diff --git a/src/DataMapper/Cache/Apc.php b/src/DataMapper/Cache/Apc.php
index 8b53b60..5bae411 100644
--- a/src/DataMapper/Cache/Apc.php
+++ b/src/DataMapper/Cache/Apc.php
@@ -1,32 +1,31 @@
 <?php
-
 namespace Owl\DataMapper\Cache;
 
 trait Apc
 {
     use Hooks;
 
-    protected function getCache($id)
+    protected function getCache(array $id)
     {
         $key = $this->getCacheKey($id);
-        $fn = $this->getFn('fetch');
+        $fn  = $this->getFn('fetch');
 
         return $fn($key) ?: [];
     }
 
-    protected function deleteCache($id)
+    protected function deleteCache(array $id)
     {
         $key = $this->getCacheKey($id);
-        $fn = $this->getFn('delete');
+        $fn  = $this->getFn('delete');
 
         return $fn($key);
     }
 
-    protected function saveCache($id, array $record, $ttl = null)
+    protected function saveCache(array $id, array $record, $ttl = null)
     {
         $key = $this->getCacheKey($id);
         $ttl = $ttl ?: $this->getCacheTTL();
-        $fn = $this->getFn('store');
+        $fn  = $this->getFn('store');
 
         return $fn($key, $record, $ttl);
     }
@@ -45,6 +44,6 @@ private function getFn($method)
             }
         }
 
-        return $prefix.$method;
+        return $prefix . $method;
     }
 }
diff --git a/src/DataMapper/Cache/Hooks.php b/src/DataMapper/Cache/Hooks.php
index 0beda2f..0854f8f 100644
--- a/src/DataMapper/Cache/Hooks.php
+++ b/src/DataMapper/Cache/Hooks.php
@@ -1,5 +1,4 @@
 <?php
-
 namespace Owl\DataMapper\Cache;
 
 /**
@@ -45,14 +44,14 @@ trait Hooks
      *
      * @return array|false
      */
-    abstract protected function getCache($id);
+    abstract protected function getCache(array $id);
 
     /**
      * @param mixed $id
      *
      * @return bool
      */
-    abstract protected function deleteCache($id);
+    abstract protected function deleteCache(array $id);
 
     /**
      * @param mixed $id
@@ -61,7 +60,7 @@ abstract protected function deleteCache($id);
      *
      * @return bool
      */
-    abstract protected function saveCache($id, array $record, $ttl = null);
+    abstract protected function saveCache(array $id, array $record, $ttl = null);
 
     /**
      * create cache after save new data, if cache policy set.
@@ -71,12 +70,11 @@ abstract protected function saveCache($id, array $record, $ttl = null);
     protected function __afterInsert(\Owl\DataMapper\Data $data)
     {
         $policy = $this->getCachePolicy();
-
-        $id = $data->id();
+        $id     = $data->id(true);
 
         if ($policy['insert']) {
             $record = $this->unpack($data);
-            $record = $this->normalizeCacheRecord($record);
+            $record = $this->removeNullValues($record);
 
             $this->saveCache($id, $record);
         } elseif ($policy['not_found']) {
@@ -94,15 +92,15 @@ protected function __afterInsert(\Owl\DataMapper\Data $data)
     protected function __afterUpdate(\Owl\DataMapper\Data $data)
     {
         $policy = $this->getCachePolicy();
+        $id     = $data->id(true);
 
         if ($policy['update']) {
-            $id = $data->id();
             $record = $this->unpack($data);
-            $record = $this->normalizeCacheRecord($record);
+            $record = $this->removeNullValues($record);
 
             $this->saveCache($id, $record);
         } else {
-            $this->deleteCache($data->id());
+            $this->deleteCache($id);
         }
 
         parent::__afterUpdate($data);
@@ -115,7 +113,7 @@ protected function __afterUpdate(\Owl\DataMapper\Data $data)
      */
     protected function __afterDelete(\Owl\DataMapper\Data $data)
     {
-        $this->deleteCache($data->id());
+        $this->deleteCache($data->id(true));
 
         parent::__afterDelete($data);
     }
@@ -129,7 +127,7 @@ protected function __afterDelete(\Owl\DataMapper\Data $data)
      */
     public function refresh(\Owl\DataMapper\Data $data)
     {
-        $this->deleteCache($data->id());
+        $this->deleteCache($data->id(true));
 
         return parent::refresh($data);
     }
@@ -142,8 +140,8 @@ public function refresh(\Owl\DataMapper\Data $data)
     protected function getCachePolicy()
     {
         $defaults = [
-            'insert' => false,
-            'update' => false,
+            'insert'    => false,
+            'update'    => false,
             'not_found' => false,
         ];
 
@@ -155,32 +153,32 @@ protected function getCachePolicy()
 
         if (is_array($policy)) {
             return array_merge($defaults, $policy);
-        } else {
-            if (DEBUG) {
-                throw new \Exception('Invalid cache policy setting');
-            }
+        }
 
-            return $defaults;
+        if (DEBUG) {
+            throw new \Exception('Invalid cache policy setting');
         }
+
+        return $defaults;
     }
 
