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Packaging Java with Javatools

Javatools replaces the existing jarwrapper package and also contains programs to help packagers in creating packages for Java programs and libraries.

Packaging tools

The javahelper package consists of several small programs which make packaging Java programs and libraries easier. They are generally designed to work in the same fashion as the debhelper programs, but start with the jh_ prefix.

All of the programs have their command line arguments documented in manpages.

jh_build

Many Java programs and libraries are distributed without sane build systems. jh_build provides a simple interface for building Java source code into Jars, including setting the appropriate entries in the manifest.

In almost all cases all that needs to be done to call jh_build is to set JAVA_HOME and CLASSPATH and then call jh_build with the name of the jar and the directory containing the source.

JAVA_HOME=/usr/lib/jvm/default-java
CLASSPATH=/usr/share/java/esd.jar:/usr/share/java/jsch.jar
jh_build weirdx.jar src
   

This command will compile all the Java files under src, set the classpath in the manifest and build it all into weirdx.jar.

A couple of other options are worth mentioning. If this jar contains an application rather than a library then the -m or --main option can be used to set the Main-Class attribute in the manifest which will allow the resulting jar file to be be executed

Alternatively, you may provide a debian/javabuild file containing one jar per line, each jar name followed by a list of source files or directories. In this case you can call jh_build with no jar or source and it will build those jars. The jars will then be removed by jh_build --clean.

jh_build also provides a --clean parameter which should be called in the clean target of debian/rules. It will be called for you by jh_clean

jh_build will also create javadoc, but only for the last jar built in each package. It can be installed automatically using jh_installjavadoc (see below).

jh_installlibs

For library packages Debian Java policy currently requires that the libraries be installed to /usr/share/java in a versioned format and with an unversioned symlink. jh_installlibs will take a jar and correctly install it.

As with debhelper programs, this can either take a jar as a parameter, or read a list of jars from a file in the Debian directory. It also follows the -p, -i and -a semantics of debhelper for selecting which packages to install the jar to. When operating on a package, jh_installlibs will read the list of library jars from debian/package.jlibs or debian/jlibs.

The jlibs file is a list of jars to install, one per line, and works exactly the same as listing them on the command line. Each jar is installed to debian/package/usr/share/java/ in the appropriate versioned and unversioned forms.

If the jars built by upstream already contain the version number, this will be stripped before installing. jh_installlibs will also try to strip the upstream version number of any dfsg suffix. Other version-mangling options or explicit version numbers can also be provided.

jh_depends

jh_depends works like dpkg-shlibdeps, but for jar files. For each jar in the package it takes the jars on which it depends and finds the packages to which they belong. These are included in the debhelper substvars as ${java:Depends}. The control file can then just list that variable which is filled in automatically.

This is done by reading the Class-Path attribute from the manifest of each jar. Jar files should include this attribute to prevent applications which use them from needing a full recursive classpath in their startup scripts and to prevent unneccessary transitions when the library changes its dependencies. If the package is not built with jh_build and the upstream build system doesn't set it correctly then jh_manifest or jh_classpath can be used to fix this.

If the application uses executable jars (see Runtime support below) then jh_depends will also add the appropriate depends on jarwrapper and the correct Java runtime.

As of version 0.32, jh_depends also checks installed javadocs for links to system installed javadocs. It will use this to populate the ${java:Recommends} variable, which can be used for the doc package.

Note that both substvars are always created even if they are empty, like debhelper does with ${misc:Depends}.

jh_manifest

Many upstream build systems do not set the Class-Path attribute in the jars they create. This leads to several unwanted problems, such as expanding the classpath which applications have to use and introducing unneccessary transitions. They also may not set the Main-Class attribute. Both of these are required for running jars with the -jar parameter.

jh_manifest can fix the manifest files of jars. It can either read from a manifest file in the Debian directory or run in a mode which updates all the jars with the CLASSPATH environment variable.

The manifest files can either be debian/package.manifest or debian/manifest. The format of this file is a list of jars and indented below each one a list of manifest elements to set:

usr/share/weirdx/weirdx.jar:
 Main-Class: com.jcraft.weirdx.WeirdX
 Debian-Java-Home: /usr/lib/jvm/default-java
   

jh_classpath

If you are just setting the classpath then this command is simpler than jh_manifest. jh_classpath can either take jars on the command line with the classpath specified on the command line or in the CLASSPATH environment variable.

