bug fixed for null contextClassLoader

src/test/java/com/alibaba/druid/bvt/bug/Bug_for_wdw1206.java

@@ -0,0 +1,36 @@
+package com.alibaba.druid.bvt.bug;
+
+import java.sql.Connection;
+
+import junit.framework.TestCase;
+
+import com.alibaba.druid.pool.DruidDataSource;
+import com.alibaba.druid.util.JdbcUtils;
+
+public class Bug_for_wdw1206 extends TestCase {
+
+    private ClassLoader     ctxClassLoader;
+    private DruidDataSource dataSource;
+
+    protected void setUp() throws Exception {
+        ctxClassLoader = Thread.currentThread().getContextClassLoader();
+        Thread.currentThread().setContextClassLoader(null);
+
+        dataSource = new DruidDataSource();
+        dataSource.setUrl("jdbc:mock:");
+        dataSource.setPoolPreparedStatements(false);
+        dataSource.setTestOnBorrow(true);
+        dataSource.setFilters("stat");
+    }
+
+    protected void tearDown() throws Exception {
+        Thread.currentThread().setContextClassLoader(ctxClassLoader);
+        
+        JdbcUtils.close(dataSource);
+    }
+
+    public void test_nullCtxClassLoader() throws Exception {
+        Connection conn = dataSource.getConnection();
+        conn.close();
+    }
+}