     /**
      * return record from cache if cache is created, or save data into cache.
      *
-     * @param mixed        $id
+     * @param array        $id
      * @param \Owl\Service $service
      * @param string       $collection
      *
      * @return array
      */
-    protected function doFind($id, \Owl\Service $service = null, $collection = null)
+    protected function doFind(array $id, \Owl\Service $service = null, $collection = null)
     {
         if ($record = $this->getCache($id)) {
             return isset($record['__IS_NOT_FOUND__']) ? false : $record;
         }
 
         if ($record = parent::doFind($id, $service, $collection)) {
-            $record = $this->normalizeCacheRecord($record);
+            $record = $this->removeNullValues($record);
             $this->saveCache($id, $record);
         } else {
             $policy = $this->getCachePolicy();
@@ -194,25 +192,6 @@ protected function doFind($id, \Owl\Service $service = null, $collection = null)
         return $record;
     }
 
-    /**
-     * remove NULL value from record.
-     *
-     * @param array $record
-     *
-     * @return array
-     */
-    protected function normalizeCacheRecord(array $record)
-    {
-        // 值为NULL的字段不用缓存
-        foreach ($record as $key => $val) {
-            if ($val === null) {
-                unset($record[$key]);
-            }
-        }
-
-        return $record;
-    }
-
     /**
      * @param string $key
      *
@@ -226,35 +205,31 @@ protected function getCacheService($key)
     }
 
     /**
-     * @param mixed $id
+     * @param array $id
      *
      * @return string
      */
-    protected function getCacheKey($id)
+    protected function getCacheKey(array $id)
     {
         $prefix = $this->hasOption('cache_key')
         ? $this->getOption('cache_key')
         : sprintf('entity:%s', str_replace('\\', ':', trim($this->class, '\\')));
 
-        $prefix = $prefix.'@';
+        $prefix = $prefix . '@';
 
         if ($this->hasOption('cache_key_prefix')) {
-            $prefix = $this->getOption('cache_key_prefix').':'.$prefix;
+            $prefix = $this->getOption('cache_key_prefix') . ':' . $prefix;
         }
 
-        if (is_array($id)) {
-            ksort($id);
-
-            $kv = [];
-            foreach ($id as $k => $v) {
-                $kv[] = sprintf('%s:%s', $k, $v);
-            }
+        ksort($id);
 
-            $key = $prefix.implode(':', $kv);
-        } else {
-            $key = $prefix.$id;
+        $kv = [];
+        foreach ($id as $k => $v) {
+            $kv[] = sprintf('%s:%s', $k, $v);
         }
 
+        $key = $prefix . implode(':', $kv);
+
         return strtolower($key);
     }
 
@@ -265,4 +240,23 @@ protected function getCacheTTL()
     {
         return $this->hasOption('cache_ttl') ? $this->getOption('cache_ttl') : 300;
     }
+
+    /**
+     * remove NULL value from record.
+     *
+     * @param array $record
+     *
+     * @return array
+     */
+    private function removeNullValues(array $record)
+    {
+        // 值为NULL的字段不用缓存
+        foreach ($record as $key => $val) {
+            if ($val === null) {
+                unset($record[$key]);
+            }
+        }
+
+        return $record;
+    }
 }
diff --git a/src/DataMapper/Cache/Memcached.php b/src/DataMapper/Cache/Memcached.php
index e989d02..2480bbd 100644
--- a/src/DataMapper/Cache/Memcached.php
+++ b/src/DataMapper/Cache/Memcached.php
@@ -1,14 +1,13 @@
 <?php
-
 namespace Owl\DataMapper\Cache;
 
 trait Memcached
 {
     use Hooks;
 
-    protected function getCache($id)
+    protected function getCache(array $id)
     {
-        $key = $this->getCacheKey($id);
+        $key       = $this->getCacheKey($id);
         $memcached = $this->getCacheService($key);
 
         try {
@@ -26,19 +25,19 @@ protected function getCache($id)
         }
     }
 
-    protected function deleteCache($id)
+    protected function deleteCache(array $id)
     {
-        $key = $this->getCacheKey($id);
+        $key       = $this->getCacheKey($id);
         $memcached = $this->getCacheService($key);
 
         return $memcached->delete($key);
     }
 
-    protected function saveCache($id, array $record, $ttl = null)
+    protected function saveCache(array $id, array $record, $ttl = null)
     {
-        $key = $this->getCacheKey($id);
+        $key       = $this->getCacheKey($id);
         $memcached = $this->getCacheService($key);
-        $ttl = $ttl ?: $this->getCacheTTL();
+        $ttl       = $ttl ?: $this->getCacheTTL();
 
         return $memcached->set($key, \Owl\safe_json_encode($record, JSON_UNESCAPED_UNICODE), $ttl);
     }
diff --git a/src/DataMapper/Cache/Redis.php b/src/DataMapper/Cache/Redis.php
index e85e13b..b50d426 100644
--- a/src/DataMapper/Cache/Redis.php
+++ b/src/DataMapper/Cache/Redis.php
@@ -1,14 +1,13 @@
 <?php
-
 namespace Owl\DataMapper\Cache;
 
 trait Redis
 {
     use Hooks;
 
