Tomcat的啓停腳本源碼解析
Tomcat是一款咱們平時開發過程當中最經常使用到的Servlet容器。本系列博客會記錄Tomcat的總體架構、主要組件、IO線程模型、請求在Tomcat內部的流轉過程以及一些Tomcat調優的相關知識。java
力求達到如下幾個目的：web
- 更加熟悉Tomcat的工做機制，工做中遇到Tomcat相關問題可以快速定位，從源頭來解決；
- 對於一些高併發場景可以對Tomcat進行調優；
- 經過對Tomcat源碼的分析，吸取一些Tomcat的設計的理念，應用到本身的軟件開發過程當中。
Tomcat的啓動和中止是經過startup.bat和shutdown.bat這兩個腳本實現的。本篇博客就分析下這兩個腳本的主要執行流程。apache
1. startup.bat腳本分析
//關閉命令自身輸出 @echo off //setlocal命令表示，這邊對環境變量的修改只對當前腳本生效 setlocal //檢查CATALINA_HOME這個環境變量有沒設置，若是有設置就使用設置的環境變量 //若是沒設置，將CATALINA_HOME設置成當前目錄。 //檢測%CATALINA_HOME%\bin\catalina.bat這個腳本存不存在，不存在整合腳本結束，報錯 rem Guess CATALINA_HOME if not defined set "CURRENT_DIR=%cd%" if not "%CATALINA_HOME%" == "" goto gotHome set "CATALINA_HOME=%CURRENT_DIR%" if exist "%CATALINA_HOME%\bin\catalina.bat" goto okHome cd .. set "CATALINA_HOME=%cd%" cd "%CURRENT_DIR%" :gotHome if exist "%CATALINA_HOME%\bin\catalina.bat" goto okHome echo The CATALINA_HOME environment variable is not defined correctly echo This environment variable is needed to run this program goto end :okHome //準備啓動腳本 set "EXECUTABLE=%CATALINA_HOME%\bin\catalina.bat" rem Check that target executable exists if exist "%EXECUTABLE%" goto okExec echo Cannot find "%EXECUTABLE%" echo This file is needed to run this program goto end :okExec //拼接catalina.bat這個腳本的命令行參數 rem Get remaining unshifted command line arguments and save them in the set CMD_LINE_ARGS= :setArgs if ""%1""=="""" goto doneSetArgs set CMD_LINE_ARGS=%CMD_LINE_ARGS% %1 shift goto setArgs :doneSetArgs //執行catalina.bat這個腳本,執行start,並添加命令行參數 call "%EXECUTABLE%" start %CMD_LINE_ARGS% :end
整個startup.bat腳本很簡單，根據CATALINA_HOME檢測catalina.bat是否存在，不存在的話就報錯，存在的話拼接命令行參數而後執行catalina.bat這個腳本。CATALINA_HOME這個環境變量的取值邏輯以下圖所示：bootstrap
若是環境變量設置了CATALINA_HOME，則直接使用環境變量設置的值做爲Tomcat安裝目錄。假如未設置環境變量CATALINA_HOME，則以當前目錄做爲CATALINA_HOME。此時，若是%CATALINA_HOME%\bin\catalina.bat存在，則批處理或命令行當前目錄做爲CATALINA_HOME。假如%CATALINA_HOME%\bin\catalina.bat不存在，則把當前目錄的上一級目錄做爲CATALINA_HOME，而後再判斷%CATALINA_HOME%\bin\catalina.bat是否存在。若是存在，則上一級目錄就是CATALINA_HOME；不然，提示找不到CATALINA_HOME環境變量並結束執行。windows
咱們能夠看出來，正真執行的腳本是catalina.bat這個腳本，那爲何還要整個startup.bat腳本呢？設計模式
其實這個startup.bat腳本就是提供給使用者用來修改的，咱們能夠在其中設置JAVA_HOME，CATALINA_HOME等環境變量，但咱們並不須要深刻到較爲複雜的catalina.bat腳本中，這正是startup.bat腳本的真正用意所在。api
咱們知道，軟件設計模式中有一個重要的原則就是開閉原則，即咱們能夠容許別人擴展咱們的程序，但在程序發佈後，咱們拒絕任何修改，由於修改會產生新的Bug，使得咱們已經Bug-free的程序又要從新測試。開閉原則是面向對象世界中的一個很是重要的原則，咱們能夠把這個原則從Java類擴展至源代碼級別。startup腳本就是要求用戶不要修改catalina.bat腳本，這是符合軟件設計思想的。咱們若是想要完全貫徹這個重要的軟件設計原則，能夠寫一個新腳本tomcat.bat，腳本內容大體以下：瀏覽器
set JAVA_HOME=C:\Program Files\Java\jdk1.5.0_09 set CATALINA_HOME=C:\carl\it\tomcat_research\jakarta-tomcat-5.0.28 call %CATALINA_HOME%\bin\startup.bat
這個tomcat.bat文件能夠存放在任何目錄並能執行，而且不須要修改tomcat自帶的任何腳本及其它環境變量，這就完全貫徹了開閉原則。tomcat
2. catalina.bat腳本簡析
當startup腳本完成環境變量的設置後，就開始調用catalina.bat腳原本啓動Tomcat。Catalina腳本的主要任務是根據環境變量和不一樣的命令行參數，拼湊出完整的java命令，調用Tomcat的主啓動類org.apache.catalina.startup.Bootstrap來啓動Tomcat。bash
