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在上一篇文章《源代码运行环境搭建》里是通过直接运行 BootStarp 的 main 函数来启动的，只是加了一个 catalina.home 的系统属性。而正常情况下启动 Tomcat 是通过运行脚本的方式，这个就涉及到建立工程时拷贝过来的 script 目录下的一堆脚本文件了。

以我的 windows 系统举例，实际上最终是执行 startup.bat 这个批处理文件来启动 tomcat 的。 那么启动分析就冲这个文件开始吧：

一、分析 startup.bat 文件

startup.bat :

 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	if "%OS%" == "Windows_NT" setlocal
18	rem ---------------------------------------------------------------------------
19	rem Start script for the CATALINA Server
20	rem
21	rem $Id: startup.bat 895392 2010-01-03 14:02:31Z kkolinko $
22	rem ---------------------------------------------------------------------------
23
24	rem Guess CATALINA_HOME if not defined
25	set "CURRENT_DIR=%cd%"
26	if not "%CATALINA_HOME%" == "" goto gotHome
27	set "CATALINA_HOME=%CURRENT_DIR%"
28	if exist "%CATALINA_HOME%\bin\catalina.bat" goto okHome
29	cd ..
30	set "CATALINA_HOME=%cd%"
31	cd "%CURRENT_DIR%"
32	:gotHome
33	if exist "%CATALINA_HOME%\bin\catalina.bat" goto okHome
34	echo The CATALINA_HOME environment variable is not defined correctly
35	echo This environment variable is needed to run this program
36	goto end
37	:okHome
38
39	set "EXECUTABLE=%CATALINA_HOME%\bin\catalina.bat"
40
41	rem Check that target executable exists
42	if exist "%EXECUTABLE%" goto okExec
43	echo Cannot find "%EXECUTABLE%"
44	echo This file is needed to run this program
45	goto end
46	:okExec
47
48	rem Get remaining unshifted command line arguments and save them in the
49	set CMD_LINE_ARGS=
50	:setArgs
51	if ""%1""=="""" goto doneSetArgs
52	set CMD_LINE_ARGS=%CMD_LINE_ARGS% %1
53	shift
54	goto setArgs
55	:doneSetArgs
56
57	call "%EXECUTABLE%" start %CMD_LINE_ARGS%
58
59	:end

第 1 行 @echo off 的是关闭显示命令行自身的意思，接下来一大堆 rem 是注释，第 17 行 if "%OS%" == "Windows_NT" setlocal 是要临时修改系统变量，方便批处理运行。第 26 到 33 行的作用是设置 CATALINA_HOME 环境变量，如果操作系统中没设置，则将当前运行脚本的目录作为该环境变量的值，最终都会跳转到 37 行。39 到 46 行验证 CATALINA_HOME 变量所示目录下的 catalina.bat 文件是否存在，不存在则批处理直接结束。48 到 55 行将运行脚本前如果设置了其他参数，将参数保存到 CMD_LINE_ARGS 变量中。最后第 57 行执行 catalina.bat 批处理文件，注意，该行后面跟着两个参数，第 1 个参数是 start。

