Laravel5.3之Container源码解析

2022-01-10 09:39:00 浏览数 (1)

说明：本文主要学习Laravel中Container的源码，主要学习Container的绑定和解析过程，和解析过程中的依赖解决。分享自己的研究心得，希望对别人有所帮助。实际上Container的绑定主要有三种方式：bind(),singleton(),instance(),且singleton()只是一种'shared' = true的bind()，这些已经在Laravel5.3之IoC Container实例化源码解析聊过，其实现方法并不复杂。当Service通过Service Provider绑定到Container中后，当需要该Service时，是需要Container帮助自动解析make()。OK,下面聊聊自动解析过程，研究下Container是如何在自动解析Service时解决该Service的依赖问题的。

开发环境： Laravel5.3 PHP7 OS X 10.11

PHPUnit测试下绑定

在聊解析过程前，先测试下IlluminateContainerContainer中绑定的源码，这里测试下bind(),singleton(),instance()三个绑定方式：

代码语言：javascript复制
<?php

namespace MyRightCapitalContainerTests;

use MyRightCapitalContainerContainer;

class ContainerBindTest extends PHPUnit_Framework_TestCase
{
    /** * @var Container $container */
    protected $container;

    public function setUp()
    {
        $this->container = new Container();
    }

    public function testBindClosure()
    {
        // Arrange
        $expected = 'Laravel is a PHP Framework.';
        $this->container->bind('PHP', function () use ($expected) {
            return $expected;
        });

        // Actual
        $actual = $this->container->make('PHP');

        // Assert
        $this->assertEquals($expected, $actual);
    }

    public function testBindInterfaceToImplement()
    {
        // Arrange
        $this->container->bind(IContainerStub::class, ContainerImplementationStub::class);

        // Actual
        $actual = $this->container->make(IContainerStub::class);

        // Assert
        $this->assertInstanceOf(IContainerStub::class, $actual);
    }

    public function testBindDependencyResolution()
    {
        // Arrange
        $this->container->bind(IContainerStub::class, ContainerImplementationStub::class);

        // Actual
        $actual = $this->container->make(ContainerNestedDependentStub::class);

        // Assert
        $this->assertInstanceOf(ContainerDependentStub::class, $actual->containerDependentStub);
        $this->assertInstanceOf(ContainerImplementationStub::class, $actual->containerDependentStub->containerStub);
    }

    public function testSingleton()
    {
        // Arrange
        $this->container->singleton(ContainerConcreteStub::class);
        $expected = $this->container->make(ContainerConcreteStub::class);

        // Actual
        $actual = $this->container->make(ContainerConcreteStub::class);

        // Assert
        $this->assertSame($expected, $actual);
    }

    public function testInstanceExistingObject()
    {
        // Arrange
        $expected = new ContainerImplementationStub();
        $this->container->instance(IContainerStub::class, $expected);

        // Actual
        $actual = $this->container->make(IContainerStub::class);

        // Assert
        $this->assertSame($expected, $actual);
    }
}

class ContainerConcreteStub
{

}

interface IContainerStub
{

}

class ContainerImplementationStub implements IContainerStub
{

}

class ContainerDependentStub
{
    /** * @var MyRightCapitalContainerTestsIContainerStub */
    public $containerStub;

    public function __construct(IContainerStub $containerStub)
    {
        $this->containerStub = $containerStub;
    }
}

class ContainerNestedDependentStub
{
    /** * @var MyRightCapitalContainerTestsContainerDependentStub */
    public $containerDependentStub;

    public function __construct(ContainerDependentStub $containerDependentStub)
    {
        $this->containerDependentStub = $containerDependentStub;
    }
}

这里测试了bind()绑定闭包，绑定接口和对应实现，依赖解析这三个feature，singleton()测试了是否为单例绑定一个feature，instance()测试了已存在对象绑定这个feature，测试结果5个tests都通过：

关于在PHPStorm中配置PHPUnit可参考这篇：Laravel5.2之基于PHPStorm编辑器的Laravel开发

make()源码解析

从以上testcase知道，make()是负责从Container中解析出service的，而且在testBindDependencyResolution()这个test中，还能发现当ContainerNestedDependentStub::class有构造依赖时，Container也会自动去解析这个依赖并注入ContainerNestedDependentStub::class的构造函数中，这个依赖是ContainerDependentStub::class，而这个依赖又有自己的依赖IContainerStub::class，从断言语句this->assertInstanceOf(ContainerImplementationStub::class,

