在Symfony2 Entity字段中添加JQuery自动完成

I have a city and voters entity in a one to many relationships.I want to convert the entity field(thousands of records in a dropdown) to a text input so that I can implement the JQuery autocomplete when users start typing 2 letters.After almost two weeks,I successfully created the DataTransformer which transform entity field in to a text input.Now my problem is I am still learning the JQuery/Ajax and I am confused how to implement it in Symfony2 forms.I have a city and voters entity in a one to man