Adds a method to get datastore map

[haroon-sheikh]

No description provided.

[zabil]

The DataStore deliberately avoided returning a Map to hide the internal storage implementation. Exposing this would make changing the implementation of the DataStore harder in the future.

Is there a good reason why the getMap methods needs to be public?

[haroon-sheikh]

I was just looking to get a list of entries. I can change these to return an entrySet instead?

[haroon-sheikh]

I've now updated to return entrySet only which we also did previously in the old DataStore.

[zabil]

Ah Ok.

From https://docs.oracle.com/javase/8/docs/api/java/util/HashMap.html#entrySet--

public Set<Map.Entry<K,V>> entrySet()
Returns a Set view of the mappings contained in this map. 
The set is backed by the map, so changes to the map are reflected in the set, 
and vice-versa. If the map is modified while an iteration over the set is in progress
 (except through the iterator's own remove operation, or through the setValue 
operation on a map entry returned by the iterator) the results of the iteration are 
undefined. The set supports element removal, which removes the corresponding
 mapping from the map, via the Iterator.remove, Set.remove, removeAll, retainAll 
and clear operations. It does not support the add or addAll operations.

The new DataStore was introduced to prevent modification of the map.
To get over this it's better to return an immutable Map
https://docs.oracle.com/javase/9/core/creating-immutable-lists-sets-and-maps.htm#JSCOR-GUID-4F3E2B7D-CE90-4862-A78A-414FC08DA6E4

You can call that method items

[haroon-sheikh]

I've now updated to return a immutable Map.

[zabil]

Thanks for making the changes @haroon-sheikh thought a bit more about this and the problem with returning the full map will create two ways of accessing the store values i.e.

ScenarioDataStore.get('key');
ScenarioDataStore.items().get('key');

Which may be redundant.
As the idea is to iterate or go through the values in the store can be try something like this instead?

         public static synchronized Set<Object> items() {
            return Collections.unmodifiableSet(map.get().keySet());
         }

The here is a re-implementation of the DataStore to show the usage

package com.company;

import java.util.Collections;
import java.util.Set;
import java.util.concurrent.ConcurrentHashMap;

public class Main {
     static class ScenarioDataStore {
        private static ThreadLocal<ConcurrentHashMap<Object, Object>> map = ThreadLocal.withInitial(ConcurrentHashMap::new);

        public static synchronized void put(Object key, Object value) {
            if (key != null && value != null)  {
                map.get().put(key, value);
            }
        }

        public static synchronized Object remove(Object key) {
            if (key != null) {
                return map.get().remove(key);
            }
            return null;
        }

        public static synchronized Object get(Object key) {
            if (key != null) {
                return map.get().get(key);
            }
            return null;
        }

         public static synchronized Set<Object> items() {
            return Collections.unmodifiableSet(map.get().keySet());
         }

        static synchronized void clear() {
            map.get().clear();
        }
     }

    public static void main(String[] args) {
       ScenarioDataStore.put("1", "one");
       ScenarioDataStore.put("2", "two");
       ScenarioDataStore.put("3", "three");
       ScenarioDataStore.items().forEach((k) -> System.out.println(ScenarioDataStore.get(k)));
    }
}

This way there is only one way to access or add items to the store. Hope this makes sense.

[haroon-sheikh]

Thanks for the feedback @zabil. I've now made the suggested changes.

[zabil]

Marked this for release. Can you bump up the version? You can refer dce766b on how to do that.