tomcat变量环境脚本setclasspath.sh分析
之所以分析setclasspath.sh脚本，是因为catalina.sh脚本会引用到这个脚本，如果不对其进行分析，之后看catalina.sh脚本就会不知道一些变量没有申明和赋值怎么会跑出来，本篇文章是为下一篇“tomcat运行控制脚本catalina.sh分析”做铺垫。1
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#!/bin/sh
# Licensed to the Apache Software Foundation (ASF) under one or more
# contributor license agreements.See the NOTICE file distributed with
# this work for additional information regarding copyright ownership.
# The ASF licenses this file to You under the Apache License, Version 2.0
# (the "License"); you may not use this file except in compliance with
# the License.You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
# -----------------------------------------------------------------------------
#Set CLASSPATH and Java options
#
#$Id: setclasspath.sh 795037 2009-07-17 10:52:16Z markt $
# -----------------------------------------------------------------------------
# Make sure prerequisite environment variables are set
#因为setclasspath.sh脚本是被catalina.sh调用，所以可以继承catalina.sh中的变量申明
if [ -z "$JAVA_HOME" -a -z "$JRE_HOME" ]; then
#判断用户有没有提前做$JAVA_HOME和$JRE_HOME全局变量声明，如果都没进行申明
# Bugzilla 37284 (reviewed).
if $darwin; then
#这个是win仿真unix不用管下面两个语句
if [ -d "/System/Library/Frameworks/JavaVM.framework/Versions/CurrentJDK/Home" ]; then
export JAVA_HOME="/System/Library/Frameworks/JavaVM.framework/Versions/CurrentJDK/Home"
fi
else
#其他环境没有申明，那么系统自己想办法找这两个变量的路径
JAVA_PATH=`which java 2>/dev/null`
#此语句可以把java命令位置找出来
if [ "x$JAVA_PATH" != "x" ]; then
#如果能找出java路径，则可以定位到java命令的路径，经过作者验证不是java的装路径
#所以通过此处就可以看出，老鸟们为什么都要自己指定这两个变量了
JAVA_PATH=`dirname $JAVA_PATH 2>/dev/null`
JRE_HOME=`dirname $JAVA_PATH 2>/dev/null`
fi
if [ "x$JRE_HOME" = "x" ]; then
#如果找不到java路径，那么就看有没有/usr/bin/java这个执行文件，有的话就它了，没有就算了
# XXX: Should we try other locations?
if [ -x /usr/bin/java ]; then
JRE_HOME=/usr
fi
fi
fi
if [ -z "$JAVA_HOME" -a -z "$JRE_HOME" ]; then
#再验证一边，有没有这两个变量，没有不好意思，我不执行了，退出
#这个exit 1 不但是结束setclasspath.sh，会彻底退出catalina.sh脚本的
#对于在脚本中引用脚本的童鞋们，就需要注意了，小心使用exit。
echo "Neither the JAVA_HOME nor the JRE_HOME environment variable is defined"
echo "At least one of these environment variable is needed to run this program"
exit 1
fi
fi
if [ -z "$JAVA_HOME" -a "$1" = "debug" ]; then
echo "JAVA_HOME should point to a JDK in order to run in debug mode."
exit 1
fi
if [ -z "$JRE_HOME" ]; then
JRE_HOME="$JAVA_HOME"
fi
# If we're running under jdb, we need a full jdk.
if [ "$1" = "debug" ] ; then
if [ "$os400" = "true" ]; then
if [ ! -x "$JAVA_HOME"/bin/java -o ! -x "$JAVA_HOME"/bin/javac ]; then
echo "The JAVA_HOME environment variable is not defined correctly"
echo "This environment variable is needed to run this program"
echo "NB: JAVA_HOME should point to a JDK not a JRE"
exit 1
fi
else
if [ ! -x "$JAVA_HOME"/bin/java -o ! -x "$JAVA_HOME"/bin/jdb -o ! -x "$JAVA_HOME"/bin/javac ]; then
echo "The JAVA_HOME environment variable is not defined correctly"
echo "This environment variable is needed to run this program"
echo "NB: JAVA_HOME should point to a JDK not a JRE"
exit 1
fi
fi
fi
#上段的代码都是在确认$JAVA_HOME和$JRE_HOME变量的申明情况及后续的解决过程
if [ -z "$BASEDIR" ]; then
#对"$BASEDIR变量的检查，木有的话就退出
echo "The BASEDIR environment variable is not defined"
echo "This environment variable is needed to run this program"
exit 1
fi
if [ ! -x "$BASEDIR"/bin/setclasspath.sh ]; then
#确认"$BASEDIR"/bin/setclasspath.sh有木有，木有还是退出
if $os400; then
# -x will Only work on the os400 if the files are:
# 1. owned by the user
# 2. owned by the PRIMARY group of the user
# this will not work if the user belongs in secondary groups
eval
#eval不清楚嘛意思
else
echo "The BASEDIR environment variable is not defined correctly"
echo "This environment variable is needed to run this program"
exit 1
fi
fi
# Don't override the endorsed dir if the user has set it previously
#这个是确认JAVA_ENDORSED_DIRS的位置
if [ -z "$JAVA_ENDORSED_DIRS" ]; then
# Set the default -Djava.endorsed.dirs argument
JAVA_ENDORSED_DIRS="$BASEDIR"/endorsed
fi
# OSX hack to CLASSPATH
JIKESPATH=
if [ `uname -s` = "Darwin" ]; then
OSXHACK="/System/Library/Frameworks/JavaVM.framework/Versions/CurrentJDK/Classes"
if [ -d "$OSXHACK" ]; then
for i in "$OSXHACK"/*.jar; do
JIKESPATH="$JIKESPATH":"$i"
done
fi
fi
# Set standard commands for invoking Java.
#这句是响当当的重要，确定了$_RUNJAVA的值
_RUNJAVA="$JRE_HOME"/bin/java
if [ "$os400" != "true" ]; then
_RUNJDB="$JAVA_HOME"/bin/jdb
fi
通过脚本分析，我们就看到，这个脚本就做了一件事情，检查各种变量是否赋值，验证tomcat启动停止需要涉及到的文件，保障tomcat顺利启动停止。
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