我遇到的400错误

错误是这样的：

HTTP Status 400 -

type Status report

message

description The request sent by the client was syntactically incorrect ().

Apache Tomcat/7.0.16

前端是这样的：

$.ajax({
url : '${pageContext.request.contextPath }/admin/xsxxtjController/findPieChart.do',
data:{type:0},
dataType : 'json',
success : function(result) {
if (result.success) {
alert(123);
}
}
});

最初的方法是这样的：

@RequestMapping("/findPieChart")
@ResponseBody
public Json findPieChart(XsxxtjPage xsxxtjPage,@RequestParam("type") String type,@RequestParam("param") String param) {
System.out.println("type"+type);
Json j = new Json();
try {
// XsxxtjPage u = xsxxtjService.edit(xsxxtjPage);
j.setSuccess(true);
j.setMsg("编辑成功！");
j.setObj(null);
} catch (Exception e) {
j.setMsg(e.getMessage());
}
return j;
}

解决办法是这样的：

@RequestMapping("/findPieChart")
@ResponseBody
public Json findPieChart(XsxxtjPage xsxxtjPage,@RequestParam(value = "type", required = false) String type,@RequestParam(value = "param", required = false) String value) {
System.out.println("type"+type);
Json j = new Json();
try {
// XsxxtjPage u = xsxxtjService.edit(xsxxtjPage);
j.setSuccess(true);
j.setMsg("编辑成功！");
j.setObj(null);
} catch (Exception e) {
j.setMsg(e.getMessage());
}
return j;
}