二、分析 catalina.bat 文件

  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	if "%OS%" == "Windows_NT" setlocal
 18	rem ---------------------------------------------------------------------------
 19	rem Start/Stop Script for the CATALINA Server
 20	rem
 21	rem Environment Variable Prerequisites
 22	rem
 23	rem   Do not set the variables in this script. Instead put them into a script
 24	rem   setenv.bat in CATALINA_BASE/bin to keep your customizations separate.
 25	rem
 26	rem   CATALINA_HOME   May point at your Catalina "build" directory.
 27	rem
 28	rem   CATALINA_BASE   (Optional) Base directory for resolving dynamic portions
 29	rem                   of a Catalina installation.  If not present, resolves to
 30	rem                   the same directory that CATALINA_HOME points to.
 31	rem
 32	rem   CATALINA_OPTS   (Optional) Java runtime options used when the "start",
 33	rem                   "run" or "debug" command is executed.
 34	rem                   Include here and not in JAVA_OPTS all options, that should
 35	rem                   only be used by Tomcat itself, not by the stop process,
 36	rem                   the version command etc.
 37	rem                   Examples are heap size, GC logging, JMX ports etc.
 38	rem
 39	rem   CATALINA_TMPDIR (Optional) Directory path location of temporary directory
 40	rem                   the JVM should use (java.io.tmpdir).  Defaults to
 41	rem                   %CATALINA_BASE%\temp.
 42	rem
 43	rem   JAVA_HOME       Must point at your Java Development Kit installation.
 44	rem                   Required to run the with the "debug" argument.
 45	rem
 46	rem   JRE_HOME        Must point at your Java Runtime installation.
 47	rem                   Defaults to JAVA_HOME if empty. If JRE_HOME and JAVA_HOME
 48	rem                   are both set, JRE_HOME is used.
 49	rem
 50	rem   JAVA_OPTS       (Optional) Java runtime options used when any command
 51	rem                   is executed.
 52	rem                   Include here and not in CATALINA_OPTS all options, that
 53	rem                   should be used by Tomcat and also by the stop process,
 54	rem                   the version command etc.
 55	rem                   Most options should go into CATALINA_OPTS.
 56	rem
 57	rem   JAVA_ENDORSED_DIRS (Optional) Lists of of semi-colon separated directories
 58	rem                   containing some jars in order to allow replacement of APIs
 59	rem                   created outside of the JCP (i.e. DOM and SAX from W3C).
 60	rem                   It can also be used to update the XML parser implementation.
 61	rem                   Defaults to $CATALINA_HOME/endorsed.
 62	rem
 63	rem   JPDA_TRANSPORT  (Optional) JPDA transport used when the "jpda start"
 64	rem                   command is executed. The default is "dt_socket".
 65	rem
 66	rem   JPDA_ADDRESS    (Optional) Java runtime options used when the "jpda start"
 67	rem                   command is executed. The default is 8000.
 68	rem
 69	rem   JPDA_SUSPEND    (Optional) Java runtime options used when the "jpda start"
 70	rem                   command is executed. Specifies whether JVM should suspend
 71	rem                   execution immediately after startup. Default is "n".
 72	rem
 73	rem   JPDA_OPTS       (Optional) Java runtime options used when the "jpda start"
 74	rem                   command is executed. If used, JPDA_TRANSPORT, JPDA_ADDRESS,
 75	rem                   and JPDA_SUSPEND are ignored. Thus, all required jpda
 76	rem                   options MUST be specified. The default is:
 77	rem
 78	rem                   -agentlib:jdwp=transport=%JPDA_TRANSPORT%,
 79	rem                       address=%JPDA_ADDRESS%,server=y,suspend=%JPDA_SUSPEND%
 80	rem
 81	rem   LOGGING_CONFIG  (Optional) Override Tomcat's logging config file
 82	rem                   Example (all one line)
 83	rem                   set LOGGING_CONFIG="-Djava.util.logging.config.file=%CATALINA_BASE%\conf\logging.properties"
 84	rem
 85	rem   LOGGING_MANAGER (Optional) Override Tomcat's logging manager
 86	rem                   Example (all one line)
 87	rem                   set LOGGING_MANAGER="-Djava.util.logging.manager=org.apache.juli.ClassLoaderLogManager"
 88	rem
 89	rem   TITLE           (Optional) Specify the title of Tomcat window. The default
