Laravel 13 桥接模式深度解析

桥接模式是一种结构型设计模式，它将抽象部分与实现部分分离，使它们可以独立变化。本文将深入探讨 Laravel 13 中桥接模式的高级用法。

桥接模式基础

什么是桥接模式

桥接模式通过将继承关系转换为组合关系，实现了抽象和实现的解耦。

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<?php

namespace App\Contracts;

interface ImplementationInterface
{
    public function operationImplementation(): string;
}
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<?php

namespace App\Abstractions;

abstract class Abstraction
{
    protected ImplementationInterface $implementation;

    public function __construct(ImplementationInterface $implementation)
    {
        $this->implementation = $implementation;
    }

    abstract public function operation(): string;
}
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<?php

namespace App\RefinedAbstractions;

use App\Abstractions\Abstraction;

class RefinedAbstraction extends Abstraction
{
    public function operation(): string
    {
        return "Refined: " . $this->implementation->operationImplementation();
    }
}

消息通知桥接

消息发送器接口

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<?php

namespace App\Contracts\Messaging;

interface MessageSenderInterface
{
    public function send(string $to, string $subject, string $body): bool;

    public function sendBatch(array $recipients, string $subject, string $body): array;

    public function getProviderName(): string;
}

具体发送器实现

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<?php

namespace App\Messaging\Senders;

use App\Contracts\Messaging\MessageSenderInterface;
use Illuminate\Support\Facades\Mail;

class EmailSender implements MessageSenderInterface
{
    public function send(string $to, string $subject, string $body): bool
    {
        try {
            Mail::raw($body, function ($message) use ($to, $subject) {
                $message->to($to)->subject($subject);
            });

            return true;
        } catch (\Exception $e) {
            return false;
        }
    }

    public function sendBatch(array $recipients, string $subject, string $body): array
    {
        $results = [];

        foreach ($recipients as $recipient) {
            $results[$recipient] = $this->send($recipient, $subject, $body);
        }

        return $results;
    }

    public function getProviderName(): string
    {
        return 'email';
    }
}
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<?php

namespace App\Messaging\Senders;

use App\Contracts\Messaging\MessageSenderInterface;
use Twilio\Rest\Client;

class SmsSender implements MessageSenderInterface
{
    protected Client $client;
    protected string $fromNumber;

    public function __construct(array $config)
    {
        $this->client = new Client($config['sid'], $config['token']);
        $this->fromNumber = $config['from'];
    }

    public function send(string $to, string $subject, string $body): bool
    {
        try {
            $this->client->messages->create($to, [
                'from' => $this->fromNumber,
                'body' => $body,
            ]);

            return true;
        } catch (\Exception $e) {
            return false;
        }
    }

    public function sendBatch(array $recipients, string $subject, string $body): array
    {
        $results = [];

        foreach ($recipients as $recipient) {
            $results[$recipient] = $this->send($recipient, $subject, $body);
        }

        return $results;
    }

    public function getProviderName(): string
    {
        return 'sms';
    }
}
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<?php

namespace App\Messaging\Senders;

use App\Contracts\Messaging\MessageSenderInterface;

class PushSender implements MessageSenderInterface
{
    public function send(string $to, string $subject, string $body): bool
    {
        try {
            $notification = [
                'to' => $to,
                'notification' => [
                    'title' => $subject,
                    'body' => $body,
                ],
            ];

            $response = Http::withToken(config('services.fcm.token'))
                ->post('https://fcm.googleapis.com/fcm/send', $notification);

            return $response->successful();
        } catch (\Exception $e) {
            return false;
        }
    }

    public function sendBatch(array $recipients, string $subject, string $body): array
    {
        $results = [];

        foreach ($recipients as $recipient) {
            $results[$recipient] = $this->send($recipient, $subject, $body);
        }

        return $results;
    }

    public function getProviderName(): string
    {
        return 'push';
    }
}

消息抽象层

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<?php

namespace App\Messaging\Messages;

use App\Contracts\Messaging\MessageSenderInterface;

abstract class Message
{
    protected MessageSenderInterface $sender;
    protected string $subject;
    protected string $body;

    public function __construct(MessageSenderInterface $sender)
    {
        $this->sender = $sender;
    }

    public function setSubject(string $subject): self
    {
        $this->subject = $subject;
        return $this;
    }

    public function setBody(string $body): self
    {
        $this->body = $body;
        return $this;
    }

    abstract public function send(string $to): bool;

    abstract public function formatBody(): string;
}
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<?php

namespace App\Messaging\Messages;

