如何解决参数化类 'ABC'
我有以下界面:
public interface AsynchronousJobRunner<T extends AsynchronousJob> extends Runnable {
public void kill();
public void addJobExecutionListener(JobExecutionListener listener);
public void removeJobExecutionListener(JobExecutionListener listener);
public AsynchronousJobRunner withJob(T job);
}
AsynchronousJob
是一个抽象类,可以扩展为使用以下抽象方法表示其他作业:
public abstract class AsynchronousJob implements JSONSerializable,HasId {...}
/**
* Returns the class of the {@link AsynchronousJobRunner} that runs this type of job.
* @return The appropriate class of the job runner for this class.
*/
public abstract Class<? extends AsynchronousJobRunner> jobRunnerClass();
我还有以下 ExportJob
扩展基类并具有以下签名和方法:
public class ExportJobRunner extends BaseJobRunner<ExportJob> { ...}
@Override
public Class<? extends AsynchronousJobRunner> jobRunnerClass() {
return ExportJobRunner.class;
}
两个 jobRunnerClass()
方法都有 Raw use of parameterized class 'AsynchronousJobRunner'
警告。
使警告消失的简单解决方案是:
public abstract Class<? extends AsynchronousJobRunner<?>> jobRunnerClass();
@Override
public Class<? extends AsynchronousJobRunner<?> jobRunnerClass() {
return ExportJobRunner.class;
}
但是正确的解决方案是什么?为什么/如何?
编辑:
我最终只是将界面的代码更改为:
public interface AsynchronousJobRunner<T extends AsynchronousJob<T>> extends Runnable {
void kill();
void addJobExecutionListener(JobExecutionListener listener);
void removeJobExecutionListener(JobExecutionListener listener);
AsynchronousJobRunner<T> withJob(T job);
}
对 AsynchronousJob
类的更改:
public abstract class AsynchronousJob<T> implements JSONSerializable,HasId { ...
/**
* Returns the class of the {@link AsynchronousJobRunner} that runs this type of job.
* @return The appropriate class of the job runner for this class.
*/
public abstract Class<? extends AsynchronousJobRunner<? extends AsynchronousJob<T>> jobRunnerClass();
}
ExportJob
类:
public public class ExportJob extends AsynchronousJob<ExportJob> {...
@Override
public Class<? extends AsynchronousJobRunner<? extends AsynchronousJob<ExportJob>>> jobRunnerClass() {
return ExportJobRunner.class;
}
}
ExportJobRunner
类保持不变。
我还忘了提到有一些注入魔法正在进行,因为作业被序列化到数据库:
/**
* Instantiates an {@link AsynchronousJobRunner} instance for the provided job.
* <p>
* In order for the creation of the runner to succeed,the {@link AsynchronousJob#jobRunnerClass()}
* method of the job must specify the appropriate class for its runner.
*
* @param job job to create runner for
* @return job runner configured for the specified {@code job} parameter
*/
private <T extends AsynchronousJob<T>> AsynchronousJobRunner<T> createJobRunner(T job) {
return ((AsynchronousJobRunner<T>)injector.getInstance(job.jobRunnerClass())).withJob(job);
}
我接受了@Andrew Vershinin 的回答,因为他让我走上了正确的思路。
解决方法
我认为,您可以使用 AsynchronousJob
的递归声明:
public abstract class AsynchronousJob<T extends AsynchronousJob<T>>
implements JSONSerializable,HasId {
public abstract Class<? extends AsynchronousJobRunner<T>> jobRunnerClass();
//...
}
不要忘记相应地更新 AsynchronousJobRunner
定义:
public interface AsynchronousJobRunner<T extends AsynchronousJob<T>> //...
然后,在您的工作类中,您可以在返回类型中使用类本身:
public class ExportJob extends AsynchronousJob<ExportJob> {
@Override
public Class<? extends AsynchronousJobRunner<ExportJob>> jobRunnerClass() {
return ExportJobRunner.class;
}
}
通过这种方式可以确保类型一致性:T
类型的作业会返回运行此类类型的作业的运行器类型 - 您无法通过在 ? extends AsynchronousJob
签名中使用 jobRunnerClass
来确保这一点,因为你可以返回任何跑步者类型,它会编译。
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