public static String doGet(String url){ StringBuffer buffer = new StringBuffer(); try { URL getUrl = new URL(url); HttpURLConnection httpUrlConn = (HttpURLConnection) getUrl.openConnection(); httpUrlConn.setDoOutput(false); httpUrlConn.setDoInput(true); httpUrlConn.setUseCaches(false); httpUrlConn.setRequestMethod("GET"); httpUrlConn.connect(); // 将返回的输入流转换成字符串 InputStream inputStream = httpUrlConn.getInputStream(); InputStreamReader inputStreamReader = new InputStreamReader(inputStream, "utf-8"); BufferedReader bufferedReader = new BufferedReader(inputStreamReader); String str = null; while ((str = bufferedReader.readLine()) != null) { buffer.append(str); } bufferedReader.close(); inputStreamReader.close(); // 释放资源 inputStream.close(); inputStream = null; httpUrlConn.disconnect(); } catch (Exception e) { e.printStackTrace(); } return buffer.toString(); }
以上是HTTP GET请求的发送方法，代码是没有问题，而且传递来的参数在浏览器和postman都测试过，也是没有问题，但是在代码执行http请求的时候会返回“Server returned HTTP response code: 400 for URL”异常信息，具体的原因是访问URL携带的参数里包含空格。
我的请求URL大概是这样子的：
String methodApi = "token.create"; String param = paramJson.toJSONString(); String timestamp = sdf.format(new Date()); String v = "2"; String url = "https://xxxxxx.xxx/token/create"; StringBuffer urlBuffer = new StringBuffer(); urlBuffer.append(url).append("?") .append("app_key=").append(appkey).append("&") .append("grant_type=authorization_code&") .append("method=").append(methodApi).append("&") .append("param_json=").append(paramJson).append("&") .append("sign=").append(md5S).append("&") .append("timestamp=").append("timestamp").append("&") .append("v=").append(v);
大概就是：https://xxxxx.xxx/xxx/xxx?xxx=xxx&xxx=xxx&xxx=xxx这种
然后因为中间有个时间戳的参数 timestamp 数据是“2021-7-19 18:08:34”这种格式的日期，中间有空格，所以导致HTTP请求报错。
解决方法为给有空格的请求参数转码使用：URLEncoder.encode("str","charset");方法
String methodApi = "token.create"; String param = paramJson.toJSONString(); String timestamp = sdf.format(new Date()); String v = "2"; String url = "https://xxxxxx.xxx/token/create"; StringBuffer urlBuffer = new StringBuffer(); urlBuffer.append(url).append("?") .append("app_key=").append(appkey).append("&") .append("grant_type=authorization_code&") .append("method=").append(methodApi).append("&") .append("param_json=").append(paramJson).append("&") .append("sign=").append(md5S).append("&") .append("timestamp=")
.append(URLEncoder.encode("timestamp","utf-8"))
.append("&") .append("v=").append(v);
记录一次Http Get请求遇到的坑，请求返回Server returned HTTP response code: 400 for URL