Refactoring, one of the key agile techniques, is a process of improving and optimizing your code without changing its behavior. This approach is well-suited to deal with the complexity, poor performance, and maintainability issues often encountered in legacy systems.
Consider a legacy system written in an older language such as COBOL. The first step in refactoring would be to break down the huge monolithic code into smaller units. You’d then gradually replace these with modern equivalents, without altering the system’s overall behavior.
For example, let’s say we’re working with a COBOL code where a single subroutine is calculating tax, discount, and final price. Those responsibilities can be separated into multiple methods in a modern language like Java:
PROCEDURE taxDiscountPrice.
Compute tax = price * 0.15.
Compute discount = price * 0.05.
Compute final_price = price - discount + tax.
END-PROCEDURE.
This could be refactored in Java as:
public class Pricing {
public float calculateTax(float price) {
return price * 0.15f;
}
public float calculateDiscount(float price) {
return price * 0.05f;
}
public float calculateFinalPrice(float price, float tax, float discount) {
return price - discount + tax;
}
}
2. Strangler Pattern
Perhaps visualized best by its namesake, the strangler fig tree, the Strangler Pattern involves gradually building a new system around the edges of the old one, and over time, the new system replaces and “strangles” the old one.
This makes the transition smoother and less risky, especially when dealing with large legacy systems integral to business operations. For example, an e-commerce website seeking to replace its legacy order management system could incrementally develop new features while still keeping the old system running. During the transition phase, both old and new systems operate simultaneously, with the new system gradually taking over duties.
| Stage | Legacy System | New System |
|---|---|---|
| Initiation | Manages all order operations | Doesn’t exist |
| During transition | Manages some order operations | Manages newly added order operations |
| Completion | No responsibilities | Manages all order operations |
3. Interface Segregation
Interface Segregation, part of SOLID principles, suggests that clients should not be forced to depend on interfaces they don’t use. This approach can make legacy systems more maintainable and organized by reducing the complexity of unnecessary interdependencies.
For instance, a legacy system might have a single interface that handles customer-related operations. Implementing Interface Segregation, we could separate this monolithic interface into smaller, more manageable units.
interface CustomerService {
void addCustomer(Customer c);
void deleteCustomer(Customer c);
Customer fetchCustomer(int id);
void updateCustomerName(int id, String newName);
void updateCustomerAddress(int id, String newAddress);
//... and so on
}
This can be segregated into:
interface CreateDeleteCustomerService {
void addCustomer(Customer c);
void deleteCustomer(Customer c);
}
interface CustomerQueryService {
Customer fetchCustomer(int id);
}
interface UpdateCustomerService {
void updateCustomerName(int id, String newName);
void updateCustomerAddress(int id, String newAddress);
//... and so on
}
These design approaches, when applied correctly, can improve legacy systems considerably, making them more maintainable, scalable, and ensuring a safer transition towards modern systems. Mastery of such strategies is invaluable for any Certified Scrum Professional for Developers (CSP-D).
Practice Test
True/False: Agile design approaches are not effective in addressing challenges with legacy systems.
- True
- False
Answer: False
Explanation: Agile design approaches are specifically designed to aid in resolving challenges with legacy systems through flexibility, adaptability, and a customer-centric focus.
Multiple Select: What are some common agile design approaches?
- a) Refactoring
- b) Feature Driven Development
- c) Traditional Waterfall Methodology
- d) Continuous Integration
Answer: a) Refactoring, b) Feature Driven Development, d) Continuous Integration
Explanation: Refactoring, Feature Driven Development, and Continuous Integration are agile methods designed to improve system designs incrementally while the traditional Waterfall Methodology is a non-agile, preset plan.
True/False: Continuous Integration reduces the risk of adding new functionality into a legacy system.
- True
- False
Answer: True
Explanation: Continuous Integration enables regular testing and feedback which reduce risks and mitigate issues at an early stage.
Single Select: What is the main objective of refactoring in Agile design approaches?
- a) To add new features
- b) To improve the design of the code
- c) To fix bugs
- d) To remove unnecessary code
Answer: b) To improve the design of the code
Explanation: Refactoring focuses on improving the internal structure of existing code while maintaining its external behavior.
True/False: Feature Driven Development (FDD) involves lengthy planning stages.
- True
- False
Answer: False
Explanation: FDD prioritizes developing small, client-valued features in short iterations.
Multiple Select: What stages are included in Feature Driven Development (FDD)?
- a) Develop an overall model
- b) Build a features list
- c) Plan by feature
- d) Design by feature
Answer: a) Develop an overall model, b) Build a features list, c) Plan by feature, d) Design by feature
Explanation: FDD includes all these stages enabling a comprehensive agile design approach.
True/False: In FDD, features are developed individually without any communication with other features.
- True
- False
Answer: False
Explanation: While features are developed in small, manageable chunks, there is still cross-communication to ensure alignment with the overall model.
