Tomcat的启停脚本源码解析
Tomcat是一款咱们平时开发过程当中最经常使用到的Servlet容器。本系列博客会记录Tomcat的总体架构、主要组件、IO线程模型、请求在Tomcat内部的流转过程以及一些Tomcat调优的相关知识。java
力求达到如下几个目的：web
- 更加熟悉Tomcat的工做机制，工做中遇到Tomcat相关问题可以快速定位，从源头来解决；
- 对于一些高并发场景可以对Tomcat进行调优；
- 经过对Tomcat源码的分析，吸取一些Tomcat的设计的理念，应用到本身的软件开发过程当中。
Tomcat的启动和中止是经过startup.bat和shutdown.bat这两个脚本实现的。本篇博客就分析下这两个脚本的主要执行流程。apache
1. startup.bat脚本分析
//关闭命令自身输出 @echo off //setlocal命令表示，这边对环境变量的修改只对当前脚本生效 setlocal //检查CATALINA_HOME这个环境变量有没设置，若是有设置就使用设置的环境变量 //若是没设置，将CATALINA_HOME设置成当前目录。 //检测%CATALINA_HOME%\bin\catalina.bat这个脚本存不存在，不存在整合脚本结束，报错 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 //准备启动脚本 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这个脚本的命令行参数 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 //执行catalina.bat这个脚本,执行start,并添加命令行参数 call "%EXECUTABLE%" start %CMD_LINE_ARGS% :end
整个startup.bat脚本很简单，根据CATALINA_HOME检测catalina.bat是否存在，不存在的话就报错，存在的话拼接命令行参数而后执行catalina.bat这个脚本。CATALINA_HOME这个环境变量的取值逻辑以下图所示：bootstrap
若是环境变量设置了CATALINA_HOME，则直接使用环境变量设置的值做为Tomcat安装目录。假如未设置环境变量CATALINA_HOME，则以当前目录做为CATALINA_HOME。此时，若是%CATALINA_HOME%\bin\catalina.bat存在，则批处理或命令行当前目录做为CATALINA_HOME。假如%CATALINA_HOME%\bin\catalina.bat不存在，则把当前目录的上一级目录做为CATALINA_HOME，而后再判断%CATALINA_HOME%\bin\catalina.bat是否存在。若是存在，则上一级目录就是CATALINA_HOME；不然，提示找不到CATALINA_HOME环境变量并结束执行。windows
咱们能够看出来，正真执行的脚本是catalina.bat这个脚本，那为何还要整个startup.bat脚本呢？设计模式
其实这个startup.bat脚本就是提供给使用者用来修改的，咱们能够在其中设置JAVA_HOME，CATALINA_HOME等环境变量，但咱们并不须要深刻到较为复杂的catalina.bat脚本中，这正是startup.bat脚本的真正用意所在。api
咱们知道，软件设计模式中有一个重要的原则就是开闭原则，即咱们能够容许别人扩展咱们的程序，但在程序发布后，咱们拒绝任何修改，由于修改会产生新的Bug，使得咱们已经Bug-free的程序又要从新测试。开闭原则是面向对象世界中的一个很是重要的原则，咱们能够把这个原则从Java类扩展至源代码级别。startup脚本就是要求用户不要修改catalina.bat脚本，这是符合软件设计思想的。咱们若是想要完全贯彻这个重要的软件设计原则，能够写一个新脚本tomcat.bat，脚本内容大体以下：浏览器
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
这个tomcat.bat文件能够存放在任何目录并能执行，而且不须要修改tomcat自带的任何脚本及其它环境变量，这就完全贯彻了开闭原则。tomcat
2. catalina.bat脚本简析
当startup脚本完成环境变量的设置后，就开始调用catalina.bat脚原本启动Tomcat。Catalina脚本的主要任务是根据环境变量和不一样的命令行参数，拼凑出完整的java命令，调用Tomcat的主启动类org.apache.catalina.startup.Bootstrap来启动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 //防止用户直接执行catalina.bat这个脚本，再次检测下CATALINA_HOME环境变量 //检测catalina.bat这个脚本存不存在 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 //检测CATALINA_BASE是否存在，不存在就设置成和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，执行setenv.bat这个脚本,不存在 //执行%CATALINA_HOME%\bin\setenv.bat这个脚原本设置环境变量 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，执行setclasspath.bat，这个脚本的主要做用是检测 //JAVA_HOME有没有正确设置 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 //将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" //设置CATALINA_TMPDIR=%CATALINA_BASE%\temp if not "%CATALINA_TMPDIR%" == "" goto gotTmpdir set "CATALINA_TMPDIR=%CATALINA_BASE%\temp" :gotTmpdir //将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 //若是没有设置JSSE_OPTS，JSSE_OPTS="-Djdk.tls.ephemeralDHKeySize=2048" //再将JAVA_OPTS设置成"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" //将日志配置文件设置成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 //配置默认的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 //通常状况下都会执行到这个脚本语句 %_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
