User:Abo/JavaPackagingDraftUpdate

(This is a draft update to Packaging:Java.)

These guidelines are laid out in order of relevance to packaging.

Introduction

Background

Traditionally, Java implementations have been available under a non-free license. Free software clean room implementations of the class library largely centred around GNU Classpath. GCJ, a Java frontend for GCC, allowed for native compilation of Java software. In 2007, Sun released its reference implementation of Java under the GPL+Classpath exception as OpenJDK. This included the bytecode interpreter, just-in-time (JIT) compiler (Hotspot), and the majority of its class library. Due to the remaining small proprietary encumbrances, a project known as IcedTea was formed to build OpenJDK with entirely free tools, and provides Free software plugs for the encumbered pieces of the class libraries. Since 2008 this has enabled Fedora to ship a package under the OpenJDK name.

The Basics

The term Java means many things to many people: a class library, a bytecode interpreter, a JIT compiler, a language specification, etc. For the vast majority of users and developers, Java is a programming language and runtime environment that is architecture- and OS-agnostic. The normal flow of code is .java (source file) .class (Java bytecode) .jar (a zip archive). In the majority of cases, a user executes a Java program by specifying a class name containing a main method (just like C and C++). Often, this is done by invoking the java binary with a list of JAR files specifying the classpath like so:

java [-cp <jar1:jar2:jar3>] <main-class> [<args>]

Java Packaging

The JPackage Project has defined standard file system locations and conventions for use in Java packages. Many distributions have inherited these conventions and in the vast majority of cases, Fedora follows them verbatim. We include relevant sections of the JPackage guidelines here but caution that the canonical document will always reside upstream: JPackage Guidelines . Over time, we would like to remove any divergences in these documents, but where they are different, these Fedora guidelines will take precedence for Fedora packages.

Package naming

Packages MUST follow the standard Fedora Packaging/NamingGuidelines.

Java API documentation MUST be placed into a sub-package called %{name}-javadoc.

Release tags

Packages may declare release tags as defined by Packaging/JPackagePolicy. That document should eventually be folded into this one.

JAR file installation

The following applies to all JAR files except JNI-using JAR files, GCJ files and application-specific JAR files (ie. JAR files that can only reasonably be used as part of an application and therefore constitute application-private data).

Split JAR files

If a project offers the choice of packaging it as a single monolithic jar or several ones, the split packaging should be preferred.

Filenames

If the package provides a single JAR and the filename provided by the build is %{name}.jar then this name MUST be used.

If the package provides a single JAR and the filename provided by the build is %{name}-%{version}.jar then this name MUST be used and a symbolic link %{name}.jar pointing to this file MUST be installed.

If the package provides a single JAR and the filename provided by the build is neither %{name}-%{version}.jar nor %{name}.jar then this file MUST be installed as %{name}.jar and a symbolic link with the usual name must be provided.

If the package provides more than one JAR file, the filenames assigned by the build must be used.

If the project usually provides alternative JAR file names by installing symbolic links then such symlinks may be installed in the same directory as the JAR files.

Installation directory

All JAR files MUST go into %{_javadir} or a Java-version specific directory %{_javadir}-* as appropriate[1].

If the number of provided JAR files exceeds two, you must place them into a sub-directory named %{name}.

Javadoc installation

Java API documentation uses a system known as javadoc. All javadocs MUST be installed into a subdirectory of %{_javadocdir}. The name of the subdirectory MUST be either %{name} or %{name}-%{version} with a symlink %{name} pointing to it.

The javadoc subpackage MAY be declared noarch.

BuildRequires and Requires

At a minimum, Java packages MUST:

BuildRequires: java-devel [>= specific_version] 
BuildRequires: jpackage-utils

Requires: java >= specific_version
Requires: jpackage-utils

For historical reasons, when specifying versions 1.6.0 or greater, an epoch of 1 must be included. Example:

Requires: java >= 1:1.6.0

build-classpath

build-classpath is a script that can be used to generate classpaths from generic names of JAR files. Example:

export CLASSPATH=$(build-classpath commons-logging commons-net)

build-jar-repository

build-jar-repository is similar to build-classpath but instead of producing a classpath entry, it creates symlinks in a given directory. Example:

$ mkdir lib
$ build-jar-repository -s -p lib commons-logging commons-net
$ ls -l lib
commons-logging.jar -> /usr/share/java/commons-logging.jar
commons-net.jar -> /usr/share/java/commons-net.jar

ant

ant is a build tool used by many Java packages. Packages built using ant ship with build.xml files which contain build targets similar to Makefiles. Packages built using ant must:

BuildRequires: ant
...
%build
...
ant

maven

maven is a tool used by many Java packages. In Fedora, the package is called maven2. Packages built using maven ship with pom.xml files. They MUST:

Requires(post): jpackage-utils
Requires(postun): jpackage-utils

and SHOULD contain common sections such as the following:

