Java HttpConnection / HttpsConnection輸入/錯誤流

Question

在java中你怎么知道你是否有來自Http（s）連接的錯誤流或者它是否是一個InputStream？ 我可以告訴它做的唯一方法是同時使用，檢查null並捕獲任何異常。

    HttpConnection con = (HttpConnection)URL.openConnection();
    //Write to output
    InputStream in = con.GetInputStream();
    //Vs
    InputStream error = con.getErrorStream();

java如何確定它具有哪個流？ 它僅僅基於連接的響應代碼嗎？ 所以，如果它> = 200且<300那么它的inputStream以外是一個errorStream嗎？

謝謝。

Answer 1

HTTP_INTERNAL_ERROR（500）不是唯一可以創建錯誤流的響應代碼，還有許多其他響應代碼：400,401,402,403,404,405,406,407,408,409,410,411,412,413 ，414,415,501,502,503,504,505等。

不僅如此，如果connection.getResponseCode()啟動連接並且HTTP響應狀態代碼是錯誤類狀態代碼，則它可能會拋出異常。 因此，在connection.getResponseCode()之后立即檢查500（HTTP_INTERNAL_ERROR）實際上可能是無法訪問的代碼，具體取決於您訪問connection 。

我已經看到實現的策略是在拋出異常時使用錯誤流，否則使用輸入流。 以下代碼提供了一個基本的結構起點 。 您可能想要添加它。

InputStream responseStream = null;
int responseCode = -1;
IOException exception = null;
try
{
    responseCode = connection.getResponseCode();  
    responseStream = connection.getInputStream();
}
catch(IOException e)
{
    exception = e;
    responseCode = connection.getResponseCode();  
    responseStream = connection.getErrorStream();    
}

// You can now examine the responseCode, responseStream, and exception variables
// For example:

if (responseStream != null)
{
    // Go ahead and examine responseCode, but
    // always read the data from the responseStream no matter what
    // (This clears the connection for reuse).
    // Probably log the exception if it's not null
}
else
{
    // This can happen if e.g. a malformed HTTP response was received
    // This should be treated as an error.  The responseCode variable
    // can be examined but should not be trusted to be accurate.
    // Probably log the exception if it's not null
}

Answer 2

你可以這樣做：

InputStream inStream = null;  
int responseCode = connection.getResponseCode();  
if (responseCode == HttpURLConnection.HTTP_INTERNAL_ERROR) {            
    inStream = connection.getErrorStream();    
}  
else{  
    inStream = connection.getInputStream();  
}  

HTTP返回代碼表示要回讀的流的類型。