Request::getArgs() can't get data from STDIN

Request::getArgs() can't get data from STDIN when client post JSON / XML to Server.
for example:
post JSON via angularjs 

``` javascript
$http({
    url: '/api/task/create',
    method: "POST",
    data: JSON.stringify(newTask)
    }).success(function(data) {
            console.log(data);
    })
})
```

in Action:

``` php
$this->request->getArgs(); // got nothing
```
