Cached object that can be refreshed automatically when cache is expired.
Make a cache instance with no initial value. In this case, initializing of a cache value is postpone until the first call of method of getting.
final ThinCache<Long> thinCache = new ThinCache<>(10, false, new Supplier<Long>() {
private long i = 0;
@Override
public Long get() {
return ++i;
}
});
thinCache.get(); // => 1L (initialize cache)
thinCache.get(); // => 1L (hit cache)
// 10 seconds spent...
thinCache.get(); // => 2L (expired, refresh cache)
// Get refreshed value even if it dosen't spend 10 seconds
thinCache.forceGet(); // => 3L (force refresh)Or you can make a cache instance with initial cache value;
final ThinCache<Long> thinCache = new ThinCache<>(0L, 10, false, new Supplier<Long>() {
private long i = 0;
@Override
public Long get() {
return ++i;
}
});
thinCache.get(); // => 0L (hit cache, initial value)
thinCache.get(); // => 0L (hit cache)
// 10 seconds spent...
thinCache.get(); // => 1L (expired, refresh cache)
// Get refreshed value even if it dosen't spend 10 seconds
thinCache.forceGet(); // => 2L (force refresh)ThinCache is a cached object that can be refreshed automatically when cache is expired.
It holds the same value until cache is expired, and it refreshes the value by given supplier automatically when cache is expired.
You can control exceptional handling through the constructor argument.
If this boolean value is true, it returns already cached value and suppresses exception when supplier (generator of cache value) raises some exception. Otherwise, it throws exception as it is.
Example:
final ThinCache<Long> notSuppressExceptionCache = new ThinCache<>(10, false, new Supplier<Long>() {
@Override
public Long get() {
// do something
throw new RuntimeException("Exception!");
}
});
notSuppressExceptionCache.get(); // throws exception
final ThinCache<Long> suppressExceptionCache = new ThinCache<>(10, true, new Supplier<Long>() {
@Override
public Long get() {
// do something
throw new RuntimeException("Exception!");
}
});
suppressExceptionCache.get(); // returns old (previous) cache and suppresses exceptionIf cache value hasn't been initialized, it throws exception as it even if the second argument of constructor is true.
This library has two asynchronously methods;
ThinCache#getWithRefreshAheadAsync()ThinCache#forceGetWithRefreshAheadAsync()
These methods delegate and schedules a task to refresh cache to the other thread.
They returns always already cached value; refreshed cache value will be available from the next calling.
This method retrieves always already cached value. And schedules a task to refresh cache when cache is expired.
Example:
final ThinCache<Long> longThinCache = new ThinCache<>(10, false, new Supplier<Long>() {
private long i = 0;
@Override
public Long get() {
return ++i;
}
});
CacheWithScheduledFuture<Long> cacheWithScheduledFuture = longThinCache.getWithRefreshAheadAsync(); // Cache value hasn't been initialized, so initialize cache *synchronously*
cacheWithScheduledFuture.getCached(); // => 1L
cacheWithScheduledFuture = longThinCache.getWithRefreshAheadAsync(); // Hit cache, it doesn't schedule a task to refresh
cacheWithScheduledFuture.getCached(); // => 1L
// 10 seconds spent...
cacheWithScheduledFuture = longThinCache.getWithRefreshAheadAsync(); // Cache expired but fetch old cache. It schedules a task to refresh
cacheWithScheduledFuture.getCached(); // => 1L
final Optional<Future<?>> maybeFuture = cacheWithScheduledFuture.getFuture();
if (maybeFuture.isPresent()) { // If a task is scheduled, `getWithRefreshAheadAsync()` returns Future with cached value
maybeFuture.get().get(); // sync here (you don't have to do this)
}
cacheWithScheduledFuture = longThinCache.getWithRefreshAheadAsync(); // Hit the new cache, it doesn't schedule a task to refresh
cacheWithScheduledFuture.getCached(); // => 2LThis method retrieves always already cached value. And always schedules a task to refresh cache.
Example:
final ThinCache<Long> longThinCache = new ThinCache<>(10, false, new Supplier<Long>() {
private long i = 0;
@Override
public Long get() {
return ++i;
}
});
CacheWithScheduledFuture<Long> cacheWithScheduledFuture = longThinCache.forceGetWithRefreshAheadAsync(); // cache value hasn't been initialized, so initialize cache *synchronously*
cacheWithScheduledFuture.getCached(); // => 1L
cacheWithScheduledFuture = longThinCache.forceGetWithRefreshAheadAsync(); // hit cache, it schedules a task to refresh
cacheWithScheduledFuture.getCached(); // => 1L
Optional<Future<?>> maybeFuture = cacheWithScheduledFuture.getFuture();
if (maybeFuture.isPresent()) { // If a task is scheduled, `forceGetWithRefreshAheadAsync()` returns Future with cached value
maybeFuture.get().get(); // sync here (you don't have to do this)
}
cacheWithScheduledFuture = longThinCache.forceGetWithRefreshAheadAsync(); // hit cache, it schedules a task to refresh
cacheWithScheduledFuture.getCached(); // => 2L
maybeFuture = cacheWithScheduledFuture.getFuture();
if (maybeFuture.isPresent()) { // If a task is scheduled, `forceGetWithRefreshAheadAsync()` returns Future with cached value
maybeFuture.get().get(); // sync here (you don't have to do this)
}
cacheWithScheduledFuture = longThinCache.forceGetWithRefreshAheadAsync(); // hit cache, it schedules a task to refresh
cacheWithScheduledFuture.getCached(); // => 3LIf cache value hasn't been initialized, these methods behaves in the same as synchronous one.
- Java8 or later
moznion (moznion@gmail.com)
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