运行startup.bat的启动过程
一、前言
一般啟動tomcat都是找到bin目錄下的startup.bat(windows)下或者startup.sh(linux下)，所以要研究tomcat的啟動，startup腳本是避不開的。那么下面就來看一看windows下面的startup.bat。
二、bat文件
要看懂startup.bat，首先得對bat文件有個基本的了解。
bat文件是dos下的批處理文件。批處理文件是無格式的文本文件，這個文件的每一行都是一條DOS命令。它的文件擴展名為 .bat 或 .cmd。在命令提示下鍵入批處理文件的名稱，或者雙擊該批處理文件，系統就會調用cmd.exe按照該文件中各個命令出現的順序來逐個運行它們。使用批處理文件（也被稱為批處理程序或腳本），可以簡化日常或重復性任務。
批處理簡單語法：
rem： 該命令用于注釋,rem起始的行不會作為代碼執行
pause： 該命令用于暫停正在執行的批處理文件，并且提示用戶按鍵，然后程序繼續執行
echo： 該命令用于在dos控制臺顯示一段文本，相當于print,如果想要顯示環境變量需要在環境變量前后加上%,例如顯示操作系統 echo %OS%
echo off： 該命令可以防止將批處理文件中的具體命令打印出來，而只會輸出執行結果。
@echo off：該命令與echo off相同，唯一的區別在于 @echo off不僅會隱藏具體命令還會連'echo off'這個自身命令也隱藏起來。
set： 設置環境變量，例如 set A = 100 設置A變量為100
label： 使用 ':'(冒號)來設置一個標簽，供給goto命令使用，例如"：init"代表一個init標簽。
goto： 該命令使正在執行的命令強制跳轉到他指定的標簽。例如我需要跳轉指定A標簽下的命令，如下：goto A
not: 該命令用來取反，相當于邏輯非。
if： 該命令表示判斷
exist: 該命令通常用來測試文件是否存在，一般和if一起使用
shift: 該命令用來將參數后移一位即將%2%賦值給%1%，%3%賦值給%2%，也可以理解為參數列表左移即刪除現有參數列表的第一位。
call： 該命令用來調用另外一條命令。
setLocal： 該命令表示該批處理文件中修改的環境變量只在本文件中起作用，或者直到endLocal命令出現，被修改的環境變量才恢復原狀。
start： 重新開啟一個dos窗口。
可以參考一下這篇博文：
Bat命令學習
三、startup.bat
用編輯器打開startup.bat文件，內容如下：
1 @echo off 2 rem Licensed to the Apache Software Foundation (ASF) under one or more 3 rem contributor license agreements. See the NOTICE file distributed with 4 rem this work for additional information regarding copyright ownership. 5 rem The ASF licenses this file to You under the Apache License, Version 2.0 6 rem (the "License"); you may not use this file except in compliance with 7 rem the License. You may obtain a copy of the License at 8 rem 9 rem http://www.apache.org/licenses/LICENSE-2.0 10 rem 11 rem Unless required by applicable law or agreed to in writing, software 12 rem distributed under the License is distributed on an "AS IS" BASIS, 13 rem WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 14 rem See the License for the specific language governing permissions and 15 rem limitations under the License. 16 17 rem --------------------------------------------------------------------------- 18 rem Start script for the CATALINA Server 19 rem --------------------------------------------------------------------------- 20 21 setlocal 22 23 rem Guess CATALINA_HOME if not defined 24 set "CURRENT_DIR=%cd%" 25 if not "%CATALINA_HOME%" == "" goto gotHome 26 set "CATALINA_HOME=%CURRENT_DIR%" 27 if exist "%CATALINA_HOME%\bin\catalina.bat" goto okHome 28 cd .. 29 set "CATALINA_HOME=%cd%" 30 cd "%CURRENT_DIR%" 31 :gotHome 32 if exist "%CATALINA_HOME%\bin\catalina.bat" goto okHome 33 echo The CATALINA_HOME environment variable is not defined correctly 34 echo This environment variable is needed to run this program 35 goto end 36 :okHome 37 38 set "EXECUTABLE=%CATALINA_HOME%\bin\catalina.bat" 39 40 rem Check that target executable exists 41 if exist "%EXECUTABLE%" goto okExec 42 echo Cannot find "%EXECUTABLE%" 43 echo This file is needed to run this program 44 goto end 45 :okExec 46 47 rem Get remaining unshifted command line arguments and save them in the 48 set CMD_LINE_ARGS= 49 :setArgs 50 if ""%1""=="""" goto doneSetArgs 51 set CMD_LINE_ARGS=%CMD_LINE_ARGS% %1 52 shift 53 goto setArgs 54 :doneSetArgs 55 56 call "%EXECUTABLE%" start %CMD_LINE_ARGS% 57 58 :end@echo off，此語句常用于開頭，表示不顯示所有的命令行信息，包括此句。
然后是一大段rem后面的內容，是注釋，對軟件的License做了說明，英文不太好，就不翻譯了。
setlocal，啟動批處理文件中環境變量的本地化，本地化將持續到出現匹配的endlocal命令或者到達批處理文件結尾為止。
下面將批處理文件拆成幾段看：
第一段：判斷CATALINA_HOME是否定義
1 setlocal 2 3 rem Guess CATALINA_HOME if not defined 4 set "CURRENT_DIR=%cd%" 5 if not "%CATALINA_HOME%" == "" goto gotHome 6 set "CATALINA_HOME=%CURRENT_DIR%" 7 if exist "%CATALINA_HOME%\bin\catalina.bat" goto okHome 8 cd .. 9 set "CATALINA_HOME=%cd%" 10 cd "%CURRENT_DIR%"設置變量CURRENT_DIR為當前目錄，一般打開的就是tomcat的bin目錄，./apache-tomcat-x.x.xx/bin；
判斷系統變量CATALINA_HOME是不是空串(一般安裝tomcat時，我們都會配置CATALINA_HOME環境變量，不知有沒有印象呢)，如果是就跳轉到gotHome標簽執行，假設CATALINA_HOME環境變量沒有定義，就繼續往下；
設置CATALINA_HOME為CURRENT_DIR指向的目錄，也就是bin目錄(./apache-tomcat-x.x.xx/bin)；
判斷CATALINA_HOME\bin\catalina.bat文件是否存在，也就是 ./apache-tomcat-x.x.xx/bin/bin/catalina.bat，如果存在就轉向okHome標簽，顯然是不存在的，所以不會跳轉到okHome，繼續往下；
