Question

我有一个网址，可根据请求返回JSON格式的字符串

{"StockID":0,"LastTradePriceOnly":"494.92","ChangePercent":"0.48"}

我使用Java

进行流式传输

InputStream in = null;
in = url.openStream();
BufferedReader reader = new BufferedReader(new InputStreamReader(in));
StringBuilder sb = new StringBuilder();

String line = null;
try {
     while ((line = reader.readLine()) != null) {
     sb.append(line + "\n");
     }


} 
catch (IOException e) {
                e.printStackTrace();
            } finally {
                try {
                    in.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            String result = sb.toString();

但reader.readLine()始终返回null

知道我在这里做错了吗？

这是实际的JSON地址http://app.myallies.com/api/quote/goog

更新

相同的代码在http://app.myallies.com/api/news上正常工作，尽管两个链接都具有相同的服务器实现来生成JSON响应。

Answer 1

它看起来像是它想要的用户代理。以下代码适用于我：

import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.net.URL;

public class JSONTest {

    public static void main(String[] args) throws Exception {

        URL url = new URL("http://app.myallies.com/api/quote/goog");

        HttpURLConnection connection = (HttpURLConnection) url.openConnection();
        connection.setRequestProperty("User-Agent", "Mozilla/5.0 (X11; Linux x86_64; rv:33.0) Gecko/20100101 Firefox/33.0");
        connection.setDoInput(true);

        BufferedReader reader = new BufferedReader(new InputStreamReader(connection.getInputStream()));
        StringBuilder sb = new StringBuilder();

        String line = null;
         while ((line = reader.readLine()) != null) {
             sb.append(line + "\n");
         }

         System.out.println(sb.toString());

    }

}

Answer 2

您获得null的原因是Java发出的请求与浏览器发出的请求不同。您的浏览器包含许多请求标头，除非您明确这样做，否则Java将不会填充。不过，我不确定为什么网络服务器不响应基本请求。您可以通过执行以下操作自行测试：

基本请求（无标题）：

curl http://app.myallies.com/api/quote/goog

结果：null

请求标题：

curl \
-H "Host: app.myallies.com" \
-H "User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:33.0) Gecko/20100101 Firefox/33.0" \
-H "Accept: text/html,application/xhtml,application/xml;q=0.9,*/*;q=0.8" \
-H "Accept-Language: en-US,en;q=0.5" \
-H "Accept-Encoding: gzip, deflate" \
-H "Connection: keep-alive" \
-H "Cache-Control: max-age=0" \
http://app.myallies.com/api/quote/goog`

结果：{"StockID":0,"LastTradePriceOnly":"496.38","ChangePercent":"0.78"}

您可能需要设置一些请求标头，以更接近地模仿浏览器发出的请求。

来自URL的JSON序列化始终返回NULL

2 个答案: