使用异常代替return null

git-svn-id: http://code.alibabatech.com/svn/druid/trunk@636 b9813039-fb51-4c41-a8b9-e21c2acb5095

src/main/java/com/alibaba/druid/pool/DruidDataSource.java

@@ -560,7 +560,7 @@ public class DruidDataSource extends DruidAbstractDataSource implements DruidDat
                 empty.signal(); // send signal to CreateThread create connection
 
                 if (estimate <= 0) {
-                    return null;
+                    throw new GetConnectionTimeoutException();
                 }
 
                 try {
@@ -580,7 +580,7 @@ public class DruidDataSource extends DruidAbstractDataSource implements DruidDat
                         continue;
                     }
 
-                    return null;
+                    throw new GetConnectionTimeoutException();
                 }
             }