_JAVA_OPTIONS、JAVA_TOOL_OPTIONS 和 JAVA_OPTS 的区别

Difference between _JAVA_OPTIONS, JAVA_TOOL_OPTIONS and JAVA_OPTS

提问by Tobber

I thought it would be great to have a comparison between _JAVA_OPTIONSand JAVA_TOOL_OPTIONS. I have been searching a bit for one, but I cannot find anything, so I hope we can find the knowledge here on Stackoverflow.

我认为在_JAVA_OPTIONS和之间进行比较会很棒JAVA_TOOL_OPTIONS。我一直在寻找一个，但我找不到任何东西，所以我希望我们可以在 Stackoverflow 上找到知识。

JAVA_OPTSis included for completeness. It is not part of the JVM, but there is a lot of questions about it out in the wild.

JAVA_OPTS包括在内是为了完整性。它不是 JVM 的一部分，但在野外有很多关于它的问题。

What I know:

我知道的：

So far I have found out that:

到目前为止，我已经发现：

• JAVA_OPTSis not used by the JDK, but by a bunch of other apps (see this post).
• JAVA_TOOL_OPTIONSand _JAVA_OPTIONSare ways to specify JVM arguments as an environment variable instead of command line parameters.
  • The are picked up by at least javaand javac
  • They have this precedence:
    1. _JAVA_OPTIONS(overwrites the others)
    2. Command line parameters
    3. JAVA_TOOL_OPTIONS(is overwritten by the others)

• JAVA_OPTS未被 JDK 使用，而是被许多其他应用程序使用（请参阅此帖子）。
• JAVA_TOOL_OPTIONS并且_JAVA_OPTIONS是将 JVM 参数指定为环境变量而不是命令行参数的方法。
  • 由至少java和javac
  • 他们有这样的优先权：
    1. _JAVA_OPTIONS（覆盖其他）
    2. 命令行参数
    3. JAVA_TOOL_OPTIONS（被其他人覆盖）

What I would like to know

我想知道什么

• Are there any official documentation comparing JAVA_TOOL_OPTIONSand _JAVA_OPTIONS
• Are there any other differences between JAVA_TOOL_OPTIONSand _JAVA_OPTIONS(except from precedence).
• Which executables pick up JAVA_TOOL_OPTIONSand _JAVA_OPTIONS(in addition to javaand javac)
• Any limitation on what can be included on JAVA_TOOL_OPTIONSand _JAVA_OPTIONS

• 是否有任何官方文件比较JAVA_TOOL_OPTIONS和_JAVA_OPTIONS
• JAVA_TOOL_OPTIONS和之间是否有任何其他差异_JAVA_OPTIONS（优先级除外）。
• 哪些可执行文件选择JAVA_TOOL_OPTIONS和_JAVA_OPTIONS（除了java和javac）
• 对可以包含的内容的任何限制JAVA_TOOL_OPTIONS和_JAVA_OPTIONS

Official Documentation

官方文档

I have not been able to find any documentation about _JAVA_OPTIONS. The documentation for JAVA_TOOL_OPTIONSdoes not shed much light on the difference:

我无法找到任何有关_JAVA_OPTIONS. 的文档JAVA_TOOL_OPTIONS并没有说明差异：

Since the command-line cannot always be accessed or modified, for example in embedded VMs or simply VMs launched deep within scripts, a JAVA_TOOL_OPTIONS variable is provided so that agents may be launched in these cases.
...

由于无法始终访问或修改命令行，例如在嵌入式 VM 或仅在脚本深处启动的 VM 中，提供了一个 JAVA_TOOL_OPTIONS 变量，以便在这些情况下可以启动代理。
...

Example script

示例脚本

This is the code I used to figure this out. Console output is included as comments:

这是我用来解决这个问题的代码。控制台输出作为注释包括在内：

export JAVA_OPTS=foobar
export JAVA_TOOL_OPTIONS= 
export _JAVA_OPTIONS="-Xmx512m -Xms64m"

java -version                          
# Picked up JAVA_TOOL_OPTIONS: 
# Picked up _JAVA_OPTIONS: -Xmx512m -Xms64m
# java version "1.7.0_40"
OpenJDK Runtime Environment (IcedTea 2.4.1) (suse-3.41.1-x86_64)
OpenJDK 64-Bit Server VM (build 24.0-b50, mixed mode)

javac -version
# Picked up JAVA_TOOL_OPTIONS: 
# Picked up _JAVA_OPTIONS: -Xmx512m -Xms64m
# javac 1.7.0_40

