PHP 中的设计模式：工厂模式与单例

1. 引言

在 PHP 项目里，随着业务代码不断膨胀，对象的创建与共享往往会变成一团乱麻：new 散落在各处、数据库连接被反复实例化、日志对象到处传递。设计模式正是解决这类问题的成熟经验总结。

本文聚焦 PHP 中最常用、也最容易被误用的两类创建型模式——工厂模式与单例模式，并给出一个可落地的日志记录器案例。

2. 为什么需要工厂模式

直接 new 一个对象看似简单，但会带来几个问题：

• 耦合：调用方必须知道具体类名与构造参数。
• 难以替换：想从 FileLogger 换成 RedisLogger，需要改动所有调用点。
• 构造复杂：对象初始化需要多步配置时，重复代码会迅速蔓延。

工厂模式的核心思想是：把「创建对象」这件事从业务逻辑中抽离出来，由专门的工厂负责。

用一张图概括「直接 new」与「工厂创建」的差别：

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工厂创建：创建逻辑集中

业务代码

LoggerFactory::create(type)

FileLogger

RedisLogger

直接 new：调用方承担创建细节

业务代码

new FileLogger(path)

new RedisLogger(host, port)

3. 简单工厂

简单工厂（Simple Factory）并不是 GoF 23 种模式之一，但它是理解工厂家族的最佳起点。

<?php

interface Logger
{
public function log(string $message): void;
}

class FileLogger implements Logger
{
public function __construct(private string $path) {}

public function log(string $message): void
{
file_put_contents($this->path, $message . PHP_EOL, FILE_APPEND);
}
}

class EchoLogger implements Logger
{
public function log(string $message): void
{
echo $message . PHP_EOL;
}
}

class LoggerFactory
{
public static function create(string $type): Logger
{
return match ($type) {
'file' => new FileLogger(__DIR__ . '/app.log'),
'echo' => new EchoLogger(),
default => throw new InvalidArgumentException("未知的日志类型: {$type}"),
};
}
}

$logger = LoggerFactory::create('file');
$logger->log('用户登录成功');

优点：调用方只需关心类型字符串，创建逻辑集中在一处。

缺点：新增类型必须修改 LoggerFactory，违反开闭原则；工厂类会随着类型增多而膨胀。

4. 工厂方法

工厂方法（Factory Method）把「创建哪个具体产品」的决定权下放给子类，从而让新增产品无需修改已有工厂。

<?php

abstract class LoggerFactory
{
abstract protected function createLogger(): Logger;

public function log(string $message): void
{
$this->createLogger()->log($message);
}
}

class FileLoggerFactory extends LoggerFactory
{
protected function createLogger(): Logger
{
return new FileLogger(__DIR__ . '/app.log');
}
}

class EchoLoggerFactory extends LoggerFactory
{
protected function createLogger(): Logger
{
return new EchoLogger();
}
}

$factory = new FileLoggerFactory();
$factory->log('订单创建成功');

优点：新增日志类型只需新增一个工厂子类，符合开闭原则。

缺点：类的数量成倍增长，每增加一个产品就要增加一个工厂。

5. 抽象工厂模式

当产品不止一个维度时（例如「日志记录器 + 日志格式化器」），抽象工厂（Abstract Factory）就派上用场了。它用于创建一系列相关或相互依赖的对象。

<?php

interface Formatter
{
public function format(string $message): string;
}

class JsonFormatter implements Formatter
{
public function format(string $message): string
{
return json_encode(['msg' => $message, 'time' => date('c')], JSON_UNESCAPED_UNICODE);
}
}

class PlainFormatter implements Formatter
{
public function format(string $message): string
{
return '[' . date('Y-m-d H:i:s') . '] ' . $message;
}
}

interface LoggerAbstractFactory
{
public function createLogger(): Logger;
public function createFormatter(): Formatter;
}

class FileLoggerAbstractFactory implements LoggerAbstractFactory
{
public function createLogger(): Logger
{
return new FileLogger(__DIR__ . '/app.log');
}

public function createFormatter(): Formatter
{
return new PlainFormatter();
}
}

class EchoLoggerAbstractFactory implements LoggerAbstractFactory
{
public function createLogger(): Logger
{
return new EchoLogger();
}

