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JAVAVM(1) |
FreeBSD General Commands Manual |
JAVAVM(1) |
javavm —
convenient wrapper for switching Java VMs
The Java VM wrapper provides a convenient system for switching between different
Java VMs. It also provides symbolic links in
/usr/local/bin to allow the use of the Java
executables without having to add the specific Java VM executable directories
to the PATH environment variable.
The javavm utility itself is currently a
synonym for “java”. However, this behaviour is deprecated and
is provided only for compatibility with the previous version of
javavm . This functionality may be removed in a
future version and should not be relied upon.
By default, javavm will select the most
“native” and up to date version of the Java VM when a given
symbolic link is used, invoking and passing the arguments to the matching
executable within the chosen Java VM. The choice of Java VM may also be
influenced by using environment variables to constrain the version, vendor
and operating system of the Java VM.
This selection process is usually achieved through the use of
/usr/ports/Mk/bsd.java.mk. However, if this is not
present then javavm will use its own internal
selection process which is designed to behave almost identically.
JAVA_HOME
- The presence of this variable in the environment when executing
javavm will override all other considerations
regarding the Java VM to be used and the Java VM located at
${JAVA_HOME}/bin/java will be used.
This variable is set by javavm when
executing the actual Java VM and will be available to it and all of its
child processes.
JAVA_OS
- A space delimited list of operating systems. The selected Java VM must
have been created for one of the operating systems in the list.
Currently allowed operating system values are
‘native ’ and
‘linux ’.
JAVA_VENDOR
- A space delimited list of Java VM vendors. The selected Java VM must have
been released by one of the vendors in the list.
Currently allowed vendors are
‘openjdk ’,
‘oracle ’, and
‘sun ’.
JAVA_VERSION
- A space delimited list of versions of the Java VM that may be used. By
appending a ‘
+ ’ to a version, any
Java VM with a version greater than or equal to the given version will be
used.
Currently allowed versions are
‘1.7 ’,
‘1.7+ ’,
‘1.8 ’,
‘1.8+ ’,
‘1.9 ’,
‘1.9+ ’,
‘7 ’,
‘7+ ’,
‘8 ’,
‘8+ ’,
‘9 ’,
‘9+ ’,
‘10 ’,
‘10+ ’,
‘11 ’,
‘11+ ’,
‘12 ’,
‘12+ ’,
‘13 ’,
‘13+ ’,
‘14 ’,
‘14+ ’,
‘15 ’,
‘15+ ’,
‘16 ’,
‘16+ ’,
‘17 ’, and
‘17+ ’.
JAVAVM_OPTS
- The contents of this environment variable will be passed to the invoked
Java VM as options. For more information on environment variables which
can be used to set options see
/usr/local/etc/javavm_opts.conf.dist.
JAVAVM_FALLBACK_ONLY
- If this variable is set then instead of selecting the Java VM based on
/usr/ports/Mk/bsd.java.mk only the internal
selection process is used. This may be useful to achieve consistent
results for Java VM selection across multiple hosts, where some have the
ports collection installed and others do not. However, this option, when
used with scripts installed by a port, may result in Java VM selection
inconsistent with that intended by the script author.
JAVAVM_DRYRUN
- When this variable is set, no Java VM is invoked. Instead, the Java VM
wrapper prints out the following information:
JAVA_HOME
- The value of the
JAVA_HOME environment
variable which the Java VM wrapper would have set before invoking the
Java VM.
JAVAVM_CONF
- The Java VM wrapper configuration file being used.
JAVAVM_OPTS_CONF
- The Java VM wrapper option configuration file being used.
JAVAVM_PROG
- The Java VM that would have been invoked.
JAVAVM_OPTS
- The options that would have been passed to the invoked Java VM. It is
important to note that this variable may not be the same as the
JAVAVM_OPTS environment variable due to
processing of the Java VM wrapper option configuration file.
JAVAVM_COMMAND
- The full command line that would have been used to invoke the Java
VM.
- /usr/local/etc/javavms
- The location of the Java VM wrapper configuration file.
- /usr/local/etc/javavm_opts.conf
- The location of the Java VM wrapper option configuration file.
- /usr/ports/Mk/bsd.java.mk
- The file usually used, along with
make , to select
the Java VM to be used.
- /usr/local/bin/java
- Execute the most up to date and “native” Java VM registered
with
javavm .
JAVA_VERSION=8+
/usr/local/bin/javac MyClass.java
- Compile MyClass.java with a registered Java VM's javac that is at least
version 8.
JAVA_OS=native
/usr/local/bin/java -jar
MyApp.jar
- Execute MyApp with the most up to date native Java VM that is registered
with
javavm . This is necessary if MyApp uses JNI,
for instance.
JAVA_VERSION="8
11" /usr/local/bin/java
-jar MyApp.jar
- Execute MyApp with either a Java VM that is either version 8 or version
11.
JAVAVM_DRYRUN=yes
/usr/local/bin/java
- Don't invoke the Java VM, but print out information about what would have
been done. This could be used in a script to determine the
JAVA_HOME that the Java VM wrapper will use, for
instance:
JAVA_HOME=`env JAVAVM_DRYRUN=yes
/usr/local/bin/java |
grep
'^JAVA_HOME' |
cut
-c11-`
The internal selection procedure of javavm is not fully
identical to that used when /usr/ports/Mk/bsd.java.mk
is present. In particular, javavm does not respect
environment variables such as JAVA_PREFERRED_PORTS
which is used by /usr/ports/Mk/bsd.java.mk and will
not use the values of such variables if they are set up as
make variables in
/etc/make.conf, for example.
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