参考https://blog.csdn.net/qq_30507287/article/details/53981851
今天在服务器的tomcat上部署.war文件，双击startup闪退，然后在tomcat/bin目录下，shift+右键，打开命令行窗口，然后把startup.bat拖进命令行窗口，回车，出现“jre_home environment variable is not defined correctly this environment variable is need”问题
在操作系统上明明已经安装了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。
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:Jdk8jdk1.8.0_101
set JRE_HOME=D:Jdk8jdk1.8.0_101jre
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%injava.exe" goto noJavaHome
if not exist "%JAVA_HOME%injavaw.exe" goto noJavaHome
if not exist "%JAVA_HOME%injdb.exe" goto noJavaHome
if not exist "%JAVA_HOME%injavac.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%injava.exe" goto noJreHome
if not exist "%JRE_HOME%injavaw.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%injava.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%injdb.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。