简介
项目中经过很久开发，会有很多当初引入后来又不再使用的依赖，靠肉眼很难分辨删除。
这时候，我们可以使用分析无用依赖插件进行处理：gradle-lint-plugin
如何使用
注意： 他可能存在删除错误的引用依赖，需要删除后进行检查和测试
并且，这里仅支持单模块项目，如果是多模块项目请参考官方文档进行处理
官方文档地址： https://github.com/nebula-plugins/gradle-lint-plugin/wiki
1.引入插件
在项目的 build.gradle 中引用该插件, 最新版本号可以 点击这里查看:
plugins {
id 'nebula.lint' version '17.7.0'
}
如何你项目中本身已经有插件，则可以在后面追加，例如我的：
plugins {
id 'org.springframework.boot' version '2.3.5.RELEASE'
id 'io.spring.dependency-management' version '1.0.10.RELEASE'
id 'java'
id 'nebula.lint' version '17.7.0'
}
2.应用插件
在 build.gradle 应用 该插件，并在任意位置，配置检测规则：
apply plugin :"nebula.lint"
gradleLint.rules=['unused-dependency']
3.使用 Gradle 进行重新载入项目
IDEA 使用 Gradle 进行重新载入项目，则会出现 Lint 菜单, 如下图所示：
4.生成报告
点击 lint -> generateGradleLintReport, 可以生成报告。
报告仅保留不同类型的省略结果，可以看到有以下四种报告结果：
- one or more classes are required by your code directly (no auto-fix available)
- this dependency is unused and can be removed
- this dependency should be removed since its artifact is empty (no auto-fix available)
- this dependency is a service provider unused at compileClasspath time and can be moved to the runtimeOnly configuration (no auto-fix available)
其中， this dependency is unused and can be removed 表示可以删除的依赖。
Executing 'generateGradleLintReport'...
> Task :generateGradleLintReport
Generated a report containing information about 83 lint violations in this project
> Task :autoLintGradle
This project contains lint violations. A complete listing of the violations follows.
Because none were serious, the build's overall status was unaffected.
warning unused-dependency one or more classes in org.mockito:mockito-core:3.3.3 are required by your code directly (no auto-fix available)
warning unused-dependency this dependency should be removed since its artifact is empty (no auto-fix available)
build.gradle:59
implementation 'org.springframework.boot:spring-boot-starter-actuator'
warning unused-dependency this dependency is a service provider unused at compileClasspath time and can be moved to the runtimeOnly configuration (no auto-fix available)
build.gradle:69
compileOnly 'org.projectlombok:lombok'
warning unused-dependency this dependency is unused and can be removed
build.gradle:101
compile group: 'ch.qos.logback', name: 'logback-core', version: '1.2.3'
? 83 problems (0 errors, 83 warnings)
To apply fixes automatically, run fixGradleLint, review, and commit the changes.
5. 删除无用依赖
我们可以看到报告的最后一句话，
To apply fixes automatically, run fixGradleLint, review, and commit the changes.
最后，可以执行 fixGradleLint 自动删除无用依赖。
修复报告如下，我们可以看到除了无用的依赖，还有一些其他的依赖也被删除了，原因是因为，他认为我们可以直接引入其对应的依赖而不是整个依赖包。
例如，compile group: 'com.baomidou', name: 'mybatis-plus-boot-starter', version: '3.3.1' 中我们只用了整个 starter 包的一部分依赖，可以仅依赖这一部分依赖，而不是整个 starter 包。这个也可以不按照他的推荐，直接手动选择保留。
Executing 'fixGradleLint'...
> Task :compileJava
> Task :processResources UP-TO-DATE
> Task :classes
> Task :compileTestJava
> Task :fixGradleLint
This project contains lint violations. A complete listing of my attempt to fix them follows. Please review and commit the changes.
needs fixing unused-dependency one or more classes in com.baomidou:mybatis-plus-core:3.3.1 are required by your code directly
fixed unused-dependency this dependency is unused and can be removed
build.gradle:105
compile 'org.ehcache:ehcache'
fixed unused-dependency this dependency is unused and can be removed
build.gradle:106
compile 'javax.cache:cache-api'
fixed unused-dependency this dependency is unused and can be removed
build.gradle:107
compile 'org.mybatis:mybatis-typehandlers-jsr310:1.0.2'
fixed unused-dependency this dependency is unused and can be removed
build.gradle:112
testImplementation 'org.springframework.security:spring-security-test'
Corrected 17 lint problems
特殊情况
Lombok
Lombok 是一个编译时自动生成 Getter/Setter 和构造器的工具。
Nebula Lint 依旧会检测无用的依赖，日志如下：
> Task :lintGradle FAILED
This project contains lint violations. A complete listing of the violations follows.
Because none were serious, the build's overall status was unaffected.
warning unused-dependency this dependency is a service provider unused at compile time and can be moved to the runtime configuration
处理方式(修改版本号)：
gradleLint.ignore('unused-dependency') {
compileOnly group: 'org.projectlombok', name: 'lombok', version:'1.16.20'
}
相关 Github issue: Nebula Lint does not handle certain @Retention(RetentionPolicy.SOURCE) annotations correctly #170
总结
使用该插件可以一定程度上帮助我们删除无用依赖，但是也可能会多删除有用的依赖。
需要在使用插件自动修复后手动检测项目，验证是否会出现问题，避免导致上线发布错误的负优化。