feat(deepresearch): Introduce HyDE into the RAG process

src/main/java/com/alibaba/cloud/ai/example/deepresearch/config/rag/RagProperties.java

@@ -175,6 +175,11 @@ public static class Pipeline {
 		 */
 		private boolean queryTranslationEnabled = false;
 
+		/**
+		 * 是否启用假设性文档嵌入功能，默认为false。
+		 */
+		private boolean hypotheticalDocumentEmbeddingEnabled = false;
+
 		/**
 		 * 查询翻译的目标语言，默认为"English"。
 		 */
@@ -220,7 +225,15 @@ public void setQueryTranslationEnabled(boolean queryTranslationEnabled) {
 			this.queryTranslationEnabled = queryTranslationEnabled;
 		}
 
-		public String getQueryTranslationLanguage() {
+        public boolean isHypotheticalDocumentEmbeddingEnabled() {
+            return hypotheticalDocumentEmbeddingEnabled;
+        }
+
+        public void setHypotheticalDocumentEmbeddingEnabled(boolean hypotheticalDocumentEmbeddingEnabled) {
+            this.hypotheticalDocumentEmbeddingEnabled = hypotheticalDocumentEmbeddingEnabled;
+        }
+
+        public String getQueryTranslationLanguage() {
 			return queryTranslationLanguage;
 		}
 

src/main/java/com/alibaba/cloud/ai/example/deepresearch/rag/core/DefaultHybridRagProcessor.java

@@ -23,6 +23,7 @@
 import com.alibaba.cloud.ai.example.deepresearch.rag.post.DocumentSelectFirstProcess;
 import com.alibaba.cloud.ai.example.deepresearch.rag.retriever.RrfHybridElasticsearchRetriever;
 import com.alibaba.cloud.ai.example.deepresearch.rag.strategy.RrfFusionStrategy;
+import com.alibaba.cloud.ai.example.deepresearch.rag.transformer.HyDeTransformer;
 import org.elasticsearch.client.RestClient;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
@@ -64,6 +65,8 @@ public class DefaultHybridRagProcessor implements HybridRagProcessor {
 
 	private final TranslationQueryTransformer queryTransformer;
 
+	private final HyDeTransformer hyDeTransformer;
+
 	private final DocumentSelectFirstProcess documentPostProcessor;
 
 	private final RrfFusionStrategy rrfFusionStrategy;
@@ -98,6 +101,9 @@ public DefaultHybridRagProcessor(@Qualifier("ragVectorStore") VectorStore vector
 					.build()
 				: null;
 
+		this.hyDeTransformer = ragProperties.getPipeline().isHypotheticalDocumentEmbeddingEnabled()
+				? HyDeTransformer.builder().chatClientBuilder(chatClientBuilder).build() : null;
+
 		// 初始化文档后处理器
 		this.documentPostProcessor = ragProperties.getPipeline().isPostProcessingSelectFirstEnabled()
 				? new DocumentSelectFirstProcess() : null;
@@ -133,7 +139,7 @@ public List<org.springframework.ai.rag.Query> preProcess(org.springframework.ai.
 		if (queryTransformer != null) {
 			queries = queries.stream().flatMap(q -> {
 				org.springframework.ai.rag.Query transformed = queryTransformer.transform(q);
-				return transformed != null ? Stream.of(transformed) : Stream.empty();
+				return Stream.of(transformed);
 			}).collect(Collectors.toList());
 		}
 
@@ -142,6 +148,14 @@ public List<org.springframework.ai.rag.Query> preProcess(org.springframework.ai.
 			queries = queries.stream().flatMap(q -> queryExpander.expand(q).stream()).collect(Collectors.toList());
 		}
 
+		// 假设性文档生成
+		if (hyDeTransformer != null) {
+			queries = queries.stream().flatMap(q -> {
+				org.springframework.ai.rag.Query transformed = hyDeTransformer.transform(q);
+				return Stream.of(transformed);
+			}).collect(Collectors.toList());
+		}
+
 		return queries;
 	}
 

src/main/java/com/alibaba/cloud/ai/example/deepresearch/rag/transformer/HyDeTransformer.java

@@ -0,0 +1,90 @@
+package com.alibaba.cloud.ai.example.deepresearch.rag.transformer;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+import org.springframework.ai.chat.client.ChatClient;
+import org.springframework.ai.chat.prompt.PromptTemplate;
+import org.springframework.ai.rag.Query;
+import org.springframework.ai.rag.preretrieval.query.transformation.QueryTransformer;
+import org.springframework.ai.rag.util.PromptAssert;
+import org.springframework.lang.Nullable;
+import org.springframework.util.Assert;
+import org.springframework.util.StringUtils;
+
+/**
+ * Generate hypothetical document for query. The implements of the Hypothetical Document
+ * Embeddings
+ * <a href="https://arxiv.org/abs/2212.10496">https://arxiv.org/abs/2212.10496</a>
+ *
+ * @author benym
+ */
+public class HyDeTransformer implements QueryTransformer {
+
+	private static final Logger logger = LoggerFactory.getLogger(HyDeTransformer.class);
+
+	private static final PromptTemplate DEFAULT_PROMPT_TEMPLATE = new PromptTemplate("""
+			Given a user question, write a comprehensive and informative passage that directly answers the question.
+
+			The passage should be factual, well-structured, and contain specific details.
+
+			Question: {query}
+
+			Passage:
+			""");
+
+	private final ChatClient chatClient;
+
+	private final PromptTemplate promptTemplate;
+
+	public HyDeTransformer(ChatClient.Builder chatClientBuilder, PromptTemplate promptTemplate) {
+		Assert.notNull(chatClientBuilder, "chatClientBuilder cannot be null");
+		this.chatClient = chatClientBuilder.build();
+		this.promptTemplate = promptTemplate != null ? promptTemplate : DEFAULT_PROMPT_TEMPLATE;
+		PromptAssert.templateHasRequiredPlaceholders(this.promptTemplate, "query");
+	}
+
+	@Override
+	public Query transform(Query query) {
+		Assert.notNull(query, "query cannot be null");
+		var hyDeQueryText = this.chatClient.prompt()
+			.user(user -> user.text(this.promptTemplate.getTemplate()).param("query", query.text()))
+			.call()
+			.content();
+		if (!StringUtils.hasText(hyDeQueryText)) {
+			logger.warn("Query generate hyDe document result is null/empty. Returning the input query unchanged.");
+			return query;
+		}
+		return query.mutate().text(hyDeQueryText).build();
+	}
+
+	public static Builder builder() {
+		return new Builder();
+	}
+
+	public static final class Builder {
+
+		private ChatClient.Builder chatClientBuilder;
+
+		@Nullable
+		private PromptTemplate promptTemplate;
+
+		private Builder() {
+		}
+
+		public Builder chatClientBuilder(ChatClient.Builder chatClientBuilder) {
+			this.chatClientBuilder = chatClientBuilder;
+			return this;
+		}
+
+		public Builder promptTemplate(PromptTemplate promptTemplate) {
+			this.promptTemplate = promptTemplate;
+			return this;
+		}
+
+		public HyDeTransformer build() {
+			return new HyDeTransformer(this.chatClientBuilder, this.promptTemplate);
+		}
+
+	}
+
+}