orm 系列之常用设计模式

orm

本文是orm系列的第一篇，内容来自github上的一个Markdown，清晰的讲述了一些数据库设计上常用的设计模式，并且阐述了orm是什么？

数据库

主要分一下几部分：

数据库设计模式
DAL(Data Access Layer)
ORM(Object Relational Mapping)
存在的组件
A Note About Domain-Driven Design

Quick note

In our context, a database is seen as a server hosting:

a set of records;
organised through tables or collections;
grouped by databases.

数据库设计模式

Row Data Gateway
Table Data Gateway
Active Record
Data Mapper
Identity Map
etc.

定义和插图来自 Catalog of Patterns of Enterprise Application Architecture

作者Martin Fowler.

Don't forget his name! Read his books!

Row Data Gateway

一个对象扮演的角色就像是数据库中单行记录的网关（Gateway）

每个对象对应一行

!php
// This is the implementation of `BananaGateway`
class Banana
{
    private $id;

    private $name;

    public function getId()
    {
        return $this->id;
    }

    public function getName()
    {
        return $this->name;
    }

    public function setName($name)
    {
        $this->name = $name;
    }
}

使用

!php
$con = new Connection('...');

$banana = new Banana();
$banana->setName('Super Banana');

// Save the banana
$banana->insert($con);

// Update it
$banana->setName('New name for my banana');
$banana->update($con);

// Delete it
$banana->delete($con);

底层实现

!php
public function insert(Connection $con)
{
    // Prepared statement
    $stmt = $this->con->prepare('INSERT INTO bananas VALUES (:name)');

    $stmt->bindValue(':name', $name);

    $stmt->execute();

    // Set the id for this banana
    //
    // It becomes easy to know whether the banana is new or not,
    // you just need to check if id is defined.
    $this->id = $this->con->lastInsertId();
}

Table Data Gateway

扮演着数据库表的网关角色（Gateway）

一个对象处理了表中所有的行记录

It's a Data Access Object.

!php
$table = new BananaGateway(new Connection('...'));

// Insert a new record
$id = $table->insert('My favorite banana');

// Update it
$table->update($id, 'THE banana');

// Delete it
$table->delete($id);

CRUD

DAO实现了CURD操作

读操作会比较负责，是一系列Finders

实现

!php
class BananaGateway
{
    private $con;

    public function __construct(Connection $con)
    {
        $this->con = $con;
    }

    public function insert($name) {}

    public function update($id, $name) {}

    public function delete($id);
}

insert操作

!php
/**
 * @param string $name The name of the banana you want to create
 *
 * @return int The id of the banana
 */
public function insert($name)
{
    // Prepared statement
    $stmt = $this->con->prepare('INSERT INTO bananas VALUES (:name)');

    $stmt->bindValue(':name', $name);

    $stmt->execute();

    return $this->con->lastInsertId();
}

update操作

!php
/**
 * @param int    $id   The id of the banana to update
 * @param string $name The new name of the banana
 *
 * @return bool Returns `true` on success, `false` otherwise
 */
public function update($id, $name)
{
    $stmt = $this->con->prepare(<<<SQL
UPDATE bananas
SET name = :name
WHERE id = :id
SQL
    );

    $stmt->bindValue(':id', $id);
    $stmt->bindValue(':name', $name);

    return $stmt->execute();
}

delete操作

!php
/**
 * @param int $id The id of the banana to delete
 *
 * @return bool Returns `true` on success, `false` otherwise
 */
public function delete($id)
{
    $stmt = $this->con->prepare('DELETE FROM bananas WHERE id = :id');

    $stmt->bindValue(':id', $id);

    return $stmt->execute();
}

Finder方法

!php
// Retrieve all bananas
$bananas = $table->findAll();

// Find bananas by name matching 'THE %'
$bananas = $table->findByName('THE %');

// Retrieve a given banana using its id
$banana = $table->find(123);

// Find one banana by name matching 'THE %'
$banana = $table->findOneByName('THE %');

使用魔术方法 __call() 来实现这些魔术般的finders
http://www.php.net/manual/en/language.oop5.overloading.php#object.call.

Active Record

封装了表中的单行记录，除此之外加上了领域逻辑

Active Record = Row Data Gateway + Domain Logic

!php
$con = new Connection('...');

$banana = new Banana();
$banana->setName('Another banana');
$banana->save($con);

// Call a method that is part of the domain logic
// What can a banana do anyway?
$banana->grow();

// Smart `save()` method
// use `isNew()` under the hood
$banana->save($con);

!php
class Banana
{
    private $height = 1;

    public function grow()
    {
        $this->height++;
    }

    public function save(Connection $con)
    {
        if ($this->isNew()) {
            // issue an INSERT query
        } else {
            // issue an UPDATE query
        }
    }

    public function isNew()
    {
        // Yoda style
        return null === $this->id;
    }
}

Data Mapper

将内存中的数据映射到数据库中，同时保持着彼此之间的解耦

Sort of "Man in the Middle".

