rails + ext 实现登陆页面的问题

[yuqi508]

form提交
simple.form.doAction('submit',{
url:'/permission/login',
method:'post',
params:'',

success:function(f,a){
if (a.result.success==true) {
window.location='main/';
} else {
Ext.Msg.alert('登陆错误',action.result.msg);
}
},

failure:function(){
Ext.Msg.alert('错误','服务器出现错误请稍后再试！');
}
});


PermissionController类

class PermissionController< ApplicationController

def login
render({:content_type => :json, :text => '{success:true}'})
end
end


测试总是提示“服务器出现错误请稍后再试”，
请问那块写的不对？