improve compatible for DBCP

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

@@ -106,6 +106,7 @@ public abstract class DruidAbstractDataSource extends WrapperAdapter implements
     protected volatile String                    password;
     protected volatile String                    jdbcUrl;
     protected volatile String                    driverClass;
+    protected volatile ClassLoader               driverClassLoader;
     protected volatile Properties                connectProperties                         = new Properties();
 
     protected volatile PasswordCallback          passwordCallback;
@@ -944,6 +945,14 @@ public abstract class DruidAbstractDataSource extends WrapperAdapter implements
         this.driverClass = driverClass;
     }
 
+    public ClassLoader getDriverClassLoader() {
+        return driverClassLoader;
+    }
+
+    public void setDriverClassLoader(ClassLoader driverClassLoader) {
+        this.driverClassLoader = driverClassLoader;
+    }
+
     @Override
     public PrintWriter getLogWriter() {
         return logWriter;
@@ -1499,4 +1508,6 @@ public abstract class DruidAbstractDataSource extends WrapperAdapter implements
     // just for code format
     public final static class ActiveConnectionTraceInfoMap extends ConcurrentIdentityHashMap<DruidPooledConnection, ActiveConnectionTraceInfo> {
     }
+
+    public abstract void discardConnection(Connection realConnection);
 }

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

@@ -379,7 +379,7 @@ public class DruidDataSource extends DruidAbstractDataSource implements DruidDat
                 if (MockDriver.class.getName().equals(driverClass)) {
                     driver = MockDriver.instance;
                 } else {
-                    driver = JdbcUtils.createDriver(driverClass);
+                    driver = JdbcUtils.createDriver(driverClassLoader, driverClass);
                 }
             } else {
                 if (this.driverClass == null) {
@@ -699,7 +699,7 @@ public class DruidDataSource extends DruidAbstractDataSource implements DruidDat
      * @param realConnection
      * @throws SQLException
      */
-    private void discardConnection(Connection realConnection) {
+    public void discardConnection(Connection realConnection) {
         JdbcUtils.close(realConnection);
 
         lock.lock();

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

@@ -109,7 +109,13 @@ public class DruidDataSourceFactory implements ObjectFactory {
             }
         }
 
-        return createDataSource(properties);
+        return createDataSourceInternal(properties);
+    }
+    
+    protected DataSource createDataSourceInternal(Properties properties) throws Exception {
+        DruidDataSource dataSource = new DruidDataSource();
+        config(dataSource, properties);
+        return dataSource;
     }
 
     @SuppressWarnings("rawtypes")

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

@@ -165,6 +165,22 @@ public class DruidPooledConnection implements javax.sql.PooledConnection, Connec
     public boolean isDisable() {
         return disable;
     }
+    
+    public void discard() {
+        if (this.disable) {
+            return;
+        }
+
+        DruidConnectionHolder holder = this.holder;
+        if (holder == null) {
+            if (dupCloseLogEnable) {
+                LOG.error("dup close");
+            }
+            return;
+        }
+        
+        holder.getDataSource().discardConnection(holder.getConnection());
+    }
 
     @Override
     public void close() throws SQLException {

src/main/java/com/alibaba/druid/util/JdbcUtils.java

@@ -497,8 +497,24 @@ public final class JdbcUtils {
             return null;
         }
     }
-
+    
     public static Driver createDriver(String driverClassName) throws SQLException {
+        return createDriver(null, driverClassName);
+    }
+
+    public static Driver createDriver(ClassLoader classLoader, String driverClassName) throws SQLException {
+        if (classLoader != null) {
+            try {
+                return (Driver) classLoader.loadClass(driverClassName).newInstance();
+            } catch (IllegalAccessException e) {
+                throw new SQLException(e.getMessage(), e);
+            } catch (InstantiationException e) {
+                throw new SQLException(e.getMessage(), e);
+            } catch (ClassNotFoundException e) {
+                throw new SQLException(e.getMessage(), e);
+            }
+        }
+        
         try {
             return (Driver) Class.forName(driverClassName).newInstance();
         } catch (IllegalAccessException e) {