Consistent initialization of all PostgreSQL repositories using the Strategy Pattern

Oct 13, 2025 by wbrum.org 7 views

Introduction

The current implementation of PostgreSQL repositories in our system lacks consistency in initialization. This inconsistency can lead to potential runtime issues and reduces maintainability. To address this, we need to refactor the repository initialization process to implement the Strategy Pattern via constructor injection. This will ensure that all repositories are initialized consistently with their respective strategies, eliminate null returns from the factory, and improve testability and maintainability.

Description

The current implementation of PostgreSQL repositories (e.g., PSQLCategoryRepository, PSQLCheckoutRepository, etc.) lacks consistency in initialization. Some repositories are not properly initialized with strategies, and the PSQLRepositoryFactory often returns null for certain repositories. This leads to potential runtime issues and reduces maintainability.

To address this, we need to refactor the repository initialization process to implement the Strategy Pattern via constructor injection. This will ensure that all repositories are initialized consistently with their respective strategies, eliminate null returns from the factory, and improve testability and maintainability.

Tasks

1. Update all PostgreSQL repository implementations to accept a `RepositoryStrategy` via their constructors.

The first step is to update all PostgreSQL repository implementations to accept a RepositoryStrategy via their constructors. This will ensure that each repository is initialized with its respective strategy. We can achieve this by modifying the constructors of each repository to accept a RepositoryStrategy object.

public class PSQLCategoryRepository {
    private final RepositoryStrategy strategy;

    public PSQLCategoryRepository(RepositoryStrategy strategy) {
        this.strategy = strategy;
        init(strategy);
    }

    // ...
}

2. Ensure each repository properly calls the `init(strategy)` method during initialization.

Once we have updated the constructors to accept a RepositoryStrategy object, we need to ensure that each repository properly calls the init(strategy) method during initialization. This will ensure that the repository is initialized with its respective strategy.

public class PSQLCategoryRepository {
    private final RepositoryStrategy strategy;

    public PSQLCategoryRepository(RepositoryStrategy strategy) {
        this.strategy = strategy;
        init(strategy);
    }

    private void init(RepositoryStrategy strategy) {
        // Initialize the repository with the given strategy
    }

    // ...
}

3. Refactor the `PSQLRepositoryFactory` to create repository instances with their corresponding strategies, replacing all `null` returns.

The next step is to refactor the PSQLRepositoryFactory to create repository instances with their corresponding strategies, replacing all null returns. We can achieve this by modifying the factory to create repository instances with their respective strategies.

public class PSQLRepositoryFactory {
    public static PSQLCategoryRepository createCategoryRepository() {
        RepositoryStrategy strategy = new DefaultRepositoryStrategy();
        return new PSQLCategoryRepository(strategy);
    }

    // ...
}

4. Verify that all repositories implement their respective interfaces (e.g., `CategoryRepository`, `CheckoutRepository`, etc.).

Once we have updated the repository implementations and the factory, we need to verify that all repositories implement their respective interfaces. This will ensure that the repositories are properly initialized and can be used as intended.

public interface CategoryRepository {
    // ...
}

public class PSQLCategoryRepository implements CategoryRepository {
    // ...
}

5. Update affected tests or test cases to reflect the new initialization approach.

Finally, we need to update affected tests or test cases to reflect the new initialization approach. This will ensure that the tests are properly updated to reflect the changes made to the repository implementations and the factory.

public class PSQLCategoryRepositoryTest {
    @Test
    public void testCreateCategoryRepository() {
        PSQLCategoryRepository repository = PSQLRepositoryFactory.createCategoryRepository();
        // ...
    }

    // ...
}

Expected Outcome

The expected outcome of this refactoring effort is:

Consistent initialization of all PostgreSQL repositories using the Strategy Pattern: All repositories will be initialized consistently with their respective strategies, ensuring that the system is properly configured and can be used as intended.
Elimination of null returns from the PSQLRepositoryFactory: The factory will no longer return null for certain repositories, ensuring that the system is properly configured and can be used as intended.
Improved maintainability, testability, and adherence to clean code principles: The refactoring effort will improve the maintainability, testability, and adherence to clean code principles of the system, ensuring that the system is properly configured and can be used as intended.