public function createFormatter(): Formatter
{
return new JsonFormatter();
}
}

优点：保证同一产品族内的对象彼此兼容，切换产品族只需替换工厂。

缺点：扩展新的产品维度（比如再加一个「日志输出目标」）需要修改所有工厂接口，代价较高。

抽象工厂的产品族关系可以这样理解：

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span{color:#333;}#mermaid-svg-jUlVjmXrCGhCRQvf .nodeLabel,#mermaid-svg-jUlVjmXrCGhCRQvf .edgeLabel{color:#131300;}#mermaid-svg-jUlVjmXrCGhCRQvf .edgeLabel .label rect{fill:#ECECFF;}#mermaid-svg-jUlVjmXrCGhCRQvf .label text{fill:#131300;}#mermaid-svg-jUlVjmXrCGhCRQvf .labelBkg{background:#ECECFF;}#mermaid-svg-jUlVjmXrCGhCRQvf .edgeLabel .label span{background:#ECECFF;}#mermaid-svg-jUlVjmXrCGhCRQvf .classTitle{font-weight:bolder;}#mermaid-svg-jUlVjmXrCGhCRQvf .node rect,#mermaid-svg-jUlVjmXrCGhCRQvf .node circle,#mermaid-svg-jUlVjmXrCGhCRQvf .node ellipse,#mermaid-svg-jUlVjmXrCGhCRQvf .node polygon,#mermaid-svg-jUlVjmXrCGhCRQvf .node path{fill:#ECECFF;stroke:#9370DB;stroke-width:1px;}#mermaid-svg-jUlVjmXrCGhCRQvf .divider{stroke:#9370DB;stroke-width:1;}#mermaid-svg-jUlVjmXrCGhCRQvf g.clickable{cursor:pointer;}#mermaid-svg-jUlVjmXrCGhCRQvf g.classGroup rect{fill:#ECECFF;stroke:#9370DB;}#mermaid-svg-jUlVjmXrCGhCRQvf g.classGroup 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.lollipop{fill:#ECECFF!important;stroke:#333333!important;stroke-width:1;}#mermaid-svg-jUlVjmXrCGhCRQvf .edgeTerminals{font-size:11px;line-height:initial;}#mermaid-svg-jUlVjmXrCGhCRQvf .classTitleText{text-anchor:middle;font-size:18px;fill:#333;}#mermaid-svg-jUlVjmXrCGhCRQvf .label-icon{display:inline-block;height:1em;overflow:visible;vertical-align:-0.125em;}#mermaid-svg-jUlVjmXrCGhCRQvf .node .label-icon path{fill:currentColor;stroke:revert;stroke-width:revert;}#mermaid-svg-jUlVjmXrCGhCRQvf :root{–mermaid-font-family:\”trebuchet ms\”,verdana,arial,sans-serif;}

创建

创建

创建

创建

«interface»

LoggerAbstractFactory

+createLogger() : Logger

+createFormatter() : Formatter

FileLoggerAbstractFactory

+createLogger() : Logger

+createFormatter() : Formatter

EchoLoggerAbstractFactory

+createLogger() : Logger

+createFormatter() : Formatter

«interface»

Logger

+log(message) : void

«interface»

Formatter

+format(message) : string

6. 单例模式实现与弊端

单例模式（Singleton）保证一个类只有一个实例，并提供全局访问点。

<?php

class Config
{
private static ?Config $instance = null;

private array $data = [];

private function __construct() {}

private function __clone() {}

public function __wakeup()
{
throw new RuntimeException('禁止反序列化单例');
}

public static function getInstance(): self
{
if (self::$instance === null) {
self::$instance = new self();
}
return self::$instance;
}

public function set(string $key, mixed $value): void
{
$this->data[$key] = $value;
}

public function get(string $key, mixed $default = null): mixed
{
return $this->data[$key] ?? $default;
}
}

Config::getInstance()->set('app_name', 'demo');
echo Config::getInstance()->get('app_name');

