Spring Boot事务管理（中）

    /**
     * Support a current transaction; create a new one if none exists.
     * Analogous to the EJB transaction attribute of the same name.
     * <p>This is typically the default setting of a transaction definition,
     * and typically defines a transaction synchronization scope.
     */
    int PROPAGATION_REQUIRED = 0;

    /**
     * Support a current transaction; execute non-transactionally if none exists.
     * Analogous to the EJB transaction attribute of the same name.
     * <p><b>NOTE:</b> For transaction managers with transaction synchronization,
     * {@code PROPAGATION_SUPPORTS} is slightly different from no transaction
     * at all, as it defines a transaction scope that synchronization might apply to.
     * As a consequence, the same resources (a JDBC {@code Connection}, a
     * Hibernate {@code Session}, etc) will be shared for the entire specified
     * scope. Note that the exact behavior depends on the actual synchronization
     * configuration of the transaction manager!
     * <p>In general, use {@code PROPAGATION_SUPPORTS} with care! In particular, do
     * not rely on {@code PROPAGATION_REQUIRED} or {@code PROPAGATION_REQUIRES_NEW}
     * <i>within</i> a {@code PROPAGATION_SUPPORTS} scope (which may lead to
     * synchronization conflicts at runtime). If such nesting is unavoidable, make sure
     * to configure your transaction manager appropriately (typically switching to
     * "synchronization on actual transaction").
     * @see org.springframework.transaction.support.AbstractPlatformTransactionManager#setTransactionSynchronization
     * @see org.springframework.transaction.support.AbstractPlatformTransactionManager#SYNCHRONIZATION_ON_ACTUAL_TRANSACTION
     */
    int PROPAGATION_SUPPORTS = 1;

    /**
     * Support a current transaction; throw an exception if no current transaction
     * exists. Analogous to the EJB transaction attribute of the same name.
     * <p>Note that transaction synchronization within a {@code PROPAGATION_MANDATORY}
     * scope will always be driven by the surrounding transaction.
     */
    int PROPAGATION_MANDATORY = 2;

    /**
     * Create a new transaction, suspending the current transaction if one exists.
     * Analogous to the EJB transaction attribute of the same name.
     * <p><b>NOTE:</b> Actual transaction suspension will not work out-of-the-box
     * on all transaction managers. This in particular applies to
     * {@link org.springframework.transaction.jta.JtaTransactionManager},
     * which requires the {@code javax.transaction.TransactionManager} to be
     * made available it to it (which is server-specific in standard Java EE).
     * <p>A {@code PROPAGATION_REQUIRES_NEW} scope always defines its own
     * transaction synchronizations. Existing synchronizations will be suspended
     * and resumed appropriately.
     * @see org.springframework.transaction.jta.JtaTransactionManager#setTransactionManager
     */
    int PROPAGATION_REQUIRES_NEW = 3;

    /**
     * Do not support a current transaction; rather always execute non-transactionally.
     * Analogous to the EJB transaction attribute of the same name.
     * <p><b>NOTE:</b> Actual transaction suspension will not work out-of-the-box
     * on all transaction managers. This in particular applies to
     * {@link org.springframework.transaction.jta.JtaTransactionManager},
     * which requires the {@code javax.transaction.TransactionManager} to be
     * made available it to it (which is server-specific in standard Java EE).
     * <p>Note that transaction synchronization is <i>not</i> available within a
     * {@code PROPAGATION_NOT_SUPPORTED} scope. Existing synchronizations
     * will be suspended and resumed appropriately.
     * @see org.springframework.transaction.jta.JtaTransactionManager#setTransactionManager
     */
    int PROPAGATION_NOT_SUPPORTED = 4;

    /**
     * Do not support a current transaction; throw an exception if a current transaction
     * exists. Analogous to the EJB transaction attribute of the same name.
     * <p>Note that transaction synchronization is <i>not</i> available within a
     * {@code PROPAGATION_NEVER} scope.
     */
    int PROPAGATION_NEVER = 5;

    /**
     * Execute within a nested transaction if a current transaction exists,
     * behave like {@link #PROPAGATION_REQUIRED} else. There is no analogous
     * feature in EJB.
     * <p><b>NOTE:</b> Actual creation of a nested transaction will only work on
     * specific transaction managers. Out of the box, this only applies to the JDBC
     * {@link org.springframework.jdbc.datasource.DataSourceTransactionManager}
     * when working on a JDBC 3.0 driver. Some JTA providers might support
     * nested transactions as well.
     * @see org.springframework.jdbc.datasource.DataSourceTransactionManager
     */
    int PROPAGATION_NESTED = 6;

public class TransactionalDemo {

    @Transactional(isolation = Isolation.DEFAULT, propagation = Propagation.REQUIRES_NEW)

    public void doSth() {

//        do something

    }

}

    /**
     * Return the transaction timeout.
     * <p>Must return a number of seconds, or {@link #TIMEOUT_DEFAULT}.
     * <p>Only makes sense in combination with {@link #PROPAGATION_REQUIRED}
     * or {@link #PROPAGATION_REQUIRES_NEW}.
     * <p>Note that a transaction manager that does not support timeouts will throw
     * an exception when given any other timeout than {@link #TIMEOUT_DEFAULT}.
     * @return the transaction timeout
     */
    int getTimeout();

//@return {@code true} if the transaction is to be optimized as read-only
boolean isReadOnly();