不存在的話，CATALINA_HOME取上級目錄的值，也就是(./apache-tomcat-x.x.xx/)；
設置CATALINA_HOME指向當前目錄，也就是Tomcat的根目錄；
進入 CURRENT_DIR(./apache-tomcat-x.x.xx/bin)；
第二段：執行gotHome標簽
1 :gotHome 2 if exist "%CATALINA_HOME%\bin\catalina.bat" goto okHome 3 echo The CATALINA_HOME environment variable is not defined correctly 4 echo This environment variable is needed to run this program 5 goto end通過上面的設置，CATALINA_HOME的值已經是: ./apache-tomcat-x.x.xx/，這時判斷./apache-tomcat-x.x.xx/catalina.bat 腳本是否存在，如果不存在，則輸出一些信息結束，一般這時是可以找到的，所以跳轉到okHome標簽處；
第三段：執行okHome標簽
1 :okHome 2 3 set "EXECUTABLE=%CATALINA_HOME%\bin\catalina.bat"設置EXECUTABLE變量指向為catalina.bat腳本；
第四段：再次檢查catalina.bat是否存在
1 rem Check that target executable exists 2 if exist "%EXECUTABLE%" goto okExec 3 echo Cannot find "%EXECUTABLE%" 4 echo This file is needed to run this program 5 goto end
雙重保險繼續判斷下EXECUTABLE指向的catalina.bat文件是否存在，不存在就輸出提示信息并且結束，存在就跳轉到okExec標簽處：
第五段：
1 :okExec 2 3 rem Get remaining unshifted command line arguments and save them in the 4 set CMD_LINE_ARGS= 5 :setArgs 6 if ""%1""=="""" goto doneSetArgs 7 set CMD_LINE_ARGS=%CMD_LINE_ARGS% %1 8 shift 9 goto setArgs 10 :doneSetArgs 11 12 call "%EXECUTABLE%" start %CMD_LINE_ARGS%**最后：**end標簽
1 :end判斷失敗跳轉的標簽，是參數不正確的時候的結束標志。
四、catalina.bat
如果startup.bat執行正確，就等同于運行catalina.bat start，進入了catalina.bat腳本中，將腳本前面的一大段注釋刪掉了，如下：
1 setlocal 2 3 rem Suppress Terminate batch job on CTRL+C 4 if not ""%1"" == ""run"" goto mainEntry 5 if "%TEMP%" == "" goto mainEntry 6 if exist "%TEMP%\%~nx0.run" goto mainEntry 7 echo Y>"%TEMP%\%~nx0.run" 8 if not exist "%TEMP%\%~nx0.run" goto mainEntry 9 echo Y>"%TEMP%\%~nx0.Y" 10 call "%~f0" %* <"%TEMP%\%~nx0.Y" 11 rem Use provided errorlevel 12 set RETVAL=%ERRORLEVEL% 13 del /Q "%TEMP%\%~nx0.Y" >NUL 2>&1 14 exit /B %RETVAL% 15 :mainEntry 16 del /Q "%TEMP%\%~nx0.run" >NUL 2>&1 17 18 rem Guess CATALINA_HOME if not defined 19 set "CURRENT_DIR=%cd%" 20 if not "%CATALINA_HOME%" == "" goto gotHome 21 set "CATALINA_HOME=%CURRENT_DIR%" 22 if exist "%CATALINA_HOME%\bin\catalina.bat" goto okHome 23 cd .. 24 set "CATALINA_HOME=%cd%" 25 cd "%CURRENT_DIR%" 26 :gotHome 27 28 if exist "%CATALINA_HOME%\bin\catalina.bat" goto okHome 29 echo The CATALINA_HOME environment variable is not defined correctly 30 echo This environment variable is needed to run this program 31 goto end 32 :okHome 33 34 rem Copy CATALINA_BASE from CATALINA_HOME if not defined 35 if not "%CATALINA_BASE%" == "" goto gotBase 36 set "CATALINA_BASE=%CATALINA_HOME%" 37 :gotBase 38 39 rem Ensure that neither CATALINA_HOME nor CATALINA_BASE contains a semi-colon 40 rem as this is used as the separator in the classpath and Java provides no 41 rem mechanism for escaping if the same character appears in the path. Check this 42 rem by replacing all occurrences of ';' with '' and checking that neither 43 rem CATALINA_HOME nor CATALINA_BASE have changed 44 if "%CATALINA_HOME%" == "%CATALINA_HOME:;=%" goto homeNoSemicolon 45 echo Using CATALINA_HOME: "%CATALINA_HOME%" 46 echo Unable to start as CATALINA_HOME contains a semicolon (;) character 47 goto end 48 :homeNoSemicolon 49 50 if "%CATALINA_BASE%" == "%CATALINA_BASE:;=%" goto baseNoSemicolon 51 echo Using CATALINA_BASE: "%CATALINA_BASE%" 52 echo Unable to start as CATALINA_BASE contains a semicolon (;) character 53 goto end 54 :baseNoSemicolon 55 56 rem Ensure that any user defined CLASSPATH variables are not used on startup, 57 rem but allow them to be specified in setenv.bat, in rare case when it is needed. 