实现要点：

• 构造函数私有化，禁止外部 new。
• 私有化 __clone，防止克隆。
• 禁止反序列化，避免绕过单例约束。
• 静态属性持有唯一实例。

弊端：

单例的获取流程与常见破坏入口如下：

#mermaid-svg-JUD0RnL8NBWqPRrx{font-family:\”trebuchet ms\”,verdana,arial,sans-serif;font-size:16px;fill:#333;}@keyframes edge-animation-frame{from{stroke-dashoffset:0;}}@keyframes dash{to{stroke-dashoffset:0;}}#mermaid-svg-JUD0RnL8NBWqPRrx .edge-animation-slow{stroke-dasharray:9,5!important;stroke-dashoffset:900;animation:dash 50s linear infinite;stroke-linecap:round;}#mermaid-svg-JUD0RnL8NBWqPRrx .edge-animation-fast{stroke-dasharray:9,5!important;stroke-dashoffset:900;animation:dash 20s linear infinite;stroke-linecap:round;}#mermaid-svg-JUD0RnL8NBWqPRrx .error-icon{fill:#552222;}#mermaid-svg-JUD0RnL8NBWqPRrx .error-text{fill:#552222;stroke:#552222;}#mermaid-svg-JUD0RnL8NBWqPRrx .edge-thickness-normal{stroke-width:1px;}#mermaid-svg-JUD0RnL8NBWqPRrx .edge-thickness-thick{stroke-width:3.5px;}#mermaid-svg-JUD0RnL8NBWqPRrx .edge-pattern-solid{stroke-dasharray:0;}#mermaid-svg-JUD0RnL8NBWqPRrx .edge-thickness-invisible{stroke-width:0;fill:none;}#mermaid-svg-JUD0RnL8NBWqPRrx .edge-pattern-dashed{stroke-dasharray:3;}#mermaid-svg-JUD0RnL8NBWqPRrx .edge-pattern-dotted{stroke-dasharray:2;}#mermaid-svg-JUD0RnL8NBWqPRrx .marker{fill:#333333;stroke:#333333;}#mermaid-svg-JUD0RnL8NBWqPRrx .marker.cross{stroke:#333333;}#mermaid-svg-JUD0RnL8NBWqPRrx svg{font-family:\”trebuchet ms\”,verdana,arial,sans-serif;font-size:16px;}#mermaid-svg-JUD0RnL8NBWqPRrx p{margin:0;}#mermaid-svg-JUD0RnL8NBWqPRrx .label{font-family:\”trebuchet ms\”,verdana,arial,sans-serif;color:#333;}#mermaid-svg-JUD0RnL8NBWqPRrx .cluster-label text{fill:#333;}#mermaid-svg-JUD0RnL8NBWqPRrx .cluster-label span{color:#333;}#mermaid-svg-JUD0RnL8NBWqPRrx .cluster-label span p{background-color:transparent;}#mermaid-svg-JUD0RnL8NBWqPRrx .label text,#mermaid-svg-JUD0RnL8NBWqPRrx span{fill:#333;color:#333;}#mermaid-svg-JUD0RnL8NBWqPRrx .node rect,#mermaid-svg-JUD0RnL8NBWqPRrx .node circle,#mermaid-svg-JUD0RnL8NBWqPRrx .node ellipse,#mermaid-svg-JUD0RnL8NBWqPRrx .node polygon,#mermaid-svg-JUD0RnL8NBWqPRrx .node path{fill:#ECECFF;stroke:#9370DB;stroke-width:1px;}#mermaid-svg-JUD0RnL8NBWqPRrx .rough-node .label text,#mermaid-svg-JUD0RnL8NBWqPRrx .node .label text,#mermaid-svg-JUD0RnL8NBWqPRrx .image-shape .label,#mermaid-svg-JUD0RnL8NBWqPRrx .icon-shape .label{text-anchor:middle;}#mermaid-svg-JUD0RnL8NBWqPRrx .node .katex path{fill:#000;stroke:#000;stroke-width:1px;}#mermaid-svg-JUD0RnL8NBWqPRrx .rough-node .label,#mermaid-svg-JUD0RnL8NBWqPRrx .node .label,#mermaid-svg-JUD0RnL8NBWqPRrx .image-shape .label,#mermaid-svg-JUD0RnL8NBWqPRrx .icon-shape .label{text-align:center;}#mermaid-svg-JUD0RnL8NBWqPRrx .node.clickable{cursor:pointer;}#mermaid-svg-JUD0RnL8NBWqPRrx .root .anchor path{fill:#333333!important;stroke-width:0;stroke:#333333;}#mermaid-svg-JUD0RnL8NBWqPRrx .arrowheadPath{fill:#333333;}#mermaid-svg-JUD0RnL8NBWqPRrx .edgePath .path{stroke:#333333;stroke-width:2.0px;}#mermaid-svg-JUD0RnL8NBWqPRrx .flowchart-link{stroke:#333333;fill:none;}#mermaid-svg-JUD0RnL8NBWqPRrx .edgeLabel{background-color:rgba(232,232,232, 0.8);text-align:center;}#mermaid-svg-JUD0RnL8NBWqPRrx .edgeLabel p{background-color:rgba(232,232,232, 0.8);}#mermaid-svg-JUD0RnL8NBWqPRrx .edgeLabel rect{opacity:0.5;background-color:rgba(232,232,232, 0.8);fill:rgba(232,232,232, 0.8);}#mermaid-svg-JUD0RnL8NBWqPRrx .labelBkg{background-color:rgba(232, 232, 232, 0.5);}#mermaid-svg-JUD0RnL8NBWqPRrx .cluster rect{fill:#ffffde;stroke:#aaaa33;stroke-width:1px;}#mermaid-svg-JUD0RnL8NBWqPRrx .cluster text{fill:#333;}#mermaid-svg-JUD0RnL8NBWqPRrx .cluster span{color:#333;}#mermaid-svg-JUD0RnL8NBWqPRrx div.mermaidTooltip{position:absolute;text-align:center;max-width:200px;padding:2px;font-family:\”trebuchet ms\”,verdana,arial,sans-serif;font-size:12px;background:hsl(80, 100%, 96.2745098039%);border:1px solid #aaaa33;border-radius:2px;pointer-events:none;z-index:100;}#mermaid-svg-JUD0RnL8NBWqPRrx .flowchartTitleText{text-anchor:middle;font-size:18px;fill:#333;}#mermaid-svg-JUD0RnL8NBWqPRrx rect.text{fill:none;stroke-width:0;}#mermaid-svg-JUD0RnL8NBWqPRrx .icon-shape,#mermaid-svg-JUD0RnL8NBWqPRrx .image-shape{background-color:rgba(232,232,232, 0.8);text-align:center;}#mermaid-svg-JUD0RnL8NBWqPRrx .icon-shape p,#mermaid-svg-JUD0RnL8NBWqPRrx .image-shape p{background-color:rgba(232,232,232, 0.8);padding:2px;}#mermaid-svg-JUD0RnL8NBWqPRrx .icon-shape .label rect,#mermaid-svg-JUD0RnL8NBWqPRrx .image-shape .label rect{opacity:0.5;background-color:rgba(232,232,232, 0.8);fill:rgba(232,232,232, 0.8);}#mermaid-svg-JUD0RnL8NBWqPRrx .label-icon{display:inline-block;height:1em;overflow:visible;vertical-align:-0.125em;}#mermaid-svg-JUD0RnL8NBWqPRrx .node .label-icon path{fill:currentColor;stroke:revert;stroke-width:revert;}#mermaid-svg-JUD0RnL8NBWqPRrx :root{–mermaid-font-family:\”trebuchet ms\”,verdana,arial,sans-serif;}

