JTA使用心得

JTA是一种J2EE分布式事务框架，用于支持多数据源的分布式事务。

1、使用JTA，在应用服务器中配置的数据源必须是XA类型的，否则JTA不生效。

2、各大应用服务器都有JTA的实现。但tomcat不支持。

3、今天遇到了事务在异步情况下的问题。如果事务中的一部分在是在独立的线程中运行，那么。。。。目前还没找到好的办法，不知道是否是无解的。

下面的这些代码片断支持嵌套JTA事务

启动事务：判断事务如果是已经被激活的，就不启动新的事务

public
 
static
 
boolean
 begin() 
throws
 TransactionException {
    UserTransaction ut = TransactionFactory.getUserTransaction();

    if
 (ut != 
null
) {
        try
 {
            if
 (ut.getStatus() == TransactionUtil.STATUS_ACTIVE) {
                Debug.debug("[TransactionUtil.begin] active transaction in place, so no transaction begun"
, module);
                return
 
false
;
            }
            ut.begin();
            //Debug.debug("[TransactionUtil.begin] transaction begun", module);
            return
 
true
;
        } catch
 (NotSupportedException e) {
            //This is Java 1.4 only, but useful for certain debuggins: Throwable t = e.getCause() == null ? e : e.getCause();
            throw
 
new
 TransactionException(
"Not Supported error, could not begin transaction (probably a nesting problem)"
, e);
        } catch
 (SystemException e) {
            //This is Java 1.4 only, but useful for certain debuggins: Throwable t = e.getCause() == null ? e : e.getCause();
            throw
 
new
 TransactionException(
"System error, could not begin transaction"
, e);
        }
    } else
 {
        Debug.debug("[TransactionUtil.begin] no user transaction, so no transaction begun"
, module);
        return
 
false
;
    }

   
 public static boolean begin() throws TransactionException {
        UserTransaction ut = TransactionFactory.getUserTransaction();
        if (ut != null) {
            try {
                if (ut.getStatus() == TransactionUtil.STATUS_ACTIVE) {
                    Debug.debug("[TransactionUtil.begin] active 
transaction in place, so no transaction begun", module);
                    return false;
                }
                ut.begin();
                //Debug.debug("[TransactionUtil.begin] transaction 
begun", module);
                return true;
            } catch (NotSupportedException e) {
                //This is Java 1.4 only, but useful for certain 
debuggins: Throwable t = e.getCause() == null ? e : e.getCause();
                throw new TransactionException("Not Supported error, 
could not begin transaction (probably a nesting problem)", e);
            } catch (SystemException e) {
                //This is Java 1.4 only, but useful for certain 
debuggins: Throwable t = e.getCause() == null ? e : e.getCause();
                throw new TransactionException("System error, could not 
begin transaction", e);
            }
        } else {
            Debug.debug("[TransactionUtil.begin] no user transaction, so
 no transaction begun", module);
            return false;
        }

事务提交：

public
 
static
 
void
 commit(
boolean
 beganTransaction) 
throws
 TransactionException {
        if
 (beganTransaction)
            TransactionUtil.commit();
    }
public
 
static
 
void
 commit() 
throws
 TransactionException {
        UserTransaction ut = TransactionFactory.getUserTransaction();

        if
 (ut != 
null
) {
            try
 {
                int
 status = ut.getStatus();

                if
 (status != STATUS_NO_TRANSACTION) {
                    ut.commit();
                    //Debug.debug("[TransactionUtil.commit] transaction committed", module);
                } else
 {
                    //十分影响性能,因为引擎中
遗留着非常多查询操作进行事务提交的代码
                    //Debug.debug("[TransactionUtil.commit] Not committing transaction, status is STATUS_NO_TRANSACTION", module);
                }
            } catch
 (RollbackException e) {
                //This is Java 1.4 only, but useful for certain debuggins: Throwable t = e.getCause() == null ? e : e.getCause();
                throw
 
new
 TransactionException(
"Roll back error, could not commit transaction, was rolled back instead"
, e);
            } catch
 (HeuristicMixedException e) {
                //This is Java 1.4 only, but useful for certain debuggins: Throwable t = e.getCause() == null ? e : e.getCause();
                throw
 
new
 TransactionException(
"Could not commit transaction, HeuristicMixed exception"
, e);
            } catch
 (HeuristicRollbackException e) {
                //This is Java 1.4 only, but useful for certain debuggins: Throwable t = e.getCause() == null ? e : e.getCause();
                throw
 
new
 TransactionException(
"Could not commit transaction, HeuristicRollback exception"
, e);
            } catch
 (SystemException e) {
                //This is Java 1.4 only, but useful for certain debuggins: Throwable t = e.getCause() == null ? e : e.getCause();
                throw
 
new
 TransactionException(
"System error, could not commit transaction"
, e);
            }
        } else
 {

            Debug.debug("[TransactionUtil.commit] UserTransaction is null, not commiting"
, module);
        }
    }

public
 static void commit(boolean beganTransaction) throws 
TransactionException {
        if (beganTransaction)
            TransactionUtil.commit();
    }
public static void commit() throws TransactionException {
        UserTransaction ut = TransactionFactory.getUserTransaction();
        if (ut != null) {
            try {
                int status = ut.getStatus();
                if (status != STATUS_NO_TRANSACTION) {
                    ut.commit();
                    //Debug.debug("[TransactionUtil.commit] transaction 
committed", module);
                } else {
                    //十分影响性能,因为引擎中遗留着非常多查询操作进行事务提交的代码
                    //Debug.debug("[TransactionUtil.commit] Not 
committing transaction, status is STATUS_NO_TRANSACTION", module);
                }
            } catch (RollbackException e) {
                //This is Java 1.4 only, but useful for certain 
debuggins: Throwable t = e.getCause() == null ? e : e.getCause();
                throw new TransactionException("Roll back error, could 
not commit transaction, was rolled back instead", e);
            } catch (HeuristicMixedException e) {
                //This is Java 1.4 only, but useful for certain 
debuggins: Throwable t = e.getCause() == null ? e : e.getCause();
                throw new TransactionException("Could not commit 
transaction, HeuristicMixed exception", e);
            } catch (HeuristicRollbackException e) {
                //This is Java 1.4 only, but useful for certain 
debuggins: Throwable t = e.getCause() == null ? e : e.getCause();
                throw new TransactionException("Could not commit 
transaction, HeuristicRollback exception", e);
            } catch (SystemException e) {
                //This is Java 1.4 only, but useful for certain 
debuggins: Throwable t = e.getCause() == null ? e : e.getCause();
                throw new TransactionException("System error, could not 
commit transaction", e);
            }
        } else {
            
            Debug.debug("[TransactionUtil.commit] UserTransaction is 
null, not commiting", module);
        }
    }

使用事务：

public
 
void
 changeState(String newState) 
throws
 fException, InvalidState, TransitionNotAllowed {
    Connection conn = null
;
    boolean
 beganTransaction = 
false
;
    try
 {
    beganTransaction = TransactionUtil.begin();
    conn = TransactionUtil.getConnection();
          //一堆数据库操作
         TransactionUtil.commit(beganTransaction);
        } catch
 (DAOException e) {
            TransactionUtil.rollbackbeganTransaction);
        } catch
 (TransactionException e) {
        TransactionUtil.rollbac(beganTransaction);
        } finally
 {
        TransactionUtil.closeConnection(conn);
        }
}