接上节继续，langchain4j的名字中既然有个chain，自然要体现出链式调用的特性。根据官网的介绍，目前langchain4j内置了2个chain
一、ConversationalChain示例
@GetMapping(value = "/chat/chain", produces = MediaType.APPLICATION_JSON_VALUE)public ResponseEntity<String> chatChain(@RequestParam String query) {try {String responseText = ConversationalChain.builder().chatModel(ollamaChatModel).chatMemory(MessageWindowChatMemory.withMaxMessages(10)).build().execute(query);return ResponseEntity.ok(responseText);} catch (Exception e) {log.error("chatChain", e);return ResponseEntity.ok("{\"error\":\"chatChain error: " + e.getMessage() + "\"}");}}
这段代码把 设置模型、对话记忆、执行查询 一并处理了
二、 ConversationalRetrievalChain示例
/*** 示例用测试文本data.txt向量化存储（按行分隔）* @return*/EmbeddingStore<TextSegment> getEmbeddingStore() {Resource resource = resourceLoader.getResource("classpath:data.txt");File file = null;try {file = resource.getFile();} catch (IOException e) {throw new RuntimeException(e);}String path = file.getAbsolutePath();EmbeddingStore<TextSegment> embeddingStore = new InMemoryEmbeddingStore<>();Document document = FileSystemDocumentLoader.loadDocument(path);DocumentByLineSplitter splitter = new DocumentByLineSplitter(100, 0);List<TextSegment> split = splitter.split(document);for (TextSegment textSegment : split) {Embedding embedding = ollamaEmbeddingModel.embed(textSegment).content();embeddingStore.add(embedding, textSegment);}return embeddingStore;}@GetMapping(value = "/rag/chain", produces = MediaType.APPLICATION_JSON_VALUE)public ResponseEntity<String> ragChain(@RequestParam String query) {try {String answer = ConversationalRetrievalChain.builder().chatModel(ollamaChatModel).contentRetriever(EmbeddingStoreContentRetriever.builder().embeddingModel(ollamaEmbeddingModel).embeddingStore(getEmbeddingStore()).maxResults(1).build()).chatMemory(MessageWindowChatMemory.withMaxMessages(10)).build().execute(query);return ResponseEntity.ok(answer);} catch (Exception e) {log.error("argChain", e);return ResponseEntity.ok("{\"error\":\"argChain error: " + e.getMessage() + "\"}");}}
与ConversationalChain相比，ConversationalRetrievalChain新增了RAG的链式处理。
文本示例完整代码：https://github.com/yjmyzz/langchain4j-study/tree/day08
参考：https://docs.langchain4j.dev/tutorials/ai-services