optimize for oracle

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

@@ -108,6 +108,8 @@ public class DruidDataSource extends DruidAbstractDataSource implements DruidDat
 
     private String                  initStackTrace;
 
+    private boolean                 isOracle                = false;
+
     public DruidDataSource(){
     }
 
@@ -286,6 +288,10 @@ public class DruidDataSource extends DruidAbstractDataSource implements DruidDat
 
             this.dbType = JdbcUtils.getDbType(jdbcUrl, driverClass.getClass().getName());
 
+            if ("oracle".equals(this.dbType)) {
+                isOracle = true;
+            }
+
             String realDriverClassName = driver.getClass().getName();
             if (realDriverClassName.equals("com.mysql.jdbc.Driver")) {
                 this.validConnectionChecker = new MySqlValidConnectionChecker();
@@ -1314,6 +1320,10 @@ public class DruidDataSource extends DruidAbstractDataSource implements DruidDat
         }
     }
 
+    public boolean isOracle() {
+        return isOracle;
+    }
+
     @Override
     public String getVersion() {
         return VERSION.MajorVersion + "." + VERSION.MinorVersion + "." + VERSION.RevisionVersion + "-2011-12-27 14:45";