-    protected function getCache($id)
+    protected function getCache(array $id)
     {
-        $key = $this->getCacheKey($id);
+        $key   = $this->getCacheKey($id);
         $redis = $this->getCacheService($key);
 
         try {
@@ -26,19 +25,19 @@ protected function getCache($id)
         }
     }
 
-    protected function deleteCache($id)
+    protected function deleteCache(array $id)
     {
-        $key = $this->getCacheKey($id);
+        $key   = $this->getCacheKey($id);
         $redis = $this->getCacheService($key);
 
         return $redis->delete($key);
     }
 
-    protected function saveCache($id, array $record, $ttl = null)
+    protected function saveCache(array $id, array $record, $ttl = null)
     {
-        $key = $this->getCacheKey($id);
+        $key   = $this->getCacheKey($id);
         $redis = $this->getCacheService($key);
-        $ttl = $ttl ?: $this->getCacheTTL();
+        $ttl   = $ttl ?: $this->getCacheTTL();
 
         return $redis->setex($key, $ttl, \Owl\safe_json_encode($record, JSON_UNESCAPED_UNICODE));
     }
diff --git a/src/DataMapper/DB/Mapper.php b/src/DataMapper/DB/Mapper.php
index 0629734..3f46fc2 100644
--- a/src/DataMapper/DB/Mapper.php
+++ b/src/DataMapper/DB/Mapper.php
@@ -1,13 +1,12 @@
 <?php
-
 namespace Owl\DataMapper\DB;
 
 class Mapper extends \Owl\DataMapper\Mapper
 {
     public function select(\Owl\Service $service = null, $collection = null)
     {
-        $service = $service ?: $this->getService();
-        $collection = $collection ?: $this->getCollection();
+        $service     = $service ?: $this->getService();
+        $collection  = $collection ?: $this->getCollection();
         $primary_key = $this->getPrimaryKey();
 
         // 只有一个主键，就可以返回以主键为key的数组结果
@@ -30,16 +29,16 @@ public function select(\Owl\Service $service = null, $collection = null)
     public function getBySQLAsIterator($sql, array $parameters = [], \Owl\Service $service = null)
     {
         $service = $service ?: $this->getService();
-        $res = $service->execute($sql, $parameters);
+        $res     = $service->execute($sql, $parameters);
 
         while ($record = $res->fetch()) {
             yield $this->pack($record);
         }
     }
 
-    protected function doFind($id, \Owl\Service $service = null, $collection = null)
+    protected function doFind(array $id, \Owl\Service $service = null, $collection = null)
     {
-        $service = $service ?: $this->getService();
+        $service    = $service ?: $this->getService();
         $collection = $collection ?: $this->getCollection();
 
         $select = $this->select($service, $collection);
@@ -52,9 +51,9 @@ protected function doFind($id, \Owl\Service $service = null, $collection = null)
 
     protected function doInsert(\Owl\DataMapper\Data $data, \Owl\Service $service = null, $collection = null)
     {
-        $service = $service ?: $this->getService();
+        $service    = $service ?: $this->getService();
         $collection = $collection ?: $this->getCollection();
-        $record = $this->unpack($data);
+        $record     = $this->unpack($data);
 
         if (!$service->insert($collection, $record)) {
             return false;
@@ -75,47 +74,32 @@ protected function doInsert(\Owl\DataMapper\Data $data, \Owl\Service $service =
 
     protected function doUpdate(\Owl\DataMapper\Data $data, \Owl\Service $service = null, $collection = null)
     {
-        $service = $service ?: $this->getService();
+        $service    = $service ?: $this->getService();
         $collection = $collection ?: $this->getCollection();
-        $record = $this->unpack($data, ['dirty' => true]);
+        $record     = $this->unpack($data, ['dirty' => true]);
 
-        list($where, $params) = $this->whereID($service, $data->id());
+        list($where, $params) = $this->whereID($service, $data->id(true));
 
         return $service->update($collection, $record, $where, $params);
     }
 
     protected function doDelete(\Owl\DataMapper\Data $data, \Owl\Service $service = null, $collection = null)
     {
-        $service = $service ?: $this->getService();
+        $service    = $service ?: $this->getService();
         $collection = $collection ?: $this->getCollection();
 
-        list($where, $params) = $this->whereID($service, $data->id());
+        list($where, $params) = $this->whereID($service, $data->id(true));
 
         return $service->delete($collection, $where, $params);
     }
 
-    protected function whereID(\Owl\Service $service, $id)
+    protected function whereID(\Owl\Service $service, array $id)
     {
+        $where       = $params       = [];
         $primary_key = $this->getPrimaryKey();
-        $key_count = count($primary_key);
 
-        if ($key_count === 1 && !is_array($id)) {
-            $key = $primary_key[0];
-            $id = [$key => $id];
-        }
-
-        if (!is_array($id)) {
-            throw new \Exception("{$this->class}: Illegal id value");
-        }
-
-        $where = $params = [];
         foreach ($primary_key as $key) {
-            $where[] = $service->quoteIdentifier($key).' = ?';
-
-            if (!isset($id[$key])) {
-                throw new \Exception("{$this->class}: Illegal id value");
-            }
-
+            $where[]  = $service->quoteIdentifier($key) . ' = ?';
             $params[] = $id[$key];
         }
         $where = implode(' AND ', $where);
diff --git a/src/DataMapper/Data.php b/src/DataMapper/Data.php
index bae5450..1266b07 100644
--- a/src/DataMapper/Data.php
+++ b/src/DataMapper/Data.php
@@ -53,27 +53,35 @@ abstract class Data implements \JsonSerializable
     public function __beforeSave()
     {
     }
+
     public function __afterSave()
     {
     }
+
     public function __beforeInsert()
     {
     }
+
     public function __afterInsert()
     {
     }
+
     public function __beforeUpdate()
     {
     }
+
     public function __afterUpdate()
     {
     }
+
     public function __beforeDelete()
     {
     }
+
     public function __afterDelete()
     {
     }
+
     /**
      * @param array [$values]
      * @param array [$options]
@@ -761,21 +769,9 @@ public static function findOrCreate($id)
             return $data;
         }
 
