Refactor ContentFormatTransformer for improved readability

- Extract Method
- Replace explicit instanceof checks and casting with pattern matching
- Change var to explicit type

Author: Seol-JY

models/spring-ai-openai/src/test/java/org/springframework/ai/openai/transformer/MetadataTransformerIT.java

@@ -189,7 +189,7 @@ public DefaultContentFormatter defaultContentFormatter() {
 
 		@Bean
 		public ContentFormatTransformer contentFormatTransformer(DefaultContentFormatter defaultContentFormatter) {
-			return new ContentFormatTransformer(defaultContentFormatter, false);
+			return new ContentFormatTransformer(defaultContentFormatter);
 		}
 
 	}

spring-ai-core/src/main/java/org/springframework/ai/transformer/ContentFormatTransformer.java

@@ -24,21 +24,38 @@
 import org.springframework.ai.document.DocumentTransformer;
 
 /**
+ * ContentFormatTransformer processes a list of documents by applying a content formatter
+ * to each document.
+ *
  * @author Christian Tzolov
+ * @since 1.0.0
  */
 public class ContentFormatTransformer implements DocumentTransformer {
 
 	/**
 	 * Disable the content-formatter template rewrite.
 	 */
-	private boolean disableTemplateRewrite = false;
+	private final boolean disableTemplateRewrite;
 
-	private ContentFormatter contentFormatter;
+	private final ContentFormatter contentFormatter;
 
+	/**
+	 * Creates a ContentFormatTransformer object with the given ContentFormatter.
+	 * @param contentFormatter the ContentFormatter to be used for transforming the
+	 * documents
+	 */
 	public ContentFormatTransformer(ContentFormatter contentFormatter) {
 		this(contentFormatter, false);
 	}
 
+	/**
+	 * The ContentFormatTransformer class is responsible for processing a list of
+	 * documents by applying a content formatter to each document.
+	 * @param contentFormatter The ContentFormatter to be used for transforming the
+	 * documents
+	 * @param disableTemplateRewrite Flag indicating whether to disable the
+	 * content-formatter template rewrite
+	 */
 	public ContentFormatTransformer(ContentFormatter contentFormatter, boolean disableTemplateRewrite) {
 		this.contentFormatter = contentFormatter;
 		this.disableTemplateRewrite = disableTemplateRewrite;
@@ -47,45 +64,50 @@ public ContentFormatTransformer(ContentFormatter contentFormatter, boolean disab
 	/**
 	 * Post process documents chunked from loader. Allows extractors to be chained.
 	 * @param documents to post process.
-	 * @return
+	 * @return processed documents
 	 */
 	public List<Document> apply(List<Document> documents) {
-
-		if (this.contentFormatter != null) {
-
-			documents.forEach(document -> {
-				// Update formatter
-				if (document.getContentFormatter() instanceof DefaultContentFormatter
-						&& this.contentFormatter instanceof DefaultContentFormatter) {
-
-					DefaultContentFormatter docFormatter = (DefaultContentFormatter) document.getContentFormatter();
-					DefaultContentFormatter toUpdateFormatter = (DefaultContentFormatter) this.contentFormatter;
-
-					var updatedEmbedExcludeKeys = new ArrayList<>(docFormatter.getExcludedEmbedMetadataKeys());
-					updatedEmbedExcludeKeys.addAll(toUpdateFormatter.getExcludedEmbedMetadataKeys());
-
-					var updatedInterfaceExcludeKeys = new ArrayList<>(docFormatter.getExcludedInferenceMetadataKeys());
-					updatedInterfaceExcludeKeys.addAll(toUpdateFormatter.getExcludedInferenceMetadataKeys());
-
-					var builder = DefaultContentFormatter.builder()
-						.withExcludedEmbedMetadataKeys(updatedEmbedExcludeKeys)
-						.withExcludedInferenceMetadataKeys(updatedInterfaceExcludeKeys)
-						.withMetadataTemplate(docFormatter.getMetadataTemplate())
-						.withMetadataSeparator(docFormatter.getMetadataSeparator());
-
-					if (!this.disableTemplateRewrite) {
-						builder.withTextTemplate(docFormatter.getTextTemplate());
-					}
-					document.setContentFormatter(builder.build());
-				}
-				else {
-					// Override formatter
-					document.setContentFormatter(this.contentFormatter);
-				}
-			});
+		if (contentFormatter != null) {
+			documents.forEach(this::processDocument);
 		}
 
 		return documents;
 	}
 
+	private void processDocument(Document document) {
+		if (document.getContentFormatter() instanceof DefaultContentFormatter docFormatter
+				&& contentFormatter instanceof DefaultContentFormatter toUpdateFormatter) {
+			updateFormatter(document, docFormatter, toUpdateFormatter);
+
+		}
+		else {
+			overrideFormatter(document);
+		}
+	}
+
+	private void updateFormatter(Document document, DefaultContentFormatter docFormatter,
+			DefaultContentFormatter toUpdateFormatter) {
+		List<String> updatedEmbedExcludeKeys = new ArrayList<>(docFormatter.getExcludedEmbedMetadataKeys());
+		updatedEmbedExcludeKeys.addAll(toUpdateFormatter.getExcludedEmbedMetadataKeys());
+
+		List<String> updatedInterfaceExcludeKeys = new ArrayList<>(docFormatter.getExcludedInferenceMetadataKeys());
+		updatedInterfaceExcludeKeys.addAll(toUpdateFormatter.getExcludedInferenceMetadataKeys());
+
+		DefaultContentFormatter.Builder builder = DefaultContentFormatter.builder()
+			.withExcludedEmbedMetadataKeys(updatedEmbedExcludeKeys)
+			.withExcludedInferenceMetadataKeys(updatedInterfaceExcludeKeys)
+			.withMetadataTemplate(docFormatter.getMetadataTemplate())
+			.withMetadataSeparator(docFormatter.getMetadataSeparator());
+
+		if (!disableTemplateRewrite) {
+			builder.withTextTemplate(docFormatter.getTextTemplate());
+		}
+
+		document.setContentFormatter(builder.build());
+	}
+
+	private void overrideFormatter(Document document) {
+		document.setContentFormatter(contentFormatter);
+	}
+
 }