Maven 的生命周期就是对所有的构建过程进行抽象和统一。包含了项目的清理（clean）、初始化（initialization）、编译（compile）、测试（test）、打包（package）、集成测试、验证、部署（deploy）和站点生成等几乎所有的构建步骤。
Maven 的生命周期是抽象的，即生命周期不做任何实际的工作，实际任务由插件完成，类似于设计模式中的模板方法。了解 Maven 的生命周期对用好 maven 至关重要，如下图：
上图展示的是 Maven 的默认（default）生命周期：
1）validate：验证工程是否正确，所有需要的资源是否可用。
2）compile：编译项目的源代码。
3）test：使用合适的单元测试框架来测试已编译的源代码，这些测试不需要打包和布署。
4）package：把已编译的代码打包成可发布的格式，比如jar。
5）verify：运行所有检查，验证包是否有效且达到质量标准。
6）install：把包安装到 Maven 本地仓库，可以被其他工程作为依赖来使用。
7）deploy：在集成或者发布环境下执行，将最终版本的包拷贝到远程的仓库（repository），使得其他的开发者或者工程可以共享。
上面通过一些理论知识，初步认识了 Maven 的声明周期。下面将创建一个简单的 Maven 项目，然后运行 Maven 的不同生命周期，观察输出的日志（其中那些插件被执行了）。
项目结构如下图：
执行项目清理，将删除项目下面的 target 目录。将执行如下插件：
（1）maven-clean-plugin：用来清理 target 目录
日志如下：
[INFO] ------------------------< com.hxstrive.demo:demo >------------------------ [INFO] Building demo 1.0-SNAPSHOT [INFO] --------------------------------[ jar ]--------------------------------- [INFO] [INFO] --- maven-clean-plugin:2.5:clean (default-clean) @ demo --- [INFO] Deleting C:\Users\Administrator\Desktop\demo\target [INFO] ------------------------------------------------------------------------ [INFO] BUILD SUCCESS
验证工程是否正确，所有需要的资源是否可用，日志如下：
[INFO] ------------------------< com.hxstrive.demo:demo >------------------------ [INFO] Building demo 1.0-SNAPSHOT [INFO] --------------------------------[ jar ]--------------------------------- [INFO] ------------------------------------------------------------------------ [INFO] BUILD SUCCESS [INFO] ------------------------------------------------------------------------ [INFO] Total time: 0.082 s [INFO] Finished at: 2020-08-26T16:57:12+08:00 [INFO] ------------------------------------------------------------------------
并没有执行任何插件。
编译项目的源代码。该生命周期将运行如下插件：
（1）maven-resources-plugin：负责处理项目资源文件并拷贝到输出目录。
（2）maven-compiler-plugin：用来编译Java代码，并且输出到 target\classes 目录。
Maven 区别对待 Java 代码文件和资源文件，maven-compiler-plugin 用来编译Java代码，maven-resources-plugin 则用来处理资源文件。
默认的主资源文件目录是 src/main/resources，很多用户会需要添加额外的资源文件目录，这个时候就可以通过配置 maven-resources-plugin 来实现。
日志如下：
[INFO] ------------------------< com.hxstrive.demo:demo >------------------------ [INFO] Building demo 1.0-SNAPSHOT [INFO] --------------------------------[ jar ]--------------------------------- [INFO] [INFO] --- maven-resources-plugin:2.6:resources (default-resources) @ demo --- [WARNING] Using platform encoding (UTF-8 actually) to copy filtered resources, i.e. build is platform dependent! [INFO] Copying 1 resource [INFO] [INFO] --- maven-compiler-plugin:3.1:compile (default-compile) @ demo --- [INFO] Changes detected - recompiling the module! [WARNING] File encoding has not been set, using platform encoding UTF-8, i.e. build is platform dependent! [INFO] Compiling 1 source file to C:\Users\Administrator\Desktop\demo\target\classes [INFO] ------------------------------------------------------------------------ [INFO] BUILD SUCCESS [INFO] ------------------------------------------------------------------------ [INFO] Total time: 1.506 s [INFO] Finished at: 2020-08-26T16:55:51+08:00 [INFO] ------------------------------------------------------------------------
使用合适的单元测试框架来测试已编译的源代码，这些测试不需要打包和布署。该生命周期将运行如下插件：
（1）maven-resources-plugin:2.6:resources：负责处理项目资源文件并拷贝到输出目录。
（2）maven-compiler-plugin:3.1:compile：编译项目 Java 代码。
（3）maven-resources-plugin:2.6:testResources：负责处理项目测试资源文件并拷贝到输出目录。
（4）maven-compiler-plugin:3.1:testCompile：编译项目测试 Java 代码
（5）maven-surefire-plugin:2.12.4:test：负责执行项目的单元测试，源码位于 src/test/java，编译后位于 target/test-class 目录。
日志如下：
