10.4 Java

Automake provides some minimal support for Java compilation with the JAVA primary.

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 section 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.)