@echo off rem --------------------------------------------------------------------------- rem Start/Stop Script for the CATALINA Server rem rem Environment Variable Prerequisites rem rem Do not set the variables in this script. Instead put them into a script rem setenv.bat in CATALINA_BASE/bin to keep your customizations separate. rem rem WHEN RUNNING TOMCAT AS A WINDOWS SERVICE: rem Note that the environment variables that affect the behavior of this rem script will have no effect at all on Windows Services. As such, any rem local customizations made in a CATALINA_BASE/bin/setenv.bat script rem will also have no effect on Tomcat when launched as a Windows Service. rem The configuration that controls Windows Services is stored in the Windows rem Registry, and is most conveniently maintained using the "tomcatXw.exe" rem maintenance utility, where "X" is the major version of Tomcat you are rem running. rem rem CATALINA_HOME May point at your Catalina "build" directory. rem rem CATALINA_BASE (Optional) Base directory for resolving dynamic portions rem of a Catalina installation. If not present, resolves to rem the same directory that CATALINA_HOME points to. rem rem CATALINA_OPTS (Optional) Java runtime options used when the "start", rem "run" or "debug" command is executed. rem Include here and not in JAVA_OPTS all options, that should rem only be used by Tomcat itself, not by the stop process, rem the version command etc. rem Examples are heap size, GC logging, JMX ports etc. rem rem CATALINA_TMPDIR (Optional) Directory path location of temporary directory rem the JVM should use (java.io.tmpdir). Defaults to rem %CATALINA_BASE%\temp. rem rem JAVA_HOME Must point at your Java Development Kit installation. rem Required to run the with the "debug" argument. rem rem JRE_HOME Must point at your Java Runtime installation. rem Defaults to JAVA_HOME if empty. If JRE_HOME and JAVA_HOME rem are both set, JRE_HOME is used. rem rem JAVA_OPTS (Optional) Java runtime options used when any command rem is executed. rem Include here and not in CATALINA_OPTS all options, that rem should be used by Tomcat and also by the stop process, rem the version command etc. rem Most options should go into CATALINA_OPTS. rem rem JPDA_TRANSPORT (Optional) JPDA transport used when the "jpda start" rem command is executed. The default is "dt_socket". rem rem JPDA_ADDRESS (Optional) Java runtime options used when the "jpda start" rem command is executed. The default is localhost:8000. rem rem JPDA_SUSPEND (Optional) Java runtime options used when the "jpda start" rem command is executed. Specifies whether JVM should suspend rem execution immediately after startup. Default is "n". rem rem JPDA_OPTS (Optional) Java runtime options used when the "jpda start" rem command is executed. If used, JPDA_TRANSPORT, JPDA_ADDRESS, rem and JPDA_SUSPEND are ignored. Thus, all required jpda rem options MUST be specified. The default is: rem rem -agentlib:jdwp=transport=%JPDA_TRANSPORT%, rem address=%JPDA_ADDRESS%,server=y,suspend=%JPDA_SUSPEND% rem rem JSSE_OPTS (Optional) Java runtime options used to control the TLS rem implementation when JSSE is used. Default is: rem "-Djdk.tls.ephemeralDHKeySize=2048" rem rem LOGGING_CONFIG (Optional) Override Tomcat's logging config file rem Example (all one line) rem set LOGGING_CONFIG="-Djava.util.logging.config.file=%CATALINA_BASE%\conf\logging.properties" rem rem LOGGING_MANAGER (Optional) Override Tomcat's logging manager rem Example (all one line) rem set LOGGING_MANAGER="-Djava.util.logging.manager=org.apache.juli.ClassLoaderLogManager" rem rem TITLE (Optional) Specify the title of Tomcat window. The default rem TITLE is Tomcat if it's not specified. rem Example (all one line) rem set TITLE=Tomcat.Cluster#1.Server#1 [%DATE% %TIME%] rem --------------------------------------------------------------------------- setlocal rem Suppress Terminate batch job on CTRL+C if not ""%1"" == ""run"" goto mainEntry if "%TEMP%" == "" goto mainEntry if exist "%TEMP%\%~nx0.run" goto mainEntry echo Y>"%TEMP%\%~nx0.run" if not exist "%TEMP%\%~nx0.run" goto mainEntry echo Y>"%TEMP%\%~nx0.Y" call "%~f0" %* <"%TEMP%\%~nx0.Y" rem Use provided errorlevel set RETVAL=%ERRORLEVEL% del /Q "%TEMP%\%~nx0.Y" >NUL 2>&1 exit /B %RETVAL% :mainEntry del /Q "%TEMP%\%~nx0.run" >NUL 2>&1 //防止用戶直接執行catalina.bat這個腳本，再次檢測下CATALINA_HOME環境變量 //檢測catalina.bat這個腳本存不存在 rem Guess CATALINA_HOME if not defined set "CURRENT_DIR=%cd%" if not "%CATALINA_HOME%" == "" goto gotHome set "CATALINA_HOME=%CURRENT_DIR%" if exist "%CATALINA_HOME%\bin\catalina.bat" goto okHome cd .. set "CATALINA_HOME=%cd%" cd "%CURRENT_DIR%" :gotHome if exist "%CATALINA_HOME%\bin\catalina.bat" goto okHome echo The CATALINA_HOME environment variable is not defined correctly echo This environment variable is needed to run this program goto end :okHome //檢測CATALINA_BASE是否存在，不存在就設置成和CATALINA_HOME一致 rem Copy CATALINA_BASE from CATALINA_HOME if not defined if not "%CATALINA_BASE%" == "" goto gotBase set "CATALINA_BASE=%CATALINA_HOME%" :gotBase rem Ensure that neither CATALINA_HOME nor CATALINA_BASE contains a semi-colon rem as this is used as the separator in the classpath and Java provides no rem mechanism for escaping if the same character appears in the path. Check this rem by replacing all occurrences of ';' with '' and checking that neither rem CATALINA_HOME nor CATALINA_BASE have changed if "%CATALINA_HOME%" == "%CATALINA_HOME:;=%" goto homeNoSemicolon echo Using CATALINA_HOME: "%CATALINA_HOME%" echo Unable to start as CATALINA_HOME contains a semicolon (;) character goto end :homeNoSemicolon if "%CATALINA_BASE%" == "%CATALINA_BASE:;=%" goto baseNoSemicolon echo Using CATALINA_BASE: "%CATALINA_BASE%" echo Unable