Fixed MapLoader hangs if loaded value is null. #1170

redisson/src/main/java/org/redisson/RedissonMap.java

@@ -1185,7 +1185,7 @@ public class RedissonMap<K, V> extends RedissonExpirable implements RMap<K, V> {
             public void run() {
                 final V value = options.getLoader().load(key);
                 if (value == null) {
-                    result.trySuccess(value);
+                    unlock(result, lock, threadId, value);
                     return;
                 }
                     

redisson/src/test/java/org/redisson/BaseMapTest.java

@@ -19,6 +19,19 @@ public abstract class BaseMapTest extends BaseTest {
     
     protected abstract <K, V> RMap<K, V> getLoaderTestMap(String name, Map<K, V> map);
 
+    @Test
+    public void testMapLoaderGetMulipleNulls() {
+        Map<String, String> cache = new HashMap<String, String>();
+        cache.put("1", "11");
+        cache.put("2", "22");
+        cache.put("3", "33");
+        
+        RMap<String, String> map = getLoaderTestMap("test", cache);
+        assertThat(map.get("0")).isNull();
+        assertThat(map.get("1")).isEqualTo("11");
+        assertThat(map.get("0")).isNull(); // This line will never return anything and the test will hang
+    }
+    
     @Test
     public void testWriterAddAndGet() {
         Map<String, Integer> store = new HashMap<>();