langchain4j自用学习笔记

参考鱼皮老师教学视频

基本依赖

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<dependency>
          <groupId>dev.langchain4j</groupId>
          <artifactId>langchain4j-community-dashscope-spring-boot-starter</artifactId>
          <version>1.1.0-beta7</version>
      </dependency>

      <dependency>
          <groupId>dev.langchain4j</groupId>
          <artifactId>langchain4j-spring-boot-starter</artifactId>
          <version>1.1.0-beta7</version>
      </dependency>

      <dependency>
          <groupId>dev.langchain4j</groupId>
          <artifactId>langchain4j</artifactId>
          <version>1.1.0</version>
      </dependency>


      <dependency>
          <groupId>dev.langchain4j</groupId>
          <artifactId>langchain4j-easy-rag</artifactId>
          <version>1.1.0-beta7</version>
      </dependency>
      
      <dependency>
          <groupId>org.springframework.boot</groupId>
          <artifactId>spring-boot-starter-test</artifactId>
          <scope>test</scope>
      </dependency>

      <!--网页爬取-->
      <dependency>
          <groupId>org.jsoup</groupId>
          <artifactId>jsoup</artifactId>
          <version>1.20.1</version>
      </dependency>

      <dependency>
          <groupId>dev.langchain4j</groupId>
          <artifactId>langchain4j-mcp</artifactId>
          <version>1.1.0-beta7</version>
      </dependency>

Service类

在resources下添加system-prompt.txt文件，里面填写角色预设

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public interface AiCodeHelperService {

    @SystemMessage(fromResource = "system-prompt.txt")
    String chat(@UserMessage String message, @MemoryId String chatId);

    @SystemMessage(fromResource = "system-prompt.txt")
    Report report(@UserMessage String message, @MemoryId String chatId);

    record Report(String name, List<String> suggestionList){}
    
    @SystemMessage(fromResource = "system-prompt.txt")
    Flux<String> chatStream(@UserMessage String message, @MemoryId String chatId);

}

Config类

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@Configuration
public class AiCodeHelperServiceFactory {

    @Resource
    private ChatModel qwenChatModel;

    @Resource
    private ContentRetriever contentRetriever;

    @Bean
    public AiCodeHelperService aiCodeHelperService() {
        ChatMemory chatMemory = MessageWindowChatMemory.withMaxMessages(10);
        //ai service
        AiCodeHelperService aiCodeHelperService = AiServices.builder(AiCodeHelperService.class)
                .chatMemory(chatMemory)
                .chatModel(qwenChatModel)
                .tools(new InterviewQuestionTool())
                .contentRetriever(contentRetriever)
                .chatMemoryProvider(chatId -> MessageWindowChatMemory.withMaxMessages(10))
                .build();
        return aiCodeHelperService;
    }



}

Rag知识库

在resources创建docs文件夹，里面放知识库文件

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@Configuration
public class AiConfiguration {

    @Resource
    private ChatModel qwenChatModel;

    @Resource
    private ContentRetriever contentRetriever;

    @Resource
    private StreamingChatModel streamingChatModel;

    @Bean
    public AiCodeHelperService aiCodeHelperService() {
        ChatMemory chatMemory = MessageWindowChatMemory.withMaxMessages(10);
        //ai service
        AiCodeHelperService aiCodeHelperService = AiServices.builder(AiCodeHelperService.class)
                .chatMemory(chatMemory)
                .chatModel(qwenChatModel)
                .streamingChatModel(streamingChatModel)
                .contentRetriever(contentRetriever)
                .chatMemoryProvider(chatId -> MessageWindowChatMemory.withMaxMessages(10))
                .build();
        return aiCodeHelperService;
    }
}

Tools 调用实例

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@Slf4j
public class InterviewQuestionTool {

    /**
     * 从面试鸭网站获取关键词相关的面试题列表
     *
     * @param keyword 搜索关键词（如"redis"、"java多线程"）
     * @return 面试题列表，若失败则返回错误信息
     */
    @Tool(name = "interviewQuestionSearch", value = """
                Retrieves relevant interview questions from mianshiya.com based on a keyword.
                Use this tool when the user asks for interview questions about specific technologies,
                programming concepts, or job-related topics. The input should be a clear search term.
                """
    )
    public String searchInterviewQuestions(@P(value = "the keyword to search") String keyword) {
        List<String> questions = new ArrayList<>();
        // 构建搜索URL（编码关键词以支持中文）
        String encodedKeyword = URLEncoder.encode(keyword, StandardCharsets.UTF_8);
        String url = "https://www.mianshiya.com/search/all?searchText=" + encodedKeyword;
        // 发送请求并解析页面
        Document doc;
        try {
            doc = Jsoup.connect(url)
                    .userAgent("Mozilla/5.0")
                    .timeout(5000)
                    .get();
        } catch (IOException e) {
            log.error("get web error", e);
            return e.getMessage();
        }
        // 提取面试题
        Elements questionElements = doc.select(".ant-table-cell > a");
        questionElements.forEach(el -> questions.add(el.text().trim()));
        return String.join("\n", questions);
    }
}

配置yml:

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langchain4j:
  community:
    dashscope:
      chat-model:
        model-name: qwen-max
        api-key: sk-xxxxx
      embedding-model:
        model-name: text-embedding-v4
        api-key: sk-xxxxx