Conclusion

Introduction

In our previous article, we discussed the importance of refactoring the repository initialization process to implement the Strategy Pattern via constructor injection. This approach ensures that all repositories are initialized consistently with their respective strategies, eliminates null returns from the factory, and improves testability and maintainability.

In this article, we will address some common questions and concerns related to refactoring the repository initialization process to implement the Strategy Pattern.

Q&A

Q: Why do we need to refactor the repository initialization process?

A: The current implementation of PostgreSQL repositories lacks consistency in initialization. Some repositories are not properly initialized with strategies, and the PSQLRepositoryFactory often returns null for certain repositories. This leads to potential runtime issues and reduces maintainability.

Q: What is the Strategy Pattern, and how does it help in this scenario?

A: The Strategy Pattern is a behavioral design pattern that allows you to define a family of algorithms, encapsulate each one as a separate class, and make them interchangeable. In this scenario, the Strategy Pattern helps us to define a family of repository strategies, encapsulate each one as a separate class, and make them interchangeable.

Q: How do we update the repository implementations to accept a `RepositoryStrategy` via their constructors?

A: We can update the repository implementations to accept a RepositoryStrategy via their constructors by modifying the constructors to accept a RepositoryStrategy object. For example:

public class PSQLCategoryRepository {
    private final RepositoryStrategy strategy;

    public PSQLCategoryRepository(RepositoryStrategy strategy) {
        this.strategy = strategy;
        init(strategy);
    }

    // ...
}

Q: How do we ensure that each repository properly calls the `init(strategy)` method during initialization?

A: We can ensure that each repository properly calls the init(strategy) method during initialization by modifying the repository implementations to call the init(strategy) method during initialization. For example:

public class PSQLCategoryRepository {
    private final RepositoryStrategy strategy;

    public PSQLCategoryRepository(RepositoryStrategy strategy) {
        this.strategy = strategy;
        init(strategy);
    }

    private void init(RepositoryStrategy strategy) {
        // Initialize the repository with the given strategy
    }

    // ...
}

Q: How do we refactor the `PSQLRepositoryFactory` to create repository instances with their corresponding strategies, replacing all `null` returns?

A: We can refactor the PSQLRepositoryFactory to create repository instances with their corresponding strategies, replacing all null returns by modifying the factory to create repository instances with their respective strategies. For example:

public class PSQLRepositoryFactory {
    public static PSQLCategoryRepository createCategoryRepository() {
        RepositoryStrategy strategy = new DefaultRepositoryStrategy();
        return new PSQLCategoryRepository(strategy);
    }

    // ...
}

Q: How do we verify that all repositories implement their respective interfaces?

A: We can verify that all repositories implement their respective interfaces by checking that each repository implements the interface that it is supposed to implement. For example:

public interface CategoryRepository {
    // ...
}

public class PSQLCategoryRepository implements CategoryRepository {
    // ...
}

Q: How do we update affected tests or test cases to reflect the new initialization approach?

A: We can update affected tests or test cases to reflect the new initialization approach by modifying the tests to use the new initialization approach. For example:

public class PSQLCategoryRepositoryTest {
    @Test
    public void testCreateCategoryRepository() {
        PSQLCategoryRepository repository = PSQLRepositoryFactory.createCategoryRepository();
        // ...
    }

    // ...
}

Conclusion

In conclusion, refactoring the repository initialization process to implement the Strategy Pattern via constructor injection is a crucial step in improving the maintainability, testability, and adherence to clean code principles of the system. By following the steps outlined in this article, we can ensure that all repositories are initialized consistently with their respective strategies, eliminate null returns from the factory, and improve the overall quality of the system.

Additional Resources

For more information on refactoring the repository initialization process to implement the Strategy Pattern, please refer to the following resources:

For more information on related topics, please refer to the following articles: