A method for modifying a middleware shared by multiple tenants by preparing a data packet comprising modification information and tenant information, the modification information comprising information of a specific class to be modified in the middleware as well as modification content for the specific class, the tenant information indicating a specific tenant of the plurality of tenants to which the modification content is directed; and in response to acquisition of the data packet: modifying the specific class in the middleware in runtime according to the modification information to create a modified specific class; and applying the modified content only to the specific tenant. When multiple tenants share a same middleware, different versions of the middleware may be provided for respective tenants, without affecting the use by other tenants, thereby satisfying sharing and customization requirements of each of the multiple tenants.