是

否

构造函数私有，被拦截

__clone 私有，被拦截

__wakeup 抛异常

调用 Config::getInstance()

$instance 是否为 null

new self() 并赋值给静态属性

直接返回已有实例

返回唯一实例

外部 new

失败

clone 对象

unserialize 反序列化

7. 依赖注入替代单例

依赖注入（Dependency Injection）把「获取依赖」变成「接收依赖」，让依赖关系显式化，同时保留「只创建一次」的能力——由容器负责生命周期管理。

<?php

class Config
{
public function __construct(private array $data = []) {}

public function get(string $key, mixed $default = null): mixed
{
return $this->data[$key] ?? $default;
}
}

class UserService
{
public function __construct(private Config $config) {}

public function register(string $name): string
{
$appName = $this->config->get('app_name', 'app');
return "{$appName}: 用户 {$name} 注册成功";
}
}

// 简易容器：同一个 key 只创建一次，等价于「受控的单例」
class Container
{
private array $instances = [];
private array $bindings = [];

public function bind(string $id, callable $resolver): void
{
$this->bindings[$id] = $resolver;
}

public function get(string $id): mixed
{
if (isset($this->instances[$id])) {
return $this->instances[$id];
}
if (!isset($this->bindings[$id])) {
throw new RuntimeException("未注册的服务: {$id}");
}
return $this->instances[$id] = ($this->bindings[$id])($this);
}
}

