Why COLA 3.0 Strips Away Complexity: An Ockham’s Razor‑Driven Refactor

Background

COLA is an application‑architecture framework for Java services that aggregates concepts from onion architecture, adapters, DDD, clean architecture and TMF. It is adopted as one of Alibaba Cloud’s Java initialization options.

Motivation for COLA 3.0

In practice the original design introduced unnecessary abstractions that made the code harder to read and maintain. The upgrade follows the principle of Ockham’s razor: remove superfluous concepts without adding new features.

Ockham’s Razor Principle

The simplest solution that works is preferred; design elements that add cognitive overhead without clear benefit should be eliminated.

Typical Over‑design Patterns

Complex pipeline designs that split a business operation into many tiny steps, obscuring the overall flow.

Command‑Bus patterns borrowed from CQRS that force commands and queries into separate executors, increasing indirection.

Convertor, Validator, and Assembler layers that duplicate naming conventions and add little functional value.

Refactor Steps

1. Remove Command

The CommandBus is eliminated and service methods are invoked directly, preserving extension points while simplifying the call chain.

public class CreateCSPUExecutor {
    @Resource private InitContextStep initContextStep;
    @Resource private CheckRequiredParamStep checkRequiredParamStep;
    // ... other steps omitted for brevity ...
    public Long create(MyCspuSaveParam param){
        SaveCSPUContext ctx = initContextStep.initContext(param);
        checkRequiredParamStep.check(ctx);
        // other checks ...
        createCSPUStep.create(ctx);
        createCSPULogStep.log(ctx);
        sendCSPUCreatedEventStep.sendEvent(ctx);
        return ctx.getCspu().getId();
    }
}

2. Remove Interceptor

Interceptors were added to the CommandBus for AOP‑style processing. Since Spring’s native AOP already satisfies most needs, the interceptor layer is removed to reduce indirection.

3. Remove Convertor, Validator, Assembler

These layers were intended only to standardise naming and provided little functional benefit. They are removed, allowing each team to define its own naming conventions.

4. Optimize Class Scanning

The original TMF‑based class‑scanning duplicated Spring’s capabilities. The refactor switches to Spring’s ListableBeanFactory.getBeansWithAnnotation to discover @Extension beans, simplifying the implementation.

String[] beanNames = beanFactory.getBeanNamesForAnnotation(Extension.class);
for (String name : beanNames) {
    Object bean = beanFactory.getBean(name);
    // register extension point
}

Result

After simplification COLA retains its core extension‑point model while shedding most heavyweight infrastructure. CQRS becomes optional rather than mandatory, and the framework now follows a minimal “Ockham‑compliant” approach that improves readability, reduces maintenance cost, and remains suitable for large‑scale Alibaba Cloud Java applications.

References

COLA open‑source repository: https://github.com/alibaba/COLA