to start as CATALINA_BASE contains a semicolon (;) character goto end :baseNoSemicolon rem Ensure that any user defined CLASSPATH variables are not used on startup, rem but allow them to be specified in setenv.bat, in rare case when it is needed. set CLASSPATH= //若是%CATALINA_BASE%\bin\setenv.bat存在，執行setenv.bat這個腳本,不存在 //執行%CATALINA_HOME%\bin\setenv.bat這個腳原本設置環境變量 rem Get standard environment variables if not exist "%CATALINA_BASE%\bin\setenv.bat" goto checkSetenvHome call "%CATALINA_BASE%\bin\setenv.bat" goto setenvDone :checkSetenvHome if exist "%CATALINA_HOME%\bin\setenv.bat" call "%CATALINA_HOME%\bin\setenv.bat" :setenvDone //若是%CATALINA_HOME%\bin\setclasspath.bat存在，執行setclasspath.bat，這個腳本的主要做用是檢測 //JAVA_HOME有沒有正確設置 rem Get standard Java environment variables if exist "%CATALINA_HOME%\bin\setclasspath.bat" goto okSetclasspath echo Cannot find "%CATALINA_HOME%\bin\setclasspath.bat" echo This file is needed to run this program goto end :okSetclasspath call "%CATALINA_HOME%\bin\setclasspath.bat" %1 if errorlevel 1 goto end //將bootstrap.jar加入classpath rem Add on extra jar file to CLASSPATH rem Note that there are no quotes as we do not want to introduce random rem quotes into the CLASSPATH if "%CLASSPATH%" == "" goto emptyClasspath set "CLASSPATH=%CLASSPATH%;" :emptyClasspath set "CLASSPATH=%CLASSPATH%%CATALINA_HOME%\bin\bootstrap.jar" //設置CATALINA_TMPDIR=%CATALINA_BASE%\temp if not "%CATALINA_TMPDIR%" == "" goto gotTmpdir set "CATALINA_TMPDIR=%CATALINA_BASE%\temp" :gotTmpdir //將tomcat-juli.jar加入classpath rem Add tomcat-juli.jar to classpath rem tomcat-juli.jar can be over-ridden per instance if not exist "%CATALINA_BASE%\bin\tomcat-juli.jar" goto juliClasspathHome set "CLASSPATH=%CLASSPATH%;%CATALINA_BASE%\bin\tomcat-juli.jar" goto juliClasspathDone :juliClasspathHome set "CLASSPATH=%CLASSPATH%;%CATALINA_HOME%\bin\tomcat-juli.jar" :juliClasspathDone //若是沒有設置JSSE_OPTS，JSSE_OPTS="-Djdk.tls.ephemeralDHKeySize=2048" //再將JAVA_OPTS設置成"JAVA_OPTS=%JAVA_OPTS% %JSSE_OPTS%" if not "%JSSE_OPTS%" == "" goto gotJsseOpts set JSSE_OPTS="-Djdk.tls.ephemeralDHKeySize=2048" :gotJsseOpts set "JAVA_OPTS=%JAVA_OPTS% %JSSE_OPTS%" rem Register custom URL handlers rem Do this here so custom URL handles (specifically 'war:...') can be used in the security policy set "JAVA_OPTS=%JAVA_OPTS% -Djava.protocol.handler.pkgs=org.apache.catalina.webresources" //將日誌配置文件設置成logging.properties if not "%LOGGING_CONFIG%" == "" goto noJuliConfig set LOGGING_CONFIG=-Dnop if not exist "%CATALINA_BASE%\conf\logging.properties" goto noJuliConfig set LOGGING_CONFIG=-Djava.util.logging.config.file="%CATALINA_BASE%\conf\logging.properties" :noJuliConfig //配置默認的LOGGING_MANAGER if not "%LOGGING_MANAGER%" == "" goto noJuliManager set LOGGING_MANAGER=-Djava.util.logging.manager=org.apache.juli.ClassLoaderLogManager :noJuliManager rem ----- Execute The Requested