Spring isolation levels and propagation behavior

Isolation level

1, dirty reads: refers to a transaction to be able to read another uncommitted transaction data 2:3, repeatable read, read and write, can solve the problem of dirty reading, reading and writing to submit, after reading data, add a user to delete, add data, read data will change (produce phantom read) 4, serialization: solve the phantom reads the questionCopy the code

Propagation behavior

Propagation behavior refers to the invocation problem between methods. In most cases, we think of things as all or nothing at once. For example, if the business is successful, but the finance is not up to standard and is rejected by the finance department, then all transactions need to be rolled back. However, there will also be special scenarios, such as credit card repayment, for repayment processing, but we find that one of the cards is abnormal, then we can not roll back all the executed credit card data, but only the abnormal card. Rolling back all credit cards that have been paid means that people who paid on time are also considered delinquent, which is obviously not reasonable. In other words, when we do each card operation, we want to have an independent transaction to control it, so that each card repayment does not interfere with each other.

mode of transmission meaning note
PROPAGATION_REQUIRED If a transaction exists, the current transaction is supported. Enable if there are no transactions This is Spring’s default propagation behavior
PROPAGATION_SUPPORTS If a transaction exists, the current transaction is supported. If there is no transaction, the execution is non-transactional –
PROPAGATION_MANDATORY If one already exists, the current transaction is supported. If there is no active transaction, an exception is thrown –
PROPAGATION_REQUIRES_NEW Always start a new transaction. If a transaction already exists, suspend the existing transaction In the credit card scenario, we often need this propagation behavior to create a separate transaction for each card
PROPAGATION_NOT_SUPPORTS Always execute nontransactionally and suspend any existing transactions –
PROPAGATION_NEVER Always execute nontransactionally, throwing an exception if there is an active transaction –
PROPAGATION_NESTED Run in a nested transaction if an active transaction exists; If there are no active transactions, follow the TransactionDefinition. The PROPAGATION_REQUIRED attribute executes –

The code example

    @Service
    public class RoleServiceImpl {
        @Transactional(isolation = Isolation.READ_COMMITTED, propagation = Propagation.REQUIRED)
        public int insertRoleList(List<Role> roles){
            for(Role role : roles){
                this.isnertRole(role);//insretRole annotations are invalid}}}Copy the code

The resources

Mybatis technology principle and actual combat