Package org.infinispan.functional

Interface FunctionalMap.ReadOnlyMap<K,​V>

  • All Superinterfaces:
    java.lang.AutoCloseable, FunctionalMap<K,​V>
    Enclosing interface:
    FunctionalMap<K,​V>
    public static interface FunctionalMap.ReadOnlyMap<K,​V>
extends FunctionalMap<K,​V>
    Exposes read-only operations that can be executed against the functional map. The information that can be read per entry in the functional map is exposed by EntryView.ReadEntryView.

    Read-only operations have the advantage that no locks are acquired for the duration of the operation and so it makes sense to have them a top-level interface dedicated to them.

    Browsing methods that provide a read-only view of the cached data are available via keys() and entries(). Having keys() makes sense since that way keys can be traversed without having to bring values. Having entries() makes sense since it allows traversing both keys, values and any meta parameters associated with them, but this is no extra cost to exposing just values since keys are the main index and hence will always be available. Hence, adding a method to only browse values offers nothing extra to the API.

    Since:
    8.0

    • Method Detail

      • eval

        <R> java.util.concurrent.CompletableFuture<R> eval​(K key,
                                                   java.util.function.Function<EntryView.ReadEntryView<K,​V>,​R> f)
        Evaluate a read-only function on the value associated with the key and return a CompletableFuture with the return type of the function. If the user is not sure if the key is present, EntryView.ReadEntryView.find() can be used to find out for sure. Typically, function implementations would return value or MetaParam information from the cache entry in the functional map.

        By returning CompletableFuture instead of the function's return type directly, the method hints at the possibility that to execute the function might require to go remote to retrieve data in persistent store or another clustered node.

        This method can be used to implement read-only single-key based operations in ConcurrentMap and javax.cache.Cache such as:

        • Map.get(Object)
        • Map.containsKey(Object)
        • javax.cache.Cache#get(Object)
        • javax.cache.Cache#containsKey(Object)

        The function must not mutate neither the key returned through EntryView.ReadEntryView.key() nor the internally stored value provided through EntryView.ReadEntryView.get() or EntryView.ReadEntryView.find().

        Type Parameters:
        R - function return type
        Parameters:
        key - the key associated with the EntryView.ReadEntryView to be passed to the function.
        f - function that takes a EntryView.ReadEntryView associated with the key, and returns a value.
        Returns:
        a CompletableFuture which will be completed with the returned value from the function

      • evalMany

        <R> Traversable<R> evalMany​(java.util.Set<? extends K> keys,
                            java.util.function.Function<EntryView.ReadEntryView<K,​V>,​R> f)
        Evaluate a read-only function on a key and potential value associated in the functional map, for each of the keys in the set passed in, and returns an Traversable to work on each computed function's result.

        The function passed in will be executed for as many keys present in keys collection set. Similar to eval(Object, Function), if the user is not sure whether a particular key is present, EntryView.ReadEntryView.find() can be used to find out for sure.

        This method can be used to implement operations such as javax.cache.Cache#getAll(Set). DESIGN RATIONALE:

        • It makes sense to expose global operation like this instead of forcing users to iterate over the keys to lookup and call get individually since Infinispan can do things more efficiently.

        The function must not mutate neither the key returned through EntryView.ReadEntryView.key() nor the internally stored value provided through EntryView.ReadEntryView.get() or EntryView.ReadEntryView.find().

        Type Parameters:
        R - function return type
        Parameters:
        keys - the keys associated with each of the EntryView.ReadEntryView passed in the function callbacks
        f - function that takes a EntryView.ReadEntryView associated with the key, and returns a value. It'll be invoked once for each key passed in
        Returns:
        a sequential Traversable that can be navigated to retrieve each function return value

      • keys

        Traversable<K> keys()
        Provides a Traversable that allows clients to navigate all cached keys.

        This method can be used to implement operations such as:

        • Map.size()
        • Map.keySet()
        • Map.isEmpty()
        Returns:
        a sequential Traversable to navigate each cached key

      • entries

        Traversable<EntryView.ReadEntryView<K,​V>> entries()
        Provides a Traversable that allows clients to navigate all cached entries.

        This method can be used to implement operations such as:

        • Map.containsValue(Object)
        • Map.values()
        • Map.entrySet()
        • javax.cache.Cache#iterator()
        Returns:
        a sequential Traversable to navigate each cached entry