ajax和servlet传值的坑

ajax代码

    var obj1={
        "name":"张三",
        "age":30
    };
    alert(JSON.stringify(obj1))
    function sendJson() {
        $.ajax({
            type:"post",
            url: "json?method=check",
            <!-- 这里contentType没加，servlet读取出来的是null!!!! -->
            contentType: "application/json",
            data: JSON.stringify(obj1),
            success: function(data){
                alert("success")
            }
        })
    }

servlet代码

    @WebServlet("/json")
    public class JsonController extends BaseServlet {
        public void check(HttpServletRequest request, HttpServletResponse response) throws IOException {
            //先创建字符流来读取json
            String collect = request.getReader().lines().collect(Collectors.joining());
            //这里用fastjson来解析
            JSONObject jo = JSON.parseObject(collect);
            //获取name和age对应的值
            String name = jo.getString("name");
            int age = jo.getInteger("age");
            System.out.println("name: "+name+";"+"age: "+age);
        }
    }

用了ajax后，在servlet无论是请求转发还是重定向都会没用，两者冲突，一般在前台进行页面跳转

JSON转换

        //把对象转换为json格式，json的键就是类的成员变量名
        JSONObject json;
        Message message = new Message(code, msg);
        String s = JSON.toJSONString(message);
        json = JSON.parseObject(s);
        
        //将map格式转换为json
        HashMap<String, Object> userInfo = (HashMap<String, Object>) session.getAttribute("userInfo");
        JSONObject json = new JSONObject();
        String s = JSON.toJSONString(userInfo);
        json = JSON.parseObject(s);
        
        //将json数据转化为对象
        String collect = request.getReader().lines().collect(Collectors.joining());
        JSONObject json = new JSONObject();
        json = JSON.parseObject(collect);
        //json是有数据的
        User user = JSON.toJavaObject(json, User.class);