Maven启动脚本分析

Maven启动脚本位于%M2_HOME%\bin\mvn.cmd。
本文基于版本3.3.9进行分析。

License声明

@REM ----------------------------------------------------------------------------@REM Licensed to the Apache Software Foundation (ASF) under one@REM or more contributor license agreements.  See the NOTICE file@REM distributed with this work for additional information@REM regarding copyright ownership.  The ASF licenses this file@REM to you under the Apache License, Version 2.0 (the@REM "License"); you may not use this file except in compliance@REM with the License.  You may obtain a copy of the License at@REM@REM    http://www.apache.org/licenses/LICENSE-2.0@REM@REM Unless required by applicable law or agreed to in writing,@REM software distributed under the License is distributed on an@REM "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY@REM KIND, either express or implied.  See the License for the@REM specific language governing permissions and limitations@REM under the License.@REM ----------------------------------------------------------------------------

脚本注释

@REM ----------------------------------------------------------------------------@REM Maven2 Start Up Batch script@REM@REM Required ENV vars:@REM JAVA_HOME - location of a JDK home dir@REM@REM Optional ENV vars@REM M2_HOME - location of maven2's installed home dir@REM MAVEN_BATCH_ECHO - set to 'on' to enable the echoing of the batch commands@REM MAVEN_BATCH_PAUSE - set to 'on' to wait for a key stroke before ending@REM MAVEN_OPTS - parameters passed to the Java VM when running Maven@REM     e.g. to debug Maven itself, use@REM set MAVEN_OPTS=-Xdebug -Xrunjdwp:transport=dt_socket,server=y,suspend=y,address=8000@REM MAVEN_SKIP_RC - flag to disable loading of mavenrc files@REM ----------------------------------------------------------------------------

预处理

@REM Begin all REM lines with '@' in case MAVEN_BATCH_ECHO is 'on'@echo off@REM enable echoing my setting MAVEN_BATCH_ECHO to 'on'@if "%MAVEN_BATCH_ECHO%" == "on"  echo %MAVEN_BATCH_ECHO%@REM set %HOME% to equivalent of $HOMEif "%HOME%" == "" (set "HOME=%HOMEDRIVE%%HOMEPATH%")@REM Execute a user defined script before this oneif not "%MAVEN_SKIP_RC%" == "" goto skipRcPre@REM check for pre script, once with legacy .bat ending and once with .cmd endingif exist "%HOME%\mavenrc_pre.bat" call "%HOME%\mavenrc_pre.bat"if exist "%HOME%\mavenrc_pre.cmd" call "%HOME%\mavenrc_pre.cmd":skipRcPre@setlocalset ERROR_CODE=0@REM To isolate internal variables from possible post scripts, we use another setlocal@setlocal

校验环境变量

@REM ==== START VALIDATION ====if not "%JAVA_HOME%" == "" goto OkJHomeecho.echo Error: JAVA_HOME not found in your environment. >&2echo Please set the JAVA_HOME variable in your environment to match the >&2echo location of your Java installation. >&2echo.goto error:OkJHomeif exist "%JAVA_HOME%\bin\java.exe" goto chkMHomeecho.echo Error: JAVA_HOME is set to an invalid directory. >&2echo JAVA_HOME = "%JAVA_HOME%" >&2echo Please set the JAVA_HOME variable in your environment to match the >&2echo location of your Java installation. >&2echo.goto error:chkMHomeif not "%M2_HOME%"=="" goto valMHomeSET "M2_HOME=%~dp0.."if not "%M2_HOME%"=="" goto valMHomeecho.echo Error: M2_HOME not found in your environment. >&2echo Please set the M2_HOME variable in your environment to match the >&2echo location of the Maven installation. >&2echo.goto error:valMHome:stripMHomeif not "_%M2_HOME:~-1%"=="_\" goto checkMCmdset "M2_HOME=%M2_HOME:~0,-1%"goto stripMHome:checkMCmdif exist "%M2_HOME%\bin\mvn.cmd" goto initecho.echo Error: M2_HOME is set to an invalid directory. >&2echo M2_HOME = "%M2_HOME%" >&2echo Please set the M2_HOME variable in your environment to match the >&2echo location of the Maven installation >&2echo.goto error@REM ==== END VALIDATION ====

