聊聊langchain4j的HTTP Client

序

本文主要研究一下langchain4j的HTTP Client

langchain4j-http-client

langchain4j提供了langchain4j-http-client模块，它实现了一个HttpClient SPI（服务提供者接口），其他模块通过该接口调用LLM提供商的REST API。这意味着底层HTTP客户端可以被自定义，通过实现HttpClient SPI，还可以集成任何其他HTTP客户端。目前，有两个现成的实现：

• langchain4j-http-client-jdk模块中的JdkHttpClient。在例如langchain4j-open-ai等有引用的模块中默认使用
• langchain4j-http-client-spring-restclient模块中的SpringRestClient。在例如langchain4j-open-ai-spring-boot-starter等有引用的spring boot starter中默认使用

HttpClient

langchain4j-http-client/src/main/java/dev/langchain4j/http/client/HttpClient.java

@Experimental
public interface HttpClient {

    /**
     * Executes a given HTTP request synchronously and returns the response.
     * This method blocks until the entire response is received.
     *
     * @param request the HTTP request to be executed.
     * @return a {@link SuccessfulHttpResponse} containing the response data for successful HTTP requests (2XX status codes)
     * @throws HttpException    if the server returns a client (4XX) or server (5XX) error response
     * @throws RuntimeException if an unexpected error occurs during request execution (e.g., network issues, timeouts)
     */
    SuccessfulHttpResponse execute(HttpRequest request) throws HttpException, RuntimeException;

    /**
     * Executes a given HTTP request asynchronously with server-sent events (SSE) handling.
     * This method returns immediately while processing continues on a separate thread.
     * Events are processed through the provided {@link ServerSentEventListener}.
     * <p>
     * The execution flow is as follows:
     * <ol>
     *   <li>The request is initiated asynchronously</li>
     *   <li>Received SSE data is parsed using the {@link DefaultServerSentEventParser}</li>
     *   <li>Parsed events are delivered to the listener's appropriate methods</li>
     *   <li>If an error occurs, {@link ServerSentEventListener#onError(Throwable)} is called</li>
     * </ol>
     * <p>
     * If any exception is thrown from the listener's methods, the stream processing
     * will be terminated and no further events will be processed.
     *
     * @param request  the HTTP request to be executed.
     * @param listener the listener to receive parsed events and error notifications.
     */
    default void execute(HttpRequest request, ServerSentEventListener listener) {
        execute(request, new DefaultServerSentEventParser(), listener);
    }

    /**
     * Executes a given HTTP request asynchronously with server-sent events (SSE) handling.
     * This method returns immediately while processing continues on a separate thread.
     * Events are processed through the provided {@link ServerSentEventListener}.
     * <p>
     * The execution flow is as follows:
     * <ol>
     *   <li>The request is initiated asynchronously</li>
     *   <li>Received SSE data is parsed using the provided parser</li>
     *   <li>Parsed events are delivered to the listener's appropriate methods</li>
     *   <li>If an error occurs, {@link ServerSentEventListener#onError(Throwable)} is called</li>
     * </ol>
     * <p>
     * If any exception is thrown from the listener's methods, the stream processing
     * will be terminated and no further events will be processed.
     *
     * @param request  the HTTP request to be executed.
     * @param parser   the parser to process incoming server-sent events.
     * @param listener the listener to receive parsed events and error notifications.
     */
    void execute(HttpRequest request, ServerSentEventParser parser, ServerSentEventListener listener);
}

HttpClient定义了execute方法，其中有一个支持ServerSentEventListener

HttpClientBuilderFact