improved jndi datasource support.

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

@@ -1788,6 +1788,16 @@ public class DruidDataSource extends DruidAbstractDataSource implements DruidDat
 
     @Override
     public Connection getConnection(String username, String password) throws SQLException {
+        if (this.username == null
+                && this.password == null
+                && username != null
+                && password != null) {
+            this.username = username;
+            this.password = password;
+
+            return getConnection();
+        }
+
         if (!StringUtils.equals(username, this.username)) {
             throw new UnsupportedOperationException("Not supported by DruidDataSource");
         }

src/test/java/com/alibaba/druid/bvt/pool/DruidDataSourceTest_getConnection_2.java

@@ -0,0 +1,39 @@
+package com.alibaba.druid.bvt.pool;
+
+import com.alibaba.druid.pool.DruidDataSource;
+import junit.framework.TestCase;
+import org.junit.Assert;
+
+import java.sql.Connection;
+
+/**
+ * 这个场景测试defaultAutoCommit
+ * 
+ * @author wenshao [szujobs@hotmail.com]
+ */
+public class DruidDataSourceTest_getConnection_2 extends TestCase {
+
+    private DruidDataSource dataSource;
+
+    protected void setUp() throws Exception {
+        dataSource = new DruidDataSource();
+        dataSource.setUrl("jdbc:mock:xxx");
+        dataSource.setTestOnBorrow(false);
+
+    }
+
+    protected void tearDown() throws Exception {
+        dataSource.close();
+    }
+
+    public void test_conn_ok() throws Exception {
+        {
+            Connection conn = dataSource.getConnection("usr1", "pwd1");
+            conn.close();
+        }
+        {
+            Connection conn = dataSource.getConnection("usr1", "pwd1");
+            conn.close();
+        }
+    }
+}