...
%build
export MAVEN_REPO_LOCAL=$(pwd)/.m2/repository
mkdir -p $MAVEN_REPO_LOCAL

mvn-jpp \
-Dmaven.repo.local=$MAVEN_REPO_LOCAL \
install javadoc:javadoc
...
%install
rm -rf $RPM_BUILD_ROOT
install -d -m 755 $RPM_BUILD_ROOT%{_javadir}
install -d -m 755 $RPM_BUILD_ROOT%{_datadir}/maven2/poms
install -pm 644 pom.xml $RPM_BUILD_ROOT/%{_datadir}/maven2/poms/JPP-maven-archiver.pom
%add_to_maven_depmap org.apache.maven maven-archiver %{version} JPP maven-archiver
...
%post
%update_maven_depmap

%postun
%update_maven_depmap
...

Wrapper Scripts

Applications wishing to provide a convenient method of execution SHOULD provide a wrapper script in %{_bindir}. These can be as simple as this example:

#!/bin/bash
. /usr/share/java-utils/java-functions

MAIN_CLASS=MyCoolApp

set_classpath "mycoolapp"

run "$@"

GCJ

Please refer to Packaging/GCJGuidelines for GCJ-specific guidelines.

-devel packages

-devel packages don't really make sense for Java packages. Header files do not exist for Java packages.

Specfile Templates

ant

Name:             # see normal package guidelines
Version:          # see normal package guidelines
Release:          1%{?dist}
Summary:          # see normal package guidelines
Group:            # see normal package guidelines
License:          # see normal package guidelines
URL:              # see normal package guidelines
Source0:          # see normal package guidelines
BuildRoot:        %{_tmppath}/%{name}-%{version}-%{release}-root-%(%{__id_u} -n)

BuildRequires:    java-devel # Optionally: >= 1:1.6.0
Requires:         java >= 1:1.6.0

BuildRequires:    jpackage-utils
Requires:         jpackage-utils

BuildRequires:    ant


%description

%package javadoc
Summary:          Javadocs for %{name}
Group:            Documentation
Requires:         jpackage-utils
BuildArch:        noarch

%description javadoc
This package contains the API documentation for %{name}.

%package manual
Summary:          Manual for %{name}
Group:            Documentation
Requires:         jpackage-utils

%description manual
The manual for %{name}.

%prep
%setup -q


find -name '*.class' -exec rm -f '{}' \;
find -name '*.jar' -exec rm -f '{}' \;



%build
ant

%install
rm -rf $RPM_BUILD_ROOT

mkdir -p $RPM_BUILD_ROOT%{_javadir}
cp -p [build path to jar]   \
$RPM_BUILD_ROOT%{_javadir}/%{name}-%{version}.jar
ln -s %{name}-%{version}.jar \
$RPM_BUILD_ROOT%{_javadir}/%{name}.jar



mkdir -p $RPM_BUILD_ROOT%{_javadocdir}/%{name}
cp -rp [javadoc directory]  \
$RPM_BUILD_ROOT%{_javadocdir}/%{name}

%clean
rm -rf $RPM_BUILD_ROOT

%files
%defattr(-,root,root,-)
%{_javadir}/*
%doc

%files javadoc
%defattr(-,root,root,-)
%{_javadocdir}/%{name}

%files manual
%defattr(-,root,root,-)
%doc [manual directory]/*

%changelog

maven

Name:             # see normal package guidelines
Version:          # see normal package guidelines
Release:          1%{?dist}
Summary:          # see normal package guidelines
Group:            # see normal package guidelines
License:          # see normal package guidelines
URL:              # see normal package guidelines
Source0:          # see normal package guidelines
BuildRoot:        %{_tmppath}/%{name}-%{version}-%{release}-root-%(%{__id_u} -n)

BuildRequires:    java-devel # Optionally: >= 1:1.6.0
Requires:         java >= 1:1.6.0

BuildRequires:    jpackage-utils
Requires:         jpackage-utils

Requires(post):   jpackage-utils
Requires(postun): jpackage-utils

BuildRequires:    maven2

BuildRequires:    maven2-plugin-compiler
BuildRequires:    maven2-plugin-install
BuildRequires:    maven2-plugin-jar
BuildRequires:    maven2-plugin-javadoc
BuildRequires:    maven2-plugin-release
BuildRequires:    maven2-plugin-resources
BuildRequires:    maven2-plugin-surefire

%description

%package javadoc
Summary:          Javadocs for %{name}
Group:            Documentation
Requires:         jpackage-utils
BuildArch:        noarch

%description javadoc
This package contains the API documentation for %{name}.

%package manual
Summary:          Manual for %{name}
Group:            Documentation
Requires:         jpackage-utils

%description manual
The manual for %{name}.

