java - HttpURLConnection:getResponseMessage()、getInputStream() 和 getContent() 之间的区别

Question

团队，

我遇到过如下代码，

private static String getResponse (HttpURLConnection connection) throws Exception
{
   String responseString = null;
   int responseCode = connection.getResponseCode();
   String responseMessage = connection.getResponseMessage();
   Log.debug("%s - Response code is \"%s\" with message \"%s\"",
          methodName, responseCode, responseMessage);
   String line = null;
   if (responseCode == HttpURLConnection.HTTP_OK) {
       BufferedReader bufferedReader = null;
       try {
           InputStream inputStream = connection.getInputStream();
           if (inputStream != null) {
               bufferedReader = Util.bufferedReader(
                   inputStream, Util.Encod.UTF8);
               StringBuilder response = new StringBuilder();
               while ((line = bufferedReader.readLine()) != null) {
                   response.append(line);
                   response.append(Util.getNewLine());
               }
               responseString = response.toString();
           }
       }
       finally {
           if (bufferedReader != null) {
               bufferedReader.close();
           }
       }
       Log.signature.debug(
           "%s - Received following JSON response : %s",
           methodName,
           responseString);
   }
   return responseString;
} 

他们已经收到了如下右图的回复？

String responseMessage = connection.getResponseMessage()

那么为什么他们又要使用 connection.getInputStream()

有什么区别吗？

如果可能的话，你能否也解释一些例子或者什么时候使用下面的而不是上面的 getResponseMessage()/getInputStream()

Class URLConnection 
   public Object getContent() throws IOException 
   public Object getContent(Class[] classes) throws IOException

Answer 1

getResponseMessage() 用于获取连接消息，例如HTTP_NOT_FOUND

HTTP Status-Code 404: Not Found.

要通过 getInputStream() 获取实际数据，请查看以下详细信息:

public InputStream getInputStream() throws IOException

返回一个从这个打开的连接中读取的输入流。如果读取超时在数据可供读取之前到期，则在从返回的输入流读取时会抛出 SocketTimeoutException。

Returns: an input stream that reads from this open connection.

Throws: IOException - if an I/O error occurs while creating the input stream. UnknownServiceException - if the protocol does not support input.

更多详情请引用以下链接: http://docs.oracle.com/javase/7/docs/api/java/net/URLConnection.html#getInputStream()