Alternatively, it can read classpaths from a debian/classpath or debian/package.classpath file. This should be one jar per line specifying the jar followed by it's space-separated classpath:

src/bar.jar /usr/share/java/quux.jar
src/foo.jar /usr/share/java/bar.jar /usr/share/java/baz.jar

jh_exec

The Runtime support section below describes running executable jars directly. jh_exec will scan package directories for jars in the paths, or symlinks to jar from the paths, and ensure that they have been set executable if necessary.

jh_installjavadoc

If you have javadoc which has been built by your build system, then jh_installjavadoc will install it in the correct location and register it with doc-base for you. Either run jh_installjavadoc with the directory containing the javadoc as a parameter, or it will read debian/javadoc or debian/package.javadoc which should contain a single path to the javadoc for that package.

If you have used jh_build that will automatically have created javadoc. To install that put the string internal in the javadoc file and it will be installed.

The second parameter, or the second string on the line in the javadoc file, can be used to override the install location, for example, so that a -doc package can install to /usr/share/doc/$library/api.

jh_makepkg

jh_makepkg will create template Debian packages for Java programs and libraries similar to dh-make. It should be run in the source directory and it will create the orig.tar.gz and most of the files in the Debian directory, which need only small changes neccessary to build the package.

jh_linkjars

If upstream ship convenience copies of third-party jar files which have been removed (see jh_repack below), but the build system refers to that directory, jh_linkjars can be used to populate the directory with symlinks to the packaged jars in /usr/share/java.

It is called either with a directory on the command line or by specifying one target directory per line in the file debian/linkjars.

jh_linkjars will scan all of the (installed) build-dependencies and create a symlink to every jar which is installed by those packages in the target directory.

jh_linkjars can be called with -u to remove all the symlinks in the clean target. This is done automatically by jh_clean.

jh_clean

jh_clean should be called in the clean target to remove files which have beenn created by other jh_ commands, such and jh_build and jh_linkjars.

jh_repack

jh_makepkg provides functionality to help clean your upstream tarball of prebuilt jars, classfiles and javadoc. If you want to do this whenever you download a new version you can use jh_repack as a uscan helper. Just put jh_repack as the command at the end of the uscan line. E.g.

version=3
http://www.matthew.ath.cx/projects/salliere/ (?:.*/)?salliere-?_?([\d+\.]+|\d+)\.(tar.*|tgz|zip|gz|bz2|) debian jh_repack

Alternatively you can run it by hand:

jh_repack --upstream-version   

jh_repack will remove any .class files, any .jar files, the whole directory tree containing javadoc and any empty directories as a result of the above.

java-propose-classpath

Some upstreams have complicated classpaths which may not be obvious to the packager when using jh_manifest to set the Class-Path attribute. java-propose-classpath will unpack a jar and look at the symbols imported to the class files, then scan all the jars in /usr/share/java. This shouldn't be run in the build since it is slow, and there may be ambiguities that the packager must resolve. It is still very useful for the packager as most of the time it will get it right automatically.

To avoid bloating the recursive build-deps of packages, java-propose-classpath is in a separate package to javahelper. It should not be on any package's build-depends.

jh_installeclipse

jh_installeclipse will install eclipse features built by eclipse's pde-build script. It supports most of debhelpers normal options. Features can either be put in the >package<.eh-install or be given per command-line. By default jh_installeclipse expects pde-build to have been run from debian/.eclipse-build; if you decide to run it from another directory, you should use --pde-build-dir to tell jh_installeclipse where pde-build was run from.

jh_installeclipse knows where pde-build dumps its output, so only the name of the feature should be given. It supports file globbing both in the files and per command-line (though in the latter case your shell may attempt to expand the globs if they are not properly escaped or quoted).

Due two the way the underlying build system works; orbit dependencies will be embedded directly into the installation. jh_installeclipse will replace any orbit dependencies imported by jh_generateorbitdir. If you add/import orbit dependencies yourself through other means, you must replace them yourselves after running jh_installeclipse.

Finally, jh_installeclipse will output a ${orbit:Depends} variable if it replaces any orbit dependency for that package.

jh_generateorbitdir

jh_generateorbitdir is an javahelper program that handles creation of an orbit dependency dir. This directory has to be populated with non-eclipse jar files. However, eclipse refers to these jars by their symbolic name. jh_generateorbitdir can extract this name from the jar's manifest (provided it has the OSGi metadata) and create a symlink to it.

jh_generateorbitdir will replace regular files with symlinks if they are present in the orbit dir and clash with the name of one of the orbit jars. If an orbit jar name clashes with a symlink in the orbit dir, then jh_generateorbitdir will assume that the given jar has already been symlinked and skip it.

jh_generateorbitdir will also check the default installation for jar files on Debian systems (at the time of writing /usr/share/java), if it cannot find the jar in the current dir.

