zookeeper报错 JAVA_HOME is not set

很多开发者安装zookeeper的时候，应该会发现到这么一个问题： JAVA_HOME is not set 

好的！那么这个是什么意思呢？

就是说你的  JAVA_HOME 变量没有设定

为什么会提示这个呢？

其实zookeeper在启动服务端的时候会基于java环境启动，所以在启动的时候会检测 jdk 是否安装

而在我们开发者的入门过程中，都会设定一下 %JAVA_HOME%的系统变量。

在 zkservice启动的时候，会找%JAVA_HOME%\bin\java.jar 进行java基础环境的启动。所以，如果没有配置的话，就要配置：

如何配置：区分两种系统（自行百度吧）

　　Linux： vim /etc/profile 文件修改后，检查是否完成 java  -version

　　window：变量添加后，检查是否完成 java -version

好的！按理说完成以上步骤之后，就是已经完成了%JAVA_HOME%的配置。

针对于window8 系统配置完成之后，使用 -version都可以发现正常进行了安装，但是启动的时候依旧报错！JAVA_HOME is not set 

这就不能忍了！于是我们看看，zkService 启动的时候，到底做了些什么？

　　1、启动加载zkEvn文件，

　　2、启动zkService文件，

也就是说，在zkEvn 文件里面可能有JAVA_HOME 的验证，于是我们进去看看

@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.

set ZOOCFGDIR=%~dp0%..\conf
set ZOO_LOG_DIR=%~dp0%..\logs
set ZOO_LOG4J_PROP=INFO,CONSOLE

REM for sanity sake assume Java 1.6
REM see: http://java.sun.com/javase/6/docs/technotes/tools/windows/java.html

REM add the zoocfg dir to classpath
set CLASSPATH=%ZOOCFGDIR%

REM make it work in the release
SET CLASSPATH=%~dp0..\*;%~dp0..\lib\*;%CLASSPATH%

REM make it work for developers
SET CLASSPATH=%~dp0..\build\classes;%~dp0..\build\lib\*;%CLASSPATH%

set ZOOCFG=%ZOOCFGDIR%\zoo.cfg

@REM setup java environment variables

if not defined JAVA_HOME (
  echo Error: JAVA_HOME is not set.
  goto :eof
)

if not exist %JAVA_HOME%\bin\java.exe (
  echo Error: JAVA_HOME is incorrectly set.
  goto :eof
)

set JAVA=%JAVA_HOME%\bin\java

果然！这里有校验！而且校验的时候肯定是不存在的，所以输出错误信息：JAVA_HOME is not set.

那么如何解决呢？

既然从系统变量获取获取不到这个变量，那么我们干脆手动设置一下试试？

@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 for sanity sake assume Java 1.6
REM see: http://java.sun.com/javase/6/docs/technotes/tools/windows/java.html

REM add the zoocfg dir to classpath
set CLASSPATH=%ZOOCFGDIR%

REM make it work in the release
SET CLASSPATH=%~dp0..\*;%~dp0..\lib\*;%CLASSPATH%

REM make it work for developers
SET CLASSPATH=%~dp0..\build\classes;%~dp0..\build\lib\*;%CLASSPATH%

set JAVA=D:\java\jdk1.8.0_77\bin\java
set JAVA_HOME=D:\java\jdk1.8.0_77

set ZOOCFG=%ZOOCFGDIR%\zoo.cfg
set ZOOCFGDIR=%~dp0%..\conf
set ZOO_LOG_DIR=%~dp0%..\logs
set ZOO_LOG4J_PROP=INFO,CONSOLE
@REM setup java environment variables

if not defined JAVA_HOME (
  echo Error: JAVA_HOME is not set.
  goto :eof
)

if not defined JAVA (
  echo Error: ----"%JAVA_HOME%"--- is set.but not found JAVA
  goto :eof
)

修改内容如上：

手动设置JAVAHOME 和JAVA 的值，为了查找问题，在判断JAVA的时候，进行JAVAHOME 的值的打印，看看是不是真的设置成功了。

再次启动，果然！成功了！

好的，咱们回顾一下。zkService 启动依赖java的环境，所以必须要能够启动java环境，对应的就是 JDK 安装目录下\bin\java.exe 需要被启动。

所以咱们要告诉JAVA的值

也就是设置： 

set JAVA=D:\java\jdk1.8.0_77\bin\java （D:\java\jdk1.8.0_77 这里是你的JDK安装路径）
再思考一点，咱们设定

set JAVA_HOME=D:\java\jdk1.8.0_77 
目的其实就是让JAVA能够使用JAVA_HOME的变量的值，所以，既然咱们都手动设定了JAVA的绝对路径，那么其实JAVA_HOME 的设置和判断都可以去掉了。
对应简化内容为：

@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 for sanity sake assume Java 1.6
REM see: http://java.sun.com/javase/6/docs/technotes/tools/windows/java.html

REM add the zoocfg dir to classpath
set CLASSPATH=%ZOOCFGDIR%

REM make it work in the release
SET CLASSPATH=%~dp0..\*;%~dp0..\lib\*;%CLASSPATH%

REM make it work for developers
SET CLASSPATH=%~dp0..\build\classes;%~dp0..\build\lib\*;%CLASSPATH%

set JAVA=D:\java\jdk1.8.0_77\bin\java

set ZOOCFG=%ZOOCFGDIR%\zoo.cfg
set ZOOCFGDIR=%~dp0%..\conf
set ZOO_LOG_DIR=%~dp0%..\logs
set ZOO_LOG4J_PROP=INFO,CONSOLE
@REM setup java environment variables


if not defined JAVA (
  echo Error: not found JAVA
  goto :eof
)

总结：这种情况目前只出现在window 8 的系统上，推测window 10 可能也会存在。但是在Linux的环境下，没遇到过。大家可以手动试试，并读懂执行代码，就可以自己修改和编写了。
感谢看官，如果有疑问大家一起讨论，关注或者留言。