Command --------------------------------------- echo Using CATALINA_BASE: "%CATALINA_BASE%" echo Using CATALINA_HOME: "%CATALINA_HOME%" echo Using CATALINA_TMPDIR: "%CATALINA_TMPDIR%" if ""%1"" == ""debug"" goto use_jdk echo Using JRE_HOME: "%JRE_HOME%" goto java_dir_displayed :use_jdk echo Using JAVA_HOME: "%JAVA_HOME%" :java_dir_displayed echo Using CLASSPATH: "%CLASSPATH%" set _EXECJAVA=%_RUNJAVA% set MAINCLASS=org.apache.catalina.startup.Bootstrap set ACTION=start set SECURITY_POLICY_FILE= set DEBUG_OPTS= set JPDA= if not ""%1"" == ""jpda"" goto noJpda set JPDA=jpda if not "%JPDA_TRANSPORT%" == "" goto gotJpdaTransport set JPDA_TRANSPORT=dt_socket :gotJpdaTransport if not "%JPDA_ADDRESS%" == "" goto gotJpdaAddress set JPDA_ADDRESS=localhost:8000 :gotJpdaAddress if not "%JPDA_SUSPEND%" == "" goto gotJpdaSuspend set JPDA_SUSPEND=n :gotJpdaSuspend if not "%JPDA_OPTS%" == "" goto gotJpdaOpts set JPDA_OPTS=-agentlib:jdwp=transport=%JPDA_TRANSPORT%,address=%JPDA_ADDRESS%,server=y,suspend=%JPDA_SUSPEND% :gotJpdaOpts shift :noJpda if ""%1"" == ""debug"" goto doDebug if ""%1"" == ""run"" goto doRun if ""%1"" == ""start"" goto doStart if ""%1"" == ""stop"" goto doStop if ""%1"" == ""configtest"" goto doConfigTest if ""%1"" == ""version"" goto doVersion echo Usage: catalina ( commands ... ) echo commands: echo debug Start Catalina in a debugger echo debug -security Debug Catalina with a security manager echo jpda start Start Catalina under JPDA debugger echo run Start Catalina in the current window echo run -security Start in the current window with security manager echo start Start Catalina in a separate window echo start -security Start in a separate window with security manager echo stop Stop Catalina echo configtest Run a basic syntax check on server.xml echo version What version of tomcat are you running? goto end :doDebug shift set _EXECJAVA=%_RUNJDB% set DEBUG_OPTS=-sourcepath "%CATALINA_HOME%\..\..\java" if not ""%1"" == ""-security"" goto execCmd shift echo Using Security Manager set "SECURITY_POLICY_FILE=%CATALINA_BASE%\conf\catalina.policy" goto execCmd :doRun shift if not ""%1"" == ""-security"" goto execCmd shift echo Using Security Manager set "SECURITY_POLICY_FILE=%CATALINA_BASE%\conf\catalina.policy" goto execCmd :doStart shift if "%TITLE%" == "" set TITLE=Tomcat set _EXECJAVA=start "%TITLE%" %_RUNJAVA% if not ""%1"" == ""-security"" goto execCmd shift echo Using Security Manager set "SECURITY_POLICY_FILE=%CATALINA_BASE%\conf\catalina.policy" goto execCmd :doStop shift set ACTION=stop set CATALINA_OPTS= goto execCmd :doConfigTest shift set ACTION=configtest set CATALINA_OPTS= goto execCmd :doVersion %_EXECJAVA% -classpath "%CATALINA_HOME%\lib\catalina.jar" org.apache.catalina.util.ServerInfo goto end :execCmd rem Get remaining unshifted command line arguments and save them in the set CMD_LINE_ARGS= :setArgs if ""%1""=="""" goto doneSetArgs set CMD_LINE_ARGS=%CMD_LINE_ARGS% %1 shift goto setArgs :doneSetArgs rem Execute Java with the applicable properties if not "%JPDA%" == "" goto doJpda if not "%SECURITY_POLICY_FILE%" == "" goto doSecurity //通常狀況下都會執行到這個腳本語句 %_EXECJAVA% %LOGGING_CONFIG% %LOGGING_MANAGER% %JAVA_OPTS% %CATALINA_OPTS% %DEBUG_OPTS% -classpath "%CLASSPATH%" -Dcatalina.base="%CATALINA_BASE%" -Dcatalina.home="%CATALINA_HOME%" -Djava.io.tmpdir="%CATALINA_TMPDIR%" %MAINCLASS% %CMD_LINE_ARGS% %ACTION% goto end :doSecurity %_EXECJAVA% %LOGGING_CONFIG% %LOGGING_MANAGER% %JAVA_OPTS% %CATALINA_OPTS% %DEBUG_OPTS% -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% goto end :doJpda if not "%SECURITY_POLICY_FILE%" == "" goto doSecurityJpda %_EXECJAVA% %LOGGING_CONFIG% %LOGGING_MANAGER% %JAVA_OPTS% %JPDA_OPTS% %CATALINA_OPTS% %DEBUG_OPTS% -classpath "%CLASSPATH%" -Dcatalina.base="%CATALINA_BASE%" -Dcatalina.home="%CATALINA_HOME%" -Djava.io.tmpdir="%CATALINA_TMPDIR%" %MAINCLASS% %CMD_LINE_ARGS% %ACTION% goto end :doSecurityJpda %_EXECJAVA% %LOGGING_CONFIG% %LOGGING_MANAGER% %JAVA_OPTS% %JPDA_OPTS% %CATALINA_OPTS% %DEBUG_OPTS% -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% goto end :end
總結下catalina.bat的整個執行流程：
- 檢查並設置CATALINA_HOME環境變量，檢測%CATALINA_HOME%\bin\catalina.bat這個腳本是否存在，不存在直接報錯；
- 檢測CATALINA_BASE是否存在，不存在就設置成和CATALINA_HOME一致；
- 若是%CATALINA_BASE%\bin\setenv.bat這個腳本存在，執行setenv.bat這個腳本,不存在的話執行%CATALINA_HOME%\bin\setenv.bat這個腳原本設置環境變量，都不存在繼續往下執行；
- 若是%CATALINA_HOME%\bin\setclasspath.bat存在，執行setclasspath.bat，這個腳本的主要做用是檢測
JAVA_HOME有沒有正確設置； - 將bootstrap.jar加入classpath；
- 設置CATALINA_TMPDIR=%CATALINA_BASE%\temp；
- 將tomcat-juli.jar加入classpath；
- 若是沒有設置環境變量JSSE_OPTS，默認設置JSSE_OPTS="-Djdk.tls.ephemeralDHKeySize=2048"
再將JAVA_OPTS設置成"JAVA_OPTS=%JAVA_OPTS% %JSSE_OPTS%" - 經過LOGGING_CONFIG變量，將日誌配置文件設置成%CATALINA_BASE%\conf\logging.properties
- 配置默認的LOGGING_MANAGER；
- 拼寫java執行命令。
拼接命令的代碼主要是下面這段：
%_EXECJAVA% %LOGGING_CONFIG% %LOGGING_MANAGER% %JAVA_OPTS% %CATALINA_OPTS% %DEBUG_OPTS% -classpath "%CLASSPATH%" -Dcatalina.base="%CATALINA_BASE%" -Dcatalina.home="%CATALINA_HOME%" -Djava.io.tmpdir="%CATALINA_TMPDIR%" %MAINCLASS% %CMD_LINE_ARGS% %ACTION%
經過這段代碼咱們能夠看到Tomcat在啓動的時候配置了哪些參數。咱們執行下面的命令：
startup.bat arg1 arg2
實際執行的命令以下：
"start "Tomcat" "C:\Program Files\Java\jdk1.8.0_73\bin\java.exe" -Djava.util.logging.config.file="D:\software\tomcat-64\apache-tomcat-9.0.0.M21-windows-x64 (1)\apache-tomcat-9.0.0.M21\conf\logging.properties" -Djava.util.logging.manager=org.apache.juli.ClassLoaderLogManager "-Djdk.tls.ephemeralDHKeySize=2048" -Djava.protocol.handler.pkgs=org.apache.catalina.webresources -classpath "D:\software\tomcat-64\apache-tomcat-9.0.0.M21-windows-x64 (1)\apache-tomcat-9.0.0.M21\bin\bootstrap.jar;D:\software\tomcat-64\apache-tomcat-9.0.0.M21-windows-x64 (1)\apache-tomcat-9.0.0.M21\bin\tomcat-juli.jar" -Dcatalina.base="D:\software\tomcat-64\apache-tomcat-9.0.0.M21-windows-x64 (1)\apache-tomcat-9.0.0.M21" -Dcatalina.home="D:\software\tomcat-64\apache-tomcat-9.0.0.M21-windows-x64 (1)\apache-tomcat-9.0.0.M21" -Djava.io.tmpdir="D:\software\tomcat-64\apache-tomcat-9.0.0.M21-windows-x64 (1)\apache-tomcat-9.0.0.M21\temp" org.apache.catalina.startup.Bootstrap arg1 arg2 start"
