Transaction management in spring (4)
Timeout and read-only properties
Because transactions can acquire locks on rows and tables, long transactions consume resources and have an impact on overall performance.
If a transaction only reads data but does not modify it, the database engine can optimize the transaction.
Timeout transaction property: How long a transaction can stay on before forcing a rollback. This prevents long-running transactions from consuming resources.
Read-only transaction attribute: Indicates that this transaction only reads data but does not update data, which can help the database engine optimize the transaction.
Timeout and read-only properties can be defined in the @Transactional annotation. The timeout property is calculated in seconds.
In transaction notifications, timeout and read-only attributes can be specified in the <tx:method> element.
Property settings in transactions (@Transactional)
| propagation attribute: used to set the propagation behavior of the transaction - Propagation.REQUIRED : default, use the caller's transaction - Propagation.REQUIRES_NEW : start a new transaction
isolation property: used to set the isolation level of the transaction - Isolation.REPEATABLE_READ : Repeatable read, Mysql default isolation level - Isolation.READ_COMMITTED : read has been committed, Oracle 's default isolation level is also a common isolation level
rollbackFor attribute: used to set the rollback when an exception occurs, the value is an array, and the type of exception is placed in it rollbackForClassName property: used to set the rollback when an exception occurs, the value is an array, and the name of the exception is placed in it noRollbackFor attribute: used to set what exception does not roll back, the value is an array, which is the type of exception norollbackForClassName property: used to set no rollback when an exception occurs, the value is an array, and the name of the exception is placed in it
timeout attribute: used to set the timeout time in seconds
readOnly attribute: used to set the current operation is a read-only operation, usually set this attribute to true when querying the database
@Transactional(propagation=Propagation.REQUIRES_NEW , isolation=Isolation.READ_COMMITTED, noRollbackFor={ArithmeticException.class},timeout=3,readOnly=false)
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pointcut expression
| 1. The format of the pointcut expression: execution([visibility] return type [declaration type]. method name (parameter) [exception])
2. Pointcut expression wildcard: *: matches all characters ..: Generally used to match multiple packages, multiple parameters +: Represents a class and its subclasses
3. The pointcut expression supports logical operators: &&, ||, !
4. Pointcut expression keywords: 1) execution: used to match subexpressions. //匹配com.cjm.model包及其子包中所有类中的所有方法，返回类型任意，方法参数任意 @Pointcut("execution(* com.cjm.model..*.*(..))") public void before(){}
2）within：用于匹配连接点所在的Java类或者包。 //匹配Person类中的所有方法 @Pointcut("within(com.cjm.model.Person)") public void before(){}
//匹配com.cjm包及其子包中所有类中的所有方法 @Pointcut("within(com.cjm..*)") public void before(){}
3） this：用于向通知方法中传入代理对象的引用。 @Before("before() && this(proxy)") public void beforeAdvide(JoinPoint point, Object proxy){ //处理逻辑 }
4）target：用于向通知方法中传入目标对象的引用。 @Before("before() && target(target) public void beforeAdvide(JoinPoint point, Object proxy){ //处理逻辑 }
5）args：用于将参数传入到通知方法中。 @Before("before() && args(age,username)") public void beforeAdvide(JoinPoint point, int age, String username){ //处理逻辑 }
6）@within ：用于匹配在类一级使用了参数确定的注解的类，其所有方法都将被匹配。 @Pointcut("@within(com.cjm.annotation.AdviceAnnotation)") － 所有被@AdviceAnnotation标注的类都将匹配 public void before(){}
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