面试题：Kotlin Gradle插件开发之专家难度题

Question

在多模块的Gradle项目中，开发一个Kotlin Gradle插件，该插件能够自动分析各个模块之间的依赖关系，并生成可视化的依赖关系图（使用Graphviz工具）。请详细说明实现方案，包括插件的架构设计、如何获取模块依赖信息以及如何与Graphviz集成，同时给出关键代码示例。

Answer 1

插件架构设计

1. 核心功能模块：负责分析模块依赖关系并生成Graphviz所需的DOT语言描述文本。
2. Graphviz集成模块：负责调用Graphviz工具将DOT文本转换为可视化图片。
3. Gradle集成模块：将插件功能集成到Gradle构建流程中，通过Gradle API获取项目相关信息。

获取模块依赖信息

1. 使用Gradle的ProjectDependency和Configuration等API。在Gradle构建生命周期的合适阶段（如afterEvaluate），遍历项目的所有模块及其配置。
2. 对于每个模块，获取其runtimeClasspath或implementation等配置的依赖项。示例代码如下：

project.afterEvaluate {
    subprojects.forEach { subproject ->
        subproject.configurations.forEach { configuration ->
            configuration.incoming.dependencies.forEach { dependency ->
                if (dependency instanceof ProjectDependency) {
                    val targetProject = (dependency as ProjectDependency).dependencyProject
                    println("${subproject.name} depends on ${targetProject.name}")
                }
            }
        }
    }
}

与Graphviz集成

1. 安装Graphviz：确保运行构建的环境中安装了Graphviz工具，并将其路径添加到系统PATH中。
2. 生成DOT文本：根据获取的模块依赖信息，按照Graphviz的DOT语言规范生成描述依赖关系的文本。示例代码如下：

val dotBuilder = StringBuilder("digraph {\n")
project.afterEvaluate {
    subprojects.forEach { subproject ->
        dotBuilder.append("\"${subproject.name}\" [label=\"${subproject.name}\"];\n")
        subproject.configurations.forEach { configuration ->
            configuration.incoming.dependencies.forEach { dependency ->
                if (dependency instanceof ProjectDependency) {
                    val targetProject = (dependency as ProjectDependency).dependencyProject
                    dotBuilder.append("\"${subproject.name}\" -> \"${targetProject.name}\";\n")
                }
            }
        }
    }
    dotBuilder.append("}\n")
    val dotFilePath = File(project.buildDir, "dependency_graph.dot")
    dotFilePath.writeText(dotBuilder.toString())
}

3. 调用Graphviz：使用Java的ProcessBuilder调用Graphviz的dot命令将DOT文本转换为图片（如PNG格式）。示例代码如下：

try {
    val dotFilePath = File(project.buildDir, "dependency_graph.dot")
    val outputImagePath = File(project.buildDir, "dependency_graph.png")
    ProcessBuilder("dot", "-Tpng", dotFilePath.path, "-o", outputImagePath.path)
      .inheritIO()
      .start()
      .waitFor()
} catch (e: Exception) {
    e.printStackTrace()
}

完整插件代码示例

import org.gradle.api.Plugin
import org.gradle.api.Project
import java.io.File

class DependencyGraphPlugin : Plugin<Project> {
    override fun apply(project: Project) {
        project.afterEvaluate {
            val dotBuilder = StringBuilder("digraph {\n")
            subprojects.forEach { subproject ->
                dotBuilder.append("\"${subproject.name}\" [label=\"${subproject.name}\"];\n")
                subproject.configurations.forEach { configuration ->
                    configuration.incoming.dependencies.forEach { dependency ->
                        if (dependency is ProjectDependency) {
                            val targetProject = dependency.dependencyProject
                            dotBuilder.append("\"${subproject.name}\" -> \"${targetProject.name}\";\n")
                        }
                    }
                }
            }
            dotBuilder.append("}\n")
            val dotFilePath = File(project.buildDir, "dependency_graph.dot")
            dotFilePath.writeText(dotBuilder.toString())
            try {
                val outputImagePath = File(project.buildDir, "dependency_graph.png")
                ProcessBuilder("dot", "-Tpng", dotFilePath.path, "-o", outputImagePath.path)
                  .inheritIO()
                  .start()
                  .waitFor()
            } catch (e: Exception) {
                e.printStackTrace()
            }
        }
    }
}

在buildSrc/src/main/kotlin目录下创建上述Kotlin文件，然后在项目根目录的settings.gradle.kts中应用该插件：

plugins {
    id("com.example.dependency-graph-plugin") version "1.0" apply true
}

以上就是实现该Kotlin Gradle插件的详细方案及关键代码示例。