การอนุญาตด้วยคำสั่งกำกับและบริบท

Welcome! In this lesson, we'll dive into authorization, a critical aspect of API security. Authorization determines what an authenticated user is allowed to do or access.

• Authentication: Verifies who you are (e.g., username/password).
• Authorization: Verifies what you can do (e.g., access admin data).

Without proper authorization, even authenticated users might access sensitive data or perform actions they shouldn't.

GraphQL's flexible nature presents unique authorization challenges compared to traditional REST APIs:

• Field-level access: Clients can request specific fields. You might need to restrict access to individual fields within a type.
• Nested data: Complex queries can fetch deeply nested data. Authorization checks need to apply throughout the query tree.
• Dynamic roles: User roles and permissions can vary, requiring dynamic checks.

We need robust mechanisms to enforce these rules effectively.

GraphQL directives are powerful features that allow you to extend the schema with custom logic. They are denoted by an @ symbol, like @deprecated or @skip.

Think of them as annotations for your schema. They can be attached to fields, types, arguments, and more, allowing you to add metadata or alter the execution behavior of your GraphQL API.

We can define our own custom directives for authorization. A common example is an @hasRole directive. This directive would allow you to specify required roles directly in your schema.

Here's how you might define it in your Schema Definition Language (SDL):

This declares a directive named hasRole that takes a mandatory role argument (a String) and can only be applied to a FIELD_DEFINITION.

To make a custom directive functional in Spring Boot, you need to 'wire' it. This involves implementing the SchemaDirectiveWiring interface from graphql-java.

This wiring class intercepts the schema parsing process and allows you to modify how fields or types behave when your directive is encountered. It's where you'll inject your authorization logic.

Inside your SchemaDirectiveWiring implementation, you'll override methods like onField. When the GraphQL engine processes a field with your @hasRole directive, this method is called.

Within onField, you can:

• Extract the required role from the directive's arguments.
• Get the current user's roles from the GraphQL Context.
• Compare the roles and, if unauthorized, throw an exception or return null.

The GraphQL Context is a crucial object that accompanies every GraphQL request. It's like a backpack for your request, carrying request-scoped data that resolvers and directive wirings can access.

For authorization, the context is where you'll typically store information about the currently authenticated user, such as their ID, username, and crucially, their roles or permissions.

Here's a minimal Spring Boot app demonstrating how to inject user roles into the GraphQLContext. This context can then be accessed by your resolvers and directive wirings.

Try running this and querying myRoles to see the injected roles.

Once your @hasRole directive is defined and wired up, you can apply it directly to your schema fields. This makes authorization rules declarative and easy to see.

For example, to restrict a field called adminDashboard to users with the ADMIN role:

Now, any attempt to query adminDashboard will trigger your directive's logic, which checks the user's roles from the context.

Let's put it all together. When a client queries a field like adminDashboard:

1. The Spring Boot GraphQL runtime receives the request.
2. The GraphQLContextBuilder populates the GraphQLContext with the authenticated user's details, including roles (as shown in the runnable example).
3. The @hasRole directive wiring intercepts the adminDashboard field.
4. Inside the directive's logic, it retrieves the required role ("ADMIN") from the directive arguments and the user's roles from the GraphQLContext.
5. If the user has the required role, the query proceeds to the field's data resolver. Otherwise, an authorization error is returned.

You've learned how to implement robust authorization in GraphQL with Spring Boot!

• Authorization controls what an authenticated user can access.
• GraphQL Directives extend schema behavior, allowing declarative authorization rules like @hasRole.
• The GraphQL Context is essential for carrying dynamic, request-scoped user information (like roles) to enable these authorization checks.

By combining directives and context, you can build secure and flexible GraphQL APIs.