%prep
%setup -q

%build

export MAVEN_REPO_LOCAL=$(pwd)/.m2/repository
mkdir -p $MAVEN_REPO_LOCAL

mvn-jpp \
-Dmaven.repo.local=$MAVEN_REPO_LOCAL \
install javadoc:javadoc

%install
rm -rf $RPM_BUILD_ROOT

mkdir -p $RPM_BUILD_ROOT%{_javadir}
cp -p [build path to jar]   \
$RPM_BUILD_ROOT%{_javadir}/%{name}-%{version}.jar
ln -s %{name}-%{version}.jar \
$RPM_BUILD_ROOT%{_javadir}/%{name}.jar


mkdir -p $RPM_BUILD_ROOT%{_javadocdir}/%{name}
cp -rp [javadoc directory]  \
$RPM_BUILD_ROOT%{_javadocdir}/%{name}

install -d -m 755 $RPM_BUILD_ROOT%{_datadir}/maven2/poms
install -pm 644 [path to pom]  \
$RPM_BUILD_ROOT%{_datadir}/maven2/poms/JPP-%{name}.pom

# artifactId and jarName are usually %{name}
%add_to_maven_depmap [groupId] [artifactId] %{version} JPP[/optional_subDir] [jarName]

%clean
rm -rf $RPM_BUILD_ROOT

%post
%update_maven_depmap

%postun
%update_maven_depmap

%files
%defattr(-,root,root,-)
%{mavenpomdir}/*
%{_mavendepmapfragdir}
%{_javadir}/*
%doc

%files javadoc
%defattr(-,root,root,-)
%{_javadocdir}/%{name}

%files manual
%defattr(-,root,root,-)
%doc [manual directory]/*

%changelog

For detailed instructions on the JPackage/Fedora maven, see Java/JPPMavenReadme.

Packaging JAR files that use JNI

Applicability

Java programs that wish to make calls into native libraries do so via the Java Native Interface (JNI) by calling the Java method System.loadLibrary or System.load to load a .so file into the Java runtime environment. If a Java package contains a .so file then it is most likely either a JNI .so file (in which case the JNI guidelines apply) or a GCJ .so file (see below).

Guideline

JAR files that require JNI shared objects MUST be installed in %{_libdir}/%{name}, with the usual filenames and optionally symlinks as provided by the build. The JNI shared objects themselves MUST also be installed in %{_libdir}/%{name}. If the JNI-using code calls System.loadLibrary it must be patched to use System.load, passing it the full path to the dynamic shared object.

If the package installs a wrapper script then the script will need to add %{_libdir}/%{name}/jar filename to CLASSPATH. Likewise, the build-classpath script will not find JAR files that uses JNI, so they need to be added manually.

Rationale

A JNI-using JAR file that was placed in %{_javadir} would be loaded even if the Java runtime environment's architecture didn't match the architecture of the corresponding JNI shared object, in which case the System.loadLibrary call would fail.

The shared object is dlopen'd specifically by the corresponding Java archive and is not meant to be loaded any other way. Thus is should not be packaged among the shared libraries in %{_libdir}.

Thus, though less convenient, it's cleaner from a packaging point-of-view to put the JAR and shared object in an arch- and library-specific directory.

The plan is to eventually eliminate patching of the System.loadLibrary line and wrapper script by making jpackage-utils multilib aware. This involves the following changes: creating %{_libdir}/java (AKA %{_jnidir}) and %{_libdir}/jni directories; giving JNI-containing packages the ability to require an architecture-specific runtime environment; adding support for specifying the required runtime architecture in a wrapper script; modifying jpackage-utils's runtime scripts to search %{_libdir}/java; modifying IcedTea to look for JNI shared objects in %{_libdir}/jni.

Things to avoid

Pre-built JAR files / Other bundled software

Many Java projects re-ship their dependencies in their own releases. This is unacceptable in Fedora. Any prebuilt binaries (.jar and .class files) MUST either be removed from the source tree in %prep or a modified source archive with the offending files remove be provided, in accordance with Packaging:Guidelines#No_inclusion_of_pre-built_binaries_or_libraries and Packaging:SourceURL. There may arise rare cases that an upstream project is distributing JAR files that are actually not re-distributable by Fedora. In this situation, a modified source archive MUST be created and used as described above.

All packages MUST be built from source and MUST enumerate their dependencies with Requires. They MUST NOT build against or re-ship the pre-included JAR files but instead use the JAR files provided by dependencies.

It is a good idea to have something similar to the following at the end of %prep:

if find -name '*.class' -o -name '*.jar' | grep . >&2; then
 echo >&2 "Prebuilt binaries found in the sources. See https://fedoraproject.org/wiki/Packaging:Java#Pre-built_JAR_files_.2F_Other_bundled_software for instructions."
 exit 1
fi

Javadoc scriptlets

Older JPackage packages contained %post scriptlets creating %ghost symlinks. These MUST not appear in Fedora Java packages and are actively being removed at JPackage.

Selected rpmlint issues

class-path-in-manifest

Use sed to remove class-path elements in MANIFEST.MF (or whatever file is being used as the JAR manifest) prior to JAR creation. Example:

sed -i '/class-path/I d' META-INF/MANIFEST.MF