在代理后面使用 google-http-client 和 google-http-client-apache-v2 會產生 NonRepeatableRequestException

Question

我正在使用google-http-client和google-http-client-apache-v2庫在代理后面發出POST請求。

// 1.- Setting ssl and proxy
HttpClientBuilder builder = HttpClientBuilder.create();
            
SSLContext sslContext = SslUtils.getTlsSslContext();
SslUtils.initSslContext(sslContext, GoogleUtils.getCertificateTrustStore(), SslUtils.getPkixTrustManagerFactory());
builder.setSSLSocketFactory(new SSLConnectionSocketFactory(sslContext));
            
builder.setProxy(new HttpHost(host, port));
CredentialsProvider credentialsProvider = new BasicCredentialsProvider();
credentialsProvider.setCredentials(new AuthScope(host, port), new UsernamePasswordCredentials(user, pass));
builder.setDefaultCredentialsProvider(credentialsProvider);

// 2.- Build request
HttpTransport httpTransport = new ApacheHttpTransport(builder.build());
HttpRequestFactory factory = httpTransport.createRequestFactory(credential);

HttpContent httpContent = new ByteArrayContent("application/json", "{}")
HttpRequest request = factory.buildRequest("POST", new GenericUrl(url), httpContent);

// 3.- Execute request
HttpResponse httpResponse = request.execute();

該請求產生一個NonRepeatableRequestException ：

org.apache.http.client.ClientProtocolException
    at org.apache.http.impl.client.InternalHttpClient.doExecute(InternalHttpClient.java:187) ~[httpclient-4.5.13.jar!/:4.5.13]
    at org.apache.http.impl.client.CloseableHttpClient.execute(CloseableHttpClient.java:83) ~[httpclient-4.5.13.jar!/:4.5.13]
    at org.apache.http.impl.client.CloseableHttpClient.execute(CloseableHttpClient.java:108) ~[httpclient-4.5.13.jar!/:4.5.13]
    at org.apache.http.impl.client.CloseableHttpClient.execute(CloseableHttpClient.java:56) ~[httpclient-4.5.13.jar!/:4.5.13]
    at com.google.api.client.http.apache.v2.ApacheHttpRequest.execute(ApacheHttpRequest.java:73) ~[google-http-client-apache-v2-1.39.2.jar!/:?]
    at com.google.api.client.http.HttpRequest.execute(HttpRequest.java:1012) ~[google-http-client-1.39.2.jar!/:1.39.2]
    at 
    ...
Caused by: org.apache.http.client.NonRepeatableRequestException: Cannot retry request with a non-repeatable request entity.
    at org.apache.http.impl.execchain.MainClientExec.execute(MainClientExec.java:225) ~[httpclient-4.5.13.jar!/:4.5.13]
    at org.apache.http.impl.execchain.ProtocolExec.execute(ProtocolExec.java:186) ~[httpclient-4.5.13.jar!/:4.5.13]
    at org.apache.http.impl.execchain.RetryExec.execute(RetryExec.java:89) ~[httpclient-4.5.13.jar!/:4.5.13]
    at org.apache.http.impl.execchain.RedirectExec.execute(RedirectExec.java:110) ~[httpclient-4.5.13.jar!/:4.5.13]
    at org.apache.http.impl.client.InternalHttpClient.doExecute(InternalHttpClient.java:185) ~[httpclient-4.5.13.jar!/:4.5.13]
    at org.apache.http.impl.client.CloseableHttpClient.execute(CloseableHttpClient.java:83) ~[httpclient-4.5.13.jar!/:4.5.13]
    at org.apache.http.impl.client.CloseableHttpClient.execute(CloseableHttpClient.java:108) ~[httpclient-4.5.13.jar!/:4.5.13]
    at org.apache.http.impl.client.CloseableHttpClient.execute(CloseableHttpClient.java:56) ~[httpclient-4.5.13.jar!/:4.5.13]
    at com.google.api.client.http.apache.v2.ApacheHttpRequest.execute(ApacheHttpRequest.java:73) ~[google-http-client-apache-v2-1.39.2.jar!/:?]
    at com.google.api.client.http.HttpRequest.execute(HttpRequest.java:1012) ~[google-http-client-1.39.2.jar!/:1.39.2]

        

似乎ApacheHttpRequest將可重復的ByteArrayContent （參見JavaDoc ）包裝在不可重復的ContentEntity中。

在谷歌庫中調試執行，代理返回“407 Proxy Authentication Required”，然后它嘗試重復請求（猜測包括憑據），並且由於谷歌庫使用的 ContentEntity 是不可重復的，因此出現異常。