$container = new Container();
$container->bind(Config::class, fn () => new Config(['app_name' => 'demo']));
$container->bind(UserService::class, fn (Container $c) => new UserService($c->get(Config::class)));

echo $container->get(UserService::class)->register('张三');

对比单例，依赖注入的优势在于：

• 依赖显式声明在构造函数中，阅读代码即可知道类需要什么。
• 单元测试可以直接传入 mock 对象，无需反射修改静态属性。
• 生命周期由容器统一管理，常驻内存场景下可按请求重建。

8. 实际案例：日志记录器

把前面的内容串起来，做一个支持多驱动、可注入、可测试的日志记录器。

<?php

interface Logger
{
public function log(string $level, string $message): void;
}

class FileLogger implements Logger
{
public function __construct(private string $path) {}

public function log(string $level, string $message): void
{
$line = sprintf('[%s] %s: %s%s', date('Y-m-d H:i:s'), strtoupper($level), $message, PHP_EOL);
file_put_contents($this->path, $line, FILE_APPEND);
}
}

class NullLogger implements Logger
{
public function log(string $level, string $message): void
{
// 测试环境静默
}
}

class LoggerFactory
{
public static function create(string $driver, array $options = []): Logger
{
return match ($driver) {
'file' => new FileLogger($options['path'] ?? __DIR__ . '/app.log'),
'null' => new NullLogger(),
default => throw new InvalidArgumentException("不支持的日志驱动: {$driver}"),
};
}
}

class OrderService
{
public function __construct(private Logger $logger) {}

public function create(int $orderId): void
{
// 业务逻辑
$this->logger->log('info', "订单 {$orderId} 创建成功");
}
}

// 组装：工厂负责创建，容器负责共享
$container = new Container();
$container->bind(Logger::class, fn () => LoggerFactory::create('file', ['path' => __DIR__ . '/order.log']));
$container->bind(OrderService::class, fn (Container $c) => new OrderService($c->get(Logger::class)));

$container->get(OrderService::class)->create(1001);

这个案例体现了三者的分工：

• 工厂：屏蔽 FileLogger 的构造细节，调用方只传驱动名。
• 容器（受控单例）：保证整个请求内只创建一个日志实例，避免重复打开文件句柄。
• 依赖注入：OrderService 不关心日志从哪来，测试时注入 NullLogger 即可。

