如何可靠的对接微信、支付宝条码支付

public order scanPay()throws PayException{
     try{
          beginTransaction
          order = createOrder
          result = wechat.scanPay
          order.makeSuccess
          commit
     }
     catch(Exception e){
          rollback
          throw new PayException("pay fail")
     }     
     return order
}

public order scanPay()throws PayException{
     try{
          beginTransaction
          order = createOrder
          order.makePaying
          commit
     }
     catch(Exception e){
          rollback
          throw new PayException("pay fail")
     }     
     try{
          result = wechat.scanPay
          if (result == fail) {
               .....
          }
          .......
     }
     catch(Exception e){
          order.makeFail
          throw new PayException("pay fail")
     }
     try{
          beginTransaction
          order.makePaySuccess
          commit
     }
     catch(Exception e){
          rollback
          throw new PayException("pay fail")
     }
     return order
} 

//创建订单，然后返回给调用者
public order createOrder(){
     order = createOrder
     return order
}
 
//调用者发起支付请求，由于异步操作，不会返回任何结果
public void reqeustScanPay(orderId,amount,code){
     mqclient.sendMessage(order);
}
 
//调用者轮询支付结果
public void checkOrder(orderId,firstQueryTime) throws PayException{
     currentTime = System.currentTime
     if (currentTime > firstQueryTime + 2min) {
          //轮询2分钟还没有获得结果，终止轮询，订单等待支付服务自动处理
     }
     order = getOrderbyId(orderId)
     if (order == null) {
          throw new PayException("order not exist")
     }
     if (order.isPaying) {
          //如果是支付中结束本次查询
     }
     else if (order.isPaySuccess) {
          //支付成功....
          //终止轮询
     }
     else if (order.isPayFail) {
          //支付失败....
          //终止轮询
     }
}

//当接收到请求扫码支付时调用。扫码返回结果可能有多种，需要一一判断，根据不同条件来决定继续查询或者是撤销支付或支付成功、失败
public void processScanPay(message){
     try{
          result = wechat.scanPay
          if (result == userpaying) {
               send query memsage into MQ 延迟3s接收消息
               delete message
               return
          }
          else if (result == error){
               send cancel message into MQ
               delete message
               return
          }
          else if (result == duplicate pay){
               send paySuccess message into MQ
               delete message
               return
          }
          else if (result == paySuccess){
               send paySuccess message into MQ
               delete message
               return
          }
          //其他情况不举例了，根据实际情况来发送查询或者撤销消息
     }
     catch(Exception e){
          send query memsage into MQ 延迟3s接收消息
          delete message
     }
}
 
//当支付结果不明确或状态为支付中、用户正在输入密码时调用。微信支付有可能不会立刻返回支付结果，例如用户需要输入密码等情况，就需要多次查询才可以获得结果，但是查询也需要有限制，例如2分钟如果超过，就强制撤销支付，这样就不会造成支付单边
public void processQueryPay(message){
     orderId = message.orderId
     firstTime = message.firstTime
     currentTime = time.currentTime
     if (currentTime - firstTime > 2min) {
          send cancel message into MO
          delete message
          return
     }
     result = wechat.query(orderId)
     if (result == userpaying) {
          //用户还在输入密码，或者微信正在跟银行交互
          send query memsage into MQ  延迟3s接收消息
          delete message
          return
     }
     else if (result == paySuccess) {
          //支付成功是最终结果
          send success message into MQ
          delete message
          return
     }
     else if (result == payFail) {
          //支付失败，是最终结果
          send fail message into MQ
          delete message
          return
     }
     else if (result == unknown) {
          //微信系统异常经常遇到，因此对未知结果进行再次查询处理
          send query memsage into MQ  延迟3s接收消息
          delete message
          return
     }
     else if (result == orderNotExist) {
          //为什么订单会不存在，刚才明明发起了支付？原因就是发起支付后，如果timeout，请求有可能没有被微信处理或者根本没有接受到请求
          send cancel message into MO
          delete message
          return
     }
 
     //其他情况不举例了
}
//接收到支付结果时调用
public void processPay(paySuccess){
     if (paySuccess) {
          beginTransaction
               lock order
               order.makePaySuccess
          commit
     }
     else{
          beginTransaction
               lock order
               order.makePayFail
          commit
     }
     delete message
}
 
//撤销支付，直到撤销成功才删除消息，否则有可能出现支付单边
public void processCancel(){
     orderId=message.orderId
     wechat.cancel(orderId)
     delete message
}

//根据订单号进行支付撤销，不管订单是否存在，只要不是关闭或者失败状态，都可以进行撤销
public void cancelOrder(orderId)throws CancelException{
     beginTransaction
     order = db.getOrderId(orderId)
     if (order != null) {
        if (order.isPayFail) {
               throw new CancelException("order is fail");
          }
          else if (order.isClosed) {
               throw new CancelException("order is fail");     
          }
          .......
          order.makeCancel//把钱退回
     }
     makeCancelByOrderId(orderId)
     commit
}