class WelcomeMessage extends Message
{
    protected string $userName;

    public function setUserName(string $name): self
    {
        $this->userName = $name;
        return $this;
    }

    public function send(string $to): bool
    {
        $formattedBody = $this->formatBody();

        return $this->sender->send($to, $this->subject, $formattedBody);
    }

    public function formatBody(): string
    {
        return str_replace('{name}', $this->userName, $this->body);
    }
}
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<?php

namespace App\Messaging\Messages;

class OrderConfirmationMessage extends Message
{
    protected string $orderNumber;
    protected float $total;

    public function setOrderNumber(string $orderNumber): self
    {
        $this->orderNumber = $orderNumber;
        return $this;
    }

    public function setTotal(float $total): self
    {
        $this->total = $total;
        return $this;
    }

    public function send(string $to): bool
    {
        $formattedBody = $this->formatBody();

        return $this->sender->send($to, $this->subject, $formattedBody);
    }

    public function formatBody(): string
    {
        return str_replace(
            ['{order_number}', '{total}'],
            [$this->orderNumber, number_format($this->total, 2)],
            $this->body
        );
    }
}

数据库驱动桥接

数据库驱动接口

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<?php

namespace App\Contracts\Database;

interface DriverInterface
{
    public function connect(array $config): void;

    public function disconnect(): void;

    public function query(string $sql, array $bindings = []): array;

    public function execute(string $sql, array $bindings = []): int;

    public function beginTransaction(): void;

    public function commit(): void;

    public function rollback(): void;

    public function getLastInsertId(): string;
}

具体驱动实现

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<?php

namespace App\Database\Drivers;

use App\Contracts\Database\DriverInterface;
use PDO;

class MySqlDriver implements DriverInterface
{
    protected ?PDO $pdo = null;

    public function connect(array $config): void
    {
        $dsn = sprintf(
            'mysql:host=%s;port=%s;dbname=%s;charset=%s',
            $config['host'],
            $config['port'] ?? 3306,
            $config['database'],
            $config['charset'] ?? 'utf8mb4'
        );

        $this->pdo = new PDO($dsn, $config['username'], $config['password'], [
            PDO::ATTR_ERRMODE => PDO::ERRMODE_EXCEPTION,
            PDO::ATTR_DEFAULT_FETCH_MODE => PDO::FETCH_ASSOC,
        ]);
    }

    public function disconnect(): void
    {
        $this->pdo = null;
    }

    public function query(string $sql, array $bindings = []): array
    {
        $stmt = $this->pdo->prepare($sql);
        $stmt->execute($bindings);
        return $stmt->fetchAll();
    }

    public function execute(string $sql, array $bindings = []): int
    {
        $stmt = $this->pdo->prepare($sql);
        $stmt->execute($bindings);
        return $stmt->rowCount();
    }

    public function beginTransaction(): void
    {
        $this->pdo->beginTransaction();
    }

    public function commit(): void
    {
        $this->pdo->commit();
    }

    public function rollback(): void
    {
        $this->pdo->rollBack();
    }

    public function getLastInsertId(): string
    {
        return $this->pdo->lastInsertId();
    }
}
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<?php

namespace App\Database\Drivers;

use App\Contracts\Database\DriverInterface;
use PDO;

class PostgresDriver implements DriverInterface
{
    protected ?PDO $pdo = null;

    public function connect(array $config): void
    {
        $dsn = sprintf(
            'pgsql:host=%s;port=%s;dbname=%s',
            $config['host'],
            $config['port'] ?? 5432,
            $config['database']
        );

        $this->pdo = new PDO($dsn, $config['username'], $config['password'], [
            PDO::ATTR_ERRMODE => PDO::ERRMODE_EXCEPTION,
            PDO::ATTR_DEFAULT_FETCH_MODE => PDO::FETCH_ASSOC,
        ]);
    }

    public function disconnect(): void
    {
        $this->pdo = null;
    }

    public function query(string $sql, array $bindings = []): array
    {
        $stmt = $this->pdo->prepare($sql);
        $stmt->execute($bindings);
        return $stmt->fetchAll();
    }

    public function execute(string $sql, array $bindings = []): int
    {
        $stmt = $this->pdo->prepare($sql);
        $stmt->execute($bindings);
        return $stmt->rowCount();
    }

    public function beginTransaction(): void
    {
        $this->pdo->beginTransaction();
    }

    public function commit(): void
    {
        $this->pdo->commit();
    }

    public function rollback(): void
    {
        $this->pdo->rollBack();
    }

    public function getLastInsertId(): string
    {
        return $this->pdo->lastInsertId();
    }
}