整个案例的组装与调用链路如下：

"OrderService""FileLogger""LoggerFactory""Container""调用方""OrderService""FileLogger""LoggerFactory""Container""调用方"#mermaid-svg-h0uEhHi1cmtSqUpF{font-family:\”trebuchet ms\”,verdana,arial,sans-serif;font-size:16px;fill:#333;}@keyframes edge-animation-frame{from{stroke-dashoffset:0;}}@keyframes dash{to{stroke-dashoffset:0;}}#mermaid-svg-h0uEhHi1cmtSqUpF .edge-animation-slow{stroke-dasharray:9,5!important;stroke-dashoffset:900;animation:dash 50s linear infinite;stroke-linecap:round;}#mermaid-svg-h0uEhHi1cmtSqUpF .edge-animation-fast{stroke-dasharray:9,5!important;stroke-dashoffset:900;animation:dash 20s linear infinite;stroke-linecap:round;}#mermaid-svg-h0uEhHi1cmtSqUpF .error-icon{fill:#552222;}#mermaid-svg-h0uEhHi1cmtSqUpF .error-text{fill:#552222;stroke:#552222;}#mermaid-svg-h0uEhHi1cmtSqUpF .edge-thickness-normal{stroke-width:1px;}#mermaid-svg-h0uEhHi1cmtSqUpF .edge-thickness-thick{stroke-width:3.5px;}#mermaid-svg-h0uEhHi1cmtSqUpF .edge-pattern-solid{stroke-dasharray:0;}#mermaid-svg-h0uEhHi1cmtSqUpF .edge-thickness-invisible{stroke-width:0;fill:none;}#mermaid-svg-h0uEhHi1cmtSqUpF .edge-pattern-dashed{stroke-dasharray:3;}#mermaid-svg-h0uEhHi1cmtSqUpF .edge-pattern-dotted{stroke-dasharray:2;}#mermaid-svg-h0uEhHi1cmtSqUpF .marker{fill:#333333;stroke:#333333;}#mermaid-svg-h0uEhHi1cmtSqUpF .marker.cross{stroke:#333333;}#mermaid-svg-h0uEhHi1cmtSqUpF svg{font-family:\”trebuchet ms\”,verdana,arial,sans-serif;font-size:16px;}#mermaid-svg-h0uEhHi1cmtSqUpF p{margin:0;}#mermaid-svg-h0uEhHi1cmtSqUpF .actor{stroke:hsl(259.6261682243, 59.7765363128%, 87.9019607843%);fill:#ECECFF;}#mermaid-svg-h0uEhHi1cmtSqUpF text.actor>tspan{fill:black;stroke:none;}#mermaid-svg-h0uEhHi1cmtSqUpF .actor-line{stroke:hsl(259.6261682243, 59.7765363128%, 87.9019607843%);}#mermaid-svg-h0uEhHi1cmtSqUpF .innerArc{stroke-width:1.5;stroke-dasharray:none;}#mermaid-svg-h0uEhHi1cmtSqUpF .messageLine0{stroke-width:1.5;stroke-dasharray:none;stroke:#333;}#mermaid-svg-h0uEhHi1cmtSqUpF .messageLine1{stroke-width:1.5;stroke-dasharray:2,2;stroke:#333;}#mermaid-svg-h0uEhHi1cmtSqUpF #arrowhead path{fill:#333;stroke:#333;}#mermaid-svg-h0uEhHi1cmtSqUpF .sequenceNumber{fill:white;}#mermaid-svg-h0uEhHi1cmtSqUpF #sequencenumber{fill:#333;}#mermaid-svg-h0uEhHi1cmtSqUpF #crosshead path{fill:#333;stroke:#333;}#mermaid-svg-h0uEhHi1cmtSqUpF .messageText{fill:#333;stroke:none;}#mermaid-svg-h0uEhHi1cmtSqUpF .labelBox{stroke:hsl(259.6261682243, 59.7765363128%, 87.9019607843%);fill:#ECECFF;}#mermaid-svg-h0uEhHi1cmtSqUpF .labelText,#mermaid-svg-h0uEhHi1cmtSqUpF .labelText>tspan{fill:black;stroke:none;}#mermaid-svg-h0uEhHi1cmtSqUpF .loopText,#mermaid-svg-h0uEhHi1cmtSqUpF .loopText>tspan{fill:black;stroke:none;}#mermaid-svg-h0uEhHi1cmtSqUpF .loopLine{stroke-width:2px;stroke-dasharray:2,2;stroke:hsl(259.6261682243, 59.7765363128%, 87.9019607843%);fill:hsl(259.6261682243, 59.7765363128%, 87.9019607843%);}#mermaid-svg-h0uEhHi1cmtSqUpF .note{stroke:#aaaa33;fill:#fff5ad;}#mermaid-svg-h0uEhHi1cmtSqUpF .noteText,#mermaid-svg-h0uEhHi1cmtSqUpF .noteText>tspan{fill:black;stroke:none;}#mermaid-svg-h0uEhHi1cmtSqUpF .activation0{fill:#f4f4f4;stroke:#666;}#mermaid-svg-h0uEhHi1cmtSqUpF .activation1{fill:#f4f4f4;stroke:#666;}#mermaid-svg-h0uEhHi1cmtSqUpF .activation2{fill:#f4f4f4;stroke:#666;}#mermaid-svg-h0uEhHi1cmtSqUpF .actorPopupMenu{position:absolute;}#mermaid-svg-h0uEhHi1cmtSqUpF .actorPopupMenuPanel{position:absolute;fill:#ECECFF;box-shadow:0px 8px 16px 0px rgba(0,0,0,0.2);filter:drop-shadow(3px 5px 2px rgb(0 0 0 / 0.4));}#mermaid-svg-h0uEhHi1cmtSqUpF .actor-man line{stroke:hsl(259.6261682243, 59.7765363128%, 87.9019607843%);fill:#ECECFF;}#mermaid-svg-h0uEhHi1cmtSqUpF .actor-man circle,#mermaid-svg-h0uEhHi1cmtSqUpF line{stroke:hsl(259.6261682243, 59.7765363128%, 87.9019607843%);fill:#ECECFF;stroke-width:2px;}#mermaid-svg-h0uEhHi1cmtSqUpF :root{–mermaid-font-family:\”trebuchet ms\”,verdana,arial,sans-serif;}get(OrderService::class)检查 instances 缓存new OrderService(logger)create('file', options)new FileLogger(path)返回 Logger 实例返回 OrderServicecreate(1001)log('info', '订单 1001 创建成功')

