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<title>Debian Java FAQ.</title>

<bookinfo>

<authorgroup>
<author><personname>Torsten Werner</personname><email>twerner@debian.org</email></author>
<author><personname>Niels Thykier</personname><email>niels@thykier.net</email></author>
<author><personname>Javier Fernández-Sanguino Peña</personname><email>jfs@debian.org</email></author>
<author><personname>Sylvestre Ledru</personname><email>sylvestre@debian.org</email></author>
<author><personname>Shirish Agarwal</personname><email>shirishag75@gmail.com</email></author>

</authorgroup>


<releaseinfo>Release: @@@debversion@@@</releaseinfo>
<pubdate>Date: @@@debdate@@@</pubdate>

<abstract>
<para>
Answers to Frequently Asked Questions on Debian and Java (Note: some
information is not up-to-date).  Any changes/corrections to this FAQ are
appreciated.  Please send them to the Debian Bug Tracking System as described
in <xref linkend="bugs"/>.
</para>
</abstract>

</bookinfo>


<chapter id="ch1"><title>Introduction</title>
<section id="s1.1"><title>Introduction to this FAQ</title>
<para>
This FAQ was started by Javier Fernández-Sanguino who on February 1st, 2000 was
enough to send a message to the debian-java mailing list with the subject "How
about a Debian-Java-FAQ?".  Of course, since "every idea is a responsibility"
he had to do this himself looking through the three month-long archive of the
newborn mailing list.
</para>
<para>
The purpose of this FAQ is to be a place to look for all kinds of questions a
developer or user might have regarding Java as far as Debian is concerned.  It
includes license issues, development packages available, and programs related
to building a Free Software Java environment.
</para>
<para>
Thanks go to all the (many) contributors from the debian-java mailing list, who
have made this document possible.  Without their knowledge this FAQ would not
be at all possible since I only have a vague knowledge of what they're talking
about when I browse the list.
</para>
<para>
Special thanks go to Paul Reavis, whose previous Debian-JDK informational page
I used to add more information, and who made useful suggestions to this
document.  Also to Peter Moulder who revised thoroughly the FAQ and provided
many suggestions, to Juergen Kreileder, maintainer of Blackdown's debian
packages who pointed out some mistakes, and to Egon Willighagen, who has
provided quite a lot of proper patches to update its content.
</para>
<para>
This document does not address issues with other Linux distributions, or with
non-Debian-specific problems.
</para>
</section>

<section id="s1.2"><title>Location of this FAQ</title>
<para>
This FAQ is published under the Debian Documentation Project at <ulink
url="https://www.debian.org/doc/manuals/debian-java-faq/">https://www.debian.org/doc/manuals/debian-java-faq/</ulink>.
The <systemitem role="package">java-policy</systemitem> (available at <ulink
url="https://packages.debian.org/java-policy">https://packages.debian.org/java-policy</ulink>)
provides an HTML version for offline reading.  The package version does not
provide Text and PDF versions currently (if you want them please submit a bug
'wishlist' to the package).  Also, the web version might be more up-to-date
than the package's offline version.
</para>
</section>

<section id="bugs"><title>Sending bugs on this FAQ</title>
<para>
Please note that this FAQ is still outdated but gets updated step by step.
</para>
<para>
Please file bug reports against the java-policy package if you find errors or
have suggestions on how to improve this document.  However, make sure you have
read the latest online version of the english text available at <ulink
url="https://www.debian.org/doc/manuals/debian-java-faq/index.html">https://www.debian.org/doc/manuals/debian-java-faq/index.html</ulink>
before filing a bug report.  Translations, if available, and the offline
version in the java-policy package might be out of date.
</para>
</section>

<section id="s1.4"><title>What is Java?</title>
<para>
Java is a programming language originally developed by James Gosling at Sun
Microsystems (which is now a subsidiary of Oracle Corporation) and released in
1995 as a core component of Sun Microsystems' Java platform.  Since May 2007,
Sun/Oracle with some partners like Red Hat provide a free implementation
released under the GNU GPL called OpenJDK.  More information can be found at
<ulink
url="https://en.wikipedia.org/wiki/Java_%28programming_language%29">Wikipedia</ulink>.
</para>
</section>

