Add field mapping config

README.md

@@ -59,6 +59,44 @@ class Article extends DataObject {
 }
 ```
 
+Example DataObject field mapping, allows aliasing fields so that public requests and responses display different field names:
+
+```php
+namespace Vendor\Project;
+
+use SilverStripe\ORM\DataObject;
+
+class Article extends DataObject {
+
+    private static $db = [
+        'Title'=>'Text',
+        'Published'=>'Boolean'
+    ];
+
+    private static $api_access = [
+        'view' => ['Title', 'Content'],
+    ];
+
+    private static $api_field_mapping = [
+        'customTitle' => 'Title',
+    ];
+}
+```
+Given a dataobject with values:
+```yml
+    ID: 12
+    Title: Title Value
+    Content: Content value
+```
+which when requesting with the url `/api/v1/Vendor-Project-Article/12?fields=customTitle,Content` and `Accept: application/json` the response will look like:
+```Javascript
+{
+    "customTitle": "Title Value",
+    "Content": "Content value"
+}
+```
+Similarly, `PUT` or `POST` requests will have fields transformed from the alias name to the DB field name.
+
 ## Supported operations
 
  - `GET /api/v1/(ClassName)/(ID)` - gets a database record

src/DataFormatter.php

@@ -356,4 +356,87 @@ abstract class DataFormatter
     {
         user_error('DataFormatter::convertStringToArray not implemented on subclass', E_USER_ERROR);
     }
+
+    /**
+     * Convert an array of aliased field names to their Dataobject field name
+     *
+     * @param string $className
+     * @param string[] $fields
+     * @return string[]
+     */
+    public function getRealFields($className, $fields)
+    {
+        $apiMapping = Config::inst()->get($className, 'api_field_mapping');
+        if (is_array($apiMapping) && is_array($fields)) {
+            $mappedFields = [];
+            foreach ($fields as $field) {
+                $mappedFields[] = $this->getMappedKey($apiMapping, $field);
+            }
+            return $mappedFields;
+        }
+        return $fields;
+    }
+
+    /**
+     * Get the DataObject field name from its alias
+     *
+     * @param string $className
+     * @param string $field
+     * @return string
+     */
+    public function getRealFieldName($className, $field)
+    {
+        $apiMapping = $this->getApiMapping($className);
+        return $this->getMappedKey($apiMapping, $field);
+    }
+
+    /**
+     * Get a DataObject Field's Alias
+     * defaults to the fieldname
+     *
+     * @param string $className
+     * @param string $field
+     * @return string
+     */
+    public function getFieldAlias($className, $field)
+    {
+        $apiMapping = $this->getApiMapping($className);
+        $apiMapping = array_flip($apiMapping);
+        return $this->getMappedKey($apiMapping, $field);
+    }
+
+    /**
+     * Get the 'api_field_mapping' config value for a class
+     * or return an empty array
+     *
+     * @param string $className
+     * @return string[]|array
+     */
+    protected function getApiMapping($className)
+    {
+        $apiMapping = Config::inst()->get($className, 'api_field_mapping');
+        if ($apiMapping && is_array($apiMapping)) {
+            return $apiMapping;
+        }
+        return [];
+    }
+
+    /**
+     * Helper function to get mapped field names
+     *
+     * @param array $map
+     * @param string $key
+     * @return string
+     */
+    protected function getMappedKey($map, $key)
+    {
+        if (is_array($map)) {
+            if (array_key_exists($key, $map)) {
+                return $map[$key];
+            } else {
+                return $key;
+            }
+        }
+        return $key;
+    }
 }

src/DataFormatter/JSONDataFormatter.php

@@ -74,7 +74,8 @@ class JSONDataFormatter extends DataFormatter
             }
 
             $fieldValue = $obj->obj($fieldName)->forTemplate();
-            $serobj->$fieldName = $fieldValue;
+            $mappedFieldName = $this->getFieldAlias($className, $fieldName);
+            $serobj->$mappedFieldName = $fieldValue;
         }
 
         if ($this->relationDepth > 0) {

src/DataFormatter/XMLDataFormatter.php

@@ -82,7 +82,8 @@ class XMLDataFormatter extends DataFormatter
                 } else {
                     $fieldValue = Convert::raw2xml($fieldValue);
                 }
-                $xml .= "<$fieldName>$fieldValue</$fieldName>\n";
+                $mappedFieldName = $this->getFieldAlias(get_class($obj), $fieldName);
+                $xml .= "<$mappedFieldName>$fieldValue</$mappedFieldName>\n";
             }
         }
 

src/RestfulServer.php

@@ -13,6 +13,7 @@ use SilverStripe\ORM\SS_List;
 use SilverStripe\Security\Member;
 use SilverStripe\Security\Security;
 use SilverStripe\CMS\Model\SiteTree;
+use TractorCow\Fluent\Task\ConvertTranslatableTask\Exception;
 
 /**
  * Generic RESTful server, which handles webservice access to arbitrary DataObjects.
