How to specify local plugins when building with gradle offline mode?

Question

I used gradle to build the project in an environment without internet, and I put all the project dependencies into the libs directory in the project root, and everything worked fine. Because it is a spring-boot project, I need to package it with the gradle plugin org.springframework.boot, so I put the jar of the plugin spring-boot-gradle-plugin-2.2.0.RELEASE.jar into the project's But I have used many ways from the Internet to specify the plugins in the plugins directory, but none of them work.

The project directory is as follows:

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

And the settings.gradle file is as follows:

pluginManagement {
    repositories {
        mavenLocal()
        flatDir { dirs 'plugins' }
    }

}
rootProject.name = 'example'

And the build.gradle file is as follows:

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')
}

But when I execute it via offline mode:./gradlew build --offline ,I get the following error:

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/)

How exactly is this situation specified? Do I need to install the two jars in the plugins directory to the local maven repository?

I have found many ways to compile specified plugins offline on the web, including this:

    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"
    }

}

I still get the same error.

Answer 1

My problem is solved. In response to this problem, I was inspired by the following link:Gradle Plugins Offline Resolution

In this answer from the gradle community, I learned how gradle parses plugins: ${pluginId}:${pluginId}.gradle.plugin:${pluginVersion}. So I changed the plugins in the plugins directory to the corresponding format.

buildscript {
    dependencies {
        classpath "io.spring.dependency-management:io.spring.dependency-management.gradle.plugin:1.0.8.RELEASE"
        classpath "org.springframework.boot:org.springframework.boot.gradle.plugin:2.2.0.RELEASE"
    }
}

But then I ran into a new problem when I executedgradlew --offline bootJar with the error:

FAILURE: Build failed with an exception.

* What went wrong:
org/springframework/boot/loader/tools/MainClassFinder
> org.springframework.boot.loader.tools.MainClassFinder

So I used org.springframework.boot.loader.tools.MainClassFinder class Google search, found that is spring-boot-loader-tools the contents of the jar package, I then added this jar to the plugins, and change the buildscript {...} block

buildscript {
    dependencies {
        classpath "io.spring.dependency-management:io.spring.dependency-management.gradle.plugin:1.0.8.RELEASE"
        classpath "org.springframework.boot:org.springframework.boot.gradle.plugin:2.2.0.RELEASE"
        classpath "org.springframework.boot:spring-boot-loader-tools:2.2.0.RELEASE"
    }
}

Now it works on my Mac. But when I put the project on an environment without internet (the build environment of the final project is no internet), there are other problems, similar to a class not being found. I guess this kind of problem is the bootJar plugin execution can not find the relevant dependencies, so I copied the .m2 file from my mac, and finally built and ran successfully.

So to summarize, there are two problems:

1. plugins directory plug-in name and gradle for the resolution of the plug-in name does not match
2. in addition to the plugins specified in buildscript{}, the plugins' related dependencies (there may be many) also need to be found in the environment. Why did I copy the .m2 over instead of putting all the related dependencies into plugins? Because there are too many dependencies...