symfony2原则映射来自现有数据库的双向链接

大家好，感谢您的帮助！

我是Symfony2框架的新手，我面临一个问题：

如何从现有数据库创建双向关系？

起初，我为我的项目创建了数据库，然后将其映射到yml文件；简单地说，DB看起来是这样的：

表user:

CREATE TABLE user (
    `id` INT NOT NULL AUTO_INCREMENT ,
    `login` VARCHAR(255) NULL ,
    `password` VARCHAR(255) NULL ,  
    `customer_id` INT NOT NULL ,    
    PRIMARY KEY (`id`) ,  
    INDEX `fk_user_customer1_idx` (`customer_id` ASC) ,
    CONSTRAINT `fk_user_customer1`
        FOREIGN KEY (`customer_id` )
        REFERENCES `customer` (`id` )  
) ENGINE = InnoDB

表customer:

CREATE  TABLE IF NOT EXISTS `customer` (
    `id` INT NOT NULL AUTO_INCREMENT ,
    `surname` VARCHAR(45) NULL ,
    `name` VARCHAR(45) NULL ,
    `midname` VARCHAR(45) NULL ,
    PRIMARY KEY (`id`) 
) ENGINE = InnoDB

如果我是对的，"用户"与"客户"有多对一的关系；"用户"是拥有的一面，"客户"是相反的一面；

然后我运行以下命令：

php app/console doctrine:mapping:import ShadowTestBundle yml --force

并得到结果：

Shadow'TestBundle'Entity'User:
    type: entity
    table: user
    fields:
        id:
            id: true
            type: integer
            unsigned: false
            nullable: false
            generator:
                strategy: IDENTITY
        login:
            type: string
            length: 255
            fixed: false
            nullable: true
        password:
            type: string
            length: 255
            fixed: false
            nullable: true
    manyToOne:
        customer:
            targetEntity: Customer
            cascade: {  }
            mappedBy: null
            inversedBy: null
            joinColumns:
                customer_id:
                    referencedColumnName: id
            orphanRemoval: false
    lifecycleCallbacks: {  }

Shadow'TestBundle'Entity'Customer:
    type: entity
    table: customer
    fields:
        id:
            id: true
            type: integer
            unsigned: false
            nullable: false
            generator:
                strategy: IDENTITY
        surname:
            type: string
            length: 45
            fixed: false
            nullable: true
        name:
            type: string
            length: 45
            fixed: false
            nullable: true
        midname:
            type: string
            length: 45
            fixed: false
            nullable: true
    lifecycleCallbacks: {  }

通过运行命令符合实体：

php app/console doctrine:generate:entities ShadowTestBundle

实体正确反映yml文件；

但是yml文件和实体都只使用单向链接；是否可以生成双向链接，或者我必须手动编写？在我看来，它应该是这样的：

Shadow'TestBundle'Entity'Customer:
    type: entity
    table: customer
    fields:
...
        midname:
            type: string
            length: 45
            fixed: false
            nullable: true
        oneToMany:
            user:
                targetEntity: User
                mappedBy: cart
lifecycleCallbacks: {  }

我还有一个小问题：为什么在由Doctrine生成的拥有方（User），字段"invertedBy"为空？