Automake provides some minimal support for Java bytecode compilation with
the JAVA primary (in addition to the support for compiling Java to
native machine code; see Compiling Java sources using gcj). Note however that
the interface and most features described here are deprecated.
Future Automake releases will strive to provide a better and cleaner
interface, which however won’t be backward-compatible; the present
interface will probably be removed altogether some time after the
introduction of the new interface (if that ever materializes). In any
case, the current JAVA primary features are frozen and will no
longer be developed, not even to take bug fixes.
Any .java files listed in a _JAVA variable will be
compiled with JAVAC at build time. By default, .java
files are not included in the distribution; you should use the
dist_ prefix to distribute them.
Here is a typical setup for distributing .java files and installing the .class files resulting from their compilation.
javadir = $(datadir)/java dist_java_JAVA = a.java b.java ...
Currently Automake enforces the restriction that only one _JAVA
primary can be used in a given Makefile.am. The reason for this
restriction is that, in general, it isn’t possible to know which
.class files were generated from which .java files, so
it would be impossible to know which files to install where. For
instance, a .java file can define multiple classes; the resulting
.class file names cannot be predicted without parsing the
.java file.
There are a few variables that are used when compiling Java sources:
JAVAC ¶The name of the Java compiler. This defaults to ‘javac’.
JAVACFLAGS ¶The flags to pass to the compiler. This is considered to be a user variable (see Variables reserved for the user).
AM_JAVACFLAGS ¶More flags to pass to the Java compiler. This, and not
JAVACFLAGS, should be used when it is necessary to put Java
compiler flags into Makefile.am.
JAVAROOT ¶The value of this variable is passed to the -d option to
javac. It defaults to ‘$(top_builddir)’.
CLASSPATH_ENV ¶This variable is a shell expression that is used to set the
CLASSPATH environment variable on the javac command line.
(In the future we will probably handle class path setting differently.)