Java HttpConnection / HttpsConnection输入/错误流

Question

在java中你怎么知道你是否有来自Http（s）连接的错误流或者它是否是一个InputStream？ 我可以告诉它做的唯一方法是同时使用，检查null并捕获任何异常。

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

java如何确定它具有哪个流？ 它仅仅基于连接的响应代码吗？ 所以，如果它> = 200且<300那么它的inputStream以外是一个errorStream吗？

谢谢。

Answer 1

HTTP_INTERNAL_ERROR（500）不是唯一可以创建错误流的响应代码，还有许多其他响应代码：400,401,402,403,404,405,406,407,408,409,410,411,412,413 ，414,415,501,502,503,504,505等。

不仅如此，如果connection.getResponseCode()启动连接并且HTTP响应状态代码是错误类状态代码，则它可能会抛出异常。 因此，在connection.getResponseCode()之后立即检查500（HTTP_INTERNAL_ERROR）实际上可能是无法访问的代码，具体取决于您访问connection 。

我已经看到实现的策略是在抛出异常时使用错误流，否则使用输入流。 以下代码提供了一个基本的结构起点 。 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

你可以这样做：

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

HTTP返回代码表示要回读的流的类型。