FeatureServer

An open source implementation of the GeoServices specification

Usage

FeatureServer is the underlying dependency of the Koop Output-Geoservices plugin. However, it can also be used on its own with Express.

Example of direct usage with Express

const express = require('express')
const app = express() // set up a basic express server
const FeatureServer = require('@koopjs/featureserver')
const cache = require('cache')


const handler = (req, res) => {
  cache.get(/* some geojson */, (err, data) => {
    if (err) res.status(500).json({error: err.message})
    else FeatureServer.query(req, res, data)
  })
}

app.route('/FeatureServer/:layer/query')
  .get(handler)
  .post(handler)

API

• FeatureServer.query
• FeatureServer.restInfo
• FeatureServer.serverInfo
• FeatureServer.layerInfo
• FeatureServer.layers
• FeatureServer.generateRenderer
• FeatureServer.queryRelatedRecords
• FeatureServer.setDefaults

FeatureServer.query

Pass in geojson and options (a valid geoservices query object), and the function will perform the query and return a valid geoservices query object. The in addition to input statistics: {}, following is an example of all query options that can be passed into the query route: '/FeatureServer/:layer/query'

e.g.

const options = {
  where: `1=1`,
  objectIds: '1,2,3',
  geometry: {
    xmin: -110, ymin: 30, xmax: -106, ymax: 50,
    spatialReference: { wkid: 4326 },
  },
  geometryType: 'esriGeometryEnvelope',
  spatialRel: 'esriSpatialRelContains',
  outFields: '*',
  returnGeometry: true,
  outSR: 102100, // output spatial reference
  returnIdsOnly: true,
  returnCountOnly: true,
  orderByFields: 'Full/Part_COUNT DESC',
  groupByFieldsForStatistics: 'Full/Part',
  outStatistics: {
  	statisticType: 'count',
  	onStatisticField: '<field>',
  	outStatisticFieldName: 'name'
  },
  returnDistinctValues: true,
  resultOffset: 0,
  resultRecordCount: 0,
  f: 'pjson'
}

FeatureServer.query(geojson, options)

FeatureServer.restInfo

Pass in a data object and the request object and return a response object that adheres to the specification of the rest/info response. The data object may contain the owningSystemUrl and the authInfo object:

{
  owningSystemUrl: 'https://domain.com/some/path'
  authInfo: {
    isTokenBasedSecurity: true,
    tokenServicesUrl: 'https://url/that/will/generate/a/token'
  }
}

The response will include the above information as well as the FeatureServer version numbers.

FeatureServer.serverInfo

Generate Geoservices server info

const server = {
  description: String // Describes the collection of layers below,
  copyrightText: String // Optional copyright text
  maxRecordCount: Number // the maximum number of features a provider can return at once,
  hasStaticData: Boolean // whether or not the server contains any data that is not changing
  hasAttachments: Boolean // whether or not the server contains any attachments for this layer
  layers: [{ // A collection of all the layers managed by the server
    type: 'FeatureCollection',
    metadata: {
      id: number, // The unique layer id.  If supplied for one layer, you should supply for all layers to avoid multiple layers having the same id.
      name: String, // The name of the layer
      description: String, // The description of the layer
      extent: Array, // valid extent array e.g. [[180,90],[-180,-90]]
      displayField: String, // The display field to be used by a client
      idField: String, // unique identifier field,
      geometryType: String, // REQUIRED if no features are returned with this object Point || MultiPoint || LineString || MultiLineString || Polygon || MultiPolygon
      maxRecordCount: Number, // the maximum number of features a provider can return at once
      limitExceeded: Boolean, // whether or not the server has limited the features returned
      timeInfo: Object, // describes the time extent and capabilities of the layer
      renderer: Object, // provider can over-ride default symbology of FeatureServer output with a renderer object. See https://developers.arcgis.com/web-map-specification/objects/simpleRenderer, for object specification.
      defaultVisibility: boolean, // The default visibility of this layer
      minScale: number, // The minScale value for this layer
      maxScale: number // The maxScale value for this layer
    }
    features: [// If all the metadata provided above is provided features are optional.
      {
        type: 'Feature',
        geometry: {
          type: 'Point',
          coordinates: [125.6, 10.1]
        },
        properties: {
          name: 'Dinagat Islands'
        }
      }]
    }
  }],
  tables: [{ // A collection of all the tables managed by the server
    type: 'FeatureCollection',
    metadata: {
      // see layer metadata
    }
  }],
  relationships: [{ // A collection of all relationships manged by the server
    id: number, // The unique relationship id.
    name: String, // The name of the relationship
  }]
}

FeatureServer.serverInfo(server)