9. 总结

实践建议：

最后用一张决策图收束全文的选型思路：

#mermaid-svg-sJJzT1gW1jjQjiIJ{font-family:\”trebuchet ms\”,verdana,arial,sans-serif;font-size:16px;fill:#333;}@keyframes edge-animation-frame{from{stroke-dashoffset:0;}}@keyframes dash{to{stroke-dashoffset:0;}}#mermaid-svg-sJJzT1gW1jjQjiIJ .edge-animation-slow{stroke-dasharray:9,5!important;stroke-dashoffset:900;animation:dash 50s linear infinite;stroke-linecap:round;}#mermaid-svg-sJJzT1gW1jjQjiIJ .edge-animation-fast{stroke-dasharray:9,5!important;stroke-dashoffset:900;animation:dash 20s linear infinite;stroke-linecap:round;}#mermaid-svg-sJJzT1gW1jjQjiIJ .error-icon{fill:#552222;}#mermaid-svg-sJJzT1gW1jjQjiIJ .error-text{fill:#552222;stroke:#552222;}#mermaid-svg-sJJzT1gW1jjQjiIJ .edge-thickness-normal{stroke-width:1px;}#mermaid-svg-sJJzT1gW1jjQjiIJ .edge-thickness-thick{stroke-width:3.5px;}#mermaid-svg-sJJzT1gW1jjQjiIJ .edge-pattern-solid{stroke-dasharray:0;}#mermaid-svg-sJJzT1gW1jjQjiIJ .edge-thickness-invisible{stroke-width:0;fill:none;}#mermaid-svg-sJJzT1gW1jjQjiIJ .edge-pattern-dashed{stroke-dasharray:3;}#mermaid-svg-sJJzT1gW1jjQjiIJ .edge-pattern-dotted{stroke-dasharray:2;}#mermaid-svg-sJJzT1gW1jjQjiIJ .marker{fill:#333333;stroke:#333333;}#mermaid-svg-sJJzT1gW1jjQjiIJ .marker.cross{stroke:#333333;}#mermaid-svg-sJJzT1gW1jjQjiIJ svg{font-family:\”trebuchet ms\”,verdana,arial,sans-serif;font-size:16px;}#mermaid-svg-sJJzT1gW1jjQjiIJ p{margin:0;}#mermaid-svg-sJJzT1gW1jjQjiIJ .label{font-family:\”trebuchet ms\”,verdana,arial,sans-serif;color:#333;}#mermaid-svg-sJJzT1gW1jjQjiIJ .cluster-label text{fill:#333;}#mermaid-svg-sJJzT1gW1jjQjiIJ .cluster-label span{color:#333;}#mermaid-svg-sJJzT1gW1jjQjiIJ .cluster-label span p{background-color:transparent;}#mermaid-svg-sJJzT1gW1jjQjiIJ .label text,#mermaid-svg-sJJzT1gW1jjQjiIJ span{fill:#333;color:#333;}#mermaid-svg-sJJzT1gW1jjQjiIJ .node rect,#mermaid-svg-sJJzT1gW1jjQjiIJ .node circle,#mermaid-svg-sJJzT1gW1jjQjiIJ .node ellipse,#mermaid-svg-sJJzT1gW1jjQjiIJ .node polygon,#mermaid-svg-sJJzT1gW1jjQjiIJ .node path{fill:#ECECFF;stroke:#9370DB;stroke-width:1px;}#mermaid-svg-sJJzT1gW1jjQjiIJ .rough-node .label text,#mermaid-svg-sJJzT1gW1jjQjiIJ .node .label text,#mermaid-svg-sJJzT1gW1jjQjiIJ .image-shape .label,#mermaid-svg-sJJzT1gW1jjQjiIJ .icon-shape .label{text-anchor:middle;}#mermaid-svg-sJJzT1gW1jjQjiIJ .node .katex path{fill:#000;stroke:#000;stroke-width:1px;}#mermaid-svg-sJJzT1gW1jjQjiIJ .rough-node .label,#mermaid-svg-sJJzT1gW1jjQjiIJ .node .label,#mermaid-svg-sJJzT1gW1jjQjiIJ .image-shape .label,#mermaid-svg-sJJzT1gW1jjQjiIJ .icon-shape .label{text-align:center;}#mermaid-svg-sJJzT1gW1jjQjiIJ .node.clickable{cursor:pointer;}#mermaid-svg-sJJzT1gW1jjQjiIJ .root .anchor path{fill:#333333!important;stroke-width:0;stroke:#333333;}#mermaid-svg-sJJzT1gW1jjQjiIJ .arrowheadPath{fill:#333333;}#mermaid-svg-sJJzT1gW1jjQjiIJ .edgePath .path{stroke:#333333;stroke-width:2.0px;}#mermaid-svg-sJJzT1gW1jjQjiIJ .flowchart-link{stroke:#333333;fill:none;}#mermaid-svg-sJJzT1gW1jjQjiIJ .edgeLabel{background-color:rgba(232,232,232, 0.8);text-align:center;}#mermaid-svg-sJJzT1gW1jjQjiIJ .edgeLabel p{background-color:rgba(232,232,232, 0.8);}#mermaid-svg-sJJzT1gW1jjQjiIJ .edgeLabel rect{opacity:0.5;background-color:rgba(232,232,232, 0.8);fill:rgba(232,232,232, 0.8);}#mermaid-svg-sJJzT1gW1jjQjiIJ .labelBkg{background-color:rgba(232, 232, 232, 0.5);}#mermaid-svg-sJJzT1gW1jjQjiIJ .cluster rect{fill:#ffffde;stroke:#aaaa33;stroke-width:1px;}#mermaid-svg-sJJzT1gW1jjQjiIJ .cluster text{fill:#333;}#mermaid-svg-sJJzT1gW1jjQjiIJ .cluster span{color:#333;}#mermaid-svg-sJJzT1gW1jjQjiIJ div.mermaidTooltip{position:absolute;text-align:center;max-width:200px;padding:2px;font-family:\”trebuchet ms\”,verdana,arial,sans-serif;font-size:12px;background:hsl(80, 100%, 96.2745098039%);border:1px solid #aaaa33;border-radius:2px;pointer-events:none;z-index:100;}#mermaid-svg-sJJzT1gW1jjQjiIJ .flowchartTitleText{text-anchor:middle;font-size:18px;fill:#333;}#mermaid-svg-sJJzT1gW1jjQjiIJ rect.text{fill:none;stroke-width:0;}#mermaid-svg-sJJzT1gW1jjQjiIJ .icon-shape,#mermaid-svg-sJJzT1gW1jjQjiIJ .image-shape{background-color:rgba(232,232,232, 0.8);text-align:center;}#mermaid-svg-sJJzT1gW1jjQjiIJ .icon-shape p,#mermaid-svg-sJJzT1gW1jjQjiIJ .image-shape p{background-color:rgba(232,232,232, 0.8);padding:2px;}#mermaid-svg-sJJzT1gW1jjQjiIJ .icon-shape .label rect,#mermaid-svg-sJJzT1gW1jjQjiIJ .image-shape .label rect{opacity:0.5;background-color:rgba(232,232,232, 0.8);fill:rgba(232,232,232, 0.8);}#mermaid-svg-sJJzT1gW1jjQjiIJ .label-icon{display:inline-block;height:1em;overflow:visible;vertical-align:-0.125em;}#mermaid-svg-sJJzT1gW1jjQjiIJ .node .label-icon path{fill:currentColor;stroke:revert;stroke-width:revert;}#mermaid-svg-sJJzT1gW1jjQjiIJ :root{–mermaid-font-family:\”trebuchet ms\”,verdana,arial,sans-serif;}

否

否

是

否

是

是

是

否

需要创建对象

是否需要全局唯一实例

产品类型是否会持续扩展

简单工厂

是否涉及多个产品维度

工厂方法

抽象工厂

是否无状态且确实需要全局访问

单例（做好防克隆/防反序列化）

依赖注入 + 容器共享实例