Support ZRANDMEMBER via RedisZSet.

Add randomValue() method to both RedisZSet and RedisSet.

See: #2049
Original Pull Request: #2104

Author: christophstrobl

src/main/java/org/springframework/data/redis/support/collections/DefaultRedisSet.java

@@ -187,6 +187,15 @@ public RedisSet<E> unionAndStore(Collection<? extends RedisSet<?>> sets, String
 		return new DefaultRedisSet<>(boundSetOps.getOperations().boundSetOps(destKey));
 	}
 
+	/*
+	 * (non-Javadoc)
+	 * @see org.springframework.data.redis.support.collections.RedisSet#randomElement()
+	 */
+	@Override
+	public E randomValue() {
+		return boundSetOps.randomMember();
+	}
+
 	/*
 	 * (non-Javadoc)
 	 * @see java.util.AbstractCollection#add(java.lang.Object)

src/main/java/org/springframework/data/redis/support/collections/DefaultRedisZSet.java

@@ -277,6 +277,15 @@ public RedisZSet<E> unionAndStore(Collection<? extends RedisZSet<?>> sets, Strin
 		return new DefaultRedisZSet<>(boundZSetOps.getOperations().boundZSetOps(destKey), getDefaultScore());
 	}
 
+	/*
+	 * (non-Javadoc)
+	 * @see org.springframework.data.redis.support.collections.RedisZSet#randomElement()
+	 */
+	@Override
+	public E randomValue() {
+		return boundZSetOps.randomMember();
+	}
+
 	/*
 	 * (non-Javadoc)
 	 * @see org.springframework.data.redis.support.collections.RedisZSet#range(long, long)

src/main/java/org/springframework/data/redis/support/collections/RedisSet.java

@@ -82,8 +82,8 @@ public interface RedisSet<E> extends RedisCollection<E>, Set<E> {
 	Set<E> diff(Collection<? extends RedisSet<?>> sets);
 
 	/**
-	 * Create a new {@link RedisSet} by intersecting this sorted set and {@link RedisSet} and store result in
-	 * destination {@code destKey}.
+	 * Create a new {@link RedisSet} by intersecting this sorted set and {@link RedisSet} and store result in destination
+	 * {@code destKey}.
 	 *
 	 * @param set must not be {@literal null}.
 	 * @param destKey must not be {@literal null}.
@@ -93,8 +93,8 @@ public interface RedisSet<E> extends RedisCollection<E>, Set<E> {
 	RedisSet<E> intersectAndStore(RedisSet<?> set, String destKey);
 
 	/**
-	 * Create a new {@link RedisSet} by intersecting this sorted set and the collection {@link RedisSet} and store
-	 * result in destination {@code destKey}.
+	 * Create a new {@link RedisSet} by intersecting this sorted set and the collection {@link RedisSet} and store result
+	 * in destination {@code destKey}.
 	 *
 	 * @param sets must not be {@literal null}.
 	 * @param destKey must not be {@literal null}.
@@ -125,6 +125,14 @@ public interface RedisSet<E> extends RedisCollection<E>, Set<E> {
 	 */
 	RedisSet<E> unionAndStore(Collection<? extends RedisSet<?>> sets, String destKey);
 
+	/**
+	 * Get random element from the set.
+	 *
+	 * @return
+	 * @since 2.6
+	 */
+	E randomValue();
+
 	/**
 	 * Create a new {@link RedisSet} by diffing this sorted set and {@link RedisSet} and store result in destination
 	 * {@code destKey}.

src/main/java/org/springframework/data/redis/support/collections/RedisZSet.java

@@ -236,6 +236,14 @@ static <E> RedisZSet<E> create(String key, RedisOperations<String, E> operations
 	 */
 	RedisZSet<E> unionAndStore(Collection<? extends RedisZSet<?>> sets, String destKey);
 
+	/**
+	 * Get random element from the set.
+	 *
+	 * @return
+	 * @since 2.6
+	 */
+	E randomValue();
+
 	/**
 	 * Get elements between {@code start} and {@code end} from sorted set.
 	 *

src/test/java/org/springframework/data/redis/support/collections/AbstractRedisSetIntegrationTests.java

@@ -302,4 +302,14 @@ void testScanWorksCorrectly() throws IOException {
 		}
 		cursor.close();
 	}
+
+	@ParameterizedRedisTest // GH-2049
+	void randMemberReturnsSomething() {
+
+		Object[] valuesArray = new Object[]{getT(), getT(), getT()};
+
+		collection.addAll((List<T>) Arrays.asList(valuesArray));
+
+		assertThat(set.randomValue()).isIn(valuesArray);
+	}
 }

src/test/java/org/springframework/data/redis/support/collections/AbstractRedisZSetTestIntegration.java

@@ -21,6 +21,7 @@
 import java.io.IOException;
 import java.util.Arrays;
 import java.util.Iterator;
+import java.util.List;
 import java.util.NoSuchElementException;
 import java.util.Set;
 import java.util.concurrent.TimeUnit;
@@ -856,4 +857,15 @@ void testZAddIfAbsentWorks() {
 		assertThat(zSet.addIfAbsent(t1, 1)).isTrue();
 		assertThat(zSet.addIfAbsent(t1, 1)).isFalse();
 	}
+
+	@ParameterizedRedisTest // GH-2049
+	@EnabledOnCommand("ZRANDMEMBER")
+	void randMemberReturnsSomething() {
+
+		Object[] valuesArray = new Object[]{getT(), getT(), getT()};
+
+		collection.addAll((List<T>) Arrays.asList(valuesArray));
+
+		assertThat(zSet.randomValue()).isIn(valuesArray);
+	}
 }