[INFO] ------------------------< com.hxstrive.demo:demo >------------------------ [INFO] Building demo 1.0-SNAPSHOT [INFO] --------------------------------[ jar ]--------------------------------- [INFO] [INFO] --- maven-resources-plugin:2.6:resources (default-resources) @ demo --- [WARNING] Using platform encoding (UTF-8 actually) to copy filtered resources, i.e. build is platform dependent! [INFO] Copying 1 resource [INFO] [INFO] --- maven-compiler-plugin:3.1:compile (default-compile) @ demo --- [INFO] Changes detected - recompiling the module! [WARNING] File encoding has not been set, using platform encoding UTF-8, i.e. build is platform dependent! [INFO] Compiling 1 source file to C:\Users\Administrator\Desktop\demo\target\classes [INFO] [INFO] --- maven-resources-plugin:2.6:testResources (default-testResources) @ demo --- [WARNING] Using platform encoding (UTF-8 actually) to copy filtered resources, i.e. build is platform dependent! [INFO] Copying 1 resource [INFO] [INFO] --- maven-compiler-plugin:3.1:testCompile (default-testCompile) @ demo --- [INFO] Changes detected - recompiling the module! [WARNING] File encoding has not been set, using platform encoding UTF-8, i.e. build is platform dependent! [INFO] Compiling 1 source file to C:\Users\Administrator\Desktop\demo\target\test-classes [INFO] [INFO] --- maven-surefire-plugin:2.12.4:test (default-test) @ demo --- [INFO] ------------------------------------------------------------------------ [INFO] BUILD SUCCESS
把已编译的代码打包成可发布的格式，比如：jar、war。该生命周期将运行如下插件：
（1）maven-resources-plugin:2.6:resources：负责处理项目资源文件并拷贝到输出目录。
（2）maven-compiler-plugin:3.1:compile：编译项目 Java 代码。
（3）maven-resources-plugin:2.6:testResources：负责处理项目测试资源文件并拷贝到输出目录。
（4）maven-compiler-plugin:3.1:testCompile：编译项目测试 Java 代码
（5）maven-surefire-plugin:2.12.4:test：负责执行项目的单元测试，源码位于 src/test/java，编译后位于 target/test-class 目录。
（6）maven-jar-plugin:2.4:jar：负责将项目打包成 jar 包，不包含测试代码和资源。如果你需要将项目打包成 war 包，则需要使用 maven-war-plugin 插件。
日志如下：
[INFO] ------------------------< com.hxstrive.demo:demo >------------------------ [INFO] Building demo 1.0-SNAPSHOT [INFO] --------------------------------[ jar ]--------------------------------- [INFO] [INFO] --- maven-resources-plugin:2.6:resources (default-resources) @ demo --- [WARNING] Using platform encoding (UTF-8 actually) to copy filtered resources, i.e. build is platform dependent! [INFO] Copying 1 resource [INFO] [INFO] --- maven-compiler-plugin:3.1:compile (default-compile) @ demo --- [INFO] Changes detected - recompiling the module! [WARNING] File encoding has not been set, using platform encoding UTF-8, i.e. build is platform dependent! [INFO] Compiling 1 source file to C:\Users\Administrator\Desktop\demo\target\classes [INFO] [INFO] --- maven-resources-plugin:2.6:testResources (default-testResources) @ demo --- [WARNING] Using platform encoding (UTF-8 actually) to copy filtered resources, i.e. build is platform dependent! [INFO] Copying 1 resource [INFO] [INFO] --- maven-compiler-plugin:3.1:testCompile (default-testCompile) @ demo --- [INFO] Changes detected - recompiling the module! [WARNING] File encoding has not been set, using platform encoding UTF-8, i.e. build is platform dependent! [INFO] Compiling 1 source file to C:\Users\Administrator\Desktop\demo\target\test-classes [INFO] [INFO] --- maven-surefire-plugin:2.12.4:test (default-test) @ demo --- [INFO] [INFO] --- maven-jar-plugin:2.4:jar (default-jar) @ demo --- [INFO] Building jar: C:\Users\Administrator\Desktop\demo\target\demo-1.0-SNAPSHOT.jar [INFO] ------------------------------------------------------------------------ [INFO] BUILD SUCCESS
运行所有检查，验证包是否有效且达到质量标准。该生命周期将运行如下插件：
（1）maven-resources-plugin:2.6:resources：负责处理项目资源文件并拷贝到输出目录。
（2）maven-compiler-plugin:3.1:compile：编译项目 Java 代码。
