Spring QueryDsl pagination filter by ACL permissions

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06-10-2024

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Spring Querydsl Pagination and Filtering with ACL Permissions

Implementing secure pagination and filtering in your Spring Boot application can be a complex task, especially when considering Access Control List (ACL) permissions. This article delves into the intricacies of combining Querydsl's powerful query capabilities with Spring Security's ACL system for robust data access control.

The Problem:

Imagine a scenario where you need to expose a REST API that allows users to retrieve a paginated list of resources. However, these resources are subject to ACL constraints, meaning users only have access to data they're authorized to view. Implementing this functionality efficiently while maintaining performance is a common challenge.

The Solution:

Spring Querydsl offers a flexible framework for building complex queries using a type-safe, fluent API. Combining this with Spring Security's ACL system enables you to create powerful, secure, and performant pagination solutions.

Scenario:

Let's say you have a Book entity and an API endpoint to fetch a paginated list of books. We need to ensure that only authorized users can access certain books, based on defined permissions.

@Entity
public class Book {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;

    private String title;

    private String author;

    // ... other fields
}

Original Code:

This code snippet demonstrates a naive approach that does not incorporate ACL checks:

@GetMapping("/books")
public Page<Book> getBooks(Pageable pageable) {
    return bookRepository.findAll(pageable);
}

Adding ACL Filtering:

Here's how to integrate ACL checks into your Querydsl-based pagination:

1. Obtain the Current User's Permissions:

   User currentUser = SecurityContextHolder.getContext().getAuthentication().getPrincipal();
   List<Permission> permissions = aclService.getPermissions(currentUser, Book.class);
   

2. Define the Query DSL:

   QBook qBook = QBook.book;
   BooleanBuilder predicate = new BooleanBuilder();
   predicate.and(qBook.id.in(permissions.stream().map(Permission::getObjectId).collect(Collectors.toList())));
   

   Here, we create a Querydsl predicate using a BooleanBuilder to dynamically build the query based on the user's permissions.

3. Paginate with the Filtered Query:

   List<Book> books = queryFactory.selectFrom(qBook)
       .where(predicate)
       .orderBy(qBook.title.asc())
       .limit(pageable.getPageSize())
       .offset(pageable.getOffset())
       .fetch();
   
   return new PageImpl<>(books, pageable, books.size());
   

   Querydsl's fetch() method executes the query, returning a list of Book objects. We then create a PageImpl to provide pagination information.

Additional Considerations:

• Performance: For large datasets, consider using indexes on relevant fields (e.g., id in the Book entity) to optimize query performance.
• ACL Implementation: Choose a suitable ACL implementation for your project. Spring Security offers built-in support for ACLs, but third-party libraries like Spring Data Envers or Apache Shiro can also be used.
• Dynamic Filtering: You can further enhance the solution by dynamically applying additional filters based on user roles or other criteria.

Conclusion:

By integrating Spring Querydsl and Spring Security's ACL system, you can build robust and secure pagination solutions that enforce data access control. This approach ensures that users only see data they are authorized to view, enhancing application security and data integrity.

References:

• Querydsl Documentation
• Spring Security ACL Documentation