added config to control the behavior of check on null values

docs/src/main/asciidoc/cache-redis-reference.adoc

@@ -151,3 +151,19 @@ quarkus.cache.redis.expensiveResourceCache.use-optimistic-locking=true
 ----
 
 When used, the key is _watched_ and the _SET_ command is executed in a transaction (`MULTI/EXEC`).
+
+== Ignore the null values
+
+As redis does not support saving null values in cache, so if the return type of method annotated with `@CacheResult`, then a `IllegalArgumentException` is thrown to prevent it from being saved in cache.
+However, if you want to safely ignore that return value and treat it as cache miss, then you use choose to ignore those null values.
+By default, this behavior is disabled, and the values will be checked.
+
+You can choose to ignore null values using:
+[source, properties]
+----
+# Default configuration
+quarkus.cache.redis.ignore-null-value=true
+
+# Configuration for `expensiveResourceCache`
+quarkus.cache.redis.expensiveResourceCache.ignore-null-value=true
+----

extensions/redis-cache/runtime/src/main/java/io/quarkus/cache/redis/runtime/RedisCacheImpl.java

@@ -194,6 +194,9 @@ public Uni<V> apply(V cached) throws Exception {
                                         @Override
                                         public Uni<?> apply(V value) {
                                             if (value == null) {
+                                                if (cacheInfo.ignoreNullValue) {
+                                                    return Uni.createFrom().nullItem();
+                                                }
                                                 throw new IllegalArgumentException("Cannot cache `null` value");
                                             }
                                             byte[] encodedValue = marshaller.encode(value);

extensions/redis-cache/runtime/src/main/java/io/quarkus/cache/redis/runtime/RedisCacheInfo.java

@@ -42,4 +42,10 @@ public class RedisCacheInfo {
      * Locking</a> for details.
      */
     public boolean useOptimisticLocking = false;
+
+    /**
+     * Specifies whether to safely ignore the calls when trying to save {@code null} in cache.
+     * If not set, then values will be checked, and {@code IllegalArgumentException} is thrown for null values.
+     */
+    public boolean ignoreNullValue = false;
 }

extensions/redis-cache/runtime/src/main/java/io/quarkus/cache/redis/runtime/RedisCacheInfoBuilder.java

@@ -66,6 +66,12 @@ public static Set<RedisCacheInfo> build(Set<String> cacheNames, RedisCachesBuild
                     cacheInfo.useOptimisticLocking = defaultRuntimeConfig.useOptimisticLocking.get();
                 }
 
+                if (namedRuntimeConfig != null && namedRuntimeConfig.ignoreNullValue.isPresent()) {
+                    cacheInfo.ignoreNullValue = namedRuntimeConfig.ignoreNullValue.get();
+                } else if (defaultRuntimeConfig.ignoreNullValue.isPresent()) {
+                    cacheInfo.ignoreNullValue = defaultRuntimeConfig.ignoreNullValue.get();
+                }
+
                 result.add(cacheInfo);
             }
             return result;

extensions/redis-cache/runtime/src/main/java/io/quarkus/cache/redis/runtime/RedisCacheRuntimeConfig.java

@@ -47,4 +47,12 @@ public class RedisCacheRuntimeConfig {
     @ConfigItem
     public Optional<Boolean> useOptimisticLocking;
 
+    /**
+     * Specifies whether to safely ignore the calls when trying to save {@code null} in cache.
+     * If not set, then values will be checked, and {@code IllegalArgumentException} is thrown for null values.
+     * Default is {@code false}.
+     */
+    @ConfigItem
+    public Optional<Boolean> ignoreNullValue;
+
 }

extensions/redis-cache/runtime/src/test/java/io/quarkus/cache/redis/runtime/RedisCacheImplTest.java

@@ -231,7 +231,7 @@ public void testGetOrDefault() {
     }
 
     @Test
-    public void testCacheNullValue() {
+    public void testCacheNullValueWithoutIgnoringNullValue() {
         RedisCacheInfo info = new RedisCacheInfo();
         info.expireAfterWrite = Optional.of(Duration.ofSeconds(10));
         info.valueType = Person.class.getName();
@@ -244,6 +244,20 @@ public void testCacheNullValue() {
         assertThatTheKeyDoesNotExist("cache:default-redis-cache:" + Json.encode(key));
     }
 
+    @Test
+    public void testCacheNullValueWithIgnoringNullValue() {
+        RedisCacheInfo info = new RedisCacheInfo();
+        info.expireAfterWrite = Optional.of(Duration.ofSeconds(10));
+        info.valueType = Person.class.getName();
+        info.ignoreNullValue = true;
+        RedisCacheImpl cache = new RedisCacheImpl(info, vertx, redis, BLOCKING_ALLOWED);
+
+        // with custom key
+        double key = 122334545.0;
+        assertThat(cache.get(key, k -> null).await().indefinitely()).isNull();
+        assertThatTheKeyDoesNotExist("cache:default-redis-cache:" + Json.encode(key));
+    }
+
     @Test
     public void testExceptionInValueLoader() {
         RedisCacheInfo info = new RedisCacheInfo();