!php
class BananaMapper
{
    private $con;

    public function __construct(Connection $con)
    {
        $this->con = $con;
    }

    public function persist(Banana $banana)
    {
        // code to save the banana
    }

    public function remove(Banana $banana)
    {
        // code to delete the banana
    }
}

使用

!php
$banana = new Banana();
$banana->setName('Fantastic Banana');

$con    = new Connection('...');
$mapper = new BananaMapper($con);

Persist = Save or Update

!php
$mapper->persist($banana);

Remove

!php
$mapper->remove($banana);

Identity Map

保证每个对象只会从数据库中加载一次，一旦加载进来，将其保存到一个map中

!php
class Finder
{
    private $identityMap = [];

    public function find($id)
    {
        if (!isset($this->identityMap[$id])) {
            // fetch the object for the given id
            $this->identityMap[$id] = ...;
        }

        return $this->identityMap[$id];
    }
}

Data Access Layer

Data Access Layer / Data Source Name

D**ata Access Layer (DAL) 是标准的操作数据的api，不管你使用哪个数据库，都是一样的

Data Source Name (DSN)则是区分到底在使用哪种数据库

PHP Data Object (PDO)

A DSN in PHP looks like: <database>:host=<host>;dbname=<dbname> where:

<database> can be: mysql, sqlite, pgsql, etc;
<host> is the IP address of the database server (e.g. localhost);
<dbname> is your database name.

http://www.php.net/manual/en/intro.pdo.php

PDO usage

!php
$dsn = 'mysql:host=localhost;dbname=test';

$con = new PDO($dsn, $user, $password);

// Prepared statement
$stmt = $con->prepare($query);
$stmt->execute();

Looks like the Connection class you used before, right?

!php
class Connection extends PDO
{
}

Usage

!php
$con = new Connection($dsn, $user, $password);

Refactoring

!php
class Connection extends PDO
{
    /**
     * @param string $query
     * @param array  $parameters
     *
     * @return bool Returns `true` on success, `false` otherwise
     */
    public function executeQuery($query, array $parameters = [])
    {
        $stmt = $this->prepare($query);

        foreach ($parameters as $name => $value) {
            $stmt->bindValue(':' . $name, $value);
        }

        return $stmt->execute();
    }
}

Usage

!php
/**
 * @param int    $id   The id of the banana to update
 * @param string $name The new name of the banana
 *
 * @return bool Returns `true` on success, `false` otherwise
 */
public function update($id, $name)
{
    $query = 'UPDATE bananas SET name = :name WHERE id = :id';

    return $this->con->executeQuery($query, [
        'id'    => $id,
        'name'  => $name,
    ]);
}

Object Relational Mapping

对象之间的关系

介绍3种关系

One-To-One;
One-To-Many;
Many-To-Many.

ORM一般认为是实现上面各种设计模式的一个工具，并且能很方便的处理对象之间的关系

One-To-One (1-1)

One-To-One

Code Snippet

!php
$profile = $banana->getProfile();

One-To-Many (1-N)

Code Snippet

!php
$bananas = $bananaTree->getBananas();

Many-To-Many (N-N)

Many-To-Many

Code Snippet

!php
$roles = [];
foreach ($banana->getBananaRoles() as $bananaRole) {
    $roles[] = $bananaRole->getRole();
}

// Or, better:
$roles = $banana->getRoles();

存在的组件

Propel ORM

An ORM that implements the Table Data Gateway and Row Data Gateway
patterns, often seen as an Active Record approach.

Documentation: www.propelorm.org.

Doctrine2 ORM

An ORM that implements the Data Mapper pattern.

Documentation: www.doctrine-project.org.

