it runs in the current transaction, and if there is no transaction, an exception is thrown, that is, the parent method must have a transaction

NEVER (never): the current method cannot be run in a transaction, and an exception is thrown if there is a transaction

Implement in the code:

@ Override

@ Transactional (propagation = Propagation.REQUIRED)

Public void addEmpByRequired (String name) {

Employee employee = new Employee ()

Employee.setDeptId (1)

Employee.setName (name)

Employee.setAddress (Handan)

EmployeeMapper.insertSelective (employee)

DepartmentService.addDept ("jishubu")

Int I = 1max 0

}

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