-        if (!is_array($id)) {
-            $primary_keys = static::getMapper()->getPrimaryKey();
-
-            if (count($primary_keys) > 1) {
-                throw new \Owl\DataMapper\Exception\PropertyException(get_called_class() . ': Illegal id value');
-            }
-
-            $props = [
-                $primary_keys[0] => $id,
-            ];
-        } else {
-            $props = $id;
-        }
+        $id = static::getMapper()->normalizeID($id);
 
-        return new static($props);
+        return new static($id);
     }
 
     /**
diff --git a/src/DataMapper/Mapper.php b/src/DataMapper/Mapper.php
index bbb1896..11a03cc 100644
--- a/src/DataMapper/Mapper.php
+++ b/src/DataMapper/Mapper.php
@@ -20,13 +20,13 @@ abstract class Mapper
     /**
      * 根据主键值返回查询到的单条记录.
      *
-     * @param string|int|array $id 主键值
+     * @param array $id 主键值
      * @param Owl\Service [$service] 存储服务连接
      * @param string [$collection] 存储集合名
      *
      * @return array 数据结果
      */
-    abstract protected function doFind($id, \Owl\Service $service = null, $collection = null);
+    abstract protected function doFind(array $id, \Owl\Service $service = null, $collection = null);
 
     /**
      * 插入数据到存储服务
@@ -70,26 +70,42 @@ public function __construct($class)
         $this->options = array_merge($this->normalizeOptions($class::getOptions()), $this->options);
     }
 
-    protected function __beforeSave(\Owl\DataMapper\Data $data) {}
-    protected function __afterSave(\Owl\DataMapper\Data $data) {}
-    protected function __beforeInsert(\Owl\DataMapper\Data $data) {}
-    protected function __afterInsert(\Owl\DataMapper\Data $data) {}
-    protected function __beforeUpdate(\Owl\DataMapper\Data $data) {}
-    protected function __afterUpdate(\Owl\DataMapper\Data $data) {}
-    protected function __beforeDelete(\Owl\DataMapper\Data $data) {}
-    protected function __afterDelete(\Owl\DataMapper\Data $data) {}
+    protected function __beforeSave(\Owl\DataMapper\Data $data)
+    {
+    }
+    protected function __afterSave(\Owl\DataMapper\Data $data)
+    {
+    }
+    protected function __beforeInsert(\Owl\DataMapper\Data $data)
+    {
+    }
+    protected function __afterInsert(\Owl\DataMapper\Data $data)
+    {
+    }
+    protected function __beforeUpdate(\Owl\DataMapper\Data $data)
+    {
+    }
+    protected function __afterUpdate(\Owl\DataMapper\Data $data)
+    {
+    }
+    protected function __beforeDelete(\Owl\DataMapper\Data $data)
+    {
+    }
+    protected function __afterDelete(\Owl\DataMapper\Data $data)
+    {
+    }
     final private function __before($event, \Owl\DataMapper\Data $data)
     {
         $event = ucfirst($event);
-        call_user_func([$data, '__before'.$event]);
-        call_user_func([$this, '__before'.$event], $data);
+        call_user_func([$data, '__before' . $event]);
+        call_user_func([$this, '__before' . $event], $data);
     }
 
     final private function __after($event, \Owl\DataMapper\Data $data)
     {
         $event = ucfirst($event);
-        call_user_func([$data, '__after'.$event]);
-        call_user_func([$this, '__after'.$event], $data);
+        call_user_func([$data, '__after' . $event]);
+        call_user_func([$this, '__after' . $event], $data);
     }
 
     /**
@@ -116,7 +132,7 @@ public function hasOption($key)
     public function getOption($key)
     {
         if (!isset($this->options[$key])) {
-            throw new \RuntimeException('Mapper: undefined option "'.$key.'"');
+            throw new \RuntimeException('Mapper: undefined option "' . $key . '"');
         }
 
         return $this->options[$key];
@@ -315,6 +331,7 @@ public function unpack(Data $data, array $options = null)
      */
     public function find($id, Data $data = null)
     {
+        $id       = $this->normalizeID($id);
         $registry = Registry::getInstance();
 
         if (!$data) {
@@ -346,7 +363,7 @@ public function refresh(Data $data)
             return $data;
         }
 
-        return $this->find($data->id(), $data);
+        return $this->find($data->id(true), $data);
     }
 
     /**
@@ -359,7 +376,7 @@ public function refresh(Data $data)
     public function save(Data $data)
     {
         if ($this->isReadonly()) {
-            throw new \RuntimeException($this->class.' is readonly');
+            throw new \RuntimeException($this->class . ' is readonly');
         }
 
         $is_fresh = $data->isFresh();
@@ -371,7 +388,7 @@ public function save(Data $data)
 
