聊聊langchain4j的AiServices

序

本文主要研究一下langchain4j的AiServices

示例

原生版本

public interface Assistant {
    String chat(String userMessage);
}

构建

Assistant assistant = AiServices.create(Assistant.class, chatLanguageModel);
String resp = assistant.chat(userMessage);

spring-boot版本

@AiService
public interface AssistantV2 {

    @SystemMessage("You are a polite assistant")
    String chat(String userMessage);
}

之后直接像使用托管的bean一样注入就可以使用

    @Autowired
    AssistantV2 assistantV2;

    @GetMapping("/ai-service")
    public String aiService(@RequestParam("prompt") String prompt) {
        return assistantV2.chat(prompt);
    }    

源码

AiServices

dev/langchain4j/service/AiServices.java

public abstract class AiServices<T> {

    protected static final String DEFAULT = "default";

    protected final AiServiceContext context;

    private boolean retrieverSet = false;
    private boolean contentRetrieverSet = false;
    private boolean retrievalAugmentorSet = false;

    protected AiServices(AiServiceContext context) {
        this.context = context;
    }

    /**
     * Creates an AI Service (an implementation of the provided interface), that is backed by the provided chat model.
     * This convenience method can be used to create simple AI Services.
     * For more complex cases, please use {@link #builder}.
     *
     * @param aiService         The class of the interface to be implemented.
     * @param chatLanguageModel The chat model to be used under the hood.
     * @return An instance of the provided interface, implementing all its defined methods.
     */
    public static <T> T create(Class<T> aiService, ChatLanguageModel chatLanguageModel) {
        return builder(aiService).chatLanguageModel(chatLanguageModel).build();
    }

    /**
     * Creates an AI Service (an implementation of the provided interface), that is backed by the provided streaming chat model.
     * This convenience method can be used to create simple AI Services.
     * For more complex cases, please use {@link #builder}.
     *
     * @param aiService                  The class of the interface to be implemented.
     * @param streamingChatLanguageModel The streaming chat model to be used under the hood.
     *                                   The return type of all methods should be {@link TokenStream}.
     * @return An instance of the provided interface, implementing all its defined methods.
     */
    public static <T> T create(Class<T> aiService, StreamingChatLanguageModel streamingChatLanguageModel) {
        return builder(aiService)
                .streamingChatLanguageModel(streamingChatLanguageModel)
                .build();
    }

    /**
     * Begins the construction of an AI Service.
     *
     * @param aiService The class of the interface to be implemented.
     * @return builder
     */
    public static <T> AiServices<T> builder(Class<T> aiService) {
        AiServiceContext context = new AiServiceContext(aiService);
        for (AiServicesFactory factory : loadFactories(AiServicesFactory.class)) {
            return factory.create(context);
        }
        return new DefaultAiServices<>(context);
    }

    /**
     * Configures chat model that will be used under the hood of the AI Service.
     * <p>
     * Either {@link ChatLanguageModel} or {@link StreamingChatLanguageModel} should be configured,
     * but not both at the same time.
     *
     * @param chatLanguageModel Chat model that will be used under the hood of the AI Service.
     * @return builder
     */
    public AiServices<T> chatLanguageModel(ChatLanguageModel chatLanguageModel) {
        context.chatModel = chatLanguageModel;
        return this;
    }

    /**
     * Configures streaming chat model that will be used under the hood of the AI Service.
     * The methods of the AI Service must return a {@link TokenStream} type.
     * <p>
     * Either {@link ChatLanguageModel} or {@link StreamingChatLanguageModel} should be configured,
     * but not both at the same time.
     *
     * @param streamingChatLanguageModel Streaming chat model that will be used under the hood of the AI Service.
     * @return builder
     */
    public AiServices<T> streamingChatLanguageModel(StreamingChatLanguageModel streamingChatLanguageModel) {
        context.streamingChatModel = streamingChatLanguageModel;
        return this;
    }

    /**
     * Configures the system message provider, which provides a system message to be used each time an AI service is invoked.
     * <br>
     * When both {@code @SystemMessage} and the system message provider are configured,
     * {@code @SystemMessage} takes precedence.
     *
     * @param systemMessageProvider A {@link Function} that accepts a chat memory ID
     *                              (a value of a method parameter annotated with @{@link MemoryId})
     *                              and returns a system message to be used.
     *                              If there is no parameter annotated with {@code @MemoryId},
     *                              the value of memory ID is "default".
     *                              The returned {@link String} can be either a complete system message
     *                              or a system message