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Round-trip

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.

Round-trip

Understanding the Round-Trip Approach

Steps in Round-Trip Development

  1. 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.
  2. 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.
  3. 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

  1. Circumvents Tooling Issues:
    • Allows developers to bypass limitations in web service tools that may not fully support desired implementations, such as EJBs.
  2. Customizable Workflow:
    • Developers can make code changes directly to adjust service behavior without altering the original schema.
  3. 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

  1. Complexity:
    • Combining steps from two methodologies adds unnecessary complexity to the development process.
  2. Reusability Issues:
    • The final WSDL produced in the bottom-up phase is often less reusable than the original WSDL with imported schema.
  3. Inconsistent Namespaces:
    • Namespace mapping between schema, DTOs, and the final WSDL may become inconsistent, requiring careful management to avoid compatibility issues.
  4. Java Type Limitations:
    • Some Java base types do not map cleanly to schema types, causing additional rework and complications.

Comparison with Other Development Approaches

AspectTop-DownBottom-UpRound-Trip
Starting PointWSDL and XSDJava codeHybrid: WSDL (initially), then code
ReusabilityHighLowModerate
Tooling DependencyHighLowHigh
ComplexityModerateLowHigh
CustomizationSchema changesCode changesCode and schema changes possible

When to Use the Round-Trip Approach

The round-trip approach is best suited for scenarios where:

  1. Tooling Gaps Exist:
    • The available tools do not fully support required features, such as EJB implementation.
  2. Customization Is Necessary:
    • Schema adjustments are not viable, and changes must be made directly in the code.
  3. 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:

  1. Reusability Is Crucial:
    • If the web service will be consumed by multiple clients or reused in other services, stick to a Top-Down approach.
  2. Tooling Issues Are Minor:
    • Most modern tools handle WSDL and schema management effectively, making round-trip unnecessary.
  3. 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? 😊

author avatar
Ahmad Gohar
With over 18 years of experience in software architecture, Java technologies, and leadership, I specialize in crafting scalable, future-proof solutions for global organizations. Whether it’s transforming legacy systems, building cutting-edge cloud-native applications, or mentoring teams to excel, I’m committed to delivering value-driven results.

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