Briefly, talk about the use of @Transactional in the project

Foreword

More specific parameter introduction, and introduction of @Transactional failure scenarios, please click the link below to learn:

• @Transactional annotation parameters detailed explanation, as well as the use of annotation features (collector's edition)
• @TransactionalThe problem that annotations cause cross-database queries to fail

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Body

I. Classification of exceptions

• Checked exceptions: exceptions other than RuntimeException under Exception;
• Unchecked exceptions: RuntimeException and its subclasses and Errors;

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Second, @Transactional attribute introduction

There are roughly nine key attributes of the @Transactional annotation (as shown in the figure):

Properties	Type	Description
value	String	optional qualifying descriptor specifying the transaction manager to use
propagation	enum: Propagation	Optional transaction propagation behavior settings
isolation	enum: Isolation	Optional transaction isolation level settings
readOnly	boolean	Read-write or read-only transaction, default read-write
timeout	int (in seconds granularity)	Transaction timeout setting
rollbackFor	Array of Class objects, must inherit from Throwable	Array of exception classes that cause transaction rollback
rollbackForClassName	Array of class names, must inherit from Throwable	Array of exception class names that caused the transaction to be rolled back
noRollbackFor	Array of Class objects, must inherit from Throwable	Array of exception classes that will not cause transaction rollback
noRollbackForClassName	Array of class names, must inherit from Throwable	Number of exception class names that do not cause transaction rollback

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Three, @Transactional use

When using the @Transaction annotation, the Alibaba Code Specification plugin will remind you to specify rollbackFor to display the rollback.

By default, the Spring framework only throws runtime exceptions (checked exceptions - checked exceptions) and unchecked exceptions (unchecked exceptions) when using @Transaction to handle transactions by default. the transaction is rolled back.That is, when an instance of RuntimeException or its subclasses is thrown, Checked exceptions thrown from transaction methods will not be flagged for transaction rollback.

• To rollback the checked exception: add @Transactional(rollbackOn=Exception.class)
before the entire method
• Make unchecked exception not rollback: @Transactional(dontRollbackOn=RunTimeException.class)
• Methods that do not require transaction management (query only): @Transactional(propagation=Propagation.NOT_SUPPORTED)

Note:

• If the exception is try-catch, the transaction will not be rolled back. If you want the transaction to be rolled back, you must throw try{}catch{throw Exception}.
• The Spring team's recommendation is to use the @Transactional annotation on concrete classes (or class methods), not on any interfaces that the class implements.You can also use the @Transactional annotation on the interface, but this will only take effect when you need to set an interface-based proxy
• The method identified by the @Transactional annotation, it is recommended that the processing process be as simple as possible.Especially the transaction method with lock, it is best not to put it in the transaction if it can not be placed in the transaction.Regular database query operations can be carried out in front of the transaction, and operations such as addition, deletion, and modification can be placed in the transaction

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Four. Test

If the code in the catch block is not written, the transaction will not be rolled back.Because the transaction is caught by catch, the transaction can only be rolled back manually.

@[email protected] class DemoService {@Autowiredprivate DemoMapper demoMapper;@Transactionalpublic Integer insert(MemberEntity memberEntity) {Integer insertResult = 0;try {insertResult = demoMapper.save(memberEntity);log.info("insertResult:{}", insertResult);int result = 1 / memberEntity.getAge();} catch (Exception e) {log.error("errorMsg:{}", e.getMessage());// catch exception, must roll back manuallyTransactionAspectSupport.currentTransactionStatus().setRollbackOnly();}return insertResult;}}

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