bug fixed for dbType

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

@@ -336,6 +336,10 @@ public class DruidDataSource extends DruidAbstractDataSource implements DruidDat
             this.id = DruidDriver.createDataSourceId();
 
             loadFilterFromSystemProperty();
+            
+            if (this.dbType == null || this.dbType.length() == 0) {
+                this.dbType = JdbcUtils.getDbType(jdbcUrl, null);
+            }
 
             for (Filter filter : filters) {
                 filter.init(this);

src/main/java/com/alibaba/druid/wall/WallFilter.java

@@ -58,6 +58,10 @@ public class WallFilter extends FilterAdapter implements WallFilterMBean {
         if (this.dbType == null || this.dbType.trim().length() == 0) {
             this.dbType = dataSource.getDbType();
         }
+        
+        if (dbType == null) {
+            dbType = JdbcUtils.getDbType(dataSource.getUrl(), null);
+        }
 
         if (JdbcUtils.MYSQL.equals(dbType)) {
             if (config == null) {