From 9b49696fbbb22c5267bd22baabc5ae727724e3b4 Mon Sep 17 00:00:00 2001 From: Omooo <869759698@qq.com> Date: Thu, 8 Aug 2019 18:02:44 +0800 Subject: [PATCH] =?UTF-8?q?Create=20=E4=BE=9D=E8=B5=96=E5=AE=9E=E7=8E=B0?= =?UTF-8?q?=E5=88=86=E6=9E=90.md?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit --- blogs/Android/Gradle/依赖实现分析.md | 241 +++++++++++++++++++++ 1 file changed, 241 insertions(+) create mode 100644 blogs/Android/Gradle/依赖实现分析.md diff --git a/blogs/Android/Gradle/依赖实现分析.md b/blogs/Android/Gradle/依赖实现分析.md new file mode 100644 index 0000000..3bb5ddb --- /dev/null +++ b/blogs/Android/Gradle/依赖实现分析.md @@ -0,0 +1,241 @@ +--- +深入理解 Gradle 框架之 依赖实现分析 +--- + +> 本文摘自:@ AllenWang [深入理解gradle框架之二:依赖实现分析](https://mp.weixin.qq.com/s/WQCqUaYDPHDIjUHlxjRIkw) + +### 目录 + +1. 引言 +2. 从 implementation 说起 + +### 引言 + +大家在日常开发中,见过最多的可能就是下面三种依赖声明: + +```groovy +implementation “org.jetbrains.kotlin:kotlin-stdlib-jdk7:$kotlin_version” +implementation project(":applemodule") +implementation fileTree(dir:‘libs’, include:[’*.jar’]) +``` + +这些不同的依赖声明,内部实现机制是怎么样的? + +### 从 implementation 说起 + +``` +implementation 'com.android.support:appcompat-v7:28.0.0' +``` + +按照 Groovy 的语法,这里要执行的是 DependencyHandler 的 implementation() 方法,参数为 'com.android.support:appcompat-v7:28.0.0'。 + +但是在 DependencyHandler 中并没有 implementation() 这个方法,这是怎么回事呢? + +```java +public interface DependencyHandler { + + Dependency add(String configurationName, Object dependencyNotation); + + Dependency create(Object dependencyNotation); + + Dependency module(Object notation); + + Dependency project(Map notation); + + Dependency gradleApi(); + + Dependency localGroovy(); + + //... +} +``` + +#### MethodMissing + +这其实涉及到了 Groovy 语言的一个重要特性:methodMissing,这个特性允许在运行时 catch 对于未定义方法的调用。 + +Gradle 对这个特性进行封装,一个类要想使用这个特性,只要实现 MixIn 接口即可,这个接口如下: + +```java +public interface MethodMixIn { + MethodAccess getAdditionalMethods(); +} +``` + +其中 MethodAccess 接口如下: + +```java +public interface MethodAccess { + boolean hasMethod(String var1, Object... var2); + + DynamicInvokeResult tryInvokeMethod(String var1, Object... var2); +} +``` + +也就是说,对于 DependencyHandler 中未定义的方法(如 implementation() 方法),只要 hasMethod 返回 true,就会调用到 MethodAccess 的实现者的 tryInvokeMethod 方法,其中 name 为 configuration 名称,arguments 就是 'com.android.support:appcompat-v7:28.0.0' 这个参数。 + +那 DependencyHandler 接口的实现者 DefaultDependencyHandler 是如何实现 MethodMixIn 这个接口的呢? + +```java + public MethodAccess getAdditionalMethods() { + return this.dynamicMethods; + } +``` + +这个 dynamicMethods 类型为 DynamicAddDependencyMethods,源码如下: + +```java +class DynamicAddDependencyMethods implements MethodAccess { + private ConfigurationContainer configurationContainer; + private DynamicAddDependencyMethods.DependencyAdder dependencyAdder; + + DynamicAddDependencyMethods(ConfigurationContainer configurationContainer, DynamicAddDependencyMethods.DependencyAdder dependencyAdder) { + this.configurationContainer = configurationContainer; + this.dependencyAdder = dependencyAdder; + } + + public boolean hasMethod(String name, Object... arguments) { + return arguments.length != 0 && this.configurationContainer.findByName(name) != null; + } + + public DynamicInvokeResult tryInvokeMethod(String name, Object... arguments) { + if (arguments.length == 0) { + return DynamicInvokeResult.notFound(); + } else { + Configuration configuration = (Configuration)this.configurationContainer.findByName(name); + if (configuration == null) { + return DynamicInvokeResult.notFound(); + } else { + List normalizedArgs = CollectionUtils.flattenCollections(arguments); + if (normalizedArgs.size() == 2 && normalizedArgs.get(1) instanceof Closure) { + return DynamicInvokeResult.found(this.dependencyAdder.add(configuration, normalizedArgs.get(0), (Closure)normalizedArgs.get(1))); + } else if (normalizedArgs.size() == 1) { + return DynamicInvokeResult.found(this.dependencyAdder.add(configuration, normalizedArgs.get(0), (Closure)null)); + } else { + Iterator var5 = normalizedArgs.iterator(); + + while(var5.hasNext()) { + Object arg = var5.next(); + this.dependencyAdder.add(configuration, arg, (Closure)null); + } + + return DynamicInvokeResult.found(); + } + } + } + } + + interface DependencyAdder { + T add(Configuration var1, Object var2, Closure var3); + } +} +``` + +注意到它是实现了 MethodAccess 这个接口的,首先看它的 hasMethod() 方法,很简单,返回 true 的条件是: + +* 参数长度不为零 +* configuration 必须是已经定义过的 + +然后再看 tryInvokeMethod(),它会先通过 configurationsContainer 找到对应的 configuration,然后分如下几种情况: + +* 参数个数为 2,并且第 2 个参数是 Closure +* 参数个数为 1 +* 其他情形 + +不过不管哪种情形,都会先调用 dependencyAdder 的 add() 方法,而 dependencyAdder 是 DefaultDependencyHandler.DirectDependencyAdder 对象,其 add() 方法如下: + +```java +public Dependency add(Configuration configuration, Object dependencyNotation, @Nullable Closure configureAction) { + return DefaultDependencyHandler.this.doAdd(configuration, dependencyNotation, configureAction); + } +``` + +可见,其实是调用外部类 DefaultDependencyHandler 的 doAdd() 方法,在下一小节分析该方法。 + +#### DefaultDependencyHandler.doAdd() 方法分析 + +```java + private Dependency doAdd(Configuration configuration, Object dependencyNotation, Closure configureClosure) { + if (dependencyNotation instanceof Configuration) { + Configuration other = (Configuration)dependencyNotation; + if (!this.configurationContainer.contains(other)) { + throw new UnsupportedOperationException("Currently you can only declare dependencies on configurations from the same project."); + } else { + configuration.extendsFrom(new Configuration[]{other}); + return null; + } + } else { + Dependency dependency = this.create(dependencyNotation, configureClosure); + configuration.getDependencies().add(dependency); + return dependency; + } + } +``` + +可见,这里会先判断 dependencyNotation 是否为 Configuration,如果是的话,就让当前的 configuration 继承自 other 这个 configuration,而继承的意思就是,后续所有添加到 other 的依赖,也会添加到当前这个 configuration 中。 + +为什么还要考虑参数中的 dependecnyNotation 是否为 Configuration 的情形呢? + +其实就是考虑到有诸如 implementation project(path: ':appmodule', configuration: 'configA') 这样的依赖声明。 + +至于依赖的创建过程,在下一节进行分析。 + +### 依赖创建过程分析 + +DefaultDependencyHandler 的 create() 方法如下: + +```java + public Dependency create(Object dependencyNotation, Closure configureClosure) { + Dependency dependency = this.dependencyFactory.createDependency(dependencyNotation); + return (Dependency)ConfigureUtil.configure(configureClosure, dependency); + } +``` + +其中的 dependencyFactory 为 DefaultDependencyFactory 对象,其 createDependency() 方法如下: + +```java + public Dependency createDependency(Object dependencyNotation) { + Dependency dependency = (Dependency)this.dependencyNotationParser.parseNotation(dependencyNotation); + this.injectAttributesFactory(dependency); + return dependency; + } +``` + +可见,它是直接调用 dependencyNotationParser 这个解析器对于 denpendencyNotation 进行解析。 + +其中的 dependencyNotationParser 是实现了接口 NotationParser\ 接口的对象。 + +为了找出这里的 dependencyNotationParser 到底是哪个类的实例,查看 DefaultDependencyFactory 的创建,在 DependencyManagementBuildScopeServices 类中,如下: + +```java + DependencyFactory createDependencyFactory(Instantiator instantiator, ProjectAccessListener projectAccessListener, StartParameter startParameter, ClassPathRegistry classPathRegistry, CurrentGradleInstallation currentGradleInstallation, FileLookup fileLookup, RuntimeShadedJarFactory runtimeShadedJarFactory, ImmutableAttributesFactory attributesFactory, SimpleMapInterner stringInterner) { + DefaultProjectDependencyFactory factory = new DefaultProjectDependencyFactory(projectAccessListener, instantiator, startParameter.isBuildProjectDependencies()); + ProjectDependencyFactory projectDependencyFactory = new ProjectDependencyFactory(factory); + return new DefaultDependencyFactory(DependencyNotationParser.parser(instantiator, factory, classPathRegistry, fileLookup, runtimeShadedJarFactory, currentGradleInstallation, stringInterner), DependencyConstraintNotationParser.parser(instantiator, stringInterner), (new ClientModuleNotationParserFactory(instantiator, stringInterner)).create(), projectDependencyFactory, attributesFactory); + } +``` + +可见,它是通过 DependencyNotationParser.parser() 方法创建的,该方法如下: + +```java + public static NotationParser parser(Instantiator instantiator, DefaultProjectDependencyFactory dependencyFactory, ClassPathRegistry classPathRegistry, FileLookup fileLookup, RuntimeShadedJarFactory runtimeShadedJarFactory, CurrentGradleInstallation currentGradleInstallation, Interner stringInterner) { + return NotationParserBuilder.toType(Dependency.class).fromCharSequence(new DependencyStringNotationConverter(instantiator, DefaultExternalModuleDependency.class, stringInterner)).converter(new DependencyMapNotationConverter(instantiator, DefaultExternalModuleDependency.class)).fromType(FileCollection.class, new DependencyFilesNotationConverter(instantiator)).fromType(Project.class, new DependencyProjectNotationConverter(dependencyFactory)).fromType(ClassPathNotation.class, new DependencyClassPathNotationConverter(instantiator, classPathRegistry, fileLookup.getFileResolver(), runtimeShadedJarFactory, currentGradleInstallation)).invalidNotationMessage("Comprehensive documentation on dependency notations is available in DSL reference for DependencyHandler type.").toComposite(); + } +``` + +这个方法其实很好理解,它其实是创建了多个实现了接口 NotationConverter 的对象,然后将这些转换器都添加在一起,构成一个综合的转换器。 + +其中,DependencyStringNotationConvert 负责将字符串类型的 notation 转换为 DefaultExternalModuleDependency,也就是对应 implementation 'com.android.support:appcompat-v7:25.1.0' 这样的声明; + +DependencyFilesNotationConverter 将 FileCollection 转换为 SelfResolvingDependency,也就是对应的 implementation fileTree(dir: 'libs', include:['*.jar']) 这样的声明; + +DependencyProjectNotationConverter 将 Project 转换为 ProjectDependency,对应 implementation project(":appmodule") 这样的情形; + +DependencyClasspathNotationConvert 将 ClasspathNotation 转换为 SelfResolvingDependency; + +到这里,就知道类似 implementation 'com.android.support:appcompat-v7:28.0.0' 和 implementation project 这样的声明,其实是被不同的转换器,转换成了 SelfResolvingDependency 或者 ProjectDependency。 + +这里可以看出,除了 project 依赖之外,其他都转换成 SelfResolvingDependency,所谓的 SelfResolvingDependency 其实是可以自解析的依赖,独立于 repository。 + +ProjectDependency 则不然,它是依赖于 repository 的,下面就分析 ProjectDependency 的独特之处。 +