Multi-Tenancy in Hibernate

What is Multi-Tenancy?

Multi-tenancy is a software architecture pattern that allows a single instance of a software application to serve multiple tenants. A tenant can be a group of users who share a common access with specific privileges to the software instance. Multi-tenancy is commonly used in SaaS (Software as a Service) applications where resources are shared among multiple users while keeping their data isolated.

Why Use Multi-Tenancy?

The major advantages of implementing multi-tenancy include:

• Resource Efficiency: Reduces the overall resource consumption by consolidating tenants on a single platform.
• Cost-Effective: Decreases operational costs as maintenance and upgrades are performed on a single instance.
• Scalability: Easily allows for the addition of new tenants without significant changes to the architecture.
• Customization: Provides options for custom configurations and features for different tenants while maintaining a core system.

Multi-Tenancy Strategies

There are three primary strategies for implementing multi-tenancy:

• Database-per-Tenant: Each tenant has its own database. This offers maximum isolation but may increase operational complexity.
• Schema-per-Tenant: Each tenant has its own schema within a shared database. This offers a balance between isolation and resource sharing.
• Shared Database, Shared Schema: All tenants share the same schema with a tenant identifier in the data. This is the most resource-efficient but may complicate data management and security.

Implementing Multi-Tenancy in Hibernate

Hibernate supports multi-tenancy in various ways, allowing you to implement a multi-tenant application efficiently. In this tutorial, we will focus on the "Shared Database, Shared Schema" strategy using a discriminator column.

To get started, follow these steps:

1. Configure Hibernate to support multi-tenancy.
2. Create a tenant-aware entity.
3. Implement a Tenant Identifier Resolver.

Step 1: Configure Hibernate

You need to set up Hibernate to use multi-tenancy. Here is a basic configuration in your hibernate.cfg.xml file:

<hibernate-configuration>
    <session-factory>
        <property name="hibernate.multiTenancy">DATABASE</property>
        <property name="hibernate.tenant_identifier_resolver_class">com.example.TenantIdentifierResolver</property>
        <property name="hibernate.multi_tenant_connection_provider_class">com.example.MultiTenantConnectionProviderImpl</property>
        
    </session-factory>
</hibernate-configuration>
                

Step 2: Create a Tenant-Aware Entity

Create an entity that includes a tenant identifier. For example:

@Entity
@Table(name = "users")
public class User {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;

    private String name;

    @Column(name = "tenant_id")
    private String tenantId;

    // Getters and Setters
}
                

Step 3: Implement Tenant Identifier Resolver

Implement a resolver to determine the current tenant based on the context. This can be done with the following code:

public class TenantIdentifierResolver implements CurrentTenantIdentifierResolver {
    @Override
    public String resolveCurrentTenantIdentifier() {
        // Logic to determine the current tenant
        return TenantContext.getCurrentTenant();
    }

    @Override
    public boolean validateExistingCurrentSessions() {
        return true;
    }
}
                

Conclusion

Multi-tenancy is a powerful pattern for building scalable and efficient applications. By using Hibernate's built-in support for multi-tenancy, you can simplify the management of tenant data while ensuring data isolation and security. This tutorial provided a basic introduction to implementing multi-tenancy using the shared schema strategy. For more advanced use cases, consider exploring additional Hibernate features and configurations.