####问题本质
对于数据源ComboPooledDataSource来说，调用close方法之后，就不能再继续getConnection了  因为数据源已经关闭，不能再继续使用,
####例子

```java
import java.lang.reflect.InvocationTargetException;
import java.sql.Connection;
import java.sql.SQLException;
 
import com.mchange.v2.c3p0.ComboPooledDataSource;
 
 
public class Main {
	private static ComboPooledDataSource ds = null;
	
	static{
		ds = new ComboPooledDataSource();
	}
	//关掉数据源
	public static void closeDataSource() throws Exception{
			ds.getClass().getMethod("close").invoke(ds);
 
	}
	//得到connection
	public static Connection getConnection() throws Exception {
			return ds.getConnection();
	}
	//关闭connection
	public static void closeConn(Connection con) throws SQLException{
			con.close();
	}
	
	public static void main(String[] args) throws Exception {
		Connection conn = getConnection();
		System.out.println(conn);
		closeConn(conn);
		
		closeDataSource();
		
		Connection conn2 = getConnection();//此处报错  [numThreadsAwaitingCheckoutDefaultUser] ] has been closed() -- you can no longer use it.
		System.out.println(conn2);
		closeConn(conn2);
		
	}
}
```
输入结果
```
com.mchange.v2.c3p0.impl.NewProxyConnection@1953895
Exception in thread "main" java.sql.SQLException: com.mchange.v2.c3p0.ComboPooledDataSource [ java.beans.IntrospectionException: java.lang.reflect.InvocationTargetException [numThreadsAwaitingCheckoutDefaultUser] ] has been closed() -- you can no longer use it.
at com.mchange.v2.c3p0.impl.AbstractPoolBackedDataSource.assertCpds(AbstractPoolBackedDataSource.java:495)
at com.mchange.v2.c3p0.impl.AbstractPoolBackedDataSource.getPoolManager(AbstractPoolBackedDataSource.java:507)
at com.mchange.v2.c3p0.impl.AbstractPoolBackedDataSource.getConnection(AbstractPoolBackedDataSource.java:128)
at Main.getConnection(Main.java:21)
at Main.main(Main.java:35)
```

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