 90	rem                   TITLE is Tomcat if it's not specified.
 91	rem                   Example (all one line)
 92	rem                   set TITLE=Tomcat.Cluster#1.Server#1 [%DATE% %TIME%]
 93	rem
 94	rem
 95	rem
 96	rem $Id: catalina.bat 1344732 2012-05-31 14:08:02Z kkolinko $
 97	rem ---------------------------------------------------------------------------
 98
 99	rem Suppress Terminate batch job on CTRL+C
100	if not ""%1"" == ""run"" goto mainEntry
101	if "%TEMP%" == "" goto mainEntry
102	if exist "%TEMP%\%~nx0.run" goto mainEntry
103	echo Y>"%TEMP%\%~nx0.run"
104	if not exist "%TEMP%\%~nx0.run" goto mainEntry
105	echo Y>"%TEMP%\%~nx0.Y"
106	call "%~f0" %* <"%TEMP%\%~nx0.Y"
107	rem Use provided errorlevel
108	set RETVAL=%ERRORLEVEL%
109	del /Q "%TEMP%\%~nx0.Y" >NUL 2>&1
110	exit /B %RETVAL%
111	:mainEntry
112	del /Q "%TEMP%\%~nx0.run" >NUL 2>&1
113
114	rem Guess CATALINA_HOME if not defined
115	set "CURRENT_DIR=%cd%"
116	if not "%CATALINA_HOME%" == "" goto gotHome
117	set "CATALINA_HOME=%CURRENT_DIR%"
118	if exist "%CATALINA_HOME%\bin\catalina.bat" goto okHome
119	cd ..
120	set "CATALINA_HOME=%cd%"
121	cd "%CURRENT_DIR%"
122	:gotHome
123
124	if exist "%CATALINA_HOME%\bin\catalina.bat" goto okHome
125	echo The CATALINA_HOME environment variable is not defined correctly
126	echo This environment variable is needed to run this program
127	goto end
128	:okHome
129
130	rem Copy CATALINA_BASE from CATALINA_HOME if not defined
131	if not "%CATALINA_BASE%" == "" goto gotBase
132	set "CATALINA_BASE=%CATALINA_HOME%"
133	:gotBase
134
135	rem Ensure that any user defined CLASSPATH variables are not used on startup,
136	rem but allow them to be specified in setenv.bat, in rare case when it is needed.
137	set CLASSPATH=
138
139	rem Get standard environment variables
140	if not exist "%CATALINA_BASE%\bin\setenv.bat" goto checkSetenvHome
141	call "%CATALINA_BASE%\bin\setenv.bat"
142	goto setenvDone
143	:checkSetenvHome
144	if exist "%CATALINA_HOME%\bin\setenv.bat" call "%CATALINA_HOME%\bin\setenv.bat"
145	:setenvDone
146
147	rem Get standard Java environment variables
148	if exist "%CATALINA_HOME%\bin\setclasspath.bat" goto okSetclasspath
149	echo Cannot find "%CATALINA_HOME%\bin\setclasspath.bat"
150	echo This file is needed to run this program
151	goto end
152	:okSetclasspath
153	call "%CATALINA_HOME%\bin\setclasspath.bat" %1
154	if errorlevel 1 goto end
155
156	rem Add on extra jar file to CLASSPATH
157	rem Note that there are no quotes as we do not want to introduce random
158	rem quotes into the CLASSPATH
159	if "%CLASSPATH%" == "" goto emptyClasspath
160	set "CLASSPATH=%CLASSPATH%;"
161	:emptyClasspath
162	set "CLASSPATH=%CLASSPATH%%CATALINA_HOME%\bin\bootstrap.jar"
163
164	if not "%CATALINA_TMPDIR%" == "" goto gotTmpdir
165	set "CATALINA_TMPDIR=%CATALINA_BASE%\temp"
166	:gotTmpdir
167
168	rem Add tomcat-juli.jar to classpath
169	rem tomcat-juli.jar can be over-ridden per instance
170	if not exist "%CATALINA_BASE%\bin\tomcat-juli.jar" goto juliClasspathHome
171	set "CLASSPATH=%CLASSPATH%;%CATALINA_BASE%\bin\tomcat-juli.jar"
172	goto juliClasspathDone
173	:juliClasspathHome
174	set "CLASSPATH=%CLASSPATH%;%CATALINA_HOME%\bin\tomcat-juli.jar"
175	:juliClasspathDone
176
177	if not "%LOGGING_CONFIG%" == "" goto noJuliConfig
178	set LOGGING_CONFIG=-Dnop
179	if not exist "%CATALINA_BASE%\conf\logging.properties" goto noJuliConfig
180	set LOGGING_CONFIG=-Djava.util.logging.config.file="%CATALINA_BASE%\conf\logging.properties"
181	:noJuliConfig
182	set JAVA_OPTS=%JAVA_OPTS% %LOGGING_CONFIG%
183
184	if not "%LOGGING_MANAGER%" == "" goto noJuliManager
185	set LOGGING_MANAGER=-Djava.util.logging.manager=org.apache.juli.ClassLoaderLogManager
186	:noJuliManager
187	set JAVA_OPTS=%JAVA_OPTS% %LOGGING_MANAGER%
188
189	rem ----- Execute The Requested Command ---------------------------------------
190
191	echo Using CATALINA_BASE:   "%CATALINA_BASE%"
192	echo Using CATALINA_HOME:   "%CATALINA_HOME%"
193	echo Using CATALINA_TMPDIR: "%CATALINA_TMPDIR%"
194	if ""%1"" == ""debug"" goto use_jdk
195	echo Using JRE_HOME:        "%JRE_HOME%"
196	goto java_dir_displayed
197	:use_jdk
198	echo Using JAVA_HOME:       "%JAVA_HOME%"
199	:java_dir_displayed
200	echo Using CLASSPATH:       "%CLASSPATH%"
201
202	set _EXECJAVA=%_RUNJAVA%