If present, jh_generateorbitdir will read debian/eclipse.orbitdeps and add the jar files listed in it to the list of orbit dependencies.

jh_setupenvironment

jh_setupenvironment is a javahelper program that handles creating an environment for building an eclipse feature. It does not setup an orbit dir (use jh_generateorbitdir for that). It will copy files specified in debian/eclipse.environment as well as those given on command line into the environment dir. If no files are given per command line and the environment file is not present (or is empty), it will default to org.eclipse.*

jh_compilefeatures

jh_compilefeatures handles compilation of eclipse features. It will read debian/eclipse.features as a list of features to compile and their dependencies. The first item on a line is the id of the feature and the remaining are either ids of previously compiled features or features installed on the system (identified by the folder they are installed in).

By default jh_compilefeatures will set the source and the target version of the class files to 1.5. This can be overriden by explicitly changing the build options (see man jh_compilefeatures for more information).

java-vars.mk

You can include /usr/share/javahelper/java-vars.mk in your debian/rules to get the following variables defined:

  • JAVA_HOME—If you haven't already set it, will default to the default JDK for the architecture (you must depend on default-jdk or -headless if you are not overriding this). To override this set JAVA_HOME before including java-vars.mk
  • JAVA_ARCH—The JVM version of the build architecture (eg ppc not powerpc)
  • JRE_HOME—If JAVA_HOME/jre exists then that, otherwise JAVA_HOME
  • JVM_CLIENT_DIR/ JVM_SERVER_DIR—set if the respective types of JVM are installed.

If you need the Java architecture in a non-make context then you can use /usr/share/javahelper/java-arch.sh instead.

Runtime support

Javatools also provides some runtime support. Unlike compiled programs, or purely interpreted programs with hash-bang lines, Java programs cannot be directly executed. Many upstreams expect them to be run using java -jar jarname or java classname. This is not generally acceptible in systems which expect to just be able to run the command or launch it from a menu. As a result, many packagers are writing wrapper scripts which just call java with the correct classpath, jar and main class.

jarwrapper

There is an alternative to wrapper scripts, however. The binfmt_misc kernel module allows the kernel to call out to a program in userspace to execute specific types of file. jarwrapper registers itself as a handler for executable jars. This is done by reading values from the manifest file.

In order for executable jars to work the following attributes must or may be defined in the manifest. These attributes can be set using jh_build and jh_manifest.

  • Main-Class: The name of the class to be run when the application starts. (REQUIRED)
  • Class-Path: The path to all the jar files on which this jar depends. (REQUIRED unless empty)
  • Debian-Java-Home: A Debian-specific property if this application depends on a specific runtime. Specify the path to the runtime which should be used. Multiple space-separated paths may be given if any of the runtimes will work. (OPTIONAL)
  • Debian-Java-Parameters: A Debian-specific property if this application needs extra options to the JVM. (OPTIONAL)

Java Architecture

If you need to know the JVM architecture name at runtime (for example to put libjvm.so on the LD_LIBRARY_PATH) then jarwrapper also provides /usr/share/jarwrapper/java-arch.sh which will either print the current one or convert a debian arch name to a JVM arch name.

Putting it together

This section shows the debian packaging generated by jh_makepkg for an application and a library using jh_build.

Sample Library Packaging

debian/control
Source: jsch
Section: libs
Priority: optional
Maintainer: Matthew Johnson <mjj29@debian.org>
Build-Depends: debhelper (>= 5), javahelper, default-jdk, libzlib-java
Standards-Version: 3.7.3
Homepage: http://www.jcraft.com/jsch/

Package: libjsch-java
Architecture: all
Depends: ${java:Depends}, ${misc:Depends}
Description: Java secure channel
 JSch is a pure Java implementation of SSH2. JSch allows you to
 connect to an sshd server and use port forwarding, X11 forwarding,
 file transfer, etc., and you can integrate its functionality
 into your own Java programs. JSch is licensed under a BSD style
 license.
   
