Java HttpClient - 通过代理发布文件

我尝试使用代理从我的网络应用程序调用外部网站。此外，还需要在此外部网站上执行 POST 请求。

我正在使用：tomcat7、org.apache.httpcomponents 4.3.4、spring。

在没有代理的情况下进行跟踪是有效的，我得到响应状态“200”；

    // uri = "https://punkte.eiv-fobi.de/upload/upload.do"
    private HttpStatus sendPost(URI uri, File file)
        throws ClientProtocolException, IOException {
    HttpClient httpClient = HttpClientBuilder.create().build();
    HttpPost httpPost = new HttpPost(uri);

    MultipartEntityBuilder builder = MultipartEntityBuilder.create();
    builder.setMode(HttpMultipartMode.BROWSER_COMPATIBLE);
    FileBody fileBody = new FileBody(file, ContentType.MULTIPART_FORM_DATA);
    builder.addPart(PART_NAME, fileBody);
    httpPost.setEntity(builder.build());

    HttpResponse response = httpClient.execute(httpPost);

    return HttpStatus.valueOf(response.getStatusLine().getStatusCode());
    }

现在我尝试添加代理：

    // uri = "https://punkte.eiv-fobi.de/upload/upload.do"
public HttpStatus sendPostWithProxy(URI uri, File file) throws Exception {
    try {
        // JVM Parameter: -Dhttps.proxyHost and -Dhttps.proxyPort
        String proxyHost = System.getProperty("https.proxyHost");
        String proxyPort = System.getProperty("https.proxyPort");

        HttpClient httpClient = HttpClientBuilder.create().build();
        // CloseableHttpClient httpClient = HttpClients.createDefault();
        HttpPost httpPost = new HttpPost(uri);
        HttpHost proxy = new HttpHost(proxyHost,
                Integer.valueOf(proxyPort), "https");

        MultipartEntityBuilder builder = MultipartEntityBuilder.create();
        builder.setMode(HttpMultipartMode.BROWSER_COMPATIBLE);
        FileBody fileBody = new FileBody(file,
                ContentType.MULTIPART_FORM_DATA);
        builder.addPart(PART_NAME, fileBody);
        httpPost.setEntity(builder.build());

        RequestConfig config = RequestConfig.custom().setProxy(proxy)
                .build();
        httpPost.setConfig(config);

        HttpResponse response = httpClient.execute(httpPost);

        return HttpStatus.valueOf(response.getStatusLine().getStatusCode());
    } catch (Exception e) {
        LOGGER.error(
                "exception occurred.",
                e);
    }
    return null;
}

出现以下异常：

javax.net.ssl.SSLException: Unrecognized SSL message, plaintext connection?

我做错了什么？备择方案？

我可以想到可能导致此问题的几个问题：

• 您确定您的 https 代理不需要身份验证吗？在这种情况下，您可能需要在上下文中设置凭据并使用上下文和客户端执行请求。检查此示例：http://www.the-swamp.info/blog/java-request-through-proxy/

• 由于您使用 https 代理并请求 https url（SSL/TLS 端点安全），因此您可能会遇到证书验证问题。检查 https 代理的这个很好的解释：使用 Http 代理与 https 代理的优缺点？