export JAVA_TOOL_OPTIONS="-Xmx1 -Xms1"
export _JAVA_OPTIONS="-Xmx512m -Xms64m"
javac -version
# Picked up JAVA_TOOL_OPTIONS: -Xmx1 -Xms1
# Picked up _JAVA_OPTIONS: -Xmx512m -Xms64m
# javac 1.7.0_40

export JAVA_TOOL_OPTIONS="-Xmx512m -Xms64m"
export _JAVA_OPTIONS="-Xmx1 -Xms1"
javac -version
# Picked up JAVA_TOOL_OPTIONS: -Xmx512m -Xms64m
# Picked up _JAVA_OPTIONS: -Xmx1 -Xms1
# Error occurred during initialization of VM
# Too small initial heap

export JAVA_TOOL_OPTIONS="-Xmx1 -Xms1"
export _JAVA_OPTIONS=
java -Xmx512m -Xms64m -version
# Picked up JAVA_TOOL_OPTIONS: -Xmx1 -Xms1
# Picked up _JAVA_OPTIONS: 
# java version "1.7.0_40"
# OpenJDK Runtime Environment (IcedTea 2.4.1) (suse-3.41.1-x86_64)
# OpenJDK 64-Bit Server VM (build 24.0-b50, mixed mode)

export JAVA_TOOL_OPTIONS=
export _JAVA_OPTIONS="-Xmx1 -Xms1"
java -Xmx512m -Xms64m -version
# Picked up JAVA_TOOL_OPTIONS: 
# Picked up _JAVA_OPTIONS: -Xmx1 -Xms1
# Error occurred during initialization of VM
# Too small initial heap

采纳答案by mkalkov

You have pretty much nailed it except that these options are picked up even if you start JVM in-process via a library call.

除了即使您通过库调用在进程内启动 JVM 也会选择这些选项之外，您几乎已经掌握了它。

The fact that _JAVA_OPTIONSis not documented suggests that it is not recommended to use this variable, and I've actually seen people abuse it by setting it in their ~/.bashrc. However, if you want to get to the bottom of this problem, you can check the source of Oracle HotSpot VM (e.g. in OpenJDK7).

_JAVA_OPTIONS未记录的事实表明不建议使用此变量，我实际上已经看到人们通过将它设置在他们的~/.bashrc. 但是，如果您想深入了解这个问题，您可以检查 Oracle HotSpot VM 的来源（例如在 OpenJDK7 中）。

You should also remember that there is no guarantee other VMs have or will continue to have support for undocumented variables.

您还应该记住，不能保证其他 VM 已经或将继续支持未记录的变量。

UPDATE 2015-08-04: To save five minutes for folks coming from search engines, _JAVA_OPTIONStrumps command-line arguments, which in turn trump JAVA_TOOL_OPTIONS.

更新 2015-08-04：为了为来自搜索引擎的人节省五分钟，_JAVA_OPTIONS胜过命令行参数，而命令行参数又胜过JAVA_TOOL_OPTIONS.

回答by Victor Havin

There is one more difference: _JAVA_OPTIONSis Oracle specific. IBM JVM is using IBM_JAVA_OPTIONSinstead. This was probably done to be able to define machine-specific options without collisions. JAVA_TOOL_OPTIONSis recognized by all VMs.

还有一个区别：_JAVA_OPTIONS是特定于 Oracle 的。IBM JVM 正在使用IBM_JAVA_OPTIONS。这样做可能是为了能够在没有冲突的情况下定义特定于机器的选项。JAVA_TOOL_OPTIONS被所有虚拟机识别。

回答by Vadzim

JAVA_OPTShave no special handlingin JVM at all.

JAVA_OPTS有没有特殊的处理都在JVM。

And according to https://bugs.openjdk.java.net/browse/JDK-4971166the JAVA_TOOL_OPTIONSis included in standard JVMTI specification, does better handling of quoted spaces and should be always preferred instead of undocumented Hotspot-specific _JAVA_OPTIONS.

而根据https://bugs.openjdk.java.net/browse/JDK-4971166将JAVA_TOOL_OPTIONS被包含在标准规格JVMTI，并更好地处理引用的空间，应始终优先，而不是热点特定无证_JAVA_OPTIONS。

Also beware that using these prints additional message to stdout that can't be suppressed.

还要注意，使用这些会向 stdout 打印无法被抑制的附加消息。

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As @ryenus noted, since JDK 9+, there's JDK_JAVA_OPTIONS as the preferred replacement, see What is the difference between JDK_JAVA_OPTIONS and JAVA_TOOL_OPTIONS when using Java 11?

As @ryenus noted, since JDK 9+, there's JDK_JAVA_OPTIONS as the preferred replacement, see What is the difference between JDK_JAVA_OPTIONS and JAVA_TOOL_OPTIONS when using Java 11?