Tomcat之the jre_home environment variable is not defined correctly this environment variable is need

         在win10上明明已经安装了JDK1.8并设置好了JAVA_HOME和JRE_HOME，可偏偏Tomcat在启动过程中找不到并且在启动startup.bat时闪退。

         先要找出问题的原因：右键编辑打开“startup.bat"文件，然后找文件的最后一行代码是:end    在:end的后面输入pause如下图所示：

接下来在DOS命令窗口运行startup.bat,此时提示报错信息如下：the jre_home environment variable is not defined correctly this environment variable is need？

原因知道了，下面来看解决办法：

1、分析startup.bat启动脚本：发现其调用了catalina.bat,而catalina.bat调用了setclasspath.bat

2、在setclasspath.bat的头部定义了JAVA_HOME和JRE_HOME的值，那么这里需要我们手动设置JAVA_HOME变量和JRE_HOME变量（红色代码为新添加）

注意：你所设置的变量要和自己的电脑中”环境变量“里的JAVA_HOME和JRE_HOME保持一致，我的是红色的代码。

@echo off
rem Licensed to the Apache Software Foundation (ASF) under one or more
rem contributor license agreements.  See the NOTICE file distributed with
rem this work for additional information regarding copyright ownership.
rem The ASF licenses this file to You under the Apache License, Version 2.0
rem (the "License"); you may not use this file except in compliance with
rem the License.  You may obtain a copy of the License at
rem
rem     http://www.apache.org/licenses/LICENSE-2.0
rem
rem Unless required by applicable law or agreed to in writing, software
rem distributed under the License is distributed on an "AS IS" BASIS,
rem WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
rem See the License for the specific language governing permissions and
rem limitations under the License.

rem ---------------------------------------------------------------------------
rem Set JAVA_HOME or JRE_HOME if not already set, ensure any provided settings
rem are valid and consistent with the selected start-up options and set up the
rem endorsed directory.
rem ---------------------------------------------------------------------------

set JAVA_HOME=D:\tomcat\apache-tomcat-7.0.65
set JRE_HOME=D:\Jdk8\jdk1.8.0_101\jre

rem Make sure prerequisite environment variables are set

rem In debug mode we need a real JDK (JAVA_HOME)
if ""%1"" == ""debug"" goto needJavaHome

rem Otherwise either JRE or JDK are fine
if not "%JRE_HOME%" == "" goto gotJreHome
if not "%JAVA_HOME%" == "" goto gotJavaHome
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
goto exit

:needJavaHome
rem Check if we have a usable JDK
if "%JAVA_HOME%" == "" goto noJavaHome
if not exist "%JAVA_HOME%\bin\java.exe" goto noJavaHome
if not exist "%JAVA_HOME%\bin\javaw.exe" goto noJavaHome
if not exist "%JAVA_HOME%\bin\jdb.exe" goto noJavaHome
if not exist "%JAVA_HOME%\bin\javac.exe" goto noJavaHome
set "JRE_HOME=%JAVA_HOME%"
goto okJava

:noJavaHome
echo The JAVA_HOME environment variable is not defined correctly.
echo It is needed to run this program in debug mode.
echo NB: JAVA_HOME should point to a JDK not a JRE.
goto exit

:gotJavaHome
rem No JRE given, use JAVA_HOME as JRE_HOME
set "JRE_HOME=%JAVA_HOME%"

:gotJreHome
rem Check if we have a usable JRE
if not exist "%JRE_HOME%\bin\java.exe" goto noJreHome
if not exist "%JRE_HOME%\bin\javaw.exe" goto noJreHome
goto okJava

:noJreHome
rem Needed at least a JRE
echo The JRE_HOME environment variable is not defined correctly
echo This environment variable is needed to run this program
goto exit

:okJava
rem Don't override the endorsed dir if the user has set it previously
if not "%JAVA_ENDORSED_DIRS%" == "" goto gotEndorseddir
rem Set the default -Djava.endorsed.dirs argument
set "JAVA_ENDORSED_DIRS=%CATALINA_HOME%\endorsed"
:gotEndorseddir

rem Don't override _RUNJAVA if the user has set it previously
if not "%_RUNJAVA%" == "" goto gotRunJava
rem Set standard command for invoking Java.
rem Also note the quoting as JRE_HOME may contain spaces.
set _RUNJAVA="%JRE_HOME%\bin\java.exe"
:gotRunJava

rem Don't override _RUNJDB if the user has set it previously
rem Also note the quoting as JAVA_HOME may contain spaces.
if not "%_RUNJDB%" == "" goto gotRunJdb
set _RUNJDB="%JAVA_HOME%\bin\jdb.exe"
:gotRunJdb

goto end

:exit
exit /b 1

:end
exit /b 0

3、添加变量后保存，并关闭文件，重新启动tomcat，然后在浏览器中敲入http://localhost:8080验证。显示如下图所示的界面则为修改成功，tomcat登录也就成功了。