这一切Container是怎么做到的？实际上并不复杂，解决依赖只是用了PHP的Reflector反射机制来实现的。先看下make()源码：

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    /** * Resolve the given type from the container. * * @param string $abstract * @param array $parameters * @return mixed */
    public function make($abstract, array $parameters = [])
    {
        $abstract = $this->getAlias($this->normalize($abstract));

        // 如果是instance()绑定的方式，就直接解析返回绑定的service
        if (isset($this->instances[$abstract])) {
            return $this->instances[$abstract];
        }

        // 获取$abstract对应绑定的$concrete
        $concrete = $this->getConcrete($abstract);

        if ($this->isBuildable($concrete, $abstract)) {
            $object = $this->build($concrete, $parameters);
        } else {
            $object = $this->make($concrete, $parameters);
        }

        foreach ($this->getExtenders($abstract) as $extender) {
            $object = $extender($object, $this);
        }

        if ($this->isShared($abstract)) {
            $this->instances[$abstract] = $object;
        }

        $this->fireResolvingCallbacks($abstract, $object);

        $this->resolved[$abstract] = true;

        return $object;
    }
    
    protected function getConcrete($abstract)
    {
        if (! is_null($concrete = $this->getContextualConcrete($abstract))) {
            return $concrete;
        }

        // 如果是$this->container->singleton(ContainerConcreteStub::class);这种方式绑定，即$concrete = null
        // 则 $abstract = $concrete，可看以上PHPUnit的testSingleton()这个test
        // 这种方式称为'自动补全'绑定
        if (! isset($this->bindings[$abstract])) {
            return $abstract;
        }

        return $this->bindings[$abstract]['concrete'];
    }
    
    protected function isBuildable($concrete, $abstract)
    {
        return $concrete === $abstract || $concrete instanceof Closure;
    }

从以上源码可知道如果绑定的是闭包或者'自动补全'绑定(concrete = null)，则需要build()这个闭包或类名，转换成对应的实例。如果是'接口实现'这种方式绑定，则需要再一次调用make()并经过getConcrete后abstract =

代码语言：javascript复制
    /** * Instantiate a concrete instance of the given type. * * @param string $concrete * @param array $parameters * @return mixed * * @throws IlluminateContractsContainerBindingResolutionException */
    public function build($concrete, array $parameters = [])
    {
        // 如果是闭包直接执行闭包并返回，e.g. PHPUnit的这个test:testBindClosure()
        if ($concrete instanceof Closure) {
            return $concrete($this, $parameters);
        }
        
        // 如这个test:testBindInterfaceToImplement()，这里的$concrete = ContainerImplementationStub::class类名称，
        // 则使用反射ReflectionClass来探测ContainerImplementationStub这个类的构造函数和构造函数的依赖
        $reflector = new ReflectionClass($concrete);

        // 如果ContainerImplementationStub不能实例化，这应该是接口或抽象类，再或者就是ContainerImplementationStub的构造函数是private的
        if (! $reflector->isInstantiable()) {
            if (! empty($this->buildStack)) {
                $previous = implode(', ', $this->buildStack);

                $message = "Target [$concrete] is not instantiable while building [$previous].";
            } else {
                $message = "Target [$concrete] is not instantiable.";
            }

            throw new BindingResolutionException($message);
        }

        $this->buildStack[] = $concrete;

        // 获取构造函数的反射
        $constructor = $reflector->getConstructor();

        // 如果构造函数是空，说明没有任何依赖，直接new返回
        if (is_null($constructor)) {
            array_pop($this->buildStack);

            return new $concrete;
        }
        
        // 获取构造函数的依赖，返回ReflectionParameter[]
        $dependencies = $constructor->getParameters();

        $parameters = $this->keyParametersByArgument(
            $dependencies, $parameters
        );

