在固定超时内缓存单个对象的最佳方法是什么？

Question

Google Guava具有CacheBuilder,允许使用过期密钥创建ConcurrentHash,允许在固定tiemout之后删除条目.但是我只需要缓存某种类型的一个实例.

使用Google Guava在固定超时内缓存单个对象的最佳方法是什么？

Answer 1

我将使用Guava的Suppliers.memoizeWithExpiration(供应商代表,持续时间长,TimeUnit单位)

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();
            }
        };
    }
}

使用JDK 8进行更新

今天,我将以不同的方式编写此代码,使用JDK 8方法引用和构造函数注入来获得更清晰的代码:

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();
    }
}