事务的传播行为和隔离级别[transaction behavior and isolated level]

This is typically the default setting of a transaction definition.   
      */   
     int PROPAGATION_REQUIRED = 0;   
  
     /**   
      * Support a current transaction, execute non-transactionally if none exists.   
      * Analogous to EJB transaction attribute of the same name.   
      *

Note: For transaction managers with transaction synchronization,   
      * PROPAGATION_SUPPORTS is slightly different from no transaction at all,   
      * as it defines a transaction scopp that synchronization will apply for.   
      * As a consequence, the same resources (JDBC Connection, Hibernate Session, etc)   
      * will be shared for the entire specified scope. Note that this depends on   
      * the actual synchronization configuration of the transaction manager.   
      * @see org.springframework.transaction.support.AbstractPlatformTransactionManager#setTransactionSynchronization   
      */   
     int PROPAGATION_SUPPORTS = 1;   
  
     /**   
      * Support a current transaction, throw an exception if none exists.   
      * Analogous to EJB transaction attribute of the same name.   
      */   
     int PROPAGATION_MANDATORY = 2;   
  
     /**   
      * Create a new transaction, suspend the current transaction if one exists.   
      * Analogous to EJB transaction attribute of the same name.   
      *

Note: Actual transaction suspension will not work on out-of-the-box   
      * on all transaction managers. This in particular applies to JtaTransactionManager,   
      * which requires the javax.transaction.TransactionManager to be   
      * made available it to it (which is server-specific in standard J2EE).   
      * @see org.springframework.transaction.jta.JtaTransactionManager#setTransactionManager   
      */   
     int PROPAGATION_REQUIRES_NEW = 3;   
  
     /**   
      * Execute non-transactionally, suspend the current transaction if one exists.   
      * Analogous to EJB transaction attribute of the same name.   
      *

Note: Actual transaction suspension will not work on out-of-the-box   
      * on all transaction managers. This in particular applies to JtaTransactionManager,   
      * which requires the javax.transaction.TransactionManager to be   
      * made available it to it (which is server-specific in standard J2EE).   
      * @see org.springframework.transaction.jta.JtaTransactionManager#setTransactionManager   
      */   
     int PROPAGATION_NOT_SUPPORTED = 4;   
  
     /**   
      * Execute non-transactionally, throw an exception if a transaction exists.   
      * Analogous to EJB transaction attribute of the same name.   
      */   
     int PROPAGATION_NEVER = 5;   
  
     /**   
      * Execute within a nested transaction if a current transaction exists,   
      * behave like PROPAGATION_REQUIRED else. There is no analogous feature in EJB.   
      *

Note: Actual creation of a nested transaction will only work on specific   
      * transaction managers. Out of the box, this only applies to the JDBC   
      * 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;