203	set MAINCLASS=org.apache.catalina.startup.Bootstrap
204	set ACTION=start
205	set SECURITY_POLICY_FILE=
206	set DEBUG_OPTS=
207	set JPDA=
208
209	if not ""%1"" == ""jpda"" goto noJpda
210	set JPDA=jpda
211	if not "%JPDA_TRANSPORT%" == "" goto gotJpdaTransport
212	set JPDA_TRANSPORT=dt_socket
213	:gotJpdaTransport
214	if not "%JPDA_ADDRESS%" == "" goto gotJpdaAddress
215	set JPDA_ADDRESS=8000
216	:gotJpdaAddress
217	if not "%JPDA_SUSPEND%" == "" goto gotJpdaSuspend
218	set JPDA_SUSPEND=n
219	:gotJpdaSuspend
220	if not "%JPDA_OPTS%" == "" goto gotJpdaOpts
221	set JPDA_OPTS=-agentlib:jdwp=transport=%JPDA_TRANSPORT%,address=%JPDA_ADDRESS%,server=y,suspend=%JPDA_SUSPEND%
222	:gotJpdaOpts
223	shift
224	:noJpda
225
226	if ""%1"" == ""debug"" goto doDebug
227	if ""%1"" == ""run"" goto doRun
228	if ""%1"" == ""start"" goto doStart
229	if ""%1"" == ""stop"" goto doStop
230	if ""%1"" == ""configtest"" goto doConfigTest
231	if ""%1"" == ""version"" goto doVersion
232
233	echo Usage:  catalina ( commands ... )
234	echo commands:
235	echo   debug             Start Catalina in a debugger
236	echo   debug -security   Debug Catalina with a security manager
237	echo   jpda start        Start Catalina under JPDA debugger
238	echo   run               Start Catalina in the current window
239	echo   run -security     Start in the current window with security manager
240	echo   start             Start Catalina in a separate window
241	echo   start -security   Start in a separate window with security manager
242	echo   stop              Stop Catalina
243	echo   configtest        Run a basic syntax check on server.xml
244	echo   version           What version of tomcat are you running?
245	goto end
246
247	:doDebug
248	shift
249	set _EXECJAVA=%_RUNJDB%
250	set DEBUG_OPTS=-sourcepath "%CATALINA_HOME%\..\..\java"
251	if not ""%1"" == ""-security"" goto execCmd
252	shift
253	echo Using Security Manager
254	set "SECURITY_POLICY_FILE=%CATALINA_BASE%\conf\catalina.policy"
255	goto execCmd
256
257	:doRun
258	shift
259	if not ""%1"" == ""-security"" goto execCmd
260	shift
261	echo Using Security Manager
262	set "SECURITY_POLICY_FILE=%CATALINA_BASE%\conf\catalina.policy"
263	goto execCmd
264
265	:doStart
266	shift
267	if not "%OS%" == "Windows_NT" goto noTitle
268	if "%TITLE%" == "" set TITLE=Tomcat
269	set _EXECJAVA=start "%TITLE%" %_RUNJAVA%
270	goto gotTitle
271	:noTitle
272	set _EXECJAVA=start %_RUNJAVA%
273	:gotTitle
274	if not ""%1"" == ""-security"" goto execCmd
275	shift
276	echo Using Security Manager
277	set "SECURITY_POLICY_FILE=%CATALINA_BASE%\conf\catalina.policy"
278	goto execCmd
279
280	:doStop
281	shift
282	set ACTION=stop
283	set CATALINA_OPTS=
284	goto execCmd
285
286	:doConfigTest
287	shift
288	set ACTION=configtest
289	set CATALINA_OPTS=
290	goto execCmd
291
292	:doVersion
293	%_EXECJAVA% -classpath "%CATALINA_HOME%\lib\catalina.jar" org.apache.catalina.util.ServerInfo
294	goto end
295
296
297	:execCmd
298	rem Get remaining unshifted command line arguments and save them in the
299	set CMD_LINE_ARGS=
300	:setArgs
301	if ""%1""=="""" goto doneSetArgs
302	set CMD_LINE_ARGS=%CMD_LINE_ARGS% %1
303	shift
304	goto setArgs
305	:doneSetArgs
306
307	rem Execute Java with the applicable properties
308	if not "%JPDA%" == "" goto doJpda
309	if not "%SECURITY_POLICY_FILE%" == "" goto doSecurity
310	%_EXECJAVA% %JAVA_OPTS% %CATALINA_OPTS% %DEBUG_OPTS% -Djava.endorsed.dirs="%JAVA_ENDORSED_DIRS%" -classpath "%CLASSPATH%" -Dcatalina.base="%CATALINA_BASE%" -Dcatalina.home="%CATALINA_HOME%" -Djava.io.tmpdir="%CATALINA_TMPDIR%" %MAINCLASS% %CMD_LINE_ARGS% %ACTION%
311	goto end
312	:doSecurity
313	%_EXECJAVA% %JAVA_OPTS% %CATALINA_OPTS% %DEBUG_OPTS% -Djava.endorsed.dirs="%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%
314	goto end
315	:doJpda
316	if not "%SECURITY_POLICY_FILE%" == "" goto doSecurityJpda
317	%_EXECJAVA% %JAVA_OPTS% %CATALINA_OPTS% %JPDA_OPTS% %DEBUG_OPTS% -Djava.endorsed.dirs="%JAVA_ENDORSED_DIRS%" -classpath "%CLASSPATH%" -Dcatalina.base="%CATALINA_BASE%" -Dcatalina.home="%CATALINA_HOME%" -Djava.io.tmpdir="%CATALINA_TMPDIR%" %MAINCLASS% %CMD_LINE_ARGS% %ACTION%
318	goto end
319	:doSecurityJpda
320	%_EXECJAVA% %JAVA_OPTS% %CATALINA_OPTS% %JPDA_OPTS% %DEBUG_OPTS% -Djava.endorsed.dirs="%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%
321	goto end
322
323	:end

