谷歌的Guava库提供了CacheBuilder,允许创建带有过期键的ConcurrentHash,这样可以在固定超时后将条目删除。然而,我只需要缓存某种类型的单个实例。
使用Google Guava,缓存单个对象的最佳方法是什么?
我会使用Guava的Suppliers.memoizeWithExpiration(Supplier delegate, long duration, TimeUnit unit)。
public class JdkVersionService {
@Inject
private JdkVersionWebService jdkVersionWebService;
// No need to check too often. Once a year will be good :)
private final Supplier<JdkVersion> latestJdkVersionCache
= Suppliers.memoizeWithExpiration(jdkVersionSupplier(), 365, TimeUnit.DAYS);
public JdkVersion getLatestJdkVersion() {
return latestJdkVersionCache.get();
}
private Supplier<JdkVersion> jdkVersionSupplier() {
return new Supplier<JdkVersion>() {
public JdkVersion get() {
return jdkVersionWebService.checkLatestJdkVersion();
}
};
}
}
今天,我会使用JDK 8的方法引用和构造函数注入来编写更简洁的代码:
import java.util.concurrent.TimeUnit;
import java.util.function.Supplier;
import javax.inject.Inject;
import org.springframework.stereotype.Service;
import com.google.common.base.Suppliers;
@Service
public class JdkVersionService {
private final Supplier<JdkVersion> latestJdkVersionCache;
@Inject
public JdkVersionService(JdkVersionWebService jdkVersionWebService) {
this.latestJdkVersionCache = Suppliers.memoizeWithExpiration(
jdkVersionWebService::checkLatestJdkVersion,
365, TimeUnit.DAYS
);
}
public JdkVersion getLatestJdkVersion() {
return latestJdkVersionCache.get();
}
}