Single Select: What is the main advantage of Continuous Integration in handling legacy systems?
- a) It decreases the software development cycle
- b) It provides ongoing feedback and testing
- c) It cost less for software development
- d) It remove bugs instantly
Answer: b) It provides ongoing feedback and testing
Explanation: With Continuous Integration, every change is built, tested, and then added to the main repository providing ongoing feedback and testing.
True/False: Agile approaches do not focus on meeting customer needs.
- True
- False
Answer: False
Explanation: Key principles of Agile emphasize customer satisfaction through continuous delivery of valuable software.
Single Select: What agile design approach encourages cleaning up and improving the design of code?
- a) Refactoring
- b) Waterfall Method
- c) FDD
- d) Continuous Integration
Answer: a) Refactoring
Explanation: Refactoring improves the structure of the code while preserving its function.
True/False: In Agile design, the only approach to handle legacy systems is Refactoring.
- True
- False
Answer: False
Explanation: While Refactoring is one method, Agile design also leverages Feature Driven Development and Continuous Integration to handle legacy systems.
Multiple Select: How do Agile design approaches add value to legacy systems?
- a) Improve quality and maintainability of the code
- b) Enable rapid responses to change
- c) Decrease customer satisfaction
- d) Simplify complex systems
Answer: a) Improve quality and maintainability of the code, b) Enable rapid responses to change, d) Simplify complex systems
Explanation: Agile design techniques enhance code quality, allow quick adaptations to change, and simplify legacy systems but also focus on customer satisfaction rather than decreasing it.
Interview Questions
What is Agile design and why is it crucial for addressing challenges with legacy systems?
Agile design is a philosophy that emphasizes flexibility, interactivity, and a customer-centric approach during software development. It is crucial for addressing challenges with legacy systems as it helps in incrementally improving the system while minimizing disruption to normal operations.
What are the three Agile design approaches that can address typical challenges with legacy systems?
The three Agile design approaches that can address typical challenges with legacy systems include refactoring, evolution, and continuous integration.
Can you explain how refactoring addresses challenges with legacy systems within Agile design?
Refactoring is the process of restructuring existing code without changing its external functionality. It addresses challenges with legacy systems by improving nonfunctional attributes of the software, making it easier to maintain and extend.
How does evolutionary architecture solve problems in legacy systems within Agile context?
Evolutionary architecture promotes the continuous development and adaptation of systems. It allows systems to adapt to changing requirements and technologies over time, thus addressing the problem of obsolescence in legacy systems.
What is continuous integration and how it can be useful for legacy systems in an Agile design approach?
Continuous Integration is a development practice where developers integrate code into a shared repository multiple times a day. It reduces the risks associated with the integration and makes the process of updating legacy systems smoother.
How can an Agile approach aid in identifying and managing technical debt in legacy systems?
Agile approach, with its iterative nature, makes it easier to identify technical debt early, manage it through constant refactoring, and prevent it from accumulating and causing major issues in the long run.
How does Agile design support the scalability of legacy systems?
Agile design approaches like refactoring and continuous integration support scalability by ensuring that the system is flexible enough to support new functionality and broadening user base without jeopardizing performance or stability.
How can Agile design approaches promote user involvement in legacy system amendment?
Agile promotes user involvement through frequent feedback loops and iterative development, enabling the development team to tailor the legacy system accurately to user needs and preferences.
What role does testing play in addressing challenges with legacy systems in Agile design?
In Agile design, testing is a continuous process. It helps in ensuring efficiency and reliability of the legacy system during each iteration, thereby reducing the risk of system failures.
How does Agile design achieve system interoperability in legacy systems?
Agile design achieves system interoperability by evolving the architecture of the legacy system to support the ability to work with other products or systems, without any restriction of access or implementation.
Can you name common challenges with legacy systems that Agile design can solve?
Agile design can solve several common challenges with legacy systems including limited scalability, obsolescence, technical debt, interoperability issues, and lack of user involvement.
How important is collaboration and communication in the Agile design approach when addressing legacy system challenges?
In Agile design, collaboration and communication are of utmost importance, ensuring the development team, users, and stakeholders are on the same page, accelerating problem-solving and strengthening the efficiency of addressing legacy system challenges.
How does Agile Design support the integration of new technologies into legacy systems?
Agile Design supports the integration of new technologies into legacy systems via incremental and iterative changes, helping organizations stay up-to-date with technology advancements while reducing the impact on their existing system.
How can Agile design approaches assist in maintaining the reliability and stability of legacy systems?
Agile design approaches help maintain the reliability and stability of legacy systems through continuous integration, thorough ongoing testing, and gradual refactoring.
Can you explain how Agile design approaches can help in improving the performance of legacy systems?
Agile design approaches, through continuous optimization and refactoring, can help in improving the performance of legacy systems, and make them more efficient, robust, and responsive.
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