HttpServletRequest获取请求体数据，

//java8 可用
String body = request.getReader().lines().collect(Collectors.joining());

request.getReader().lines()得到一个stream流

.collect(Collectors.joining())相当于是拼接字符串

例：List list = Arrays.asList("1","2","3");

String s =  list.stream.collect(Collectors.joining(","))

打印：s = 1,2,3