A Note About Domain-Driven Design

Entities

可以通过id进行区分的对象entity:

!php
class Customer
{
    private $id;

    private $name;

    public function __construct($id, Name $name)
    {
        $this->id   = $id;
        $this->name = $name;
    }

    public function getId()
    {
        return $this->id;
    }

    public function getName()
    {
        return $this->name;
    }
}

Value Objects

直接通过值来分区，无id的对象，Value Object:

!php
class Name
{
    private $firstName;

    private $lastName;

    public function __construct($firstName, $lastName)
    {
        $this->firstName = $firstName;
        $this->lastName  = $lastName;
    }

    public function getFirstName()
    {
        return $this->firstName;
    }

    public function getLastName()
    {
        return $this->lastName;
    }
}

The Repository Pattern

Repository协调了领域对象和数据映射层的关系，扮演着内存中领域对象集合（ in-memory domain object collection）的角色。

!php
interface CustomerRepository
{
    /**
     * @return Customer
     */
    public function find($customerId);

    /**
     * @return Customer[]
     */
    public function findAll();

    public function add(Customer $user);

    public function remove(Customer $user);
}

The Repository Pattern

客户端通过构造声明式的query specifications去Repository进行查询。

对象可以被添加进Repository，同样的也能从Repository中移除，从这个角度讲，Repository有点类似于集合的概念，其内部封装了对象和数据库记录之间的映射关系，Repository提供了persistence的一个更面向对象的视角。

Repository同时很好的解决了领域对象和数据映射层之间的耦合关系，充分的分离的关注点，领域对象和数据映射层可以独自的开发，演化。

The Specification Pattern

Specification Pattern

Specification pattern可以将业务规则建模为独立的对象，其主要思想是关注一个对象的问题，可以通过isSatisfiedBy()来回答：

!php
interface CustomerSpecification
{
    /**
     * @return boolean
     */
    public function isSatisfiedBy(Customer $customer);
}

!php
class CustomerIsPremium implements CustomerSpecification
{
    /**
     * {@inheritDoc}
     */
    public function isSatisfiedBy(Customer $customer)
    {
        // figure out if the customer is indeed premium,
        // and return true or false.
    }
}

Repository ♥ Specification

A findSatisfying() method can be added to the CustomerRepository:

!php
interface CustomerRepository
{
    ...

    /**
     * @return Customer[]
     */
    public function findSatisfying(CustomerSpecification $specification);
}

Usage

!php
$specification = new CustomerIsPremium();
$customers     = $repository->findSatisfying($specification);

Combine Them!

!php
class OrSpecification implements CustomerSpecification
{
    public function __construct(
        CustomerSpecification $s1,
        CustomerSpecification $s2
    ) {
        $this->s1 = $s1;
        $this->s2 = $s2;
    }

    public function isSatisfiedBy(Customer $c)
    {
        return $this->s1->isSatisfiedBy($c) || $this->s2->isSatisfiedBy($c);
    }
}

!php
class AndSpecification implements CustomerSpecification
{
    ...

    public function isSatisfiedBy(Customer $c)
    {
        return $this->s1->isSatisfiedBy($c) && $this->s2->isSatisfiedBy($c);
    }
}

!php
class NotSpecification implements CustomerSpecification
{
    public function __construct(CustomerSpecification $s)
    {
        $this->s = $s;
    }

    public function isSatisfiedBy(Customer $c)
    {
        return !$this->s->isSatisfiedBy($c);
    }
}

Usage

!php
// Find customers who have ordered exactly three times,
// but who are not premium customers (yet?)
$specification = new AndSpecification(
    new CustomerHasOrderedThreeTimes(),
    new NotSpecification(
        new CustomerIsPremium()
    )
);

$customers = $repository->findSatisfying($specification);

Specification For Business Rules

在业务层复用specifications

!php
class AwesomeOfferSender
{
    private $specification;

    public function __construct(CustomerIsPremium $specification)
    {
        $this->specification = $specification;
    }

    public function sendOffersTo(Customer $customer)
    {
        if ($this->specification->isSatisfiedBy($customer)) {
            // send offers
        }
    }
}

原文地址是：

https://github.com/willdurand-edu/php-slides/blob/master/src/common/09_databases.md

