java - 输入流丢失

Question

我有一个名为:ServiceCaller.java的类

此类包含用于调用 Web 服务的方法:

public static Response callService(String strURL, String Token, int timeout, Boolean isPostMethod) {

    String error = "";
    int statusCode = HttpStatus.SC_INTERNAL_SERVER_ERROR;

    HttpURLConnection urlConnection = null;

    try
    {
        URL url = new URL(strURL);

        // Allow non trusted ssl certificates
        if(strURL.startsWith("https"))
        {               
            TrustManagerManipulator.allowAllSSL();
        }

        urlConnection = (HttpURLConnection) url.openConnection();

        if (isPostMethod) {
            urlConnection.setRequestMethod("POST");
        }
        else {
            urlConnection.setRequestMethod("GET");
        }

        // Allow Inputs                                                     
        urlConnection.setDoInput(true);                                              

        // Allow Outputs                                                    
        urlConnection.setDoOutput(true);                                             

        // Don't use a cached copy.                                         
        urlConnection.setUseCaches(false);       

        urlConnection.setRequestProperty("Connection", "Keep-Alive");                

        urlConnection.setRequestProperty("Content-Type", "application/json");     

        urlConnection.setRequestProperty("Token", Helpers.getUTF8Encode(Token));

        urlConnection.setConnectTimeout(timeout);   

        DataOutputStream dos = new DataOutputStream(urlConnection.getOutputStream());
        dos.flush();
        dos.close();

        statusCode = urlConnection.getResponseCode();

        Response r = new Response(statusCode, urlConnection.getInputStream(), "No Exception");

        return r;

    } catch (Exception ex) {

        error = ex.getMessage();

        if (error != null && !error.equals("") && error.contains("401"))
            statusCode = HttpStatus.SC_UNAUTHORIZED;

    } finally {

        urlConnection.disconnect();

    }

    return new Response(statusCode, null, error);

}

这是 Response 类:

public static class Response
{
    private int statusCode;
    private InputStream responseStream;
    private String exception;

    public int getStatusCode() {
        return statusCode;
    }

    public InputStream getResponseStream() {
        return responseStream;
    }

    public String getExceptionError() {
        return exception;
    }

    public Response(int code, InputStream stream, String strException)
    {
        this.statusCode = code;
        this.responseStream = stream;
        this.exception = strException;
    }
}

这是我用来测试 ServiceCaller 中的函数的 Test 类:

    public class TestDemo {

        private static final String EncriptionKey = "keyValueToUse";

        public static void main(String[] args) {

            try {

                String strURL = "http://...";
                String strURL2 = "http://...";
                String Token = "iTcakW5...";
                int timeout = 120000;
                Boolean isPostMethod = true;

                ServiceCaller.Response resp = ServiceCaller.CallService(strURL2, Token, timeout, isPostMethod);

                InputStream inputStream = resp.getResponseStream();
                StringWriter writer = new StringWriter();
                IOUtils.copy(inputStream, writer);
                String resultJSON = writer.toString();

                System.out.println("Status Code: " + resp.getStatusCode());
                System.out.println("JSON String:\n" + resultJSON);
                System.out.println("Exception: " + resp.getExceptionError());

            } catch (Exception e) {

                e.printStackTrace();

            }
        }
    }

这是执行之前代码的输出:

<小时/>

Status Code: 200
JSON String:

Exception: No Exception

<小时/>

问题在于，Test 类中返回的 InputString 似乎是空的，因为转换为字符串会返回空字符串，但是如果我在 CallService 函数内执行相同的代码来转换 InputString，则转换会成功，另请注意，状态代码和异常(字符串)已正确返回。

Answer 1

public static Response CallService(String strURL, String Token, int timeout, Boolean isPostMethod) {

     HttpURLConnection urlConnection = ...

     ...

     new Response(statusCode, urlConnection.getInputStream(), "No Exception");
}

...中缺少的这段代码可能是最重要的部分。我猜您在返回调用者之前关闭了 HttpURLConnection。您执行此操作的方式可能会有所不同:

• 您只需在返回之前将其关闭
• try-catch-finally:您将在finally block 中关闭它。
• 您正在使用 Java 7 中引入的 try-with-resource 构造。HttpURLConnection 可能会自动关闭。这种情况不太可能发生，因为 HttpURLConnection 没有实现 AutoClosable。