java - 我应该为 POST HTTP 请求的 Content-Length 使用什么值？

Question

我正在尝试发送 HTTP 请求。目前我一直坚持添加 Content-Length 属性:我已经

httpPost.addHeader("Accept", "application/json");
httpPost.addHeader("Content-Type", "application/json;charset=utf-8");
httpPost.addHeader("Content-Length", ""+json.length() );

如果我评论最后一行(内容长度)服务器返回我错过的错误，我最后一行保持未注释 - 然后我在尝试执行时捕获异常

HttpResponse httpResponse = httpclient.execute(httpPost);

请告诉我设置标题时做错了什么。

PS 我正在发送简单的 JSON 对象

 JSONObject jsonObject = new JSONObject();
 jsonObject.accumulate("phone", phone);

我的帖子方法的完整代码 fragment :

public static JSONObject POST(String url, String phone){
        InputStream inputStream = null;
        String result = "";
        try {

            // 1. create HttpClient
            HttpClient httpclient = new DefaultHttpClient();

            // 2. make POST request to the given URL
            HttpPost httpPost = new HttpPost(url);

            String json = "";

            // 3. build jsonObject
            Log.d("ANT", "JSONObject jsonObject = new JSONObject(); PHONE:"+phone);
            JSONObject jsonObject = new JSONObject();
            jsonObject.accumulate("phone", phone);

            // 4. convert JSONObject to JSON to String
            json = jsonObject.toString();

            // 5. set json to StringEntity
            StringEntity se = new StringEntity(json);

            // 6. set httpPost Entity
            httpPost.setEntity(se);

            Log.d("ANT", "json"+json.length());

            // 7. Set some headers to inform server about the type of the content

            httpPost.addHeader("Accept", "application/json");
            httpPost.addHeader("Content-Type", "application/json;");
//            httpPost.addHeader("Content-Length", ""+json.length() );


            // 8. Execute POST request to the given URL
            Log.d("ANT", "httpPost:"+getStringFromInputStream(httpPost.getEntity().getContent()));
            for (Header s : httpPost.getAllHeaders())
                Log.i("ANT", "header::"+s.getName() + ":"+s.getValue());


            HttpResponse httpResponse = httpclient.execute(httpPost);

            // 9. receive response as inputStream
            inputStream = httpResponse.getEntity().getContent();
            Log.d("ANT", "httpResponse.getEntity().getContent();");

            // 10. convert inputstream to string
            if (inputStream != null) {
                result = getStringFromInputStream(inputStream);
                Log.d("ANT", "getStringFromInputStream : "+result);
                JSONObject obj = new JSONObject(result);
                Log.d("ANT", "JSONObject");
                return obj;
            }
            else
                result = "Did not work!";

        } catch (ClientProtocolException e) {
            Log.d("ANT", "ClientProtocolException : "+ e.getLocalizedMessage());
        } catch (IOException e) {
            Log.d("ANT", "IOException:"+ e.getLocalizedMessage());
        } catch (Exception e) {
            Log.d("ANT", "Exception:"+ e.getLocalizedMessage());
        }

        // 11. return result
        return null;
    }

Answer 1

您能详细说明一下服务器错误代码是什么以及异常发生时的堆栈跟踪吗？

编辑:

我尝试了你的代码的某些部分。我没有设置内容长度(因为这应该自动完成):

public class App 
{
    public static void main( String[] args )
    {
        post("http://www.baidu.com","+8912345");
    }

    public static JSONObject post(String url, String phone){
        InputStream inputStream = null;
        String result = "";

        try {
            // 1. create HttpClient
            HttpClient httpclient = new DefaultHttpClient();

            // 2. make POST request to the given URL
            HttpPost httpPost = new HttpPost(url);

            String json = "";

            // 3. build jsonObject
            JSONObject jsonObject = new JSONObject();
            jsonObject.accumulate("phone", phone);

            // 4. convert JSONObject to JSON to String
            json = jsonObject.toString();

            // 5. set json to StringEntity
            StringEntity se = new StringEntity(json);

            // 6. set httpPost Entity
            httpPost.setEntity(se);

            // 7. Set some headers to inform server about the type of the content
            httpPost.addHeader("Accept", "application/json");
            httpPost.addHeader("Content-Type", "application/json;");

            // 8. Execute
            HttpResponse httpResponse = httpclient.execute(httpPost);

            // 9. receive response as inputStream
            inputStream = httpResponse.getEntity().getContent();

        } catch (ClientProtocolException e) {
            System.out.println("ClientProtocolException : "+e.getLocalizedMessage());
        } catch (IOException e) {
            System.out.println("IOException:"+ e.getLocalizedMessage());
        } catch (Exception e) {
            System.out.println("Exception:"+ e.getLocalizedMessage());
        }

        return null;
    }
}

我使用wireshark并可以验证以下请求是否发送至baidu:

POST / HTTP/1.1
Accept: application/json
Content-Type: application/json;
Content-Length: 20
Host: www.baidu.com
Connection: Keep-Alive
User-Agent: Apache-HttpClient/4.3.6 (java 1.5)

{"phone":"+8912345"}

这表明请求已正确发送，这意味着客户端似乎没有问题。这就是为什么我建议检查服务器端是否有错误。正如我已经提到的，我认为您应该使用 tcpdump 或wireshark 来检查客户端和服务器之间的流量。这可能会让您更好地了解出了什么问题。