<section id="s1.5"><title>Where can I ask questions about Java on Debian?</title>
<para>
The appropriate place to ask such questions is <email>debian-java at
lists.debian.org</email>.  You can subscribe at the <ulink
url="https://lists.debian.org/debian-java/">Debian Mailing Lists</ulink> page.
</para>
</section>

<section id="moreinfo"><title>Complementary information</title>
<para>
Users might want to access some online sources to complement the information
available in this FAQ which might be, sometimes, too out of date.  The main
source of information is the <ulink url="https://wiki.debian.org/Java">Java
entry</ulink> at the Debian's wiki.
</para>
<para>
Since Ubuntu is based on Debian, some users might find it helpful to check the
tips on <ulink url="https://help.ubuntu.com/community/Java">Installing
Java</ulink> on Ubuntu's wiki.
</para>
</section>

<section id="pending"><title>Uncovered issues</title>
<para>
This FAQ does not describe some issues due to lack of time and/or information.
If you are able to help in any of these, please, provide them to the
documentation maintainer:
</para>
<itemizedlist>
<listitem>
<para>
Information on how to setup a fully working Servlet engine (Application Server)
using Apache and Tomcat or information on how to setup non-free application
servers (such as WebSphere) in Debian.
</para>
</listitem>
<listitem>
<para>
Specific information targeted for non-i386 users (PowerPC users and AMD64
users), some can be found in Ubuntu's wiki.
</para>
</listitem>
</itemizedlist>
</section>

</chapter>

<chapter id="ch2"><title>Java Development</title>
<section id="s2.1"><title>What full-fledged Java development platforms are available in Debian?</title>
<para>
If you are looking for an integrated, java virtual machine, compiler and
runtime environment Debian does provide them.  Of course that would depend on
the Debian GNU/Linux version you are using, generally speaking they would be:
</para>
<itemizedlist>
<listitem>
<para>
Sun's OpenJDK 7, available since the Debian 8.0 <emphasis>Jessie</emphasis>
release in the <emphasis>main</emphasis> section.
</para>
</listitem>
<listitem>
<para>
Oracle's OpenJDK 8, available since the Debian 9.0 <emphasis>Strech</emphasis>
release in the <emphasis>main</emphasis> section.
</para>
</listitem>
</itemizedlist>
<para>
It is recommended to install one of the default-jdk or default-jre meta
packages which installs the default version of OpenJDK for the current Debian version.
</para>
</section>

<section id="free"><title>What free platforms are there and how can I contribute?</title>
<para>
Please help one of the Free Java implementations if you want to use Java in
Debian.  There are a lot of projects that you can choose from:
</para>
<itemizedlist>
<listitem>
<para>
openjdk: <ulink url="https://openjdk.java.net/">https://openjdk.java.net/</ulink>
</para>
</listitem>
<listitem>
<para>
Mauve <ulink
url="https://sources.redhat.com/mauve/">https://sources.redhat.com/mauve/</ulink>
is a free suite to test if these tools are 'compliant'.
</para>
</listitem>
</itemizedlist>
</section>

<section id="license-concerns"><title>Questions on platforms and license concerns</title>
<section id="java6"><title>Java 7 and 8</title>
<para>
There are binary packages available for the Java 7 and Java 8 platforms since
the Debian 8.0 ('Jessie') release and Debian 9.0 ('Stretch') release.  Once
this is done and you have updated your package database.  You can either
install the Java development kit in Jessie:
</para>
<screen>
apt-get install openjdk-7-jdk
</screen>
<para>
or the Java runtime environment:
</para>
<screen>
apt-get install openjdk-7-jre
</screen>
<para>
Similarly, you can install the Java 8 development kit in Stretch:
</para>
<screen>
apt-get install openjdk-8-jdk
</screen>
<para>
or the Java 8 runtime environment:
</para>
<screen>
apt-get install openjdk-8-jre
</screen>
<para>
You might want to update the alternatives system to have Sun's tools as the
default:
</para>
<screen>
update-java-alternatives -s java-1.7.0-openjdk-amd64
</screen>
<para>
Or for java 8:
</para>
<screen>
update-java-alternatives -s java-1.8.0-openjdk-amd64
</screen>
</section>