1 到 99 行一大堆注释说明就不看了，100 到 110 行一堆 run 文件校验之类的一般用不到，直接跳到 111 行，接下来先删除上面可能产生的中间文件，接着按照正常流程，在上面的 startup.bat 文件中已经设置过CATALINA_HOME变量，并且校验了改变量下 bin\catalina.bat 文件已经存在（我猜作者写这一段是防止用户直接运行 catalina.bat 文件）。经过这些判断后跳转到 128 行，130 到 133 行设置CATALINA_BASE变量，中间几行注释略过，139 到 144 行如果有 setenv.bat 文件则执行一下该文件。147 到 153 行执行 setclasspath.bat 文件（该文件在同级目录下已经提供，具体脚本下面已经贴出来了，可以读一下，这里不再做分析。主要功能校验是否设置JAVA_HOME变量，没有则在控制台显示出提示信息。注意该文件中第 79 行将会设置_RUNJAVA变量，该变量的值即JAVA_HOME或JRE_HOME的 bin 目录下的 java.exe 文件）。从 156 到 224 行校验并设置一堆变量（注意第 202、203 和 204 行，最后启动分析时将会用到）。226 到 231 行将根据调用 catalina.bat 时设置的参数决定跳转，按照上一段的最后的说明，此时将会跳转到 doStart 标记行。从 265 行开始，校验和设置一些变量之后（注意第 269 行）将会跳转到 execCmd 标记行，即 297 行。297 到 305 行作用是将系统参数保存到CMD_LINE_ARGS变量中。