58 set CLASSPATH= 59 60 rem Get standard environment variables 61 if not exist "%CATALINA_BASE%\bin\setenv.bat" goto checkSetenvHome 62 call "%CATALINA_BASE%\bin\setenv.bat" 63 goto setenvDone 64 :checkSetenvHome 65 if exist "%CATALINA_HOME%\bin\setenv.bat" call "%CATALINA_HOME%\bin\setenv.bat" 66 :setenvDone 67 68 rem Get standard Java environment variables 69 if exist "%CATALINA_HOME%\bin\setclasspath.bat" goto okSetclasspath 70 echo Cannot find "%CATALINA_HOME%\bin\setclasspath.bat" 71 echo This file is needed to run this program 72 goto end 73 :okSetclasspath 74 call "%CATALINA_HOME%\bin\setclasspath.bat" %1 75 if errorlevel 1 goto end 76 77 rem Add on extra jar file to CLASSPATH 78 rem Note that there are no quotes as we do not want to introduce random 79 rem quotes into the CLASSPATH 80 if "%CLASSPATH%" == "" goto emptyClasspath 81 set "CLASSPATH=%CLASSPATH%;" 82 :emptyClasspath 83 set "CLASSPATH=%CLASSPATH%%CATALINA_HOME%\bin\bootstrap.jar" 84 85 if not "%CATALINA_TMPDIR%" == "" goto gotTmpdir 86 set "CATALINA_TMPDIR=%CATALINA_BASE%\temp" 87 :gotTmpdir 88 89 rem Add tomcat-juli.jar to classpath 90 rem tomcat-juli.jar can be over-ridden per instance 91 if not exist "%CATALINA_BASE%\bin\tomcat-juli.jar" goto juliClasspathHome 92 set "CLASSPATH=%CLASSPATH%;%CATALINA_BASE%\bin\tomcat-juli.jar" 93 goto juliClasspathDone 94 :juliClasspathHome 95 set "CLASSPATH=%CLASSPATH%;%CATALINA_HOME%\bin\tomcat-juli.jar" 96 :juliClasspathDone 97 98 if not "%JSSE_OPTS%" == "" goto gotJsseOpts 99 set JSSE_OPTS="-Djdk.tls.ephemeralDHKeySize=2048" 100 :gotJsseOpts 101 set "JAVA_OPTS=%JAVA_OPTS% %JSSE_OPTS%" 102 103 rem Register custom URL handlers 104 rem Do this here so custom URL handles (specifically 'war:...') can be used in the security policy 105 set "JAVA_OPTS=%JAVA_OPTS% -Djava.protocol.handler.pkgs=org.apache.catalina.webresources" 106 107 if not "%LOGGING_CONFIG%" == "" goto noJuliConfig 108 set LOGGING_CONFIG=-Dnop 109 if not exist "%CATALINA_BASE%\conf\logging.properties" goto noJuliConfig 110 set LOGGING_CONFIG=-Djava.util.logging.config.file="%CATALINA_BASE%\conf\logging.properties" 111 :noJuliConfig 112 113 if not "%LOGGING_MANAGER%" == "" goto noJuliManager 114 set LOGGING_MANAGER=-Djava.util.logging.manager=org.apache.juli.ClassLoaderLogManager 115 :noJuliManager 116 117 rem Configure JAVA 9 specific start-up parameters 118 set "JDK_JAVA_OPTIONS=%JDK_JAVA_OPTIONS% --add-opens=java.base/java.lang=ALL-UNNAMED" 119 set "JDK_JAVA_OPTIONS=%JDK_JAVA_OPTIONS% --add-opens=java.base/java.io=ALL-UNNAMED" 120 set "JDK_JAVA_OPTIONS=%JDK_JAVA_OPTIONS% --add-opens=java.rmi/sun.rmi.transport=ALL-UNNAMED" 121 122 rem Java 9 no longer supports the java.endorsed.dirs 123 rem system property. Only try to use it if 124 rem JAVA_ENDORSED_DIRS was explicitly set 125 rem or CATALINA_HOME/endorsed exists. 126 set ENDORSED_PROP=ignore.endorsed.dirs 127 if "%JAVA_ENDORSED_DIRS%" == "" goto noEndorsedVar 128 set ENDORSED_PROP=java.endorsed.dirs 129 goto doneEndorsed 130 :noEndorsedVar 131 if not exist "%CATALINA_HOME%\endorsed" goto doneEndorsed 132 set ENDORSED_PROP=java.endorsed.dirs 133 :doneEndorsed 134 135 rem ----- Execute The Requested Command --------------------------------------- 136 137 echo Using CATALINA_BASE: "%CATALINA_BASE%" 138 echo Using CATALINA_HOME: "%CATALINA_HOME%" 139 echo Using CATALINA_TMPDIR: "%CATALINA_TMPDIR%" 140 if ""%1"" == ""debug"" goto use_jdk 141 echo Using JRE_HOME: "%JRE_HOME%" 142 goto java_dir_displayed 143 :use_jdk 144 echo Using JAVA_HOME: "%JAVA_HOME%" 145 :java_dir_displayed 146 echo Using CLASSPATH: "%CLASSPATH%" 147 148 set _EXECJAVA=%_RUNJAVA% 149 set MAINCLASS=org.apache.catalina.startup.Bootstrap 150 set ACTION=start 151 set SECURITY_POLICY_FILE= 152 set DEBUG_OPTS= 153 set JPDA= 154 155 if not ""%1"" == ""jpda"" goto noJpda 156 set JPDA=jpda 157 if not "%JPDA_TRANSPORT%" == "" goto gotJpdaTransport 158 set JPDA_TRANSPORT=dt_socket 159 :gotJpdaTransport 160 if not "%JPDA_ADDRESS%" == "" goto gotJpdaAddress 161 set JPDA_ADDRESS=localhost:8000 162 :gotJpdaAddress 163 if not "%JPDA_SUSPEND%" == "" goto gotJpdaSuspend 164 set JPDA_SUSPEND=n 165 :gotJpdaSuspend 166 if not "%JPDA_OPTS%" == "" goto gotJpdaOpts 167 set JPDA_OPTS=-agentlib:jdwp=transport=%JPDA_TRANSPORT%,address=%JPDA_ADDRESS%,server=y,suspend=%JPDA_SUSPEND% 168 :gotJpdaOpts 169 shift 170 :noJpda 171 172 if ""%1"" == ""debug"" goto doDebug 173 if ""%1"" == ""run"" goto doRun 174 if ""%1"" == ""start"" goto doStart 175 if ""%1"" == ""stop"" goto