（3）maven-resources-plugin:2.6:testResources：负责处理项目测试资源文件并拷贝到输出目录。
（4）maven-compiler-plugin:3.1:testCompile：编译项目测试 Java 代码
（5）maven-surefire-plugin:2.12.4:test：负责执行项目的单元测试，源码位于 src/test/java，编译后位于 target/test-class 目录。
（6）maven-jar-plugin:2.4:jar：负责将项目打包成 jar 包，不包含测试代码和资源。如果你需要将项目打包成 war 包，则需要使用 maven-war-plugin 插件。
细心的读者会发现，它和 package 生命周期执行的插件顺序和个数一样。日志如下：
[INFO] ------------------------< com.hxstrive.demo:demo >------------------------ [INFO] Building demo 1.0-SNAPSHOT [INFO] --------------------------------[ jar ]--------------------------------- [INFO] [INFO] --- maven-resources-plugin:2.6:resources (default-resources) @ demo --- [WARNING] Using platform encoding (UTF-8 actually) to copy filtered resources, i.e. build is platform dependent! [INFO] Copying 1 resource [INFO] [INFO] --- maven-compiler-plugin:3.1:compile (default-compile) @ demo --- [INFO] Changes detected - recompiling the module! [WARNING] File encoding has not been set, using platform encoding UTF-8, i.e. build is platform dependent! [INFO] Compiling 1 source file to C:\Users\Administrator\Desktop\demo\target\classes [INFO] [INFO] --- maven-resources-plugin:2.6:testResources (default-testResources) @ demo --- [WARNING] Using platform encoding (UTF-8 actually) to copy filtered resources, i.e. build is platform dependent! [INFO] Copying 1 resource [INFO] [INFO] --- maven-compiler-plugin:3.1:testCompile (default-testCompile) @ demo --- [INFO] Changes detected - recompiling the module! [WARNING] File encoding has not been set, using platform encoding UTF-8, i.e. build is platform dependent! [INFO] Compiling 1 source file to C:\Users\Administrator\Desktop\demo\target\test-classes [INFO] [INFO] --- maven-surefire-plugin:2.12.4:test (default-test) @ demo --- [INFO] [INFO] --- maven-jar-plugin:2.4:jar (default-jar) @ demo --- [INFO] Building jar: C:\Users\Administrator\Desktop\demo\target\demo-1.0-SNAPSHOT.jar [INFO] ------------------------------------------------------------------------ [INFO] BUILD SUCCESS
把包安装到 Maven 本地仓库，可以被其他工程作为依赖来使用。该生命周期将运行如下插件：
（1）maven-resources-plugin:2.6:resources：负责处理项目资源文件并拷贝到输出目录。
（2）maven-compiler-plugin:3.1:compile：编译项目 Java 代码。
（3）maven-resources-plugin:2.6:testResources：负责处理项目测试资源文件并拷贝到输出目录。
（4）maven-compiler-plugin:3.1:testCompile：编译项目测试 Java 代码
（5）maven-surefire-plugin:2.12.4:test：负责执行项目的单元测试，源码位于 src/test/java，编译后位于 target/test-class 目录。
（6）maven-jar-plugin:2.4:jar：负责将项目打包成 jar 包，不包含测试代码和资源。如果你需要将项目打包成 war 包，则需要使用 maven-war-plugin 插件。
（7）maven-install-plugin:2.4:install：将打包好的 jar 安装到本地 Maven 仓库，供其他项目引用。
日志如下：
[INFO] ------------------------< com.hxstrive.demo:demo >------------------------ [INFO] Building demo 1.0-SNAPSHOT [INFO] --------------------------------[ jar ]--------------------------------- [INFO] [INFO] --- maven-resources-plugin:2.6:resources (default-resources) @ demo --- [WARNING] Using platform encoding (UTF-8 actually) to copy filtered resources, i.e. build is platform dependent! [INFO] Copying 1 resource [INFO] [INFO] --- maven-compiler-plugin:3.1:compile (default-compile) @ demo --- [INFO] Changes detected - recompiling the module! [WARNING] File encoding has not been set, using platform encoding UTF-8, i.e. build is platform dependent! [INFO] Compiling 1 source file to C:\Users\Administrator\Desktop\demo\target\classes [INFO] [INFO] --- maven-resources-plugin:2.6:testResources (default-testResources) @ demo --- [WARNING] Using platform encoding (UTF-8 actually) to copy filtered resources, i.e. build is platform dependent! [INFO] Copying 1 resource [INFO] [INFO] --- maven-compiler-plugin:3.1:testCompile (default-testCompile) @ demo --- [INFO] Changes detected - recompiling the module! [WARNING] File encoding has not been set, using platform encoding UTF-8, i.e. build is platform dependent! [INFO] Compiling 1 source file to C:\Users\Administrator\Desktop\demo\target\test-classes [INFO] [INFO] --- maven-surefire-plugin:2.12.4:test (default-test) @ demo --- [INFO] [INFO] --- maven-jar-plugin:2.4:jar (default-jar) @ demo --- [INFO] [INFO] --- maven-install-plugin:2.4:install (default-install) @ demo --- [INFO] Installing C:\Users\Administrator\Desktop\demo\target\demo-1.0-SNAPSHOT.jar to D:\Repository\Maven\com\huangx\demo\demo\1.0-SNAPSHOT\demo-1.0-SNAPSHOT.jar [INFO] Installing C:\Users\Administrator\Desktop\demo\pom.xml to D:\Repository\Maven\com\huangx\demo\demo\1.0-SNAPSHOT\demo-1.0-SNAPSHOT.pom [INFO] ------------------------------------------------------------------------ [INFO] BUILD SUCCESS
在集成或者发布环境下执行，将最终版本的包拷贝到远程的仓库（repository），使得其他的开发者或者工程可以共享。该生命周期将运行如下插件：
（1）maven-resources-plugin:2.6:resources：负责处理项目资源文件并拷贝到输出目录。
（2）maven-compiler-plugin:3.1:compile：编译项目 Java 代码。
（3）maven-resources-plugin:2.6:testResources：负责处理项目测试资源文件并拷贝到输出目录。
（4）maven-compiler-plugin:3.1:testCompile：编译项目测试 Java 代码
（5）maven-surefire-plugin:2.12.4:test：负责执行项目的单元测试，源码位于 src/test/java，编译后位于 target/test-class 目录。
（6）maven-jar-plugin:2.4:jar：负责将项目打包成 jar 包，不包含测试代码和资源。如果你需要将项目打包成 war 包，则需要使用 maven-war-plugin 插件。
（7）maven-install-plugin:2.4:install：将打包好的 jar 安装到本地 Maven 仓库，供其他项目引用。
（8）maven-deploy-plugin:2.7:deploy：将打包好的 jar 安装到远程 Maven 仓库。
日志如下：
[INFO] ------------------------< com.hxstrive.demo:demo >------------------------ [INFO] Building demo 1.0-SNAPSHOT [INFO] --------------------------------[ jar ]--------------------------------- [INFO] [INFO] --- maven-resources-plugin:2.6:resources (default-resources) @ demo --- [WARNING] Using platform encoding (UTF-8 actually) to copy filtered resources, i.e. build is platform dependent! [INFO] Copying 1 resource [INFO] [INFO] --- maven-compiler-plugin:3.1:compile (default-compile) @ demo --- [INFO] Changes detected - recompiling the module! [WARNING] File encoding has not been set, using platform encoding UTF-8, i.e. build is platform dependent! [INFO] Compiling 1 source file to C:\Users\Administrator\Desktop\demo\target\classes [INFO] [INFO] --- maven-resources-plugin:2.6:testResources (default-testResources) @ demo --- [WARNING] Using platform encoding (UTF-8 actually) to copy filtered resources, i.e. build is platform dependent! [INFO] Copying 1 resource [INFO] [INFO] --- maven-compiler-plugin:3.1:testCompile (default-testCompile) @ demo --- [INFO] Changes detected - recompiling the module! [WARNING] File encoding has not been set, using platform encoding UTF-8, i.e. build is platform dependent! [INFO] Compiling 1 source file to C:\Users\Administrator\Desktop\demo\target\test-classes [INFO] [INFO] --- maven-surefire-plugin:2.12.4:test (default-test) @ demo --- [INFO] [INFO] --- maven-jar-plugin:2.4:jar (default-jar) @ demo --- [INFO] [INFO] --- maven-install-plugin:2.4:install (default-install) @ demo --- [INFO] Installing C:\Users\Administrator\Desktop\demo\target\demo-1.0-SNAPSHOT.jar to D:\Repository\Maven\com\huangx\demo\demo\1.0-SNAPSHOT\demo-1.0-SNAPSHOT.jar [INFO] Installing C:\Users\Administrator\Desktop\demo\pom.xml to D:\Repository\Maven\com\huangx\demo\demo\1.0-SNAPSHOT\demo-1.0-SNAPSHOT.pom [INFO] [INFO] --- maven-deploy-plugin:2.7:deploy (default-deploy) @ demo --- [INFO] ------------------------------------------------------------------------ [INFO] BUILD FAILURE
到这里 Maven 常用生命周期就介绍完了，通过上面的介绍我们就可以清晰的知道 Maven 每个生命周期具体执行了那些插件，以及他们的顺序。
