SpringMVC ajax请求出现415异常

在写ajax请求时出现了415异常

```javascript
 $("#btn4").click(function () {
                //准备好要发送到服务器端的数据
                var student = {
                    stuId: 5,
                    stuName: "tom",
                    address: {
                        province:"广东",
                        city:"深圳",
                        street:"后瑞"
                    },
                    subjects: [
                        {
                            subjectName: "JavaSE",
                            subjectScore: 100
                        }, {
                            subjectName: "SSM",
                            subjectScore: 99
                        }
                    ],
                    "map": {
                        k1: "v1",
                        k2: "v2"
                    }
                };
                //将JSON数组转换为JSON字符串
                var requestBody = JSON.stringify(student);
                alert(typeof(requestBody))

                $.ajax({
                    url: "send/compose/object.json",
                    type: "post",
                    contentType: "application/json;charset=utf-8",
                    dataType: "json",
                    data: requestBody,
                    success: function (response) {
                        console.log(response);
                        alert("成功");
                    },
                    error: function (response) {
                        console.log(response);
                        alert("失败");
                    }
                });

            });
常见的原因是:contentType: "application/json;charset=UTF-8",
但是我加了以后还是没有解决，
查找了半天的原因，发现是SpringMVC配置文件中配置SpringMVC注解驱动时引错了依赖
<mvc:annotation-driven/>
正确的是
xmlns:mvc="http://www.springframework.org/schema/mvc"
所以说还是SpringBoot方便啊hhh,害我找了半天的错

ajax出问题，一个是注解驱动一个是jackson包这两个地方容易忽略