doStop 176 if ""%1"" == ""configtest"" goto doConfigTest 177 if ""%1"" == ""version"" goto doVersion 178 179 echo Usage: catalina ( commands ... ) 180 echo commands: 181 echo debug Start Catalina in a debugger 182 echo debug -security Debug Catalina with a security manager 183 echo jpda start Start Catalina under JPDA debugger 184 echo run Start Catalina in the current window 185 echo run -security Start in the current window with security manager 186 echo start Start Catalina in a separate window 187 echo start -security Start in a separate window with security manager 188 echo stop Stop Catalina 189 echo configtest Run a basic syntax check on server.xml 190 echo version What version of tomcat are you running? 191 goto end 192 193 :doDebug 194 shift 195 set _EXECJAVA=%_RUNJDB% 196 set DEBUG_OPTS=-sourcepath "%CATALINA_HOME%\..\..\java" 197 if not ""%1"" == ""-security"" goto execCmd 198 shift 199 echo Using Security Manager 200 set "SECURITY_POLICY_FILE=%CATALINA_BASE%\conf\catalina.policy" 201 goto execCmd 202 203 :doRun 204 shift 205 if not ""%1"" == ""-security"" goto execCmd 206 shift 207 echo Using Security Manager 208 set "SECURITY_POLICY_FILE=%CATALINA_BASE%\conf\catalina.policy" 209 goto execCmd 210 211 :doStart 212 shift 213 if "%TITLE%" == "" set TITLE=Tomcat 214 set _EXECJAVA=start "%TITLE%" %_RUNJAVA% 215 if not ""%1"" == ""-security"" goto execCmd 216 shift 217 echo Using Security Manager 218 set "SECURITY_POLICY_FILE=%CATALINA_BASE%\conf\catalina.policy" 219 goto execCmd 220 221 :doStop 222 shift 223 set ACTION=stop 224 set CATALINA_OPTS= 225 goto execCmd 226 227 :doConfigTest 228 shift 229 set ACTION=configtest 230 set CATALINA_OPTS= 231 goto execCmd 232 233 :doVersion 234 %_EXECJAVA% -classpath "%CATALINA_HOME%\lib\catalina.jar" org.apache.catalina.util.ServerInfo 235 goto end 236 237 238 :execCmd 239 rem Get remaining unshifted command line arguments and save them in the 240 set CMD_LINE_ARGS= 241 :setArgs 242 if ""%1""=="""" goto doneSetArgs 243 set CMD_LINE_ARGS=%CMD_LINE_ARGS% %1 244 shift 245 goto setArgs 246 :doneSetArgs 247 248 rem Execute Java with the applicable properties 249 if not "%JPDA%" == "" goto doJpda 250 if not "%SECURITY_POLICY_FILE%" == "" goto doSecurity 251 %_EXECJAVA% %LOGGING_CONFIG% %LOGGING_MANAGER% %JAVA_OPTS% %CATALINA_OPTS% %DEBUG_OPTS% -D%ENDORSED_PROP%="%JAVA_ENDORSED_DIRS%" -classpath "%CLASSPATH%" -Dcatalina.base="%CATALINA_BASE%" -Dcatalina.home="%CATALINA_HOME%" -Djava.io.tmpdir="%CATALINA_TMPDIR%" %MAINCLASS% %CMD_LINE_ARGS% %ACTION% 252 goto end 253 :doSecurity 254 %_EXECJAVA% %LOGGING_CONFIG% %LOGGING_MANAGER% %JAVA_OPTS% %CATALINA_OPTS% %DEBUG_OPTS% -D%ENDORSED_PROP%="%JAVA_ENDORSED_DIRS%" -classpath "%CLASSPATH%" -Djava.security.manager -Djava.security.policy=="%SECURITY_POLICY_FILE%" -Dcatalina.base="%CATALINA_BASE%" -Dcatalina.home="%CATALINA_HOME%" -Djava.io.tmpdir="%CATALINA_TMPDIR%" %MAINCLASS% %CMD_LINE_ARGS% %ACTION% 255 goto end 256 :doJpda 257 if not "%SECURITY_POLICY_FILE%" == "" goto doSecurityJpda 258 %_EXECJAVA% %LOGGING_CONFIG% %LOGGING_MANAGER% %JAVA_OPTS% %JPDA_OPTS% %CATALINA_OPTS% %DEBUG_OPTS% -D%ENDORSED_PROP%="%JAVA_ENDORSED_DIRS%" -classpath "%CLASSPATH%" -Dcatalina.base="%CATALINA_BASE%" -Dcatalina.home="%CATALINA_HOME%" -Djava.io.tmpdir="%CATALINA_TMPDIR%" %MAINCLASS% %CMD_LINE_ARGS% %ACTION% 259 goto end 260 :doSecurityJpda 261 %_EXECJAVA% %LOGGING_CONFIG% %LOGGING_MANAGER% %JAVA_OPTS% %JPDA_OPTS% %CATALINA_OPTS% %DEBUG_OPTS% -D%ENDORSED_PROP%="%JAVA_ENDORSED_DIRS%" -classpath "%CLASSPATH%" -Djava.security.manager -Djava.security.policy=="%SECURITY_POLICY_FILE%" -Dcatalina.base="%CATALINA_BASE%" -Dcatalina.home="%CATALINA_HOME%" -Djava.io.tmpdir="%CATALINA_TMPDIR%" %MAINCLASS% %CMD_LINE_ARGS% %ACTION% 262 goto end 263 264 :end第一段：
