nested RESTful resources

问题:

I'm using the support for REST introduced by Grails in 2.3. My app includes the following domain classes:

@Resource(formats=['json', 'xml'])
class Sensor {
    String name
    static hasMany = [metrics: Metric]
}

@Resource(formats=['json', 'xml'])
class Metric {

    String name
    String value

    static belongsTo = [sensor: Sensor]
}

And in UrlMappings.groovy I've defined the following nested RESTful URL mappings:

"/api/sensors"(resources: 'sensor') {
    "/metrics"(resources: "metric")
}

If I navigate to the URL /api/sensors/1/metrics I expect the response to show all Metric instances associated with the Sensor with ID 1, but in fact it returns all Metric instances (up to a limit of 10)

• Is there a URL that will return only Metric instances associated with a particular Sensor instance (without implementing my own controller)?
• Is there a way to override the default limit of 10 results (without adding a max parameter to the request)?

回答1:

Looks like it isn't that simple. :) We can get a vivid picture if this command is run:

grails url-mapping-report

to see

Controller: metric
 |   GET    | /api/sensors/${sensorId}/metrics           | Action: index  |
 |   GET    | /api/sensors/${sensorId}/metrics/create    | Action: create |
 |   POST   | /api/sensors/${sensorId}/metrics           | Action: save   |
 |   GET    | /api/sensors/${sensorId}/metrics/${id}     | Action: show   |
 |   GET    | /api/sensors/${sensorId}/metrics/${id}/edit| Action: edit   |
 |   PUT    | /api/sensors/${sensorId}/metrics/${id}     | Action: update |
 |  DELETE  | /api/sensors/${sensorId}/metrics/${id}     | Action: delete |

So, we would at least need a MetricController inheriting RestfulController and override index() to do an additional check for Metric and return list based on Sensor as shown below:

class MetricController extends RestfulController<Metric> {
    static responseFormats = ['json', 'xml']

    MetricController() {
        super(Metric)
    }

    @Override
    def index() {
        def sensorId = params.sensorId
        respond Metric.where {
            sensor.id == sensorId
        }.list()
    }
}

Above changed would provide the expected result (including the restriction on paginated results) for /api/sensors/1/metrics when hit.