What is the Difference Between _JAVA_OPTIONS, JAVA_TOOL_OPTIONS, and JAVA_OPTS?

Understanding the Distinction Between _JAVA_OPTIONS, JAVA_TOOL_OPTIONS, and JAVA_OPTS

Often, developers encounter confusion surrounding the purpose and differences between _JAVA_OPTIONS, JAVA_TOOL_OPTIONS, and JAVA_OPTS. This article will delve into the details of each and explore their usage in specifying JVM arguments.

JAVA_OPTS: A Legacy Option

Unlike JAVA_TOOL_OPTIONS and _JAVA_OPTIONS, JAVA_OPTS is not inherent to the Java Virtual Machine (JVM). However, many applications recognize JAVA_OPTS, making it prevalent in discussions. Its utility lies in setting JVM arguments.

JAVA_TOOL_OPTIONS and _JAVA_OPTIONS: Environment Variable-Based JVM Parameters

JAVA_TOOL_OPTIONS and _JAVA_OPTIONS provide an alternative approach to specifying JVM arguments. These environment variables enable the setting of parameters without requiring command-line arguments.

Key Differences

Precedence: _JAVA_OPTIONS takes precedence over JAVA_TOOL_OPTIONS and command-line parameters, as demonstrated in your example.

Supported Executables: Both JAVA_TOOL_OPTIONS and _JAVA_OPTIONS are recognized by the java and javac executables. Other executables may also support these variables, including the jdb debugger.

General Usage: JAVA_TOOL_OPTIONS is intended for setting JVM parameters related to specific tools. For example, if you need to configure compiler flags for javac, you can use JAVA_TOOL_OPTIONS.

In contrast, _JAVA_OPTIONS is used more generally to set JVM parameters that apply to the Java runtime environment.

Official Documentation and Undocumented Variables

Oracle's documentation for the JVM includes information about JAVA_TOOL_OPTIONS but not _JAVA_OPTIONS. This omission suggests that _JAVA_OPTIONS may be an undocumented variable. Additionally, external libraries can also leverage these environment variables for their specific purposes.

Conclusion

Understanding the differences between _JAVA_OPTIONS, JAVA_TOOL_OPTIONS, and JAVA_OPTS is essential for effectively configuring JVM parameters. Always refer to official documentation when possible. While JAVA_TOOL_OPTIONS and _JAVA_OPTIONS are valuable tools, they may not be universally supported by all Java implementations.

The above is the detailed content of What is the Difference Between _JAVA_OPTIONS, JAVA_TOOL_OPTIONS, and JAVA_OPTS?. For more information, please follow other related articles on the PHP Chinese website!