         $result = $is_fresh ? $this->insert($data) : $this->update($data);
         if (!$result) {
-            throw new \RuntimeException($this->class.' save failed');
+            throw new \RuntimeException($this->class . ' save failed');
         }
 
         $this->__after('save', $data);
@@ -389,7 +406,7 @@ public function save(Data $data)
     public function destroy(Data $data)
     {
         if ($this->isReadonly()) {
-            throw new \RuntimeException($this->class.' is readonly');
+            throw new \RuntimeException($this->class . ' is readonly');
         }
 
         if ($data->isFresh()) {
@@ -399,16 +416,44 @@ public function destroy(Data $data)
         $this->__before('delete', $data);
 
         if (!$this->doDelete($data)) {
-            throw new \Exception($this->class.' destroy failed');
+            throw new \Exception($this->class . ' destroy failed');
         }
 
         $this->__after('delete', $data);
 
-        Registry::getInstance()->remove($this->class, $data->id());
+        Registry::getInstance()->remove($this->class, $data->id(true));
 
         return true;
     }
 
+    /**
+     * 把ID值格式化为数组形式.
+     *
+     * @param mixed $id
+     *
+     * @return array
+     */
+    public function normalizeID($id)
+    {
+        $primary_keys = $this->getPrimaryKey();
+
+        if (!is_array($id)) {
+            $key = $primary_keys[0];
+            $id  = [$key => $id];
+        }
+
+        $result = [];
+        foreach ($primary_keys as $key) {
+            if (!isset($id[$key])) {
+                throw new Exception\UnexpectedPropertyValueException('Illegal id value');
+            }
+
+            $result[$key] = $id[$key];
+        }
+
+        return $result;
+    }
+
     /**
      * 把新的Data数据插入到存储集合中.
      *
diff --git a/src/DataMapper/Mongo/Mapper.php b/src/DataMapper/Mongo/Mapper.php
index 06d2f32..c785aa0 100644
--- a/src/DataMapper/Mongo/Mapper.php
+++ b/src/DataMapper/Mongo/Mapper.php
@@ -1,5 +1,4 @@
 <?php
-
 namespace Owl\DataMapper\Mongo;
 
 class Mapper extends \Owl\DataMapper\Mapper
@@ -54,21 +53,21 @@ public function unpack(\Owl\DataMapper\Data $data, array $options = null)
         return $record;
     }
 
-    protected function doFind($id, \Owl\Service $service = null, $collection = null)
+    protected function doFind(array $id, \Owl\Service $service = null, $collection = null)
     {
-        $service = $service ?: $this->getService();
+        $service    = $service ?: $this->getService();
         $collection = $collection ?: $this->getCollection();
 
-        return $service->findOne($collection, ['_id' => $this->normalizeID($id)]);
+        return $service->findOne($collection, ['_id' => $this->normalizeIDValue($id)]);
     }
 
     protected function doInsert(\Owl\DataMapper\Data $data, \Owl\Service $service = null, $collection = null)
     {
-        $service = $service ?: $this->getService();
+        $service    = $service ?: $this->getService();
         $collection = $collection ?: $this->getCollection();
 
-        $record = $this->unpack($data);
-        $record['_id'] = $this->normalizeID($data->id());
+        $record        = $this->unpack($data);
+        $record['_id'] = $this->normalizeIDValue($data->id());
 
         $service->insert($collection, $record);
 
@@ -79,9 +78,9 @@ protected function doInsert(\Owl\DataMapper\Data $data, \Owl\Service $service =
 
     protected function doUpdate(\Owl\DataMapper\Data $data, \Owl\Service $service = null, $collection = null)
     {
-        $service = $service ?: $this->getService();
+        $service    = $service ?: $this->getService();
         $collection = $collection ?: $this->getCollection();
-        $record = $this->unpack($data, ['dirty' => true]);
+        $record     = $this->unpack($data, ['dirty' => true]);
 
         $new = ['$set' => [], '$unset' => []];
         foreach ($record as $key => $value) {
@@ -100,15 +99,15 @@ protected function doUpdate(\Owl\DataMapper\Data $data, \Owl\Service $service =
             unset($new['$unset']);
         }
 
-        return $service->update($collection, ['_id' => $this->normalizeID($data)], $new);
+        return $service->update($collection, ['_id' => $this->normalizeIDValue($data)], $new);
     }
 
     protected function doDelete(\Owl\DataMapper\Data $data, \Owl\Service $service = null, $collection = null)
     {
-        $service = $service ?: $this->getService();
+        $service    = $service ?: $this->getService();
         $collection = $collection ?: $this->getCollection();
 
-        return $service->remove($collection, ['_id' => $this->normalizeID($data)]);
+        return $service->remove($collection, ['_id' => $this->normalizeIDValue($data)]);
     }
 
     protected function normalizeOptions(array $options)
@@ -124,7 +123,7 @@ protected function normalizeOptions(array $options)
         return $options;
     }
 
-    protected function normalizeID($data)
+    protected function normalizeIDValue($data)
     {
         $id = $data instanceof \Owl\DataMapper\Data
             ? $data->id()
diff --git a/src/DataMapper/Registry.php b/src/DataMapper/Registry.php
index 560fec6..59ca3a0 100644
--- a/src/DataMapper/Registry.php
+++ b/src/DataMapper/Registry.php
@@ -3,6 +3,8 @@
 
 class Registry
 {
+    use \Owl\Traits\Singleton;
+
     /**
      * 是否开启DataMapper的Data注册表功能.
      *
@@ -59,7 +61,7 @@ public function set(Data $data)
             return false;
         }
 