        // 然后就是获取相关依赖，如testBindDependencyResolution()这个test中，
        // ContainerNestedDependentStub::class是依赖于ContainerDependentStub::class的
        $instances = $this->getDependencies(
            $dependencies, $parameters
        );

        array_pop($this->buildStack);

        return $reflector->newInstanceArgs($instances);
    }

从源码可知道，比较麻烦的是当ContainerNestedDependentStub::class的构造函数有依赖ContainerDependentStub::class时，通过getDependencies()来解决的，看下getDependencies()的源码：

代码语言：javascript复制
    // 这里$parameters = ReflectionParameter[]
    protected function getDependencies(array $parameters, array $primitives = [])
    {
        $dependencies = [];

        foreach ($parameters as $parameter) {
            $dependency = $parameter->getClass();

            // 如果某一依赖值已给，就赋值
            if (array_key_exists($parameter->name, $primitives)) {
                $dependencies[] = $primitives[$parameter->name];
            } 
            // 如果类名为null，说明是基本类型，如'int','string' and so on.
            elseif (is_null($dependency)) {
                $dependencies[] = $this->resolveNonClass($parameter);
            } 
            // 如果是类名，如ContainerDependentStub::class，则resolveClass去解析成对象
            else {
                $dependencies[] = $this->resolveClass($parameter);
            }
        }

        return $dependencies;
    }

通过上面注释，看下resolveClass()的源码：

代码语言：javascript复制
    protected function resolveClass(ReflectionParameter $parameter)
    {
        try {
            // $parameter->getClass()->name返回的是类名，如ContainerNestedDependentStub依赖于$containerDependentStub
            // $containerDependentStub的typehint是ContainerDependentStub，所以类名是'ContainerDependentStub'
            // 然后递归继续make(ContainerDependentStub::class)
            // 又和PHPUnit中这个测试$this->container->make(ContainerNestedDependentStub::class)相类似了
            // ContainerNestedDependentStub又依赖于IContainerStub::class，
            // IContainerStub::class是绑定于ContainerImplementationStub::class
            // 直到ContainerImplementationStub没有依赖或者是构造函数是基本属性，
            // 最后build()结束
            return $this->make($parameter->getClass()->name);
        } catch (BindingResolutionException $e) {
            if ($parameter->isOptional()) {
                return $parameter->getDefaultValue();
            }

            throw $e;
        }
    }

从以上代码注释直到build()是个递归过程，A类依赖于B类,B类依赖于C类和D类，那就从A类开始build，发现依赖于B类，再从Container中解析make()即再build()出B类，发现依赖于C类，再make() and build()，发现B类又同时依赖于D类，再make() and build()，以此类推直到没有依赖或依赖基本属性，解析结束。这样一步步解析完后，发现Container的解析make()并不是很神秘很复杂中的过程。

从以上源码发现PHP的反射Reflector是个很好用的技术，这里给出个test，看下Reflector能干些啥：

代码语言：javascript复制
<?php

class ConstructorParameter
{

}

class ReflectorTest
{
    private $refletorProperty1;

    protected $refletorProperty2;

    public $refletorProperty3;

    /** * @var int */
    private $request;

    public function __construct(int $request = 10, string $response, ConstructorParameter $constructorParameter, Closure $closure)
    {

        $this->request = $request;
    }

    private function reflectorMethod1()
    {
    }

    protected function reflectorMethod2()
    {
    }

    public function reflectorMethod3()
    {
    }
}

$reflector_class        = new ReflectionClass(ReflectorTest::class);
$methods                = $reflector_class->getMethods();
$properties             = $reflector_class->getProperties();
$constructor            = $reflector_class->getConstructor();
$constructor_parameters = $constructor->getParameters();

foreach ($constructor_parameters as $constructor_parameter) {
    $dependency = $constructor_parameter->getClass();
    var_dump($dependency);

    if ($constructor_parameter->isDefaultValueAvailable()) {
        var_dump($constructor_parameter->getDefaultValue());
    }
}

var_dump($methods);
var_dump($properties);
var_dump($constructor);
var_dump($constructor_parameters);

打印结果太长了，就不粘贴了。可以看下PHP官方文档：Reflector

总结：本文学习了下Container的核心功能：service resolve的过程，并学习了service的依赖是如何被自动解析的。遇到好的心得再分享，到时见。

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