Refactoring C2B Valuation Logic with the Chain of Responsibility Pattern

The article introduces the online C2B recycling business of ZhaiZhai, which provides precise price estimates for 3C digital products as the first step in the valuation workflow.

Early issues included rough code, rapid product changes, complex business logic, and performance bottlenecks, prompting a redesign of the valuation module.

It then explains the Chain of Responsibility pattern, describing its definition, advantages (single responsibility, open‑closed principle) and disadvantages (long chain, slower debugging).

Typical valuation flow is shown as a chain structure where each module has a single responsibility.

Implementation starts with defining an abstract handler interface and concrete handlers, illustrated with Java code examples:

public interface ValuationResponsibilityChainHandle<ChainResponsibilityContext, ChainResponsibilityRequest, ChainResponsibilityResponse> {
    void handle(ChainResponsibilityContext context, ChainResponsibilityRequest request, ChainResponsibilityResponse response);
    void setNextHandler(ValuationResponsibilityChainHandle<ChainResponsibilityContext, ChainResponsibilityRequest, ChainResponsibilityResponse> nextHandle);
    ValuationResponsibilityChainHandle<ChainResponsibilityContext, ChainResponsibilityRequest, ChainResponsibilityResponse> getNextHandler();
}

A sample BlacklistHandler demonstrates how a concrete handler performs blacklist validation and forwards the request.

public class BlacklistHandler extends AbstractValuationChainValuationResponsibilityHandle<ValuationContext, ValuationRequest, BmDealPriceDto> {
    @Autowired
    private ValuationApolloService valuationApolloService;
    @Override
    public void handle(ValuationContext context, ValuationRequest request, BmDealPriceDto bmDealPriceDto) {
        log.info("精准估价-黑名单校验, context={}, bmDealPriceDto={}", context, bmDealPriceDto);
        if (Objects.isNull(request.getUid())) { return; }
        if (!valuationApolloService.getBmValuationBlackList().contains(request.getUid())) { return; }
        context.setSkipNode(true);
        this.invokeNext(context, chainResponsibilityRequest, chainResponsibilityResponse);
    }
    @Override
    public void setNextHandler(ValuationResponsibilityChainHandle<ChainResponsibilityContext, ChainResponsibilityRequest, ChainResponsibilityResponse> nextHandler) {
        this.nextHandler = nextHandler;
    }
}

To support dynamic chain assembly, a Builder class creates a list of handlers based on business scenario keys, and the chain is executed by iterating over the list.

public List<AbstractValuationChainValuationResponsibilityHandle> buildChain(Integer type) {
    List<AbstractValuationChainValuationResponsibilityHandle> chain = Lists.newArrayList();
    switch (type) {
        case BuildChainConstant.SCENE_A:
            buildSceneA(chain);
            break;
        default:
            break;
    }
    return chain;
}

The article also shows how to control flow interruption by adding a skipNode method to handlers, allowing conditional execution based on context.

public interface ValuationResponsibilityChainHandle<ChainResponsibilityContext, ChainResponsibilityRequest, ChainResponsibilityResponse> {
    void handle(ChainResponsibilityContext context, ChainResponsibilityRequest request, ChainResponsibilityResponse response);
    boolean skipNode(ChainResponsibilityContext context, ChainResponsibilityRequest request, ChainResponsibilityResponse response);
}

Finally, it discusses broader applications of the pattern, such as Netty’s inbound/outbound channel handlers, Spring Security, Spring AOP, MyBatis plugins, and Dubbo filters, and provides performance‑related advice (push, split, reduce, pressure‑test, monitor, guard).

The article concludes that using the Chain of Responsibility pattern reduces code complexity, improves robustness, and helps developers handle rapidly evolving business requirements.