java - Guava 缓存 RemovalListener 未调用

Question

我使用以下参数创建了一个缓存:

cacheTempFiles = CacheBuilder.newBuilder().maximumSize(250).expireAfterWrite(15, TimeUnit.SECONDS).removalListener(new RemovalListener<String, Path>()
        {

            @Override
            public void onRemoval(RemovalNotification<String, Path> notification)
            {
                deleteTemporaryFile(notification.getValue());

            }
        }).build();

此外，我每 2 分钟调用一次 cacheTempFiles.cleanUp();。但是，似乎从未调用过onRemoval。

我的实现中缺少什么？

Answer 1

它绝对应该有效，请参见下面的示例:

@Test
public void shouldCallRemovalListener() {
    AtomicInteger counter = new AtomicInteger();
    MutableClock clock = MutableClock.epochUTC();
    Ticker ticker = new Ticker() {
        @Override
        public long read() {
            return TimeUnit.MILLISECONDS.toNanos(clock.millis());
        }
    };
    Path tmpPath = Path.of("/tmp");

    Cache<String, Path> cacheTempFiles = CacheBuilder.newBuilder()
            .ticker(ticker)
            .maximumSize(250)
            .expireAfterWrite(15, TimeUnit.SECONDS)
            .removalListener(
                    (RemovalNotification<String, Path> notification) ->
                            System.out.println(String.format(
                                    "Delete '%s -> %s' (%d times)",
                                    notification.getKey(), notification.getValue(), counter.incrementAndGet())))
            .build();
    cacheTempFiles.put("tmp", tmpPath);

    assertThat(cacheTempFiles.asMap()).containsOnly(Assertions.entry("tmp", tmpPath));
    assertThat(counter).hasValue(0);

    clock.add(Duration.ofSeconds(20));
    cacheTempFiles.cleanUp();

    assertThat(cacheTempFiles.asMap()).isEmpty();
    assertThat(counter).hasValue(1);
}

传递并输出删除'tmp ->/tmp'(1次)。