FeatureServer.layerInfo

Generate Geoservices information about a single layer

FeatureServer.layerInfo(geojson, options)

Note that the layer info is modified with properties metadata and capabilites found at the top-level of the GeoJSON object.

|GeoJSON property| Layer info result| |---|---| |metadata.id| overrides default| |metadata.name| overrides default| |metadata.description| overrides default | |metadata.geometryType| overrides value determined from data | |metadata.extent| overrides value determined from data | |metadata.timeInfo| overrides default | |metadata.maxRecordCount| overrides default (2000) | |metadata.displayField| overrides default (OBJECTID) | |metadata.objectIdField| overrides default (OBJECTID) | |metadata.hasStaticData| overrides default (false) | |metadata.hasAttachments| overrides default (false) | |metadata.renderer| overrides default | |metadata.defaultVisibility| overrides default | |metadata.minScale| overrides default | |metadata.maxScale| overrides default | |metadata.relationships | overrides default | |capabilities.extract| when set to true, Extract added to capabilites (e.g., capabilities: "Query,Extract") | |capabilities.quantization| when set to true, supportsCoordinatesQuantization: true |

metadata.relationships

This defined the server managed relationships for the layer

e.g.

const metadata = {
  //...
  relationships: [{ // A collection of all relationships manged by the server
    id: number, // The unique relationship id.
    name: String, // The name of the relationship
    relatedTableId: number, // Id of the layer/table related records are found
    cardinality: String, // esriRelCardinalityOneToMany | esriRelCardinalityManyToMany
    role: String, // esriRelRoleOrigin | esriRelRoleDestination
    keyField: String, // key field name in the related Table 
    composite: Boolean // likely to false
  }]
  //...
}

FeatureServer.layers

Generate Geoservices information about one or many layers

Can pass a single geojson object or an array of geojson objects

FeatureServer.layers(geojson, options)

FeatureServer.generateRenderer

Pass in geojson and options, and the function will return a valid generateRenderer object. Two classificationDef classification types are supported, classBreaksDef and uniqueValueDef.

classBreaksDef is used to classify numeric data based on a number of breaks and a statistical method. Features can also be normalized before being classified. uniqueValueDef is used to classify data based on a unique field(s). If classification breaks are not supplied through in statistics, they will be generated using classificationDef options. The output is a generateRenderer object.

classBreaksDef

In addition to class breaks as input statistics: [], the following is an example of all classBreaksDef options that can be passed into the generateRenderer route: '/FeatureServer/:layer/generateRenderer'

e.g.

const options = {
 *'classificationDef': {
   *'type': 'classBreaksDef',
   *'classificationField': '<field1>',
   *'classificationMethod': 'esriClassifyEqualInterval' | 'esriClassifyNaturalBreaks' | 'esriClassifyQuantile' | 'esriClassifyStandardDeviation',
   *'breakCount': 9,
    'normalizationType': 'esriNormalizeByField' | 'esriNormalizeByLog' | 'esriNormalizeByPercentOfTotal',
    'normalizationField': '<field2>' // mandatory if 'normalizationType' === 'esriNormalizeByField'
    'baseSymbol': {
      'type': 'esriSMS',
      'style': 'esriSMSCircle',
      'width': 2
    },
    'colorRamp': {
      'type': 'algorithmic',
      'fromColor': [115,76,0,255],
      'toColor': [255,25,86,255],
      'algorithm': 'esriHSVAlgorithm'
    }
  },
  'where': '<field2> > 39'
}

FeatureServer.generateRender(geojson, options)

*required

Output:

{
  type: 'classBreaks',
  field: '<field1>',
  classificationMethod: 'esriClassifyEqualInterval',
  minValue: 0,
  classBreakInfos: [
    {
      classMinValue: 0,
      classMaxValue: 5,
      label: '0-5',
      description: '',
      symbol: {
        type: 'esriSMS',
        style: 'esriSMSCircle',
        width: 2,
        color: [115, 76, 0]
      }
    },
    {
      classMinValue: 6,
      classMaxValue: 11,
      label: '6-11',
      description: '',
      symbol: {
        type: 'esriSMS',
        style: 'esriSMSCircle',
        width: 2,
        color: [156, 67, 0]
      }
    },
    ...
  ]
}

uniqueValueDef

The following is an example of all uniqueValueDef options that can be passed into the generateRenderer route: '/FeatureServer/:layer/generateRenderer'

e.g.

