Question

我有一个名为ServiceCaller.java的课程

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();

            }
        }
    }

这是执行前面代码的输出：

Status Code: 200
JSON String:

Exception: No Exception

这就是问题，在Test类中返回的InputString似乎是空的，因为转换为string返回一个空字符串但是如果我在CallService函数中转换InputString时使用相同的代码然后转换成功，另请注意，正确返回状态代码和异常（字符串）。

Answer 1

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

     HttpURLConnection urlConnection = ...

     ...

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

......中缺少此代码可能是最重要的部分。我猜你在返回调用者之前关闭了HttpURLConnection。你如何做到这一点可能会有所不同：

您只需在return
try-catch-finally：你正在finally块中关闭它。
您正在使用Java 7中引入的try-with-resource构造.HttpURLConnection可能会自动关闭。由于HttpURLConnection没有实现AutoClosable，因此这种可能性更小。

Answer 2

我已经解决了首先从HttpURLConnection获取InputStream，然后将其转换为字节数组，然后将该字节数组放入ByteArrayInputStream

byte[] bytes = IOUtils.toByteArray(urlConnection.getInputStream());
ByteArrayInputStream byteStream = new ByteArrayInputStream(bytes);

return new Response(statusCode, byteStream, "");

根据文档a ByteArrayInputStream：

public ByteArrayInputStream（byte [] buf）创建一个ByteArrayInputStream 所以它使用buf作为缓冲区数组。缓冲区数组不是复制。 pos的初始值是0和count的初始值是buf的长度。参数：buf - 输入缓冲区。

Answer 3

问题是您已经在使用InputStream方法中的CallService

了

statusCode = urlConnection.getResponseCode();
Response resp = new Response(statusCode, urlConnection.getInputStream(), "");
InputStream inputStream = resp.getResponseStream();
StringWriter writer = new StringWriter();
IOUtils.copy(inputStream, writer); // consuming the stream
String resultJSON = writer.toString(); // you never use this, so why is it here?

因此，当您尝试在main()中再次读取时，没有剩余字节。

您只能从中读取一次字节。

这不会抛出任何异常，因为IOUtils只是调用InputStream#read(...)，如果已达到EOF，则会-1返回。

请注意，Java命名约定规定方法名称应以小写字符开头。

InputStream丢失了

3 个答案: