Use Guava CacheBuilder correctly

Question

Could somebody explain me please how to use the Guava CacheBuilder correctly.

Should getFromNetwork() raise an exception or return null, if the data is not reachable? Should I raise the Execution Exception and use guavaCache.get(). I am just not sure what the documentation means with unchecked exceptions?

Do I use the CacheBuilder as is it supposed to be used? I dont use guavaCache.put()? this is done automatically. right?

        guavaCache = CacheBuilder.newBuilder()
            .maximumSize(maxCapacity)
            .expireAfterWrite(1, TimeUnit.HOURS)
            .removalListener(new RemovalListener<Object, Object>() {
                @Override
                public void onRemoval(RemovalNotification<Object, Object> notification) {}
            })
            .build(
                    new CacheLoader<String, byte[]>() {
                        public byte[] load(String key) throws Exception {
                            return getFromNetwork(key);
                        }
                    });

private byte[] get(Object... params) {
    String url = paramsToUri(params).toString();

    byte[] data = null;
    data = guavaCache.get(url); //?
    data = guavaCache.getUnchecked(url); //?
    return data;
}

Andy Turner · Accepted Answer · 2015-12-10T00:09:53.613

I think the Javadoc for load is quite clear:

Returns:
the value associated with key; must not be null
Throws:
Exception - if unable to load the result

If the data is not reachable, you are unable to load the result, so throw an Exception.

Do I use the CacheBuilder as is it supposed to be used? I dont use guavaCache.put()? this is done automatically. right?

Yes, this looks fine to me, although you only need to call one of get or getUnchecked. You definitely don't need to put.

Use Guava CacheBuilder correctly

1 Answers1