const options = {
 *'classificationDef': {
   *'type': 'uniqueValueDef',
   *'uniqueValueFields': ['Genus', '<field2>', '<field3>'],
   *'fieldDelimiter': ', '
    'baseSymbol': {
      'type': 'esriSMS',
      'style': 'esriSMSCircle',
      'width': 2
    },
    'colorRamp': {
      'type': 'algorithmic',
      'fromColor': [115,76,0,255],
      'toColor': [255,25,86,255],
      'algorithm': 'esriHSVAlgorithm'
    }
  },
  'where': 'latitude > 39'
}

FeatureServer.generateRender(geojson, options)

*required

Output:

{
  type: 'uniqueValue',
  field1: 'Genus',
  field2: '',
  field3: '',
  fieldDelimiter: ', ',
  defaultSymbol: {},
  defaultLabel: '',
  uniqueValueInfos: [
    {
      value: 'MAGNOLIA',
      count: 5908,
      label: 'MAGNOLIA',
      description: '',
      symbol: {
        type: 'esriSMS',
        style: 'esriSMSCircle',
        width: 2,
        color: [115, 76, 0]
  	   }
    },
    {
      value: 'QUERCUS',
      count: 12105,
      label: 'QUERCUS',
      description: '',
      symbol: {
        type: 'esriSMS',
        style: 'esriSMSCircle',
        width: 2,
        color: [116, 76, 0]
  	  }
   },
   ...
  ]

FeatureServer.queryRelatedRecords

Pass in geojson and options, and the function will return a valid queryRelatedRecords object. Required attributes within options are objectIds and relationshipId.

The geojson should be in the special FeatureCollection of FeatureCollections format to show the relationship between requested Features within the layer/table and the referenced relatinoship's features. e.g.

  const geojson = {
    "type": "FeatureCollection",
    "features": [ // Array of FeatureCollections by objectId with the related records as features
      {
        "type": "FeatureCollection",
        "properties": {
          "OBJECTID": 37
        },
        "features": [
          {
            "type": "Feature",
            "geometry": {...},
            "properties": {...}
          }
        ]
      } 
    ]
  }
  
  const options = {
    objectIds: "37, 462", // comma separated string of object ids within the layer to get related records 
    relationshipId: 4, // relationship Id of the server manged relationship of the layer, see FeatureServer.layerInfo
  }

FeatureServer.queryRelatedRecords(geojson, options)

Output:

{
  "geometryType": "esriGeometryPolygon",
  "spatialReference": {
    "wkid": 4267
  },
  "fields": [
    {
      "name": "OBJECTID", 
      "type": "esriFieldTypeOID", 
      "alias": "OBJECTID"
    }, 
    {
      "name": "FIELD1", 
      "type": "esriFieldTypeString", 
      "alias": "FIELD1", 
      "length": 25
    }
  ],
  "relatedRecordGroups": [
    {
      "objectId": 37,
      "relatedRecords": [
        {
          "attributes": {
            "OBJECTID": 5540,
            "FIELD1": "1000147595"
          },
          "geometry": {...}
        }
      ]
    }
  ]
}

FeatureServer.setDefaults

FeatureServer allows setting some server and layer metadata values that are returned by the FeatureServer.serverInfo and FeatureServer.layerInfo methods. You can use the setDefaults method with an object that follows the following schema, though it need not have all properties listed below.

{
  currentVersion, // number; feature server version,
  fullVersion, // string; feature server full version
  maxRecordCount // number; max record count for queries
  server: {
    serviceDescription, // string; default serviceDescription returned in server metadata
    description, // string; default description returned in server metadata
    copyrightText, // string; default copyrightText return in server metadata
    hasStaticData, // boolean; 
    spatialReference, // ArcGIS spatial reference; https://developers.arcgis.com/web-map-specification/objects/spatialReference/
    initialExtent, // ArcGIS extent; https://developers.arcgis.com/web-map-specification/objects/extent/
    fullExtent // ArcGIS extent; https://developers.arcgis.com/web-map-specification/objects/extent/
  }),
  layer: {
    description, // string; default description returned in server metadata
    copyrightText, // string; default copyrightText return in server metadata
    extent // ArcGIS extent; https://developers.arcgis.com/web-map-specification/objects/extent/
  }
}

Examples:

If you are using FeatureServer directly (i.e., not via Koop):

const FeatureServer = require('@koopjs/featureserver');
FeatureServer.setDefaults({ currentVersion: 99.0 })

If you are using FeatureServer as part of a Koop instance, FeatureServer is registered on instantiation. But you can pass the geoservicesDefaults option to the Koop constructor:

const koop = new Koop({
  geoservicesDefaults: { 
    currentVersion: 99.0 // set your own version number
    fullVersion: '99.9.9'
    layer: {
      supportedQueryFormats: 'JSON' // allowed values include 'JSON', 'JSON,geojson'; default is 'JSON,geojson,PBF'
    }
  }
});