java - 如何禁用 Guava 缓存？

Question

JavaCachingWithGuava建议关闭缓存的规范方法是设置 maximumSize=0。 但是，我希望下面的测试能够通过:

public class LoadingCacheTest {
    private static final Logger LOG = LoggerFactory.getLogger(LoadingCacheTest.class);

    LoadingCache<String, Long> underTest;

    @Before
    public void setup() throws Exception {
        underTest = CacheBuilder.from("maximumSize=0").newBuilder()
                .recordStats()
                .removalListener(new RemovalListener<String, Long>() {
                    @Override
                    public void onRemoval(RemovalNotification<String, Long> removalNotification) {
                        LOG.info(String.format("%s cached value %s for key %s is evicted.", removalNotification.getCause().name(), removalNotification.getValue(), removalNotification.getKey()));
                    }
                })
                .build(new CacheLoader<String, Long>() {
                    private final AtomicLong al = new AtomicLong(0);
                    @Override
                    public Long load(@NotNull final String key) throws Exception {
                        LOG.info(String.format("Cache miss for key '%s'.", key));
                        return al.incrementAndGet();
                    }
                });
    }

    @Test
    public void testAlwaysCacheMissIfCacheDisabled() throws Exception {
        String key1 = "Key1";
        String key2 = "Key2";
        underTest.get(key1);
        underTest.get(key1);
        underTest.get(key2);
        underTest.get(key2);
        LOG.info(underTest.stats().toString());
        Assert.assertThat(underTest.stats().missCount(), is(equalTo(4L)));
    }
}

也就是说，关闭缓存总是会导致缓存未命中。

不过，测试失败了。我的解释不正确吗？

Answer 1

方法newBuilder构造一个新的 CacheBuilder具有默认设置的实例，忽略对 from 的调用.但是，您想构造一个 CacheBuilder具有特定的最大尺寸。因此，删除对 newBuider 的调用.您应该调用 build得到 CacheBuilder匹配您的规范而不是使用默认设置:

underTest = CacheBuilder.from("maximumSize=0")
                .recordStats()
                .removalListener(new RemovalListener<String, Long>() {
                    @Override
                    public void onRemoval(RemovalNotification<String, Long> removalNotification) {
                        LOG.info(String.format("%s cached value %s for key %s is evicted.", removalNotification.getCause().name(), removalNotification.getValue(), removalNotification.getKey()));
                    }
                })
                .build(new CacheLoader<String, Long>() {
                    private final AtomicLong al = new AtomicLong(0);
                    @Override
                    public Long load(@NotNull final String key) throws Exception {
                        LOG.info(String.format("Cache miss for key '%s'.", key));
                        return al.incrementAndGet();
                    }
                });