这是orm的第一篇，你的鼓励是我继续写下去的动力，期待我们共同进步。

最后编辑于：2017.12.04 16:27:09

人面猴
序言：七十年代末，一起剥皮案震惊了整个滨河市，随后出现的几起案子，更是在滨河造成了极大的恐慌，老刑警刘岩，带你破解...
沈念sama阅读 203,362评论 5赞 477
死咒
序言：滨河连续发生了三起死亡事件，死亡现场离奇诡异，居然都是意外死亡，警方通过查阅死者的电脑和手机，发现死者居然都...
沈念sama阅读 85,330评论 2赞 381
救了他两次的神仙让他今天三更去死
文/潘晓璐我一进店门，熙熙楼的掌柜王于贵愁眉苦脸地迎上来，“玉大人，你说我怎么就摊上这事。” “怎么了？”我有些...
开封第一讲书人阅读 150,247评论 0赞 337
道士缉凶录：失踪的卖姜人
文/不坏的土叔我叫张陵，是天一观的道长。经常有香客问我，道长，这世上最难降的妖魔是什么？我笑而不...
开封第一讲书人阅读 54,560评论 1赞 273
港岛之恋（遗憾婚礼）
正文为了忘掉前任，我火速办了婚礼，结果婚礼上，老公的妹妹穿的比我还像新娘。我一直安慰自己，他们只是感情好，可当我...
茶点故事阅读 63,580评论 5赞 365
恶毒庶女顶嫁案：这布局不是一般人想出来的
文/花漫我一把揭开白布。她就那样静静地躺着，像睡着了一般。火红的嫁衣衬着肌肤如雪。梳的纹丝不乱的头发上，一...
开封第一讲书人阅读 48,569评论 1赞 281
城市分裂传说
那天，我揣着相机与录音，去河边找鬼。笑死，一个胖子当着我的面吹牛，可吹牛的内容都是我干的。我是一名探鬼主播，决...
沈念sama阅读 37,929评论 3赞 395
双鸳鸯连环套：你想象不到人心有多黑
文/苍兰香墨我猛地睁开眼，长吁一口气：“原来是场噩梦啊……” “哼！你这毒妇竟也来了？” 一声冷哼从身侧响起，我...
开封第一讲书人阅读 36,587评论 0赞 258
万荣杀人案实录
序言：老挝万荣一对情侣失踪，失踪者是张志新（化名）和其女友刘颖，没想到半个月后，有当地人在树林里发现了一具尸体，经...
沈念sama阅读 40,840评论 1赞 297
护林员之死
正文独居荒郊野岭守林人离奇死亡，尸身上长有42处带血的脓包…… 初始之章·张勋以下内容为张勋视角年9月15日...
茶点故事阅读 35,596评论 2赞 321
白月光启示录
正文我和宋清朗相恋三年，在试婚纱的时候发现自己被绿了。大学时的朋友给我发了我未婚夫和他白月光在一起吃饭的照片。...
茶点故事阅读 37,678评论 1赞 329
活死人
序言：一个原本活蹦乱跳的男人离奇死亡，死状恐怖，灵堂内的尸体忽然破棺而出，到底是诈尸还是另有隐情，我是刑警宁泽，带...
沈念sama阅读 33,366评论 4赞 318
日本核电站爆炸内幕
正文年R本政府宣布，位于F岛的核电站，受9级特大地震影响，放射性物质发生泄漏。R本人自食恶果不足惜，却给世界环境...
茶点故事阅读 38,945评论 3赞 307
男人毒药：我在死后第九天来索命
文/蒙蒙一、第九天我趴在偏房一处隐蔽的房顶上张望。院中可真热闹，春花似锦、人声如沸。这庄子的主人今日做“春日...
开封第一讲书人阅读 29,929评论 0赞 19
一桩弑父案，背后竟有这般阴谋
文/苍兰香墨我抬头看了看天上的太阳。三九已至，却和暖如春，着一层夹袄步出监牢的瞬间，已是汗流浃背。一阵脚步声响...
开封第一讲书人阅读 31,165评论 1赞 259
情欲美人皮
我被黑心中介骗来泰国打工，没想到刚下飞机就差点儿被人妖公主榨干…… 1. 我叫王不留，地道东北人。一个月前我还...
沈念sama阅读 43,271评论 2赞 349
代替公主和亲
正文我出身青楼，却偏偏与公主长得像，于是被迫代替她去往敌国和亲。传闻我的和亲对象是个残疾皇子，可洞房花烛夜当晚...
茶点故事阅读 42,403评论 2赞 342

orm 系列 之 常用设计模式

数据库

Quick note

数据库设计模式

Row Data Gateway

使用

底层实现

Table Data Gateway

CRUD

实现

insert操作

update操作

delete操作

Finder方法

Active Record

Active Record = Row Data Gateway + Domain Logic

Data Mapper

使用

Persist = Save or Update

Remove

Identity Map

Data Access Layer

Data Access Layer / Data Source Name

PHP Data Object (PDO)

PDO usage

Usage

Refactoring

Usage

Object Relational Mapping

对象之间的关系

One-To-One (1-1)

One-To-Many (1-N)

Many-To-Many (N-N)

存在的组件

Propel ORM

Doctrine2 ORM

A Note About Domain-Driven Design

Entities

Value Objects

The Repository Pattern

The Repository Pattern

The Specification Pattern

Repository ♥ Specification

Usage

Combine Them!

Usage

Specification For Business Rules

推荐阅读更多精彩内容

orm 系列之常用设计模式