fix: be more resilient to DLG models accessibility issues by using a NoopFeatureExtractor fallback

Author: bsbodden

redis-om-spring/src/main/java/com/redis/om/spring/RedisModulesConfiguration.java

@@ -27,6 +27,7 @@
 import com.redis.om.spring.serialization.gson.*;
 import com.redis.om.spring.vectorize.DefaultFeatureExtractor;
 import com.redis.om.spring.vectorize.FeatureExtractor;
+import com.redis.om.spring.vectorize.NoopFeatureExtractor;
 import com.redis.om.spring.vectorize.face.FaceDetectionTranslator;
 import com.redis.om.spring.vectorize.face.FaceFeatureTranslator;
 import org.apache.commons.lang3.ObjectUtils;
@@ -273,7 +274,7 @@ public FeatureExtractor featureExtractor(
       @Nullable @Qualifier("djlSentenceTokenizer") HuggingFaceTokenizer sentenceTokenizer,
       RedisOMProperties properties,
       ApplicationContext ac) {
-    return properties.getDjl().isEnabled() ? new DefaultFeatureExtractor( ac, imageEmbeddingModel, faceEmbeddingModel, imageFactory, defaultImagePipeline, sentenceTokenizer) : null;
+    return properties.getDjl().isEnabled() ? new DefaultFeatureExtractor( ac, imageEmbeddingModel, faceEmbeddingModel, imageFactory, defaultImagePipeline, sentenceTokenizer) : new NoopFeatureExtractor();
   }
 
   @Bean(name = "redisJSONKeyValueAdapter")

redis-om-spring/src/main/java/com/redis/om/spring/vectorize/NoopFeatureExtractor.java

@@ -0,0 +1,38 @@
+package com.redis.om.spring.vectorize;
+
+import ai.djl.translate.TranslateException;
+
+import java.io.IOException;
+import java.io.InputStream;
+
+public class NoopFeatureExtractor implements FeatureExtractor {
+  @Override
+  public void processEntity(byte[] redisKey, Object item) {
+    // NOOP
+  }
+
+  @Override
+  public byte[] getImageEmbeddingsFor(InputStream is) {
+    return new byte[0];
+  }
+
+  @Override
+  public byte[] getFacialImageEmbeddingsFor(InputStream is) throws IOException, TranslateException {
+    return new byte[0];
+  }
+
+  @Override
+  public byte[] getSentenceEmbeddingsFor(String text) {
+    return new byte[0];
+  }
+
+  @Override
+  public void processEntity(Object item) {
+    // NOOP
+  }
+
+  @Override
+  public boolean isReady() {
+    return false;
+  }
+}