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.Dd November 12, 2019
.Os
.Dt JAVAVM 1
.Sh NAME
.Nm javavm
.Nd convenient wrapper for switching Java VMs
.Sh SYNOPSIS
.Nm
.Op Ar arguments ...
.Sh DESCRIPTION
The Java VM wrapper provides a convenient system for switching between
different Java VMs.
It also provides symbolic links in
.Pa %%LOCALBASE%%/bin
to allow the use of
the Java executables without having to add the specific Java VM executable
directories to the
.Ev PATH
environment variable.
.Pp
The
.Nm
utility itself is currently a synonym for
.Dq java .
However, this behaviour
is deprecated and is provided only for compatibility with the previous
version of
.Nm .
This functionality may be removed in a future version and should not be
relied upon.
.Pp
By default,
.Nm
will select the most
.Dq 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.
.Pp
This selection process is usually achieved through the use of
.Pa %%PORTSDIR%%/Mk/bsd.java.mk .
However, if this is not present then
.Nm
will use its own internal selection process which is
designed to behave almost identically.
.Sh ENVIRONMENT
.Bl -tag -width indent
.It Ev JAVA_HOME
The presence of this variable in the environment when executing
.Nm
will override all other considerations regarding the Java VM to be used
and the Java VM located at
.Pa ${JAVA_HOME}/bin/java
will be used.
.Pp
This variable is set by
.Nm
when executing the actual Java VM and will be available to it and all of
its child processes.
.It Ev 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.
.Pp
Currently allowed operating system values are
.Ql native
and
.Ql linux .
.It Ev 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.
.Pp
Currently allowed vendors are
.Ql openjdk ,
.Ql oracle ,
and
.Ql sun .
.It Ev JAVA_VERSION
A space delimited list of versions of the Java VM that may be used.
By appending a
.Ql +
to a version, any Java VM with a version greater than or
equal to the given version will be used.
.Pp
Currently allowed versions are
.Ql 8 ,
.Ql 8+ ,
.Ql 11 ,
.Ql 11+ ,
.Ql 17 ,
.Ql 17+ ,
.Ql 18 ,
.Ql 18+ ,
.Ql 19 ,
.Ql 19+ ,
.Ql 20 ,
.Ql 20+ ,
.Ql 21 ,
and
.Ql 21+ .
.It Ev 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
.Pa %%PREFIX%%/etc/javavm_opts.conf.dist .
.It Ev JAVAVM_FALLBACK_ONLY
If this variable is set then instead of selecting the Java VM based on
.Pa %%PORTSDIR%%/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.
.It Ev JAVAVM_DRYRUN
When this variable is set, no Java VM is invoked.
Instead, the Java VM wrapper prints out the following information:
.Bl -tag -width indent
.It Ev JAVA_HOME
The value of the
.Ev JAVA_HOME
environment variable which the Java VM wrapper would have set before
invoking the Java VM.
.It Ev JAVAVM_CONF
The Java VM wrapper configuration file being used.
.It Ev JAVAVM_OPTS_CONF
The Java VM wrapper option configuration file being used.
.It Ev JAVAVM_PROG
The Java VM that would have been invoked.
.It Ev 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
.Ev JAVAVM_OPTS
environment variable due to processing of the Java VM wrapper option
configuration file.
.It Ev JAVAVM_COMMAND
The full command line that would have been used to invoke the Java VM.
.El
.El
.Sh FILES
.Bl -tag -width indent
.It Pa %%PREFIX%%/etc/javavms
The location of the Java VM wrapper configuration file.
.It Pa %%PREFIX%%/etc/javavm_opts.conf
The location of the Java VM wrapper option configuration file.
.It Pa %%PORTSDIR%%/Mk/bsd.java.mk
The file usually used, along with
.Nm make ,
to select the Java VM to be used.
.El
.Sh EXAMPLES
.Bl -tag -width indent
.It Pa %%LOCALBASE%%/bin/java
Execute the most up to date and
.Dq native
Java VM registered with
.Nm .
.It Ev JAVA_VERSION=8+ Pa %%LOCALBASE%%/bin/javac MyClass.java
Compile MyClass.java with a registered Java VM's javac that is at least
version 8.
.It Ev JAVA_OS=native Pa %%LOCALBASE%%/bin/java Fl jar Pa MyApp.jar
Execute MyApp with the most up to date native Java VM that is registered
with
.Nm .
This is necessary if MyApp uses JNI, for instance.
.It Ev JAVA_VERSION="8 11" Pa %%LOCALBASE%%/bin/java Fl jar Pa MyApp.jar
Execute MyApp with either a Java VM that is either version 8 or version 11.
.It Ev JAVAVM_DRYRUN=yes Pa %%LOCALBASE%%/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
.Ev JAVA_HOME
that the Java VM wrapper will use, for instance:
.Lp
.Ev JAVA_HOME=`env JAVAVM_DRYRUN=yes %%LOCALBASE%%/bin/java | grep '^JAVA_HOME' | cut -c11-`
.El
.Sh SEE ALSO
.Xr checkvms 1 ,
.Xr make 1 ,
.Xr manvm 1 ,
.Xr registervm 1 ,
.Xr unregistervm 1 ,
.Xr javavm_opts.conf 5 ,
.Xr javavms 5
.Sh BUGS
The internal selection procedure of
.Nm
is not fully identical to that used when
.Pa %%PORTSDIR%%/Mk/bsd.java.mk
is present.
In particular,
.Nm
does not respect environment variables such as
.Ev JAVA_PREFERRED_PORTS
which is used by
.Pa %%PORTSDIR%%/Mk/bsd.java.mk
and will not use the values of such variables if they are set up as
.Nm make
variables in
.Pa /etc/make.conf ,
for example.