修正连接池不能正确被回收的问题

git-svn-id: http://code.alibabatech.com/svn/druid/trunk@537 b9813039-fb51-4c41-a8b9-e21c2acb5095

src/main/java/com/alibaba/druid/proxy/jdbc/DataSourceProxyImpl.java

@@ -58,6 +58,7 @@ public class DataSourceProxyImpl implements DataSourceProxy, DataSourceProxyImpl
     private final AtomicLong            connectionIdSeed  = new AtomicLong(10000);
     private final AtomicLong            statementIdSeed   = new AtomicLong(20000);
     private final AtomicLong            resultSetIdSeed   = new AtomicLong(50000);
+    private final AtomicLong            transactionIdSeed  = new AtomicLong(0);
 
     public DataSourceProxyImpl(Driver rawDriver, DataSourceProxyConfig config){
         super();
@@ -442,4 +443,9 @@ public class DataSourceProxyImpl implements DataSourceProxy, DataSourceProxyImpl
     public long createResultSetId() {
         return resultSetIdSeed.getAndIncrement();
     }
+
+    @Override
+    public long createTransactionId() {
+        return transactionIdSeed.getAndIncrement();
+    }
 }