Debian policy for Java Ola Lundqvist Stephane Bortzmeyer Abstract This is the java policy for Debian. It begins with a background description, continues with the real policy, some issues to discuss and ends with some advices to java packagers. The policy covers java virtual machines, java compilers, java programs and java libraries. _________________________________________________________ Table of Contents 1. Background 2. Policy 2.1. Virtual machines 2.2. Java compilers 2.3. Java programs 2.4. Java libraries 2.5. Main, contrib or non-free 3. Issues to discuss 4. Advices to Java packagers _________________________________________________________ Chapter 1. Background There are several "subpolicies" in Debian. They all want to make the Debian Policy more precise when it comes to a specific subject. See the Emacs subpolicy in package emacsen-common for instance. As far as I know, the only subpolicy for a programming language, is that of Perl. Feel free to report comments, suggestions and/or disagreements to the java-common package () or the Debian Java mailing list . Change requests should be sent as a bug to the java-common package. _________________________________________________________ Chapter 2. Policy Virtual packages are created: java-compiler, java2-compiler, java-virtual-machine, java1-runtime and java2-runtime. All Java code must be shipped as Java bytecode (*.class files, packaged in a *.jar archive) and with "Architecture: all". Packages written in Java are separated in two categories: programs and libraries. Programs are intended to be run by end-users. Libraries are intended to help programs to run and to be used by developers. Both are shipped as Java bytecode (*.class files, packaged in a *.jar archive) and with an "Architecture: all" since Java bytecode is supposed to be portable. It may additionally be shipped as machine code, as produced for example by the GNU Compiler for Java, in a separate architecture-specific package. This policy does not yet address the issue of documentation (for instance HTML pages made with javadoc). _________________________________________________________ 2.1. Virtual machines Java virtual machines must provide java-virtual-machine and depend on java-common. They can also provide the runtime environment that the package contains (java1-runtime and/or java2-runtime). If it does not provide the files itself it must depend on the needed runtime environment. Packages that contain a runtime conforming to the Java 1.1 specification should provide java1-runtime. Packages that contain a runtime conforming to the Java 2 specification should provide java2-runtime. If a package conforms to both, then it should provide both; however, packages that do not implement the methods from Java 1.1 that have been deprecated in Java 2 must not provide java1-runtime. They should use /etc/alternatives for the name 'java' if they are command-line compatible with the Sun's java program. They should have a CLASSPATH predefined which include the needed runtime environment. If a given source (like the JDK does) brings both a compiler and a virtual machine, you may name the compiler package xxxx-dev. Some Java classes implement their routines using a "native" language (such as C). This native code is compiled and stored in dynamic libraries (such as JNI modules) that are loaded at runtime. If a virtual machine supports native code, it must include the directory /usr/lib/jni in its search path for these dynamic libraries. _________________________________________________________ 2.2. Java compilers Java compilers must provide java-compiler and/or java2-compiler and depend on java-common. They must also depend on the needed runtime environment (java1-runtime and/or java2-runtime). They should use /etc/alternatives for the name 'javac' if they are command-line compatible with Sun's JDK javac. They should have a CLASSPATH predefined to include the java core classes need for the compiler. _________________________________________________________ 2.3. Java programs Programs must have executable(s) in /usr/bin and be executable. They can be Java classes (using binfmt_misc) or wrappers. In any case, they must run without specific environment variables (see Policy 10.9), for instance CLASSPATH. They must respect the Policy rules for executables (for instance a manual page per executable, see Policy 13.1). If they have their own auxiliary classes, they must be in a jar file in /usr/share/java. The name of the jar should follow the same naming conventions as for libraries. Programs must depend on java-virtual-machine and the needed runtime environment (java1-runtime and/or java2-runtime). There is no naming rules for programs, they are ordinary programs, from the user point of view. _________________________________________________________ 2.4. Java libraries Libraries are not separated between developers (-dev) and users versions, since this is meaningless in Java. Java libraries packages must be named libXXX[version]-java (without the brackets), where the version part is optional and should only contain the necessary part. The version part should only be used to avoid naming collisions. The XXX part is the actual package name used in the text below. Their classes must be in jar archive(s) in the directory /usr/share/java, with the name packagename[-extraname]-fullversion.jar. The extraname is optional and used internally within the package to separate the different jars provided by the package. The fullversion is the version of that jar file. In some cases that is not the same as the package version. Some package must also provide a symbolic link from packagename-extraname.jar to the most compatible version of the available packagename-extraname-version.jar files. Java libraries must depend on the needed runtime environment (java1-runtime and/or java2-runtime) but should not depend (only suggest) java-virtual-machine. All jar files must have a well-documented CLASSPATH, so that developers should know what to add to their wrappers. This applies only to libraries, not to the core classes provided by a the runtime environment. Some Java libraries rely on code written in a "native" language, such as JNI (Java Native Interface) code. This native code is compiled into separate dynamic libraries which are loaded by the Java virtual machine at runtime. If a Java library relies on native code, the dynamic libraries containing this compiled native code should be installed into the directory /usr/lib/jni. These dynamic libraries should be shipped in a separate architecture-specific package named libXXX[version]-jni. The package containing the Java bytecode (generally libXXX[version]-java) should depend on this package. There may be situations, such as with very small packages, where it is better to bundle the Java code and the native code together into a single package. Such packages should be architecture-specific and follow the usual libXXX[version]-java naming convention. _________________________________________________________ 2.5. Main, contrib or non-free About politics: packaging Java stuff changes nothing to the rules Debian uses to find if a program is free or not. Since there are not many free Java tools, keep in mind the following: * If your source package can compile (correctly) only with non-free tools (the only free Java compilers seem to be guavac, gcj and jikes, it cannot go to main. If your package itself is free, it must go to contrib. * If your binary package can run only with non-free virtual machines (GNU-Classpath has a list of free versions), it cannot go to main. If your package itself is free, it must go to contrib. _________________________________________________________ Chapter 3. Issues to discuss The following points are discussions about the policy, either because they have to be studied more, or are controversial. * Name and existence of the repository. It was removed in the latest version. * The symbolic links in /usr/share/java be made by a script instead, similar to the c-libraries. * Core classes (java.*). More study needed. * Sun's Community Source Licence. Can we use it? How? The 2.3 version of the text can be found here. * All jars must have a good CLASSPATH documentation, but how should it be documented. The best solution is probably in some computer parsable format to make it even easier for the developer. It should exist some tool to parse this. How should it work? Should the tool also be used to create the necessary symbolic links needed by servlets under tomcat? * Should there be a default CLASSPATH, similar to a repository? Which jars should be included in that? A standard and one optional part? If there are a default CLASSPATH (in the wrapper) how should it be overridden? * How to check for a good enough jvm, and to select a proper one to use. Are /etc/alternatives not good enough? * Should the jvm internal classes be possible to override entirely and how? _________________________________________________________ Chapter 4. Advices to Java packagers Warning: These are just advices, they are not part of the policy. * Be sure to manage all dependencies by hand in debian/control. Debian development tools cannot find them automatically like they do with C programs and libraries (or like dh_perl does it for Perl, a volunteer to write dh_java would be welcome). * You can suppress many calls in debian/rules which are meaningless for Java, like dh_strip and dh_shlibdeps. * Source package handling is painful, since most Java upstream programs come with .class files. I suggest to make a new .orig tarball after cleaning them, otherwise, dpkg-source will complain. * Java properties files are probably better under /etc and flagged as configuration files (this will be integrated in the policy, one day).