查询构建器抽象

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<?php

namespace App\Database\Query;

use App\Contracts\Database\DriverInterface;

abstract class QueryBuilder
{
    protected DriverInterface $driver;
    protected string $table;
    protected array $wheres = [];
    protected array $columns = ['*'];
    protected array $bindings = [];

    public function __construct(DriverInterface $driver)
    {
        $this->driver = $driver;
    }

    public function table(string $table): self
    {
        $this->table = $table;
        return $this;
    }

    public function select(array $columns = ['*']): self
    {
        $this->columns = $columns;
        return $this;
    }

    public function where(string $column, string $operator, mixed $value): self
    {
        $this->wheres[] = compact('column', 'operator', 'value');
        $this->bindings[] = $value;
        return $this;
    }

    abstract public function get(): array;

    abstract public function first(): ?array;

    abstract protected function compileSelect(): string;
}
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<?php

namespace App\Database\Query;

class MySqlQueryBuilder extends QueryBuilder
{
    public function get(): array
    {
        $sql = $this->compileSelect();
        return $this->driver->query($sql, $this->bindings);
    }

    public function first(): ?array
    {
        $results = $this->get();
        return $results[0] ?? null;
    }

    protected function compileSelect(): string
    {
        $columns = implode(', ', $this->columns);
        $sql = "SELECT {$columns} FROM {$this->table}";

        if (!empty($this->wheres)) {
            $clauses = array_map(
                fn($where) => "{$where['column']} {$where['operator']} ?",
                $this->wheres
            );
            $sql .= ' WHERE ' . implode(' AND ', $clauses);
        }

        return $sql;
    }
}

渲染器桥接

渲染器接口

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<?php

namespace App\Contracts\Rendering;

interface RendererInterface
{
    public function renderTitle(string $title): string;

    public function renderText(string $text): string;

    public function renderLink(string $text, string $url): string;

    public function renderImage(string $src, string $alt): string;

    public function renderList(array $items): string;

    public function renderTable(array $headers, array $rows): string;
}

具体渲染器实现

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<?php

namespace App\Rendering\Renderers;

use App\Contracts\Rendering\RendererInterface;

class HtmlRenderer implements RendererInterface
{
    public function renderTitle(string $title): string
    {
        return "<h1>{$title}</h1>";
    }

    public function renderText(string $text): string
    {
        return "<p>{$text}</p>";
    }

    public function renderLink(string $text, string $url): string
    {
        return "<a href=\"{$url}\">{$text}</a>";
    }

    public function renderImage(string $src, string $alt): string
    {
        return "<img src=\"{$src}\" alt=\"{$alt}\">";
    }

    public function renderList(array $items): string
    {
        $listItems = array_map(fn($item) => "<li>{$item}</li>", $items);
        return "<ul>" . implode('', $listItems) . "</ul>";
    }

    public function renderTable(array $headers, array $rows): string
    {
        $headerCells = array_map(fn($h) => "<th>{$h}</th>", $headers);
        $headerRow = "<tr>" . implode('', $headerCells) . "</tr>";

        $bodyRows = array_map(function ($row) {
            $cells = array_map(fn($cell) => "<td>{$cell}</td>", $row);
            return "<tr>" . implode('', $cells) . "</tr>";
        }, $rows);

        return "<table><thead>{$headerRow}</thead><tbody>" . implode('', $bodyRows) . "</tbody></table>";
    }
}
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<?php

namespace App\Rendering\Renderers;

use App\Contracts\Rendering\RendererInterface;

class MarkdownRenderer implements RendererInterface
{
    public function renderTitle(string $title): string
    {
        return "# {$title}\n\n";
    }

    public function renderText(string $text): string
    {
        return "{$text}\n\n";
    }

    public function renderLink(string $text, string $url): string
    {
        return "[{$text}]({$url})";
    }

    public function renderImage(string $src, string $alt): string
    {
        return "![{$alt}]({$src})";
    }

    public function renderList(array $items): string
    {
        $listItems = array_map(fn($item) => "- {$item}", $items);
        return implode("\n", $listItems) . "\n\n";
    }

    public function renderTable(array $headers, array $rows): string
    {
        $headerLine = "| " . implode(" | ", $headers) . " |";
        $separatorLine = "| " . implode(" | ", array_fill(0, count($headers), "---")) . " |";