接下来便是谜底解开的时候，正常情况下将会执行到 310 行，这里单独贴出来分析一下： %_EXECJAVA% %JAVA_OPTS% %CATALINA_OPTS% %DEBUG_OPTS% -Djava.endorsed.dirs="%JAVA_ENDORSED_DIRS%" -classpath "%CLASSPATH%" -Dcatalina.base="%CATALINA_BASE%" -Dcatalina.home="%CATALINA_HOME%" -Djava.io.tmpdir="%CATALINA_TMPDIR%" %MAINCLASS% %CMD_LINE_ARGS% %ACTION% 按照 202 行的提示_EXECJAVA一开始的值等于_RUNJAVA，但在 269 行将该值改成了start "%TITLE%" %_RUNJAVA%，这里的作用是另启动一个命令行窗口，并给窗口起名，最终还是执行 java.exe 文件。从%JAVA_OPTS%开始到%MAINCLASS%之前都是在设置运行时参数和系统属性，%MAINCLASS%即 203 行的 org.apache.catalina.startup.Bootstrap，后面是其它的命令行参数，最后一个参数%ACTION%在 204 行时被设置成 start。归结起来一句话，即执行 Bootstrap 类的 main 方法。

setclasspath.bat:

 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 Set JAVA_HOME or JRE_HOME if not already set, ensure any provided settings
19	rem are valid and consistent with the selected start-up options and set up the
20	rem endorsed directory.
21	rem
22	rem $Id: setclasspath.bat 1202062 2011-11-15 06:50:02Z mturk $
23	rem ---------------------------------------------------------------------------
24
25	rem Make sure prerequisite environment variables are set
26
27	rem In debug mode we need a real JDK (JAVA_HOME)
28	if ""%1"" == ""debug"" goto needJavaHome
29
30	rem Otherwise either JRE or JDK are fine
31	if not "%JRE_HOME%" == "" goto gotJreHome
32	if not "%JAVA_HOME%" == "" goto gotJavaHome
33	echo Neither the JAVA_HOME nor the JRE_HOME environment variable is defined
34	echo At least one of these environment variable is needed to run this program
35	goto exit
36
37	:needJavaHome
38	rem Check if we have a usable JDK
39	if "%JAVA_HOME%" == "" goto noJavaHome
40	if not exist "%JAVA_HOME%\bin\java.exe" goto noJavaHome
41	if not exist "%JAVA_HOME%\bin\javaw.exe" goto noJavaHome
42	if not exist "%JAVA_HOME%\bin\jdb.exe" goto noJavaHome
43	if not exist "%JAVA_HOME%\bin\javac.exe" goto noJavaHome
44	set "JRE_HOME=%JAVA_HOME%"
45	goto okJava
46
47	:noJavaHome
48	echo The JAVA_HOME environment variable is not defined correctly.
49	echo It is needed to run this program in debug mode.
50	echo NB: JAVA_HOME should point to a JDK not a JRE.
51	goto exit
52
53	:gotJavaHome
54	rem No JRE given, use JAVA_HOME as JRE_HOME
55	set "JRE_HOME=%JAVA_HOME%"
56
57	:gotJreHome
58	rem Check if we have a usable JRE
59	if not exist "%JRE_HOME%\bin\java.exe" goto noJreHome
60	if not exist "%JRE_HOME%\bin\javaw.exe" goto noJreHome
61	goto okJava
62
63	:noJreHome
64	rem Needed at least a JRE
65	echo The JRE_HOME environment variable is not defined correctly
66	echo This environment variable is needed to run this program
67	goto exit
68
69	:okJava
70	rem Don't override the endorsed dir if the user has set it previously
71	if not "%JAVA_ENDORSED_DIRS%" == "" goto gotEndorseddir
72	rem Set the default -Djava.endorsed.dirs argument
73	set "JAVA_ENDORSED_DIRS=%CATALINA_HOME%\endorsed"
74	:gotEndorseddir
75
76	rem Set standard command for invoking Java.
77	rem Note that NT requires a window name argument when using start.
78	rem Also note the quoting as JAVA_HOME may contain spaces.
79	set _RUNJAVA="%JRE_HOME%\bin\java"
80	set _RUNJDB="%JAVA_HOME%\bin\jdb"
81
82	goto end
83
84	:exit
85	exit /b 1
86
87	:end
88	exit /b 0

三、总结

以上即 tomcat 的启动脚本中的总体流程，只是讲了默认的脚本运行方式，但在脚本阅读中可以看到能根据 catalina.bat 里可以根据不同参数以不同方式运行 tomcat ：

debug             Start Catalina in a debugger
debug -security   Debug Catalina with a security manager
jpda start        Start Catalina under JPDA debugger
run               Start Catalina in the current window
run -security     Start in the current window with security manager
start             Start Catalina in a separate window
start -security   Start in a separate window with security manager
stop              Stop Catalina
configtest        Run a basic syntax check on server.xml

只要能看懂基本 dos 命令，这几个脚本的阅读其实很简单，其他 bat 文件可以大体浏览一下，会发现转了半天，最终都会执行 catalina.bat 文件，而 catalina.bat 文件里最终会执行 Bootstrap 文件的 main 方法，不同的是调用 main 方法时会各自添加不同的入参而已。bat 文件用于 windows 操作系统下启动 tomcat，而 sh 文件则用于 unix 环境下的启动，原理是一致的。

文章目录
  1. 1. 一、分析 startup.bat 文件
  2. 2. 二、分析 catalina.bat 文件
  3. 3. 三、总结