1 rem Suppress Terminate batch job on CTRL+C 2 if not ""%1"" == ""run"" goto mainEntry 3 if "%TEMP%" == "" goto mainEntry 4 if exist "%TEMP%\%~nx0.run" goto mainEntry 5 echo Y>"%TEMP%\%~nx0.run" 6 if not exist "%TEMP%\%~nx0.run" goto mainEntry 7 echo Y>"%TEMP%\%~nx0.Y" 8 call "%~f0" %* <"%TEMP%\%~nx0.Y" 9 rem Use provided errorlevel 10 set RETVAL=%ERRORLEVEL% 11 del /Q "%TEMP%\%~nx0.Y" >NUL 2>&1 12 exit /B %RETVAL% 13 :mainEntry 14 del /Q "%TEMP%\%~nx0.run" >NUL 2>&1首先注釋是說，禁止使用 CTRL+C 來終止批處理任務；
if not ""%1"" == ""run"" goto mainEntry，第一個參數不是run，就轉向mainEntry標簽，通過調用startup.bat啟動的第一個參數應該是start；
if "%TEMP%" == "" goto mainEntry，%TEMP%是系統的環境變量值，通常裝完windows系統的話, 系統會自動配置上這個環境變量，一般是C:\Users\用戶名\AppData\Local\Temp（AppData是一個隱藏文件夾）。這句是說，如果%TEMP%是空串，就轉向mainEntry標簽；
if exist "%TEMP%\%~nx0.run" goto mainEntry， 在批處理中，%1 表示的是程序之后的第一個參數，%0表示這個可執行程序的名稱， %~nx0 的話就是程序的名稱+擴展名，在這里就是catalina.bat（可以寫一個腳本測試下）；
echo Y>"%TEMP%\%~nx0.run"，寫入字符Y到%TEMP%\catalina.bat.run 文件中；
if not exist "%TEMP%\%~nx0.run" goto mainEntry，又判斷了一下 %TEMP%\catalina.bat.run 文件是否存在；
echo Y>"%TEMP%\%~nx0.Y"，寫入Y到%TEMP%\catalina.bat.Y，如果文件不存在， 則新建一個；
call "%~f0" %* <"%TEMP%\%~nx0.Y"，- “%~f0” : 簡單說就是表示當前命令的絕對路徑。- “%” : %1表示第一個參數，%2表示第二個，%代表所有參數。<”%TEMP%\%~nx0.Y”是讀取 %TEMP%\catalina.bat.Y文件中的內容，之后又通過call進行調用；
set RETVAL=%ERRORLEVEL%，Windows中和linux一樣，命令執行完之后都有自己的退出碼，%ERRORLEVEL%就是取的上面的call 命令的退出碼，賦值給一個變量RETVAL；
del /Q "%TEMP%\%~nx0.Y" >NUL 2>&1，del 命令，很容易聯想到delete， 那么/Q是什么意思呢?靜默刪除，不會給出任何提示，就比如Linux中的rm -f 一樣。這里是刪除%TEMP%\catalina.bat.Y這個文件。后面的 >NUL 2>&1又是什么意思呢? >NUL : 表示將輸出重定向到 NUL 中，你什么也看不到；2>&1 : 2:錯誤輸出，&1: 標準輸出， 意思就是將錯誤消息輸出到標準輸出中；>NUL 2>&1 : 就是先將錯誤消息輸出到標準輸出中，然后再輸出到 NUL 中；
exit /B %RETVAL%，退出當前批處理， /B 指定退出時的編號， 把 RETVAL 作為 退出碼, 也就是 call 執行的命令的退出碼；
:mainEntry del /Q “%TEMP%\%~nx0.run” >NUL 2>&1，定義一個 mainEntry 標簽，然后刪除臨時目錄中的 catalina.bat.run 文件。
?這段代碼的作用就是調用本身，判斷臨時目錄中的文件是否存在來避免二次回調自己
第二段：
1 rem Guess CATALINA_HOME if not defined 2 set "CURRENT_DIR=%cd%" 3 if not "%CATALINA_HOME%" == "" goto gotHome 4 set "CATALINA_HOME=%CURRENT_DIR%" 5 if exist "%CATALINA_HOME%\bin\catalina.bat" goto okHome 6 cd .. 7 set "CATALINA_HOME=%cd%" 8 cd "%CURRENT_DIR%" 9 :gotHome 10 11 if exist "%CATALINA_HOME%\bin\catalina.bat" goto okHome 12 echo The CATALINA_HOME environment variable is not defined correctly 13 echo This environment variable is needed to run this program 14 goto end 15 :okHome 16 17 rem Copy CATALINA_BASE from CATALINA_HOME if not defined 18 if not "%CATALINA_BASE%" == "" goto gotBase 19 set "CATALINA_BASE=%CATALINA_HOME%" 20 :gotBaseset "CURRENT_DIR=%cd%"，設置CURRENT_DIR為當前目錄bin(假如你是在bin目錄中啟動）；
if not "%CATALINA_HOME%" == "" goto gotHome，CATALINA_HOME不是空就轉向gotHome；
set "CATALINA_HOME=%CURRENT_DIR%"，設置CATALINA_HOME指向CURRENT_DIR的目錄，也就是bin目錄；
if exist "%CATALINA_HOME%\bin\catalina.bat" goto okHome，如果存在%CATALINA_HOME%\bin\catalina.bat，那么就轉向okHome，否則退出到父目錄，(顯然不存在bin\bin\catalina.bat)；
set "CATALINA_HOME=%cd%"，設置CATALINA_HOME為當前目錄(也就是Tomcat的根目錄）；
cd "%CURRENT_DIR%"，進入CURRENT_HOME指向的目錄，也就是bin目錄，執行gotHome標簽；
if exist "%CATALINA_HOME%\bin\catalina.bat" goto okHome，gotHome標簽下，如果存在%CATALINA_HOME%\bin\catalina.bat，就轉向okHome，因為CATALINA_HOME現在指向的目錄是Tomcat的安裝目錄，所以\bin\catalina.bat文件是存在的，所以轉向okHome標簽；
if not "%CATALINA_BASE%" == "" goto gotBase，如果CATALINA_BASE變量不是空，就轉向gotBase標簽(顯然為空)；
set "CATALINA_BASE=%CATALINA_HOME%"，設置CATALINA_BASE的值等同與CATALINA_HOME的值(現在CATALINA_BASE也指向的Tomcat的根目錄了)。
這段主要是設置了兩個環境變量 CATALINA_HOME 和 CATALINA_BASE。如果沒有配置 CATALINA_BASE 環境變量的話, 直接引用 CATALINA_HOME 的值。
第三段：
1 rem Ensure that neither CATALINA_HOME nor CATALINA_BASE contains a semi-colon 2 rem as this is used as the separator in the classpath and Java provides no 3 rem mechanism for escaping if the same character appears in the path. Check this 4 rem by replacing all occurrences of ';' with '' and checking that neither 5 rem CATALINA_HOME nor CATALINA_BASE have changed 6 if "%CATALINA_HOME%" == "%CATALINA_HOME:;=%" goto homeNoSemicolon 7 echo Using CATALINA_HOME: "%CATALINA_HOME%" 8 echo Unable to start as CATALINA_HOME contains a semicolon (;) character 9 goto end 10 :homeNoSemicolon 11 12 if "%CATALINA_BASE%" == "%CATALINA_BASE:;=%" goto baseNoSemicolon 13 echo Using CATALINA_BASE: "%CATALINA_BASE%" 14 echo Unable to start as CATALINA_BASE contains a semicolon (;) character 15 goto end 16 :baseNoSemicolon這里主要是判斷 CATALINA_HOME 環境變量的值 和 CATALINA_BASE 環境變量的值是否以分號為結尾，如果以分號為結尾的話，就報錯退出。