        $bodyLines = array_map(function ($row) {
            return "| " . implode(" | ", $row) . " |";
        }, $rows);

        return $headerLine . "\n" . $separatorLine . "\n" . implode("\n", $bodyLines) . "\n\n";
    }
}
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<?php

namespace App\Rendering\Renderers;

use App\Contracts\Rendering\RendererInterface;

class JsonRenderer implements RendererInterface
{
    protected array $data = [];

    public function renderTitle(string $title): string
    {
        $this->data['title'] = $title;
        return json_encode(['type' => 'title', 'content' => $title]);
    }

    public function renderText(string $text): string
    {
        return json_encode(['type' => 'text', 'content' => $text]);
    }

    public function renderLink(string $text, string $url): string
    {
        return json_encode(['type' => 'link', 'text' => $text, 'url' => $url]);
    }

    public function renderImage(string $src, string $alt): string
    {
        return json_encode(['type' => 'image', 'src' => $src, 'alt' => $alt]);
    }

    public function renderList(array $items): string
    {
        return json_encode(['type' => 'list', 'items' => $items]);
    }

    public function renderTable(array $headers, array $rows): string
    {
        return json_encode(['type' => 'table', 'headers' => $headers, 'rows' => $rows]);
    }
}

页面抽象

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<?php

namespace App\Rendering\Pages;

use App\Contracts\Rendering\RendererInterface;

abstract class Page
{
    protected RendererInterface $renderer;

    public function __construct(RendererInterface $renderer)
    {
        $this->renderer = $renderer;
    }

    abstract public function render(): string;
}
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<?php

namespace App\Rendering\Pages;

class ArticlePage extends Page
{
    protected string $title;
    protected string $content;
    protected array $links = [];

    public function setTitle(string $title): self
    {
        $this->title = $title;
        return $this;
    }

    public function setContent(string $content): self
    {
        $this->content = $content;
        return $this;
    }

    public function addLink(string $text, string $url): self
    {
        $this->links[] = ['text' => $text, 'url' => $url];
        return $this;
    }

    public function render(): string
    {
        $output = $this->renderer->renderTitle($this->title);
        $output .= $this->renderer->renderText($this->content);

        foreach ($this->links as $link) {
            $output .= $this->renderer->renderLink($link['text'], $link['url']);
        }

        return $output;
    }
}

测试桥接模式

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<?php

namespace Tests\Unit\Bridge;

use Tests\TestCase;
use App\Messaging\Messages\WelcomeMessage;
use App\Messaging\Senders\EmailSender;
use App\Messaging\Senders\SmsSender;
use App\Rendering\Pages\ArticlePage;
use App\Rendering\Renderers\HtmlRenderer;
use App\Rendering\Renderers\MarkdownRenderer;

class BridgeTest extends TestCase
{
    public function test_message_with_different_senders(): void
    {
        $emailSender = new EmailSender();
        $smsSender = $this->createMock(\App\Contracts\Messaging\MessageSenderInterface::class);

        $emailMessage = new WelcomeMessage($emailSender);
        $smsMessage = new WelcomeMessage($smsSender);

        $this->assertInstanceOf(WelcomeMessage::class, $emailMessage);
        $this->assertInstanceOf(WelcomeMessage::class, $smsMessage);
    }

    public function test_page_with_different_renderers(): void
    {
        $htmlRenderer = new HtmlRenderer();
        $markdownRenderer = new MarkdownRenderer();

        $htmlPage = new ArticlePage($htmlRenderer);
        $markdownPage = new ArticlePage($markdownRenderer);

        $htmlPage->setTitle('Test Title')->setContent('Test Content');
        $markdownPage->setTitle('Test Title')->setContent('Test Content');

        $htmlOutput = $htmlPage->render();
        $markdownOutput = $markdownPage->render();

        $this->assertStringContainsString('<h1>Test Title</h1>', $htmlOutput);
        $this->assertStringContainsString('# Test Title', $markdownOutput);
    }
}

最佳实践

1. 优先组合而非继承

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<?php

class GoodBridge
{
    protected ImplementationInterface $implementation;

    public function __construct(ImplementationInterface $implementation)
    {
        $this->implementation = $implementation;
    }
}

2. 接口设计要稳定

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<?php

interface StableInterface
{
    public function coreOperation(): mixed;
}

3. 抽象层应委托给实现

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<?php

abstract class Abstraction
{
    protected ImplementationInterface $implementation;

    public function operation(): string
    {
        return $this->implementation->operationImplementation();
    }
}

总结

Laravel 13 的桥接模式提供了一种灵活的方式来分离抽象和实现。通过合理使用桥接模式，可以创建可扩展、可维护的系统架构，同时支持多个维度的独立变化。