使用entity_metadata_wrapper在自定义实体中保存图像文件

function mymodule_entity_info() {
  $info['mymodule_entity'] = array(
    'label' => t('My Custom Entity'),
    'entity class' => 'MyModuleEntity',
    'base table' => 'mymodule_entity',
    'fieldable' => TRUE,
    'entity keys' => array(
      'id' => 'id',
      'label' => 'name',
    ),
    'bundles' => array(
      'mymodule_entity' => array(
        'label' => t('My Custom Entity'),
        'admin' => array(
          'path' => 'admin/structure/mymodule-entity',
          'access arguments' => array('administer mymodule_entity'),
        ),
      ),
    ),
  );

  return $info;
}

function mymodule_entity_form($entity, &$form_state) {
  $form = array();

  // Add file upload field
  $form['image'] = array(
    '#type' => 'file',
    '#title' => t('Image'),
    '#description' => t('Upload an image file.'),
    '#upload_location' => 'public://mymodule_entity/',
    '#upload_validators' => array(
      'file_validate_extensions' => array('png gif jpg jpeg'),
    ),
  );

  return $form;
}

function mymodule_entity_save($entity, $type) {
  // Load entity using entity_metadata_wrapper
  $wrapper = entity_metadata_wrapper('mymodule_entity', $entity);

  // Get uploaded file object
  $file = file_save_upload('image', array(
    'file_validate_extensions' => array('png gif jpg jpeg'),
    'file_validate_size' => array(1024 * 1024 * 10),
  ));

  if ($file) {
    // Save file to server
    $file->status = FILE_STATUS_PERMANENT;
    file_save($file);

    // Save file URI to entity field
    $wrapper->field_image->file->set($file);
  }

  // Save entity
  $wrapper->save();
}