我正在寻找从通用框架调用特定接口的替代方法。我将以代码为例。看 问题部分 ，主要包括示例代码，以确保透彻性，并将示例置于真实场景中。

例

假设我们要基于组件列表构建报告。假设我们有两种特定的组件类型：

public interface Component { ... }
public class PDFComponents extends Component { ... }
public class WordComponents extends Component { ... }

每个组件都有一个ReportBuilder实现，例如

public interface ReportBuilder { ... }
public class PDFReportBuilder extends ReportBuilder { ... }
public class WordReportBuilder extends ReportBuilder { ... }

构建特定的报告实现

public interface Report { ... }
public class PDFReport extends ReportBuilder { ... }
public class WordReport extends ReportBuilder { ... }

最后，我们提供了定位组件并生成组件报告的服务。

public class ReportService {
    ReportComponentRepository repo;
    List<ReportBuilder> builders;

    public <T extends Report> T getReport(Class<T> reportType) {
        // Get report components. E.g., this might return List<PDFComponent>
        List<Component> reportComponents = repo.getReportComponents(id);

        // Build report from components using one of the registered builders
        for (ReportBuilder builder : builders) {
            if (builder.buildFor(reportType) {
                return builder.buildReport(report);
            }
        }
    }
}

使用服务的例子

List<PDFReport> reports = new ReportService().getReport(PDFReport.class);

题

现在到问题。如何设计允许其类型安全的通用ReportBuilder接口？

例如，选择界面：

public Report buildReport(List<? extends Component> components);

会在其实现中造成难看：

public class PDFReportBuilder implements ReportBuilder {

    @Override
    public Report buildReport(List<? extends Component> components) {
         PDFReport report;

         for (Component component : components) {
            if (component instanceOf PDFComponent) {
                // assemble report ... 
                report.includeComponent(component);
            }
        }

        return report;
    }
}

当我们真的希望PDFReportBuilder的界面例如

 public Report buildReport(List<PDFComponent> component) { ... }