总结下catalina.bat的整个执行流程：
- 检查并设置CATALINA_HOME环境变量，检测%CATALINA_HOME%\bin\catalina.bat这个脚本是否存在，不存在直接报错；
- 检测CATALINA_BASE是否存在，不存在就设置成和CATALINA_HOME一致；
- 若是%CATALINA_BASE%\bin\setenv.bat这个脚本存在，执行setenv.bat这个脚本,不存在的话执行%CATALINA_HOME%\bin\setenv.bat这个脚原本设置环境变量，都不存在继续往下执行；
- 若是%CATALINA_HOME%\bin\setclasspath.bat存在，执行setclasspath.bat，这个脚本的主要做用是检测
JAVA_HOME有没有正确设置； - 将bootstrap.jar加入classpath；
- 设置CATALINA_TMPDIR=%CATALINA_BASE%\temp；
- 将tomcat-juli.jar加入classpath；
- 若是没有设置环境变量JSSE_OPTS，默认设置JSSE_OPTS="-Djdk.tls.ephemeralDHKeySize=2048"
再将JAVA_OPTS设置成"JAVA_OPTS=%JAVA_OPTS% %JSSE_OPTS%" - 经过LOGGING_CONFIG变量，将日志配置文件设置成%CATALINA_BASE%\conf\logging.properties
- 配置默认的LOGGING_MANAGER；
- 拼写java执行命令。
拼接命令的代码主要是下面这段：
%_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%
经过这段代码咱们能够看到Tomcat在启动的时候配置了哪些参数。咱们执行下面的命令：
startup.bat arg1 arg2
实际执行的命令以下：
"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"
上面命令中开头的start Tomcat的意思是从新开启一个叫tomcat的窗口执行Java命令。
咱们看到上面的代码中，有个jpda模式，它是Java平台调试体系结构，能够提供很方便的远程调试，通常状况下咱们不会用到这个模式。若是咱们想启动这个模式的话能够执行catalina.bat jpda start这个命令。这个模式下咱们能够对另外的环境变量JPDA_OPTS进行配置。
3. 关于配置的一些建议
经过上面的脚本，咱们能够看到在启动过程当中咱们能够配置不少环境变量。
- CATALINA_HOME：能够不配置，默认使用安装目录；
- CATALINA_BASE：建议不要本身配置，不配置的话会自动配置成和CATALINA_HOME一致；
- CATALINA_OPTS：能够配置；
- CATALINA_TMPDIR：建议不要本身配置，默认%CATALINA_BASE%\temp；
- JAVA_OPTS：能够配置；
- JSSE_OPTS：不建议本身配置，默认值-Djdk.tls.ephemeralDHKeySize=2048；
- LOGGING_CONFIG：建议不要本身配置，这个配置用于配置日志的配置文件，默认会使用LOGGING_CONFIG="-Djava.util.logging.config.file=%CATALINA_BASE%\conf\logging.properties"
- LOGGING_MANAGER：建议不要本身配置，默认会使用LOGGING_MANAGER="-Djava.util.logging.manager=org.apache.juli.ClassLoaderLogManager"
经过上面介绍咱们发现大多数配置都不须要咱们本身进行配置，通常状况下咱们只须要配置CATALINA_OPTS和JAVA_OPTS这两个配置选项就能够了。这两个参数均可以配置Java运行时所需的一些参数，下面给出两个列子。
在startup脚本中添加配置：
//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脚本分析
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 //这边是关键 call "%EXECUTABLE%" stop %CMD_LINE_ARGS% :end
咱们能够发现shutdown.bat的逻辑和startup.bat的逻辑是同样的，也是先设置CATALINA_HOME，拼接命令行参数，不同是最后执行的是catalina.bat stop。
这边仍是有必要来分析下Tomcat的关闭原理的。咱们知道，Tomcat中的工做线程都是demo线程，若是没有一个主线程的话那么Tomcat会当即中止运行的。（前台线程死亡后，demo线程会自动消失。）那么Tomcat是在哪里启动的这个主线程的呢？经过代码跟踪，咱们发现是StandardServer这个类的await方法建立了这个主线程，这个线程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默认监听的端口是8005端口（注意这个端口和Connector组件监听端口的区别），当发现监听到的链接的输入流中的内容与默认配置的值匹配（该值默认为字符串SHUTDOWN）则跳出循环。不然该方法会一直循环执行下去。因此只要没人向8005端口发送shutdown，这个线程就会一直运行，其余的守护线程也就不会消失。
固然咱们能够将StandardServer的监听端口设置成-1（SpringBoot中内嵌的Tomcat就是这么作的），此时Tomcat不会再监听具体的端口，主线程会每10秒睡眠一次，知道咱们手动将stopAwait设置为true。
知道了这个原理，咱们只要将这个主线程结束掉，整个Tomcat程序就结束了。经过上面的分析，能够有两种方式来关闭Tomcat：
- 经过shutdown.bat脚本，这个脚本最终会调用到Catalina的stopServer方法，这个方法中建立了一个Socket，并向StandardServer监听的端口发送了一个shutdown命令，主线程接收到后就退出了，其余守护线程也随之结束；
若是咱们将server.xml配置文件修改为：
<Server port="8005" shutdown="GET /SHUTDOWN HTTP/1.1">
这样直接在浏览器中输入http://localhost:8005/SHUTDOWN就能够关闭Tomcat了。
- 另外的一种方式就是直接调用StandardServer的stop方法。
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