第四段：
1 rem Ensure that any user defined CLASSPATH variables are not used on startup, 2 rem but allow them to be specified in setenv.bat, in rare case when it is needed. 3 set CLASSPATH= 4 5 rem Get standard environment variables 6 if not exist "%CATALINA_BASE%\bin\setenv.bat" goto checkSetenvHome 7 call "%CATALINA_BASE%\bin\setenv.bat" 8 goto setenvDone 9 :checkSetenvHome 10 if exist "%CATALINA_HOME%\bin\setenv.bat" call "%CATALINA_HOME%\bin\setenv.bat" 11 :setenvDone 12 13 rem Get standard Java environment variables 14 if exist "%CATALINA_HOME%\bin\setclasspath.bat" goto okSetclasspath 15 echo Cannot find "%CATALINA_HOME%\bin\setclasspath.bat" 16 echo This file is needed to run this program 17 goto end 18 :okSetclasspath 19 call "%CATALINA_HOME%\bin\setclasspath.bat" %1 20 if errorlevel 1 goto end主要是說，如果Tomcat的bin目錄下面存在setenv.bat腳本的話(setenv.bat是干什么的？上面的注釋說是用戶自定義的環境變量，但并不是啟動時必須的定義在setenv.bat中)，就執行它，通常情況下是沒有的，繼而又判斷setclasspath.bat腳本是否存在，如果不存在的話， 直接報錯，停止啟動 Tomcat。如果存在的話，就去調用它，并把 第一個參數傳進去。
可以進入setclasspath.bat腳本看下，主要設置了以下幾個環境變量：
- JAVA_HOME
- JRE_HOME
- JAVA_ENDORSED_DIRS = %CATALINA_HOME%\endorsed
- _RUNJAVA = %JRE_HOME%\bin\java.exe
- _RUNJDB = %JAVA_HOME%\bin\jdb.exe
所以這段是設置一個臨時環境變量: CLASSPATH。
第五段：
1 rem Add on extra jar file to CLASSPATH 2 rem Note that there are no quotes as we do not want to introduce random 3 rem quotes into the CLASSPATH 4 if "%CLASSPATH%" == "" goto emptyClasspath 5 set "CLASSPATH=%CLASSPATH%;" 6 :emptyClasspath 7 set "CLASSPATH=%CLASSPATH%%CATALINA_HOME%\bin\bootstrap.jar" 8 9 if not "%CATALINA_TMPDIR%" == "" goto gotTmpdir 10 set "CATALINA_TMPDIR=%CATALINA_BASE%\temp" 11 :gotTmpdir 12 13 rem Add tomcat-juli.jar to classpath 14 rem tomcat-juli.jar can be over-ridden per instance 15 if not exist "%CATALINA_BASE%\bin\tomcat-juli.jar" goto juliClasspathHome 16 set "CLASSPATH=%CLASSPATH%;%CATALINA_BASE%\bin\tomcat-juli.jar" 17 goto juliClasspathDone 18 :juliClasspathHome 19 set "CLASSPATH=%CLASSPATH%;%CATALINA_HOME%\bin\tomcat-juli.jar" 20 :juliClasspathDone這段代碼主要做了三件事:
- 把 Tomcat bin 目錄下的 bootstrap.jar 加入到環境變量中；
- 設置 CATALINA_TMPDIR 環境變量的值為 Tomcat 目錄下的 temp 目錄；
- 把 Tomcat bin 目錄下的 tomcat-juli.jar 加入到環境變量中；
第六段：
1 if not "%JSSE_OPTS%" == "" goto gotJsseOpts 2 set JSSE_OPTS="-Djdk.tls.ephemeralDHKeySize=2048" 3 :gotJsseOpts 4 set "JAVA_OPTS=%JAVA_OPTS% %JSSE_OPTS%" 5 6 rem Register custom URL handlers 7 rem Do this here so custom URL handles (specifically 'war:...') can be used in the security policy 8 set "JAVA_OPTS=%JAVA_OPTS% -Djava.protocol.handler.pkgs=org.apache.catalina.webresources" 9 10 if not "%LOGGING_CONFIG%" == "" goto noJuliConfig 11 set LOGGING_CONFIG=-Dnop 12 if not exist "%CATALINA_BASE%\conf\logging.properties" goto noJuliConfig 13 set LOGGING_CONFIG=-Djava.util.logging.config.file="%CATALINA_BASE%\conf\logging.properties" 14 :noJuliConfig 15 16 if not "%LOGGING_MANAGER%" == "" goto noJuliManager 17 set LOGGING_MANAGER=-Djava.util.logging.manager=org.apache.juli.ClassLoaderLogManager 18 :noJuliManager 19 20 rem Configure JAVA 9 specific start-up parameters 21 set "JDK_JAVA_OPTIONS=%JDK_JAVA_OPTIONS% --add-opens=java.base/java.lang=ALL-UNNAMED" 22 set "JDK_JAVA_OPTIONS=%JDK_JAVA_OPTIONS% --add-opens=java.base/java.io=ALL-UNNAMED" 23 set "JDK_JAVA_OPTIONS=%JDK_JAVA_OPTIONS% --add-opens=java.rmi/sun.rmi.transport=ALL-UNNAMED"主要是追加一系列的啟動參數到 JAVA_OPTS 這個環境變量中。
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1 rem Java 9 no longer supports the java.endorsed.dirs 2 rem system property. Only try to use it if 3 rem JAVA_ENDORSED_DIRS was explicitly set 4 rem or CATALINA_HOME/endorsed exists. 5 set ENDORSED_PROP=ignore.endorsed.dirs 6 if "%JAVA_ENDORSED_DIRS%" == "" goto noEndorsedVar 7 set ENDORSED_PROP=java.endorsed.dirs 8 goto doneEndorsed 9 :noEndorsedVar 10 if not exist "%CATALINA_HOME%\endorsed" goto doneEndorsed 11 set ENDORSED_PROP=java.endorsed.dirs 12 :doneEndorsed?
