HttpURLConnection的一個坑

引言

    最近在使用HttpURLConnection請求到另一個應用去獲取數據，剛開始用下面的url請求數據：

String url = "http://localhost:8888/example/queryData.do?query=" +  
"{\"start\":0,\"tableid\":\"EVTS\",\"rows\":10,\"token\":\"76ecc4c399e56792c5fd0905f8ffaa86\","
                + "\"order\":{},\"query\":[]}";

HttpURLConnection conn = (HttpURLConnection)new URL(url).openConnection();
conn.setDoInput(true);
conn.setDoOutput(false);
conn.setUseCaches(false);
conn.setRequestMethod("GET");
conn.setRequestProperty("Host", "www.awebsite.com");
conn.setRequestProperty("User-Agent", "Mozilla/4.0");
conn.setRequestProperty("Accept", "text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8");
conn.setRequestProperty("Accept-Language", "en-us,en;q=0.5");
conn.setRequestProperty("Accept-Charset", "ISO-8859-1,utf-8;q=0.7,*;q=0.7");
conn.setRequestProperty("Keep-Alive", "115");
conn.setRequestProperty("Connection", "keep-alive");
BufferedReader br = new BufferedReader(new InputStreamReader(conn.getInputStream()));
StringBuilder data = new StringBuilder();
String s = "";
while((s = br.readLine()) != null)
    data.append(s);
String pageData = data.toString();

    上面的請求很正常，能拿到預計的數據，可是後續url須要增長一個日期時間的入參後，出問題了，修改後的url變成了下面的這樣：

String url = "http://localhost:8888/example/queryData.do?query=" +  
"{\"start\":0,\"tableid\":\"EVTS\",\"rows\":10,\"token\":\"76ecc4c399e56792c5fd0905f8ffaa86\","
                + "\"order\":{},\"query\":[{"startTime":"2018-03-27 14:00:00","endTime":"2018-03-27 14:30:00"]}";

    HttpURLConnection就會報下面的這種錯誤：

java.io.IOException: <h1>Bad Message 400</h1><pre>reason: Unknown Version</pre>

    一直排查都沒有發現先後有什麼問題。

解決

    只能上網找解決辦法， stackoverflow上也有人遇到這問題：

https://stackoverflow.com/questions/25088269/structr-badmessage-400-unknown-version-for-httpchanneloverhttp

    解決的辦法就是：把空格用轉譯符號代替。

總結

    這還真是一個坑，比較隱蔽。