415不支持的媒体类型”错误

我在从JSON到Spring MVC的工作中获取JSON时遇到问题。我的表单是动态的，JSON作为保存的对象返回。处理机箱时，不断出现415错误，即不支持媒体类型。请帮助我，下面是我的代码流程。我也尝试了不同的方法，但对我没有用，我做错了什么？

HTML格式

        <form:form modelAttribute="bp" action="saveUser" method="post" 
   name="bpForm" id="submitForm">


    <div class="form-group form-inline">
        <label>Name</label>
        <form:input type="text" path="bpName" name="bpName"
        class="form-control" />
    </div>
    <button type="submit" class="btn btn-success"
                            >save</button>          
    </form:form>

JQUERY CODE ############################################## ###########

     <script type="text/javascript">
        data = "";

    $(document).ready(function() {
        console.log("ready ....");
        $('#submitForm').submit(function(e) {


            var frm = $('#submitForm');
            e.preventDefault();
            console.log("submitting ....");
            var data = {}
            var Form = this;

            //Gather Data also remove undefined keys(buttons)
            $.each(this, function(i, v){
                    var input = $(v);
                data[input.attr("name")] = input.val();
                delete data["undefined"];
            });
            console.log("JSON : "+JSON.stringify(data))
        $.ajax({
             headers: { 
                    'Accept': 'application/json',
                    'Content-Type': 'application/json' 
                },

            type: frm.attr('method'),
            url: frm.attr('action'),
            dataType : 'json',
            data : JSON.stringify(data),
            success : function(callback){
                alert("Response: Name:");
               // $(this).html("Success!");
            },
            error : function(){
              //  $(this).html("Error!");
            }
        });
        });
    });
</script>

################################################ ####################控制器

 @RequestMapping(value="/saveUser", method = RequestMethod.POST)
public @ResponseBody BusinessPartner  submittedFromData(@RequestBody BusinessPartner user, HttpServletRequest request) {
    System.out.println("!!!!!!!!!!!! ==================="+user.getBpId());
    return user;
}   

###################################

模型类

@Entity
@Table(name="bp_master")
public class BusinessPartner {


@Id
//@GeneratedValue(strategy=GenerationType.AUTO)
@Column(name="BPId")
private int bpId;

@Column(name="BPName")
private String bpName;



public BusinessPartner(){

}

public BpType getBpType() {
    return bpType;
}

public void setBpType(BpType bpType) {
    this.bpType = bpType;
}

public int getBpId() {
    return bpId;
}

public void setBpId(int bpId) {
    this.bpId = bpId;
}

public String getBpName() {
    return bpName;
}

public void setBpName(String bpName) {
    this.bpName = bpName;
}


}