第七段：
1 echo Using CATALINA_BASE: "%CATALINA_BASE%" 2 echo Using CATALINA_HOME: "%CATALINA_HOME%" 3 echo Using CATALINA_TMPDIR: "%CATALINA_TMPDIR%" 4 if ""%1"" == ""debug"" goto use_jdk 5 echo Using JRE_HOME: "%JRE_HOME%" 6 goto java_dir_displayed 7 :use_jdk 8 echo Using JAVA_HOME: "%JAVA_HOME%" 9 :java_dir_displayed 10 echo Using CLASSPATH: "%CLASSPATH%"打印相關的環境變量信息。
第八段：
1 set _EXECJAVA=%_RUNJAVA% 2 set MAINCLASS=org.apache.catalina.startup.Bootstrap 3 set ACTION=start 4 set SECURITY_POLICY_FILE= 5 set DEBUG_OPTS= 6 set JPDA=設置一些環境變量:
_RUNJAVA : %JRE_HOME%\bin\java.exe；
MAINCLASS : 指定了 Tomcat 的啟動類；
ACTION : 動作， 就是啟動；
SECURITY_POLICY_FILE : 安全策略文件，如果啟動的時候加上了 -security 參數的話，下面會對這個參數指定到 Tomcat 的 conf 目錄下的 catalina.policy 文件；
JPDA : 還不清楚 。
第九段：
1 if not ""%1"" == ""jpda"" goto noJpda 2 set JPDA=jpda 3 if not "%JPDA_TRANSPORT%" == "" goto gotJpdaTransport 4 set JPDA_TRANSPORT=dt_socket 5 :gotJpdaTransport 6 if not "%JPDA_ADDRESS%" == "" goto gotJpdaAddress 7 set JPDA_ADDRESS=localhost:8000 8 :gotJpdaAddress 9 if not "%JPDA_SUSPEND%" == "" goto gotJpdaSuspend 10 set JPDA_SUSPEND=n 11 :gotJpdaSuspend 12 if not "%JPDA_OPTS%" == "" goto gotJpdaOpts 13 set JPDA_OPTS=-agentlib:jdwp=transport=%JPDA_TRANSPORT%,address=%JPDA_ADDRESS%,server=y,suspend=%JPDA_SUSPEND% 14 :gotJpdaOpts 15 shift 16 :noJpda好像直接從第一行跳到了最后一行，一般啟動的時候沒有加 jpda 參數的話， 這里會直接跳過，里面的腳本是關于 JPDA 的設置等。
第十段：
1 if ""%1"" == ""debug"" goto doDebug 2 if ""%1"" == ""run"" goto doRun 3 if ""%1"" == ""start"" goto doStart 4 if ""%1"" == ""stop"" goto doStop 5 if ""%1"" == ""configtest"" goto doConfigTest 6 if ""%1"" == ""version"" goto doVersion 7 8 echo Usage: catalina ( commands ... ) 9 echo commands: 10 echo debug Start Catalina in a debugger 11 echo debug -security Debug Catalina with a security manager 12 echo jpda start Start Catalina under JPDA debugger 13 echo run Start Catalina in the current window 14 echo run -security Start in the current window with security manager 15 echo start Start Catalina in a separate window 16 echo start -security Start in a separate window with security manager 17 echo stop Stop Catalina 18 echo configtest Run a basic syntax check on server.xml 19 echo version What version of tomcat are you running? 20 goto end如果用 startup.bat 啟動 Tomcat 的話， 這里的 “%1” 的值是 start；?