-        if (!$id = $data->id()) {
+        if (!$id = $data->id(true)) {
             return false;
         }
 
@@ -71,11 +73,11 @@ public function set(Data $data)
      * 根据类名和主键值，获得缓存结果.
      *
      * @param string $class
-     * @param string|int|array $id
+     * @param array $id
      *
      * @return Data|false
      */
-    public function get($class, $id)
+    public function get($class, array $id)
     {
         if (!$this->isEnabled()) {
             return false;
@@ -94,7 +96,7 @@ public function get($class, $id)
      * @param string $class
      * @param mixed  $id
      */
-    public function remove($class, $id)
+    public function remove($class, array $id)
     {
         if (!$this->isEnabled()) {
             return false;
@@ -120,29 +122,19 @@ public function clear()
      *
      * @return string
      */
-    private static function key($class, $id)
+    private static function key($class, array $id)
     {
+        $class = strtolower(ltrim($class, '\\'));
+        ksort($id);
+
         $key = '';
-        if (is_array($id)) {
-            ksort($id);
-
-            foreach ($id as $prop => $val) {
-                if ($key) {
-                    $key .= ';';
-                }
-                $key .= "{$prop}:{$val}";
+        foreach ($id as $prop => $val) {
+            if ($key) {
+                $key .= ';';
             }
-        } else {
-            $key = $id;
+            $key .= "{$prop}:{$val}";
         }
 