· 关于字符串截取的语法，参见syntax-substring
· 关于参数扩展的语法，参见syntax-args

初始化

:initset MAVEN_CMD_LINE_ARGS=%*@REM Find the project base dir, i.e. the directory that contains the folder ".mvn".@REM Fallback to current working directory if not found.set MAVEN_PROJECTBASEDIR=%MAVEN_BASEDIR%IF NOT "%MAVEN_PROJECTBASEDIR%"=="" goto endDetectBaseDirset EXEC_DIR=%CD%set WDIR=%EXEC_DIR%:findBaseDirIF EXIST "%WDIR%\.mvn" goto baseDirFoundcd ..IF "%WDIR%"=="%CD%" goto baseDirNotFoundset WDIR=%CD%goto findBaseDir:baseDirFoundset MAVEN_PROJECTBASEDIR=%WDIR%cd "%EXEC_DIR%"goto endDetectBaseDir:baseDirNotFoundif "_%EXEC_DIR:~-1%"=="_\" set EXEC_DIR=%EXEC_DIR:~0,-1%set MAVEN_PROJECTBASEDIR=%EXEC_DIR%cd "%EXEC_DIR%":endDetectBaseDirIF NOT EXIST "%MAVEN_PROJECTBASEDIR%\.mvn\jvm.config" goto endReadAdditionalConfig@setlocal EnableExtensions EnableDelayedExpansionfor /F "usebackq delims=" %%a in ("%MAVEN_PROJECTBASEDIR%\.mvn\jvm.config") do set JVM_CONFIG_MAVEN_PROPS=!JVM_CONFIG_MAVEN_PROPS! %%a@endlocal & set JVM_CONFIG_MAVEN_PROPS=%JVM_CONFIG_MAVEN_PROPS%:endReadAdditionalConfig

· 关于setlocal
　　· EnableExtensions ： 启用命令扩展
　　· EnableDelayedExpansion ： 启用变量延迟扩展
· 可在Windows命令行中输入for /?或shift /?查看命令信息
· 更详细的信息参见setlocal
· 关于延迟扩展的语法，参见delayedexpansion
· 关于%MAVEN_PROJECTBASEDIR%，这是Maven的一个新特性，详见Maven开始逃离 XML 阵营

执行命令

SET MAVEN_JAVA_EXE="%JAVA_HOME%\bin\java.exe"for %%i in ("%M2_HOME%"\boot\plexus-classworlds-*) do set CLASSWORLDS_JAR="%%i"set CLASSWORLDS_LAUNCHER=org.codehaus.plexus.classworlds.launcher.Launcher%MAVEN_JAVA_EXE% %JVM_CONFIG_MAVEN_PROPS% %MAVEN_OPTS% %MAVEN_DEBUG_OPTS%-classpath %CLASSWORLDS_JAR% "-Dclassworlds.conf=%M2_HOME%\bin\m2.conf""-Dmaven.home=%M2_HOME%""-Dmaven.multiModuleProjectDirectory=%MAVEN_PROJECTBASEDIR%"%CLASSWORLDS_LAUNCHER% %MAVEN_CMD_LINE_ARGS%if ERRORLEVEL 1 goto errorgoto end:errorset ERROR_CODE=1

· 可见Maven的启动类是org.codehaus.plexus.classworlds.launcher.Launcher，可以从它入手来分析Maven源码
· 更详细的信息参见Plexus – Plexus Overview

结束

:end@endlocal & set ERROR_CODE=%ERROR_CODE%if not "%MAVEN_SKIP_RC%" == "" goto skipRcPost@REM check for post script, once with legacy .bat ending and once with .cmd endingif exist "%HOME%\mavenrc_post.bat" call "%HOME%\mavenrc_post.bat"if exist "%HOME%\mavenrc_post.cmd" call "%HOME%\mavenrc_post.cmd":skipRcPost@REM pause the script if MAVEN_BATCH_PAUSE is set to 'on'if "%MAVEN_BATCH_PAUSE%" == "on" pauseif "%MAVEN_TERMINATE_CMD%" == "on" exit %ERROR_CODE%exit /B %ERROR_CODE%