debian/rules
#!/usr/bin/make -f

export JAVA_HOME=/usr/lib/jvm/default-java
export CLASSPATH=/usr/share/java/zlib.jar

build: build-stamp
build-stamp:
	dh_testdir
	jh_build jsch.jar src
	touch $@

clean:
	dh_testdir
	dh_testroot
	jh_build --clean
	dh_clean
	rm -f build-stamp jsch.jar

install: build
	dh_testdir
	dh_testroot
	dh_prep
	dh_installdirs

binary-arch: build install
	# Java packages are arch: all, nothing to do here

binary-indep: build install
	# Create the package here
	dh_testdir
	dh_testroot
	dh_prep
	dh_install -i
	jh_installjavadoc -i
	dh_installdocs -i
	dh_installchangelogs -i
	jh_installlibs -i
	jh_depends -i
	dh_compress -i
	dh_fixperms -i
	dh_installdeb -i
	dh_gencontrol -i
	dh_md5sums -i
	dh_builddeb -i

binary: binary-indep binary-arch
.PHONY: build clean binary-indep binary-arch binary install
   
debian/libjsch-java.jlibs
jsch.jar
   
debian/libjsch-java.javadoc
internal
   

Sample Application Packaging

debian/control
Source: salliere
Section: misc
Priority: optional
Maintainer: Matthew Johnson <mjj29@debian.org>
Build-Depends: debhelper (>= 5), default-jdk,
               libmatthew-debug-java, libcsv-java,
               libitext-java, javahelper
Standards-Version: 3.7.3

Package: salliere
Architecture: all
Depends: ${java:Depends}, ${misc:Depends}
Description: Short Description
 Long Description
   
debian/rules
#!/usr/bin/make -f
export JAVA_HOME=/usr/lib/jvm/default-java
export CLASSPATH=/usr/share/java/csv.jar:/usr/share/java/debug-disable.jar:/usr/share/java/itext.jar

build: build-stamp
build-stamp:
   dh_testdir
   # Build the package
   jh_build salliere.jar src
   touch $@

clean:
   dh_testdir
   dh_testroot
   jh_build --clean
   dh_clean
   rm -f build-stamp salliere.jar

install: build
   dh_testdir
   dh_testroot
   dh_prep
   dh_installdirs

binary-arch: build install
   # Java packages are arch: all, nothing to do here

binary-indep: build install
   # Create the package here
   dh_testdir
   dh_testroot
   dh_prep
   dh_install -i
   dh_installdocs -i
   dh_installchangelogs -i
   jh_manifest -i
   dh_link -i
   jh_exec -i
   jh_depends -i
   dh_compress -i
   dh_fixperms -i
   dh_installdeb -i
   dh_gencontrol -i
   dh_md5sums -i
   dh_builddeb -i

binary: binary-indep binary-arch
.PHONY: build clean binary-indep binary-arch binary install
   
debian/salliere.install
salliere.jar usr/share/salliere
   
debian/salliere.links
usr/share/salliere/salliere.jar usr/bin
   

Using javahelper with CDBS

Javahelper 0.18 introduces a CDBS class for javahelper. It runs all the jh_ commands after dh_install* and dh_link and has options for running jh_build under the build target.

The jh_ commands are invoked once per package. You can pass options to all the invocations using the JH_EXEC_ARGS, JH_INSTALLLIBS_ARGS, JH_MANIFEST_ARGS and JH_DEPENDS_ARGS variables.

To invoke jh_build you must set JH_BUILD_JAR and JH_BUILD_SOURCE and JAVA_HOME. Optionally you can also set CLASSPATH and JH_BUILD_ARGS.

Please note: you must include javahelper.mk before ant.mk.

The above debian/rules can be rewritten with CDBS as follows:

#!/usr/bin/make -f
export JAVA_HOME=/usr/lib/jvm/default-java
export CLASSPATH=/usr/share/java/csv.jar:/usr/share/java/debug-disable.jar:/usr/share/java/itext.jar
JH_BUILD_JAR=salliere.jar
JH_BUILD_SRC=src

include /usr/share/cdbs/1/class/javahelper.mk

Using javahelper with dh

Javahelper 0.20 introduces a dh extension for javahelper. It runs all the jh_ commands after dh_install* and dh_link and also runs jh_build if you have a debian/javabuild file.

The above debian/rules can be rewritten with dh 7 as follows:

debian/javabuild
salliere.jar src
debian/rules
#!/usr/bin/make -f

export JAVA_HOME=/usr/lib/jvm/default-java
export CLASSPATH=/usr/share/java/csv.jar:/usr/share/java/debug-disable.jar:/usr/share/java/itext.jar

%:
	dh $@ --with javahelper