-        return $class.'@'.$key;
-    }
-
-    private static $instance;
-
-    public static function getInstance()
-    {
-        return self::$instance ?: (self::$instance = new self());
+        return $class . '@' . $key;
     }
 }
diff --git a/tests/DataMapper/Cache/HooksTest.php b/tests/DataMapper/Cache/HooksTest.php
new file mode 100644
index 0000000..5652575
--- /dev/null
+++ b/tests/DataMapper/Cache/HooksTest.php
@@ -0,0 +1,70 @@
+<?php
+namespace Tests\DataMapper\Cache;
+
+class HooksTest extends \PHPUnit_Framework_TestCase
+{
+    protected $class = '\Tests\Mock\DataMapper\Data';
+
+    protected function setUp()
+    {
+        ($this->class)::setMapper('\Tests\Mock\DataMapper\CacheMapper');
+    }
+
+    protected function tearDown()
+    {
+        ($this->class)::getMapper()->clearCachedData();
+        ($this->class)::setMapper('\Tests\Mock\DataMapper\Mapper');
+    }
+
+    protected function setAttributes(array $attributes)
+    {
+        ($this->class)::getMapper()->setAttributes($attributes);
+    }
+
+    public function test()
+    {
+        $this->setAttributes([
+            'id'  => ['type' => 'uuid', 'primary_key' => true],
+            'foo' => ['type' => 'string'],
+        ]);
+
+        $class  = $this->class;
+        $mapper = $class::getMapper();
+
+        // cache "NOT FOUND"
+        $id = '5fd55767-1e1d-4c6d-843a-b2a816970300';
+        $class::find($id);
+
+        $this->assertTrue($mapper->hasCached(['id' => $id]));
+        $this->assertSame(['__IS_NOT_FOUND__' => 1], $mapper->getCachedData(['id' => $id]));
+
+        // cache insert
+        $data = new $class([
+            'id'  => $id,
+            'foo' => 'FOO',
+        ]);
+        $data->save();
+        $this->assertSame(
+            [
+                'id'  => $id,
+                'foo' => 'FOO',
+            ],
+            $mapper->getCachedData(['id' => $id])
+        );
+
+        // cache update
+        $data->foo = 'bar';
+        $data->save();
+        $this->assertSame(
+            [
+                'id'  => $id,
+                'foo' => 'bar',
+            ],
+            $mapper->getCachedData(['id' => $id])
+        );
+
+        // remove cache after data destroy
+        $data->destroy();
+        $this->assertFalse($mapper->hasCached(['id' => $id]));
+    }
+}
diff --git a/tests/DataMapper/MapperTest.php b/tests/DataMapper/MapperTest.php
new file mode 100644
index 0000000..e9a7b46
--- /dev/null
+++ b/tests/DataMapper/MapperTest.php
@@ -0,0 +1,59 @@
+<?php
+namespace Tests\DataMapper;
+
+class MapperTest extends \PHPUnit_Framework_TestCase
+{
+    protected $class = '\Tests\Mock\DataMapper\Data';
+
+    protected function setAttributes(array $attributes)
+    {
+        ($this->class)::getMapper()->setAttributes($attributes);
+    }
+
+    public function testNormalizeID()
+    {
+        $this->setAttributes([
+            'id' => ['type' => 'uuid', 'primary_key' => true],
+        ]);
+
+        $mapper = ($this->class)::getMapper();
+
+        $id = $mapper->normalizeID('f6c7339d-9d68-41b1-9f16-860f29ea5dee');
+        $this->assertSame(['id' => 'f6c7339d-9d68-41b1-9f16-860f29ea5dee'], $id);
+
+        $id = $mapper->normalizeID(['id' => '3ed0d7a8-e51e-44ee-a2a1-09d435d94cc5']);
+        $this->assertSame(['id' => '3ed0d7a8-e51e-44ee-a2a1-09d435d94cc5'], $id);
+
+        ////////////////////////////////////////////////////////////////////////
+        $this->setAttributes([
+            'foo' => ['type' => 'uuid', 'primary_key' => true],
+            'bar' => ['type' => 'uuid', 'primary_key' => true],
+        ]);
+
+        $id = [
+            'foo' => 'cfd04278-6c98-4cf2-a26d-345c1ab729a2',
+            'bar' => '7b76caa2-08fa-4e85-8cb8-744a1c5704ac',
+            'baz' => 'ab8b9e5d-087a-458d-a595-29eda8ed38fb',
+        ];
+
+        $this->assertSame(
+            [
+                'foo' => 'cfd04278-6c98-4cf2-a26d-345c1ab729a2',
+                'bar' => '7b76caa2-08fa-4e85-8cb8-744a1c5704ac',
+            ],
+            $mapper->normalizeID($id)
+        );
+
+        try {
+            $mapper->normalizeID('1f47f18c-40d4-47c8-954b-c2d8a6fe4c2a');
+            $this->fail('test Mapper::normalizeID() failed');
+        } catch (\Owl\DataMapper\Exception\UnexpectedPropertyValueException $ex) {
+        }
+
+        try {
+            $mapper->normalizeID(['foo' => '1f47f18c-40d4-47c8-954b-c2d8a6fe4c2a']);
+            $this->fail('test Mapper::normalizeID() failed');
+        } catch (\Owl\DataMapper\Exception\UnexpectedPropertyValueException $ex) {
+        }
+    }
+}
diff --git a/tests/DataMapper/RegistryTest.php b/tests/DataMapper/RegistryTest.php
new file mode 100644
index 0000000..211a9e2
--- /dev/null
+++ b/tests/DataMapper/RegistryTest.php
@@ -0,0 +1,39 @@
+<?php
+namespace Tests\DataMapper;
+
+use Owl\DataMapper\Registry;
+
+class RegistryTest extends \PHPUnit_Framework_TestCase
+{
+    protected $class = '\Tests\Mock\DataMapper\Data';
+
+    protected function setAttributes(array $attributes)
+    {
+        ($this->class)::getMapper()->setAttributes($attributes);
+    }
+
+    public function test()
+    {
+        $this->setAttributes([
+            'id' => ['type' => 'uuid', 'primary_key' => true],
+        ]);
+        $id = '710c825e-20ea-4c98-b313-30d9eec2b2dc';
+
+        $class = $this->class;
+        $data  = new $class([
+            'id' => $id,
+        ]);
+
+        $registry = Registry::getInstance();
+
+        $this->assertFalse((bool) $registry->get($class, $data->id(true)));
+        $data->save();
+        $this->assertFalse((bool) $registry->get($class, $data->id(true)));
+
+        $data = $class::find($id);
+        $this->assertTrue((bool) $registry->get($class, $data->id(true)));
+
+        $data->destroy();
+        $this->assertFalse((bool) $registry->get($class, ['id' => $id]));
+    }
+}
diff --git a/tests/Mock/DataMapper/Cache/Memory.php b/tests/Mock/DataMapper/Cache/Memory.php
new file mode 100644
index 0000000..91bf4fe
--- /dev/null
+++ b/tests/Mock/DataMapper/Cache/Memory.php
@@ -0,0 +1,32 @@
+<?php
+namespace Tests\Mock\DataMapper\Cache;
+
+trait Memory
+{
+    use \Owl\DataMapper\Cache\Hooks;
+
+    protected static $__cache__ = [];
+
+    protected function getCache(array $id)
+    {
+        $key = $this->getCacheKey($id);
+
+        return static::$__cache__[$key] ?? [];
+    }
+
+    protected function deleteCache(array $id)
+    {
+        $key = $this->getCacheKey($id);
+
+        unset(static::$__cache__[$key]);
+    }
+
+    protected function saveCache(array $id, array $record, $ttl = null)
+    {
+        $key = $this->getCacheKey($id);
+
+        static::$__cache__[$key] = $record;
+
+        // var_dump(static::$__cache__);
+    }
+}
diff --git a/tests/Mock/DataMapper/CacheMapper.php b/tests/Mock/DataMapper/CacheMapper.php
new file mode 100644
index 0000000..1d0ad0b
--- /dev/null
+++ b/tests/Mock/DataMapper/CacheMapper.php
@@ -0,0 +1,35 @@
+<?php
+namespace Tests\Mock\DataMapper;
+
+class CacheMapper extends Mapper
+{
+    use Cache\Memory;
+
+    public function hasCached(array $id)
+    {
+        $key = $this->getCacheKey($id);
+
+        return isset(static::$__cache__[$key]);
+    }
+
+    public function getCachedData(array $id)
+    {
+        $key = $this->getCacheKey($id);
+
+        return static::$__cache__[$key] ?? false;
+    }
+
+    public function clearCachedData()
+    {
+        static::$__cache__ = [];
+    }
+
+    protected function getCachePolicy()
+    {
+        return [
+            'insert'    => true,
+            'update'    => true,
+            'not_found' => true,
+        ];
+    }
+}
diff --git a/tests/Mock/DataMapper/Data.php b/tests/Mock/DataMapper/Data.php
index c13c3ca..fd8333a 100644
--- a/tests/Mock/DataMapper/Data.php
+++ b/tests/Mock/DataMapper/Data.php
@@ -13,4 +13,9 @@ class Data extends \Owl\DataMapper\Data
     protected static $attributes = [
         'id' => ['type' => 'integer', 'primary_key' => true, 'auto_generate' => true],
     ];
+
+    public static function setMapper(string $mapper_class)
+    {
+        static::$mapper = $mapper_class;
+    }
 }
diff --git a/tests/Mock/DataMapper/Mapper.php b/tests/Mock/DataMapper/Mapper.php
index ba545ac..90d7510 100644
--- a/tests/Mock/DataMapper/Mapper.php
+++ b/tests/Mock/DataMapper/Mapper.php
@@ -1,5 +1,4 @@
 <?php
-
 namespace Tests\Mock\DataMapper;
 
