Sample Application to demonstrate Multi-tenancy based on discriminator field using Spring Boot & Hibernate.

Since hibernate (5.x) has some issues (refer the link below) in supporting the 'Discriminator' based multi-tenancy strategy. This following workaround will help to achieve the same.

Approach:

• Uses hibernate filter to limit the query results based on tenant.
• Uses hibernate interceptors to enforce tenant details during creating/updating entities.
• Uses Spring AOP (AspectJ) to set the filter parameters.

Explanation:

• Each request goes thru a custom servlet filter which checks for X-TenantID http header and set's it in the ThreadLocal variable using TenantContext class. If http header is not present in request, it'll be rejected.
• Controller routes the request to Service class and the Spring AOP (UserServiceAspect class) intercepts the service call and set's the hibernate tenant filter.
• All the service method has to be annotated with @Transactional for UserServiceAspect to work.
• Above method works only for read queries, for write queries, we have to use hibernate interceptors.
• Custom Entity interceptor (using EmptyInterceptor) class which sets the tenantId value during the save/delete/flush-dirty entity events.
• Entity class should implement TenantSupport interface for the Entity interceptor to work.

Refer:

• https://hibernate.atlassian.net/browse/HHH-6054
• https://docs.jboss.org/hibernate/orm/5.2/userguide/html_single/Hibernate_User_Guide.html#multitenacy
• https://docs.jboss.org/hibernate/orm/5.2/userguide/html_single/Hibernate_User_Guide.html#mapping-column-filter
• https://docs.jboss.org/hibernate/orm/5.2/userguide/html_single/Hibernate_User_Guide.html#events