如果通過 catalina.bat run 啟動 Tomcat 的話，這里的 “%1” 的值是 run；
第十一段：
1 :doDebug 2 shift 3 set _EXECJAVA=%_RUNJDB% 4 set DEBUG_OPTS=-sourcepath "%CATALINA_HOME%\..\..\java" 5 if not ""%1"" == ""-security"" goto execCmd 6 shift 7 echo Using Security Manager 8 set "SECURITY_POLICY_FILE=%CATALINA_BASE%\conf\catalina.policy" 9 goto execCmd 10 11 :doRun 12 shift 13 if not ""%1"" == ""-security"" goto execCmd 14 shift 15 echo Using Security Manager 16 set "SECURITY_POLICY_FILE=%CATALINA_BASE%\conf\catalina.policy" 17 goto execCmd 18 19 :doStart 20 shift 21 if "%TITLE%" == "" set TITLE=Tomcat 22 set _EXECJAVA=start "%TITLE%" %_RUNJAVA% 23 if not ""%1"" == ""-security"" goto execCmd 24 shift 25 echo Using Security Manager 26 set "SECURITY_POLICY_FILE=%CATALINA_BASE%\conf\catalina.policy" 27 goto execCmd 28 29 :doStop 30 shift 31 set ACTION=stop 32 set CATALINA_OPTS= 33 goto execCmd 34 35 :doConfigTest 36 shift 37 set ACTION=configtest 38 set CATALINA_OPTS= 39 goto execCmd 40 41 :doVersion 42 %_EXECJAVA% -classpath "%CATALINA_HOME%\lib\catalina.jar" org.apache.catalina.util.ServerInfo 43 goto end分別對應前面的標簽，啟動主要涉及doRun和doStart。
第一個 shift 是把 start 或者 run 參數移除，然后下面 還是利用 “%1” 來取參數， 這時候， 取出來的就是參數列表中的第二個；
第二個 shift 是把第二個參數移除掉。
我們再來比較一下 start 和 run 的啟動區別.
如果是 startup.bat 腳本啟動的話， 會啟動一個新的 cmd 窗口， 并且把 cmd 的 title 設置為 Tomcat。
如果是 catalina.bat run 啟動的話， 不會新建 cmd 窗口, 也不會設置 cmd 的 title。
最后都跳到了 execCmd 標簽處。
第十二段：
1 :execCmd 2 rem Get remaining unshifted command line arguments and save them in the 3 set CMD_LINE_ARGS= 4 :setArgs 5 if ""%1""=="""" goto doneSetArgs 6 set CMD_LINE_ARGS=%CMD_LINE_ARGS% %1 7 shift 8 goto setArgs 9 :doneSetArgs這里還是利用 “%1” 來取出啟動命令之后的參數， 如果存在， 追加到 CMD_LINE_ARGS 環境變量上，并把這個參數移除。通常情況下，這里是不會有什么參數。
最后一段：
1 rem Execute Java with the applicable properties 2 if not "%JPDA%" == "" goto doJpda 3 if not "%SECURITY_POLICY_FILE%" == "" goto doSecurity 4 %_EXECJAVA% %LOGGING_CONFIG% %LOGGING_MANAGER% %JAVA_OPTS% %CATALINA_OPTS% %DEBUG_OPTS% -D%ENDORSED_PROP%="%JAVA_ENDORSED_DIRS%" -classpath "%CLASSPATH%" -Dcatalina.base="%CATALINA_BASE%" -Dcatalina.home="%CATALINA_HOME%" -Djava.io.tmpdir="%CATALINA_TMPDIR%" %MAINCLASS% %CMD_LINE_ARGS% %ACTION% 5 goto end 6 :doSecurity 7 %_EXECJAVA% %LOGGING_CONFIG% %LOGGING_MANAGER% %JAVA_OPTS% %CATALINA_OPTS% %DEBUG_OPTS% -D%ENDORSED_PROP%="%JAVA_ENDORSED_DIRS%" -classpath "%CLASSPATH%" -Djava.security.manager -Djava.security.policy=="%SECURITY_POLICY_FILE%" -Dcatalina.base="%CATALINA_BASE%" -Dcatalina.home="%CATALINA_HOME%" -Djava.io.tmpdir="%CATALINA_TMPDIR%" %MAINCLASS% %CMD_LINE_ARGS% %ACTION% 8 goto end 9 :doJpda 10 if not "%SECURITY_POLICY_FILE%" == "" goto doSecurityJpda 11 %_EXECJAVA% %LOGGING_CONFIG% %LOGGING_MANAGER% %JAVA_OPTS% %JPDA_OPTS% %CATALINA_OPTS% %DEBUG_OPTS% -D%ENDORSED_PROP%="%JAVA_ENDORSED_DIRS%" -classpath "%CLASSPATH%" -Dcatalina.base="%CATALINA_BASE%" -Dcatalina.home="%CATALINA_HOME%" -Djava.io.tmpdir="%CATALINA_TMPDIR%" %MAINCLASS% %CMD_LINE_ARGS% %ACTION% 12 goto end 13 :doSecurityJpda 14 %_EXECJAVA% %LOGGING_CONFIG% %LOGGING_MANAGER% %JAVA_OPTS% %JPDA_OPTS% %CATALINA_OPTS% %DEBUG_OPTS% -D%ENDORSED_PROP%="%JAVA_ENDORSED_DIRS%" -classpath "%CLASSPATH%" -Djava.security.manager -Djava.security.policy=="%SECURITY_POLICY_FILE%" -Dcatalina.base="%CATALINA_BASE%" -Dcatalina.home="%CATALINA_HOME%" -Djava.io.tmpdir="%CATALINA_TMPDIR%" %MAINCLASS% %CMD_LINE_ARGS% %ACTION% 15 goto end 16 17 :end正常啟動，不會有jdpa，也不會有security，所以這大段代碼主要是加一些環境變量，然后帶上參數去啟動org.apache.catalina.startup.Bootstrap的main方法。
五、總結
啟動tomcat可以雙擊startup.bat，也可以在命令行直接catalina.bat run，大致的流程是這樣：
首先判斷一下用戶直接使用 catalina.bat run 來啟動 Tocmat；
設置 CATALINA_HOME 和 CATALINA_BASE 環境變量值；
驗證 CATALINA_HOME 和 CATALINA_BASE 環境變量值的正確性；
調用 setnv.bat 腳本；
調用 setclasspath.bat 腳本；
添加 bootstrap.jar 和 tomcat-juli.jar 到 CLASSPATH 中；
設置 CATALINA_TMPDIR 臨時目錄的值為 Tomcat 目錄下的 temp；
追加一系列的參數到 JAVA_OPTS 中；
整合相關的啟動信息，參數；
啟動 Tomcat。
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轉載于:https://www.cnblogs.com/grasp/p/10029871.html
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