Round-Trip Web Services Development: When to Use and Avoid
Web services development typically follows two primary methodologies: Top-Down and Bottom-Up. However, in cases of tooling limitations or knowledge gaps, developers sometimes resort to the Round-Trip approach. This hybrid method combines top-down and bottom-up development elements to create web services.
In this article, we’ll explore the steps, benefits, and drawbacks of round-trip web services development to help you decide if and when it’s the right choice.
Understanding the Round-Trip Approach
Steps in Round-Trip Development
- Start with Top-Down Steps (1-3a):
- Define XML Schema (XSD) and use it to produce Data Transfer Objects (DTOs).
- Develop a WSDL document with types referencing the XSD.
- Use tools to generate DTOs from the WSDL.
- Manually Implement POJO/EJB:
- Create a POJO (Plain Old Java Object) or EJB (Enterprise JavaBean) manually.
- Include public methods that correspond to the portType operations defined in the WSDL.
- Switch to Bottom-Up Steps (2-4):
- Use the POJO or EJB to generate a new WSDL and other artifacts needed for deployment and client-side integration.
- Skip client-side WSDL generation from the top-down approach, as the bottom-up WSDL is used.
Advantages of Round-Trip Development
- Circumvents Tooling Issues:
- Allows developers to bypass limitations in web service tools that may not fully support desired implementations, such as EJBs.
- Customizable Workflow:
- Developers can make code changes directly to adjust service behavior without altering the original schema.
- Adaptability:
- Useful in environments where top-down or bottom-up approaches alone are not feasible due to tooling gaps or schema complexities.
Disadvantages of Round-Trip Development
- Complexity:
- Combining steps from two methodologies adds unnecessary complexity to the development process.
- Reusability Issues:
- The final WSDL produced in the bottom-up phase is often less reusable than the original WSDL with imported schema.
- Inconsistent Namespaces:
- Namespace mapping between schema, DTOs, and the final WSDL may become inconsistent, requiring careful management to avoid compatibility issues.
- Java Type Limitations:
- Some Java base types do not map cleanly to schema types, causing additional rework and complications.
Comparison with Other Development Approaches
Aspect | Top-Down | Bottom-Up | Round-Trip |
---|---|---|---|
Starting Point | WSDL and XSD | Java code | Hybrid: WSDL (initially), then code |
Reusability | High | Low | Moderate |
Tooling Dependency | High | Low | High |
Complexity | Moderate | Low | High |
Customization | Schema changes | Code changes | Code and schema changes possible |
When to Use the Round-Trip Approach
The round-trip approach is best suited for scenarios where:
- Tooling Gaps Exist:
- The available tools do not fully support required features, such as EJB implementation.
- Customization Is Necessary:
- Schema adjustments are not viable, and changes must be made directly in the code.
- Short-Term Goals:
- The focus is on quick adaptations rather than creating long-term reusable services.
When to Avoid the Round-Trip Approach
Avoid round-trip development when:
- Reusability Is Crucial:
- If the web service will be consumed by multiple clients or reused in other services, stick to a Top-Down approach.
- Tooling Issues Are Minor:
- Most modern tools handle WSDL and schema management effectively, making round-trip unnecessary.
- Consistency Is Key:
- Namespace mismatches and type incompatibilities can lead to significant maintenance challenges.
Conclusion
The Round-Trip Web Services Development approach is a practical workaround for tooling limitations or knowledge gaps. However, it introduces complexity and may produce less reusable artifacts. It’s best used as a last resort when neither Top-Down nor Bottom-Up development meets project requirements.
Whenever possible, aim for a Top-Down approach for standards-based, reusable services, or a Bottom-Up approach for quick integration of legacy systems. Use Round-Trip sparingly and with caution.
Would you like a detailed example of implementing the round-trip approach with real-world tools? 😊