Gradle离线模式下指定本地插件失败求助（Spring Boot项目）

问题背景 #

无网络环境下使用Gradle构建Spring Boot项目，项目依赖已放入根目录libs目录，这部分工作正常。需使用org.springframework.boot插件打包，已将spring-boot-gradle-plugin-2.2.0.RELEASE.jar与dependency-management-plugin-1.0.11.RELEASE.jar放入项目plugins目录，但多种配置方法均无效。

项目目录结构 #

projectRoot
├── build.gradle
├── gradle
│	└── wrapper
├── gradlew
├── gradlew.bat
├── libs
│	└── xxx.jar
├── plugins
│	├── dependency-management-plugin-1.0.11.RELEASE.jar
│	└── spring-boot-gradle-plugin-2.2.0.RELEASE.jar
├── resource
├── settings.gradle
└── src
    ├── main
    └── test

当前配置文件 #

settings.gradle #

pluginManagement {
    repositories {
        mavenLocal()
        flatDir { dirs 'plugins' }
    }
}
rootProject.name = 'example'

build.gradle #

plugins {
    id 'org.springframework.boot' version '2.2.0.RELEASE'
    id 'io.spring.dependency-management' version '1.0.11.RELEASE'
    id 'java'
}

apply plugin: 'org.springframework.boot'
apply plugin: 'io.spring.dependency-management'

group = 'com.example'
version = '1.0.0-SNAPSHOT'
sourceCompatibility = '1.8'

repositories {
    mavenLocal()
}

dependencies {
    implementation files('libs/xxx.jar','libs/others_of_libs.jar')
}

离线构建错误信息 #

执行命令 ./gradlew build --offline 时出现以下错误：

Plugin [id: 'org.springframework.boot', version: '2.2.0.RELEASE'] was not found in any of the following sources:

- Gradle Core Plugins (plugin is not in 'org.gradle' namespace)
- Plugin Repositories (could not resolve plugin artifact 'org.springframework.boot:org.springframework.boot.gradle.plugin:2.2.0.RELEASE')
  Searched in the following repositories:
    maven(file:/User/myName/example/plugins/)

已尝试的无效配置 #

曾尝试使用buildscript配置，仍报相同错误：

buildscript {
    repositories {
        mavenLocal()
        maven { url('plugins') }
    }

    dependencies {
        classpath fileTree(include: ['*.jar'], dir: 'plugins')
        classpath files('plugins/dependency-management-plugin-1.0.11.RELEASE.jar')
        classpath files('plugins/spring-boot-gradle-plugin-2.2.0.RELEASE.jar')
        classpath "io.spring.dependency-management:io.spring.dependency-management.gradle.plugin:1.0.11.RELEASE"
        classpath "org.springframework.boot:spring-boot-gradle-plugin:2.2.0.RELEASE"
    }
}

解决方案 #

错误原因 #

Gradle的plugins DSL通过插件ID查找对应的marker artifact（如org.springframework.boot:org.springframework.boot.gradle.plugin:2.2.0.RELEASE），而非直接查找插件实现jar。你仅放入了插件的核心实现jar，缺少关联ID的marker artifact，导致Gradle无法解析插件ID。

方案1：安装插件到本地Maven仓库（推荐） #

通过Maven命令将插件jar安装到本地仓库，让Gradle能通过插件ID正常解析：

1. 安装Spring Boot插件：

mvn install:install-file -Dfile=plugins/spring-boot-gradle-plugin-2.2.0.RELEASE.jar -DgroupId=org.springframework.boot -DartifactId=spring-boot-gradle-plugin -Dversion=2.2.0.RELEASE -Dpackaging=jar

2. 安装依赖管理插件：

mvn install:install-file -Dfile=plugins/dependency-management-plugin-1.0.11.RELEASE.jar -DgroupId=io.spring.dependency-management -DartifactId=dependency-management-plugin -Dversion=1.0.11.RELEASE -Dpackaging=jar

3. 同时需要安装对应的marker artifact（可从有网络环境下载后安装）：
   • Spring Boot插件对应marker jar：org.springframework.boot:org.springframework.boot.gradle.plugin:2.2.0.RELEASE.jar
   • 依赖管理插件对应marker jar：io.spring.dependency-management:io.spring.dependency-management.gradle.plugin:1.0.11.RELEASE.jar

完成后，原settings.gradle和build.gradle配置即可正常工作，执行离线构建命令即可成功。

方案2：跳过plugins DSL，直接用buildscript加载插件 #

无需依赖marker artifact，直接通过buildscript指定插件classpath并应用插件，修改build.gradle如下：

buildscript {
    dependencies {
        // 直接加载本地插件jar
        classpath files('plugins/spring-boot-gradle-plugin-2.2.0.RELEASE.jar')
        classpath files('plugins/dependency-management-plugin-1.0.11.RELEASE.jar')
    }
}

// 直接应用插件的类或ID
apply plugin: org.springframework.boot.gradle.plugin.SpringBootPlugin
apply plugin: io.spring.gradle.dependencymanagement.DependencyManagementPlugin
apply plugin: 'java'

group = 'com.example'
version = '1.0.0-SNAPSHOT'
sourceCompatibility = '1.8'

repositories {
    // 本地依赖仓库
    flatDir { dirs 'libs' }
}

dependencies {
    implementation fileTree(dir: 'libs', include: ['*.jar'])
}

此配置无需修改settings.gradle，直接执行./gradlew build --offline即可完成离线构建。

内容的提问来源于stack exchange，提问作者leowangzz