HttpRequestRetryHandler 重写的一个小坑

最新推荐文章于 2022-05-27 15:50:38 发布

fighter1945

最新推荐文章于 2022-05-27 15:50:38 发布

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分类专栏： java基础文章标签： HttpRequestRetryHandler httpclient

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本文探讨了在使用Apache HttpClient时遇到的POST请求重试失败问题，并提供了解决方案。通过对HttpRequestRetryHandler的正确配置，确保了POST请求也能被正确重试。

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HttpRequestRetryHandler myRetryHandler = new HttpRequestRetryHandler() {

    public boolean retryRequest(
            IOException exception,
            int executionCount,
            HttpContext context) {
        if (executionCount >= 5) {
            // Do not retry if over max retry count
            return false;
        }
        if (exception instanceof InterruptedIOException) {
            // Timeout
            return false;
        }
        if (exception instanceof UnknownHostException) {
            // Unknown host
            return false;
        }
        if (exception instanceof ConnectTimeoutException) {
            // Connection refused
            return false;
        }
        if (exception instanceof SSLException) {
            // SSL handshake exception
            return false;
        }
        HttpClientContext clientContext = HttpClientContext.adapt(context);
        HttpRequest request = clientContext.getRequest();
        boolean idempotent = !(request instanceof HttpEntityEnclosingRequest);
        if (idempotent) {
            // Retry if the request is considered idempotent
            return true;
        }
        return false;
    }

};
CloseableHttpClient httpclient = HttpClients.custom()
        .setRetryHandler(myRetryHandler)
        .build();

https://hc.apache.org/httpcomponents-client-ga/tutorial/html/fundamentals.html

不知道有多少人在重写HttpRequestRetryHandler 的时候直接copy了官网的这段代码，然后修改

结果综合测试里，get可以retry没问题，post死活过不了

查了几个小时后，终于发现在1.4.2里有以下说明

HttpClient assumes non-entity enclosing methods such as GET and HEAD to be idempotent and entity enclosing methods such as POST and PUT to be not.

一切恍然大悟

删掉以下代码，直接返回true进行retry即可

        HttpClientContext clientContext = HttpClientContext.adapt(context);
        HttpRequest request = clientContext.getRequest();
        boolean idempotent = !(request instanceof HttpEntityEnclosingRequest);
        if (idempotent) {