如何从已存在的数据库中生成实体

CREATE TABLE `blog_post` (
  `id` BIGINT(20) NOT NULL AUTO_INCREMENT,
  `title` VARCHAR(100) COLLATE utf8_unicode_ci NOT NULL,
  `content` longtext COLLATE utf8_unicode_ci NOT NULL,
  `created_at` datetime NOT NULL,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=1 DEFAULT CHARSET=utf8 COLLATE=utf8_unicode_ci;
 
CREATE TABLE `blog_comment` (
  `id` BIGINT(20) NOT NULL AUTO_INCREMENT,
  `post_id` BIGINT(20) NOT NULL,
  `author` VARCHAR(20) COLLATE utf8_unicode_ci NOT NULL,
  `content` longtext COLLATE utf8_unicode_ci NOT NULL,
  `created_at` datetime NOT NULL,
  PRIMARY KEY (`id`),
  KEY `blog_comment_post_id_idx` (`post_id`),
  CONSTRAINT `blog_post_id` FOREIGN KEY (`post_id`) REFERENCES `blog_post` (`id`) ON DELETE CASCADE
) ENGINE=InnoDB AUTO_INCREMENT=1 DEFAULT CHARSET=utf8 COLLATE=utf8_unicode_ci;

<?xml version="1.0" encoding="utf-8"?>
<doctrine-mapping xmlns="http://doctrine-project.org/schemas/orm/doctrine-mapping" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://doctrine-project.org/schemas/orm/doctrine-mapping http://doctrine-project.org/schemas/orm/doctrine-mapping.xsd">
  <entity name="Acme\BlogBundle\Entity\BlogPost" table="blog_post">
    <id name="id" type="bigint" column="id">
      <generator strategy="IDENTITY"/>
    </id>
    <field name="title" type="string" column="title" length="100" nullable="false"/>
    <field name="content" type="text" column="content" nullable="false"/>
    <field name="createdAt" type="datetime" column="created_at" nullable="false"/>
  </entity>
</doctrine-mapping>

// src/Acme/BlogBundle/Entity/BlogComment.php
namespace Acme\BlogBundle\Entity;
 
use Doctrine\ORM\Mapping as ORM;
 
/**
 * Acme\BlogBundle\Entity\BlogComment
 *
 * @ORM\Table(name="blog_comment")
 * @ORM\Entity
 */
class BlogComment
{
    /**
     * @var integer $id
     *
     * @ORM\Column(name="id", type="bigint")
     * @ORM\Id
     * @ORM\GeneratedValue(strategy="IDENTITY")
     */
    private $id;
 
    /**
     * @var string $author
     *
     * @ORM\Column(name="author", type="string", length=100, nullable=false)
     */
    private $author;
 
    /**
     * @var text $content
     *
     * @ORM\Column(name="content", type="text", nullable=false)
     */
    private $content;
 
    /**
     * @var datetime $createdAt
     *
     * @ORM\Column(name="created_at", type="datetime", nullable=false)
     */
    private $createdAt;
 
    /**
     * @var BlogPost
     *
     * @ORM\ManyToOne(targetEntity="BlogPost")
     * @ORM\JoinColumn(name="post_id", referencedColumnName="id")
     */
    private $post;
}