接收ajax使用post方法传的json

servlet部分

protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
		
		/*ServletInputStream inputStream = req.getInputStream();
		System.out.println(inputStream);
		BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(inputStream));*/
		
		/*用到io流的方式来获取body中的内容*/
		BufferedReader reader = req.getReader();
		/*读取内容*/
		StringBuffer buffer = new StringBuffer();
		String string;
		while ((string = reader.readLine())!=null) {
			buffer.append(string);
		}
		System.out.println("post请求body中的内容："+buffer);
		/*内容转换*/
		JSONObject parseObject = JSONObject.parseObject(buffer.toString());
		User user = JSONObject.toJavaObject(parseObject, User.class);
		String jsonString = JSONObject.toJSONString(user);
		/*返回json*/
		resp.setContentType("application/json;charset=utf-8");//不加的话，前端识别不出来
		resp.getWriter().println(jsonString);
	}

ajax部分

<script type="text/javascript">
function requestByJson(){
	alert('可以')
	/* JSON.stringify将 JavaScript 对象转换为 JSON 字符串 */
	var params = JSON.stringify({"username":"wei", "password":"toor"})
	$.ajax({
		type:'post',
		url:'${pageContext.request.contextPath }/login',
		contentType:'application/json;charset=utf-8',
		data:params,
		dataType:'json',//后台返回数据
		success:function(data){
			alert(data.username)
			alert(data.password)
		},
		error:function(textStatus,errorThrown){
			alert(textStatus)
		}
	})
	
}

</script>