发送http请求并接收返回数据

public static String getDocumentAt(String urlString) {
StringBuffer sb = new StringBuffer();
try {
URL url = new URL(urlString);// 生成url对象
URLConnection urlConnection = url.openConnection();// 打开url连接
BufferedReader br = new BufferedReader(new InputStreamReader(urlConnection.getInputStream(),"utf-8"));
String line = null;
while ((line = br.readLine()) != null) {
sb.append(line);
}
} catch (MalformedURLException e) {
System.out.println("不能连接到URL：" + urlString);
e.printStackTrace();
} catch (IOException e) {
System.out.println("不能连接到URL：" + urlString);
e.printStackTrace();
}
return sb.toString();
}