有什么方法可以避免與代理握手，包括在第一個請求中的憑據以避免重用實體？

有沒有辦法告訴谷歌圖書館使用可重復的實體？

嘗試了以下庫版本：

• google-api-client-1.31.5
• google-http-client-jackson2-1.39.2
• google-oauth-client-1.31.5
• google-http-client-apache-v2-1.39.2
• google-http-client-1.39.2
• httpclient-4.5.13
• httpcore-4.4.14

Answer 1

我在github上發布的解決方法，以防它對某人有所幫助：

作為解決方法，我正在嘗試將ApacheHttpTransport包裝在CustomApacheHttpTransport 中，它將方法的結果委托給ApacheHttpTransport，但buildRequest方法除外。

在此CustomApacheHttpTransport buildRequest方法生成類型CustomApacheHttpRequest的定制請求。

public final class CustomApacheHttpTransport extends HttpTransport {
    
    private ApacheHttpTransport apacheHttpTransport;
    
    public CustomApacheHttpTransport (HttpClient httpClient) {
        this.apacheHttpTransport = new ApacheHttpTransport(httpClient);
    }
    
    @Override
    protected LowLevelHttpRequest buildRequest (String method, String url) {
        HttpRequestBase requestBase;
        if (method.equals("DELETE")) {
            requestBase = new HttpDelete(url);
        } else if (method.equals("GET")) {
            requestBase = new HttpGet(url);
        } else if (method.equals("HEAD")) {
            requestBase = new HttpHead(url);
        } else if (method.equals("PATCH")) {
            requestBase = new HttpPatch(url);
        } else if (method.equals("POST")) {
            ..
        }
        return new CustomApacheHttpRequest(apacheHttpTransport.getHttpClient(), requestBase);
    }
}

此自定義請求與ApacheHttpRequest類似，不同之處在於它在執行時會創建一個自定義實體CustomContentEntity ，根據請求內容是否支持重試，該實體將是可重復的。

final class CustomApacheHttpRequest extends LowLevelHttpRequest {
    
    private final HttpClient httpClient;
    private final HttpRequestBase request;
    private RequestConfig.Builder requestConfig;
    
    CustomApacheHttpRequest (HttpClient httpClient, HttpRequestBase request) {
        this.httpClient = httpClient;
        this.request = request;
        this.requestConfig = RequestConfig.custom().setRedirectsEnabled(false).setNormalizeUri(false).setStaleConnectionCheckEnabled(false);
    }
    
    ...
        
    @Override
    public LowLevelHttpResponse execute () throws IOException {
        if (this.getStreamingContent() != null) {
            Preconditions.checkState(request instanceof HttpEntityEnclosingRequest, "Apache HTTP client does not support %s requests with content.", request.getRequestLine().getMethod());
            
            CustomContentEntity entity = new CustomContentEntity(this.getContentLength(), this.getStreamingContent());
            entity.setContentEncoding(this.getContentEncoding());
            entity.setContentType(this.getContentType());
            if (this.getContentLength() == -1L) {
                entity.setChunked(true);
            }
            ((HttpEntityEnclosingRequest) request).setEntity(entity);
        }
        
        request.setConfig(requestConfig.build());
        return new CustomApacheHttpResponse(request, httpClient.execute(request));
    }
}

CustomContentEntity 中的關鍵是isRepeatable方法，它不像ContentEntity那樣總是返回false 。

final class CustomContentEntity extends AbstractHttpEntity {
    
    private final long contentLength;
    private final StreamingContent streamingContent;
    
    CustomContentEntity (long contentLength, StreamingContent streamingContent) {
        this.contentLength = contentLength;
        this.streamingContent = streamingContent;
    }
    
    @Override
    public boolean isRepeatable () {
        return ((HttpContent) streamingContent).retrySupported();
    }
    ...
}

此外，我要創造CustomApacheHttpResponse作為響應的CustomApacheHttpRequest因為ApacheHttpResponse是包私有（CustomApacheHttpResponse酷似ApacheHttpResponse）。

Answer 2

庫返回的錯誤是“您的請求不可重試”，這是正確的。 它按預期工作。

POST 請求從根本上被認為是不可重試的，因為它們最有可能有服務器存儲數據，並且建議服務器返回 201 (Created) 作為響應。 重試 POST 請求可能會多次插入、上傳或發布數據。 這就是為什么有時 Web 瀏覽器會顯示以下提示以避免“重復的信用卡交易”：

POST 的潛在重試邏輯應該在用戶應用程序級別實現，而不是在庫級別。

在您的情況下，錯誤的原因是您無權使用代理。 因此，您需要在嘗試使用代理之前先對其進行身份驗證，然后發送（或重新發送）POST 請求。