fix: return boolean for exists queries instead of throwing ClassCastException (#622)

Both RediSearchQuery and RedisEnhancedQuery were returning entity objects
for existsBy* query methods, causing ClassCastException when the repository
method expected a boolean return type.

Modified executeQuery methods in both query classes to detect when the
return type is boolean/Boolean and return the result of checking if
any documents were found (searchResult.getTotalResults() > 0) instead
of attempting to return the entity object.

Added tests to verify existsBy* methods work correctly for both
@document and @RedisHash entities.

Author: bsbodden

redis-om-spring/src/main/java/com/redis/om/spring/repository/query/RediSearchQuery.java

@@ -677,7 +677,12 @@ private Object executeQuery(Object[] parameters) {
     // what to return
     Object result = null;
 
-    if (queryMethod.getReturnedObjectType() == SearchResult.class) {
+    // Check if this is an exists query
+    if (processor.getReturnedType().getReturnedType() == boolean.class || processor.getReturnedType()
+        .getReturnedType() == Boolean.class) {
+      // For exists queries, return true if we have any results, false otherwise
+      result = searchResult.getTotalResults() > 0;
+    } else if (queryMethod.getReturnedObjectType() == SearchResult.class) {
       result = searchResult;
     } else if (queryMethod.isPageQuery()) {
       List<Object> content = searchResult.getDocuments().stream().map(this::parseDocumentResult).toList();

redis-om-spring/src/main/java/com/redis/om/spring/repository/query/RedisEnhancedQuery.java

@@ -577,7 +577,12 @@ private Object executeQuery(Object[] parameters) {
     // what to return
     Object result;
 
-    if (queryMethod.getReturnedObjectType() == SearchResult.class) {
+    // Check if this is an exists query
+    if (processor.getReturnedType().getReturnedType() == boolean.class || processor.getReturnedType()
+        .getReturnedType() == Boolean.class) {
+      // For exists queries, return true if we have any results, false otherwise
+      result = searchResult.getTotalResults() > 0;
+    } else if (queryMethod.getReturnedObjectType() == SearchResult.class) {
       result = searchResult;
     } else if (queryMethod.isPageQuery()) {
       List<Object> content = searchResult.getDocuments().stream().map(d -> {

tests/src/test/java/com/redis/om/spring/annotations/document/BasicRedisDocumentMappingTest.java

@@ -916,4 +916,23 @@ void testEffectOfNotNullAnnotation() {
     assertThat(fields).hasSize(1);
     assertThat(fields).first().isEqualTo("001");
   }
+
+  @Test
+  void testIssue622_ExistsByQueryReturnsBoolean() {
+    // Test for issue #622: existsBy* queries should return boolean instead of throwing ClassCastException
+    Company redis = Company.of("RedisInc", 2011, LocalDate.of(2021, 5, 1), 
+        new Point(-122.066540, 37.377690), "[email protected]");
+    repository.save(redis);
+    
+    // Test exists query returns true for existing email
+    boolean exists = repository.existsByEmail("[email protected]");
+    assertTrue(exists, "Should return true for existing email");
+    
+    // Test exists query returns false for non-existing email
+    boolean notExists = repository.existsByEmail("[email protected]");
+    assertFalse(notExists, "Should return false for non-existing email");
+    
+    // Clean up
+    repository.delete(redis);
+  }
 }

tests/src/test/java/com/redis/om/spring/annotations/hash/BasicRedisHashMappingTest.java

@@ -756,4 +756,35 @@ void testRepositoryGetKeyFor() {
     assertThat(redisKey).isEqualTo(getKey(Company.class.getName(), redis.getId()));
     assertThat(microsoftKey).isEqualTo(getKey(Company.class.getName(), microsoft.getId()));
   }
+
+  @Test
+  void testIssue622_HashExistsByQueryReturnsBoolean() {
+    // Test for issue #622: existsBy* queries should return boolean for hash entities
+    Person john = new Person();
+    john.setName("John Doe");
+    john.setEmail("[email protected]");
+    john.setNickname("johnd");
+    john.setRoles(Set.of("admin"));
+    john.setFavoriteFoods(Set.of("pizza"));
+    personRepo.save(john);
+    
+    // Test exists query returns true for existing email
+    boolean existsByEmail = personRepo.existsByEmail("[email protected]");
+    assertTrue(existsByEmail, "Should return true for existing email");
+    
+    // Test exists query returns true for existing nickname
+    boolean existsByNickname = personRepo.existsByNickname("johnd");
+    assertTrue(existsByNickname, "Should return true for existing nickname");
+    
+    // Test exists query returns false for non-existing email
+    boolean notExistsByEmail = personRepo.existsByEmail("[email protected]");
+    assertFalse(notExistsByEmail, "Should return false for non-existing email");
+    
+    // Test exists query returns false for non-existing nickname
+    boolean notExistsByNickname = personRepo.existsByNickname("nonexisting");
+    assertFalse(notExistsByNickname, "Should return false for non-existing nickname");
+    
+    // Clean up
+    personRepo.delete(john);
+  }
 }