上面命令中開頭的start Tomcat的意思是從新開啓一個叫tomcat的窗口執行Java命令。
咱們看到上面的代碼中，有個jpda模式，它是Java平臺調試體系結構，能夠提供很方便的遠程調試，通常狀況下咱們不會用到這個模式。若是咱們想啓動這個模式的話能夠執行catalina.bat jpda start這個命令。這個模式下咱們能夠對另外的環境變量JPDA_OPTS進行配置。
3. 關於配置的一些建議
經過上面的腳本，咱們能夠看到在啓動過程當中咱們能夠配置不少環境變量。
- CATALINA_HOME：能夠不配置，默認使用安裝目錄；
- CATALINA_BASE：建議不要本身配置，不配置的話會自動配置成和CATALINA_HOME一致；
- CATALINA_OPTS：能夠配置；
- CATALINA_TMPDIR：建議不要本身配置，默認%CATALINA_BASE%\temp；
- JAVA_OPTS：能夠配置；
- JSSE_OPTS：不建議本身配置，默認值-Djdk.tls.ephemeralDHKeySize=2048；
- LOGGING_CONFIG：建議不要本身配置，這個配置用於配置日誌的配置文件，默認會使用LOGGING_CONFIG="-Djava.util.logging.config.file=%CATALINA_BASE%\conf\logging.properties"
- LOGGING_MANAGER：建議不要本身配置，默認會使用LOGGING_MANAGER="-Djava.util.logging.manager=org.apache.juli.ClassLoaderLogManager"
經過上面介紹咱們發現大多數配置都不須要咱們本身進行配置，通常狀況下咱們只須要配置CATALINA_OPTS和JAVA_OPTS這兩個配置選項就能夠了。這兩個參數均可以配置Java運行時所需的一些參數，下面給出兩個列子。
在startup腳本中添加配置：
//windows set JAVA_OPTS=-server -Xms1024m -Xmx2048m -XX:PermSize=256m -XX:MaxPermSize=512m //Linux JAVA_OPTS="-server -Dfile.encoding=UTF-8 -Xms=512m -Xmx1024m -XX:PermSize=128m -XX:MaxPermSize=256m"
4. shutdown.bat腳本分析
setlocal rem Guess CATALINA_HOME if not defined set "CURRENT_DIR=%cd%" if not "%CATALINA_HOME%" == "" goto gotHome set "CATALINA_HOME=%CURRENT_DIR%" if exist "%CATALINA_HOME%\bin\catalina.bat" goto okHome cd .. set "CATALINA_HOME=%cd%" cd "%CURRENT_DIR%" :gotHome if exist "%CATALINA_HOME%\bin\catalina.bat" goto okHome echo The CATALINA_HOME environment variable is not defined correctly echo This environment variable is needed to run this program goto end :okHome set "EXECUTABLE=%CATALINA_HOME%\bin\catalina.bat" rem Check that target executable exists if exist "%EXECUTABLE%" goto okExec echo Cannot find "%EXECUTABLE%" echo This file is needed to run this program goto end :okExec rem Get remaining unshifted command line arguments and save them in the set CMD_LINE_ARGS= :setArgs if ""%1""=="""" goto doneSetArgs set CMD_LINE_ARGS=%CMD_LINE_ARGS% %1 shift goto setArgs :doneSetArgs //這邊是關鍵 call "%EXECUTABLE%" stop %CMD_LINE_ARGS% :end
咱們能夠發現shutdown.bat的邏輯和startup.bat的邏輯是同樣的，也是先設置CATALINA_HOME，拼接命令行參數，不同是最後執行的是catalina.bat stop。
這邊仍是有必要來分析下Tomcat的關閉原理的。咱們知道，Tomcat中的工做線程都是demo線程，若是沒有一個主線程的話那麼Tomcat會當即中止運行的。（前臺線程死亡後，demo線程會自動消失。）那麼Tomcat是在哪裏啓動的這個主線程的呢？經過代碼跟蹤，咱們發現是StandardServer這個類的await方法建立了這個主線程，這個線程hold了Tomcat程序不中止。
public void await() {
// Negative values - don't wait on port - tomcat is embedded or we just don't like ports
if (getPortWithOffset() == -2) {
// undocumented yet - for embedding apps that are around, alive.