 use Owl\Service;
@@ -8,15 +7,15 @@ class Mapper extends \Owl\DataMapper\Mapper
 {
     public function setAttributes(array $attributes)
     {
-        $options = $this->getOptions();
+        $options               = $this->getOptions();
         $options['attributes'] = $attributes;
 
         $this->options = $this->normalizeOptions($options);
     }
 
-    protected function doFind($id, Service $service = null, $collection = null)
+    protected function doFind(array $id, Service $service = null, $collection = null)
     {
-        $service = $service ?: $this->getService();
+        $service    = $service ?: $this->getService();
         $collection = $collection ?: $this->getCollection();
 
         return $service->find($collection, $id);
@@ -24,15 +23,15 @@ protected function doFind($id, Service $service = null, $collection = null)
 
     protected function doInsert(\Owl\DataMapper\Data $data, Service $service = null, $collection = null)
     {
-        $service = $service ?: $this->getService();
+        $service    = $service ?: $this->getService();
         $collection = $collection ?: $this->getCollection();
-        $record = $this->unpack($data);
+        $record     = $this->unpack($data);
 
-        if (!$service->insert($collection, $record, $data->id())) {
+        if (!$service->insert($collection, $record, $data->id(true))) {
             return false;
         }
 
-        $id = array();
+        $id = [];
         foreach ($this->getPrimaryKey() as $key) {
             if (!isset($record[$key])) {
                 if (!$last_id = $service->getLastId($collection, $key)) {
@@ -47,18 +46,18 @@ protected function doInsert(\Owl\DataMapper\Data $data, Service $service = null,
 
     protected function doUpdate(\Owl\DataMapper\Data $data, Service $service = null, $collection = null)
     {
-        $service = $service ?: $this->getService();
+        $service    = $service ?: $this->getService();
         $collection = $collection ?: $this->getCollection();
-        $record = $this->unpack($data, array('dirty' => true));
+        $record     = $this->unpack($data, ['dirty' => true]);
 
-        return $service->update($collection, $record, $data->id());
+        return $service->update($collection, $record, $data->id(true));
     }
 
     protected function doDelete(\Owl\DataMapper\Data $data, Service $service = null, $collection = null)
     {
-        $service = $service ?: $this->getService();
+        $service    = $service ?: $this->getService();
         $collection = $collection ?: $this->getCollection();
 
-        return $service->delete($collection, $data->id());
+        return $service->delete($collection, $data->id(true));
     }
 }
diff --git a/tests/Mock/DataMapper/Service.php b/tests/Mock/DataMapper/Service.php
index bfe4ebd..ce2ad05 100644
--- a/tests/Mock/DataMapper/Service.php
+++ b/tests/Mock/DataMapper/Service.php
@@ -13,7 +13,7 @@ public function disconnect()
     {
     }
 
-    public function find($table, $id)
+    public function find($table, array $id)
     {
         $key = $this->keyOfId($id);
 
@@ -24,17 +24,11 @@ public function find($table, $id)
         return $this->data[$table][$key];
     }
 
-    public function insert($table, array $row, $id = null)
+    public function insert($table, array $row, array $id = null)
     {
-        if (!$id) {
-            if (is_array($id)) {
-                foreach ($id as $k => $v) {
-                    if (!$v) {
-                        $id[$k] = StorageSequence::getInstance()->next();
-                    }
-                }
-            } else {
-                $id = StorageSequence::getInstance()->next();
+        foreach ($id as $k => $v) {
+            if (!$v) {
+                $id[$k] = StorageSequence::getInstance()->next();
             }
         }
 
@@ -45,7 +39,7 @@ public function insert($table, array $row, $id = null)
         return $id;
     }
 
-    public function update($table, array $row, $id)
+    public function update($table, array $row, array $id)
     {
         if (!$this->find($table, $id)) {
             return false;
@@ -57,7 +51,7 @@ public function update($table, array $row, $id)
         return true;
     }
 
-    public function delete($table, $id)
+    public function delete($table, array $id)
     {
         $key = $this->keyOfId($id);
 
@@ -84,12 +78,8 @@ public function clear($table = null)
         }
     }
 
-    protected function keyOfId($id)
+    protected function keyOfId(array $id)
     {
-        if (!is_array($id)) {
-            return $id;
-        }
-
         ksort($id);
 
         return md5(strtolower(json_encode($id)));