@@ -257,7 +258,8 @@ class RestfulServer extends Controller
         $this->getResponse()->addHeader('Content-Type', $responseFormatter->getOutputContentType());
 
         $rawFields = $this->request->getVar('fields');
-        $fields = $rawFields ? explode(',', $rawFields) : null;
+        $realFields = $responseFormatter->getRealFields($className, explode(',', $rawFields));
+        $fields = $rawFields ? $realFields : null;
 
         if ($obj instanceof SS_List) {
             $objs = ArrayList::create($obj->toArray());
@@ -345,10 +347,12 @@ class RestfulServer extends Controller
 
         // set custom fields
         if ($customAddFields = $this->request->getVar('add_fields')) {
-            $formatter->setCustomAddFields(explode(',', $customAddFields));
+            $customAddFields = $formatter->getRealFields($className, explode(',', $customAddFields));
+            $formatter->setCustomAddFields($customAddFields);
         }
         if ($customFields = $this->request->getVar('fields')) {
-            $formatter->setCustomFields(explode(',', $customFields));
+            $customFields = $formatter->getRealFields($className, explode(',', $customFields));
+            $formatter->setCustomFields($customFields);
         }
         $formatter->setCustomRelations($this->getAllowedRelations($className));
 
@@ -488,6 +492,13 @@ class RestfulServer extends Controller
                 return $this->notFound();
             }
 
+            $reqFormatter = $this->getRequestDataFormatter($className);
+            if (!$reqFormatter) {
+                return $this->unsupportedMediaType();
+            }
+
+            $relation = $reqFormatter->getRealFieldName($className, $relation);
+
             if (!$obj->hasMethod($relation)) {
                 return $this->notFound();
             }
@@ -561,16 +572,23 @@ class RestfulServer extends Controller
         }
 
         if (!empty($body)) {
-            $data = $formatter->convertStringToArray($body);
+            $rawdata = $formatter->convertStringToArray($body);
         } else {
             // assume application/x-www-form-urlencoded which is automatically parsed by PHP
-            $data = $this->request->postVars();
+            $rawdata = $this->request->postVars();
+        }
+
+        $className = $this->unsanitiseClassName($this->request->param('ClassName'));
+        // update any aliased field names
+        $data = [];
+        foreach ($rawdata as $key => $value) {
+            $newkey = $formatter->getRealFieldName($className, $key);
+            $data[$newkey] = $value;
         }
 
         // @todo Disallow editing of certain keys in database
         $data = array_diff_key($data, ['ID', 'Created']);
 
-        $className = $this->unsanitiseClassName($this->request->param('ClassName'));
         $apiAccess = singleton($className)->config()->api_access;
         if (is_array($apiAccess) && isset($apiAccess['edit'])) {
             $data = array_intersect_key($data, array_combine($apiAccess['edit'], $apiAccess['edit']));