return;
}
//
if (getPortWithOffset() == -1) {
try {
awaitThread = Thread.currentThread();
while(!stopAwait) {
try {
Thread.sleep( 10000 );
} catch( InterruptedException ex ) {
// continue and check the flag
}
}
} finally {
awaitThread = null;
}
return;
}
// Set up a server socket to wait on
try {
awaitSocket = new ServerSocket(getPortWithOffset(), 1,
InetAddress.getByName(address));
} catch (IOException e) {
log.error(sm.getString("standardServer.awaitSocket.fail", address,
String.valueOf(getPortWithOffset()), String.valueOf(getPort()),
String.valueOf(getPortOffset())), e);
return;
}
try {
awaitThread = Thread.currentThread();
// Loop waiting for a connection and a valid command
while (!stopAwait) {
ServerSocket serverSocket = awaitSocket;
if (serverSocket == null) {
break;
}
// Wait for the next connection
Socket socket = null;
StringBuilder command = new StringBuilder();
try {
InputStream stream;
long acceptStartTime = System.currentTimeMillis();
try {
socket = serverSocket.accept();
socket.setSoTimeout(10 * 1000); // Ten seconds
stream = socket.getInputStream();
} catch (SocketTimeoutException ste) {
// This should never happen but bug 56684 suggests that
// it does.
log.warn(sm.getString("standardServer.accept.timeout",
Long.valueOf(System.currentTimeMillis() - acceptStartTime)), ste);
continue;
} catch (AccessControlException ace) {
log.warn("StandardServer.accept security exception: "
+ ace.getMessage(), ace);
continue;
} catch (IOException e) {
if (stopAwait) {
// Wait was aborted with socket.close()
break;
}
log.error("StandardServer.await: accept: ", e);
break;
}
// Read a set of characters from the socket
int expected = 1024; // Cut off to avoid DoS attack
while (expected < shutdown.length()) {
if (random == null)
random = new Random();
expected += (random.nextInt() % 1024);
}
while (expected > 0) {
int ch = -1;
try {
ch = stream.read();
} catch (IOException e) {
log.warn("StandardServer.await: read: ", e);
ch = -1;
}
// Control character or EOF (-1) terminates loop
if (ch < 32 || ch == 127) {
break;
}
command.append((char) ch);
expected--;
}
} finally {
// Close the socket now that we are done with it
try {
if (socket != null) {
socket.close();
}
} catch (IOException e) {
// Ignore
}
}
// Match against our command string
boolean match = command.toString().equals(shutdown);
if (match) {
log.info(sm.getString("standardServer.shutdownViaPort"));
break;
} else
log.warn("StandardServer.await: Invalid command '"
+ command.toString() + "' received");
}
} finally {
ServerSocket serverSocket = awaitSocket;
awaitThread = null;
awaitSocket = null;
// Close the server socket and return
if (serverSocket != null) {
try {
serverSocket.close();
} catch (IOException e) {
// Ignore
}
}
}
}
StandardServer默認監聽的端口是8005端口（注意這個端口和Connector組件監聽端口的區別），當發現監聽到的鏈接的輸入流中的內容與默認配置的值匹配（該值默認爲字符串SHUTDOWN）則跳出循環。不然該方法會一直循環執行下去。因此只要沒人向8005端口發送shutdown，這個線程就會一直運行，其餘的守護線程也就不會消失。
固然咱們能夠將StandardServer的監聽端口設置成-1（SpringBoot中內嵌的Tomcat就是這麼作的），此時Tomcat不會再監聽具體的端口，主線程會每10秒睡眠一次，知道咱們手動將stopAwait設置爲true。
知道了這個原理，咱們只要將這個主線程結束掉，整個Tomcat程序就結束了。經過上面的分析，能夠有兩種方式來關閉Tomcat：
- 經過shutdown.bat腳本，這個腳本最終會調用到Catalina的stopServer方法，這個方法中建立了一個Socket，並向StandardServer監聽的端口發送了一個shutdown命令，主線程接收到後就退出了，其餘守護線程也隨之結束；
若是咱們將server.xml配置文件修改爲：
<Server port="8005" shutdown="GET /SHUTDOWN HTTP/1.1">
這樣直接在瀏覽器中輸入http://localhost:8005/SHUTDOWN就能夠關閉Tomcat了。
- 另外的一種方式就是直接調用StandardServer的stop方法。
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