<section id="openjdk"><title>Oracle proprietary JVM</title>
<para>
Since the version 7 of the OpenJDK, the proprietary JVM developments are done
on the OpenJDK.  That means that the OpenJDK is strongly tested and high
quality.
</para>
<para>
However, some users might want to use the Oracle JVM for the proprietary
extensions (for example: the browser plugin).  For such need, Debian provides a
tool called <ulink
url="https://packages.debian.org/sid/java-package">java-package</ulink>.  The
program make-jpkg will take an upstream archive and convert it to a Debian
package.  For example:
</para>
<screen>
    make-jpkg jdk-6u31-linux-x64.bin
</screen>
<para>
For more information see <ulink
url="https://www.oracle.com/technetwork/java/index.html">Oracle Technology
Network Java</ulink>.
</para>
</section>

</section>

<section id="s2.4"><title>Making Debian packages for Java programs.</title>
<section id="s2.4.1"><title>Can the package go into main?</title>
<para>
Yes, <emphasis>but only if</emphasis> it can be build and run with Java
programs/tools in main, and if it has a Debian compliant open source license.
If it needs programs from contrib or non-free, then is
<emphasis>must</emphasis> go into contrib or non-free, depending on the license
of the program itself.
</para>
</section>

<section id="s2.4.2"><title>Is there a good example Debian package?</title>
<para>
There are many Debian packages of both Java applications and libraries.  These
may serve as an good starting point, as it can serve as an example for making a
new Debian package.
</para>
<para>
A good start would be to check out the pkg-java project on Salsa: <ulink
url="https://salsa.debian.org/java-team/">https://salsa.debian.org/java-team/</ulink>.
</para>
<para>
Note that there are many ways to make a Debian package, making use of Ant or
Makefiles does not really matter.  But, some tips for good practice are given
on the Debian Java packaging page: <ulink
url="https://java.debian.net/">https://java.debian.net/</ulink>.
</para>
</section>

<section id="s2.4.3"><title>What tools are available to make maintaining a Java packages easier?</title>
<para>
Both cdbs and debhelper (dh9) have support for ant scripts.  There are also a
number of specialized tools or build helpers.  Have a look at <systemitem
role="package">javahelper</systemitem> or <systemitem
role="package">maven-debian-helper</systemitem>.
</para>
</section>

<section id="s2.4.4"><title>Linking package Javadoc to system javadoc.</title>
<para>
The java-policy mandates that documentation must be linked with the javadoc
installed on the system.  This can be done by passing javadoc the "-link"
argument or by using the &lt;link&gt; tag in ant.  An example:
</para>
<screen>
# command line example of linking against system doc.
javadoc -link /usr/share/doc/default-jdk-doc/api [other arguments]

&lt;!-- Ant example of linking against system doc --&gt;
&lt;javadoc [attributes]&gt;
    &lt;link href="/usr/share/doc/default-jdk-doc/api/" /&gt;
    [other tags]
&lt;/javadoc&gt;
</screen>
<para>
The documentation must be installed at the time the linking is done; so in the
example cases above the package would need a Build-Depends or a
Build-Depends-Indep on <systemitem role="package">default-jdk-doc</systemitem>.
</para>
<para>
Here is a short list of packages that can be used for reference:
</para>
<itemizedlist>
<listitem>
<para>
<systemitem role="package">libcommons-jci-java</systemitem>
</para>
</listitem>
<listitem>
<para>
<systemitem role="package">libhamcrest-java</systemitem>
</para>
</listitem>
</itemizedlist>
</section>

</section>

</chapter>

<chapter id="ch3"><title>Managing Java (for users and administrators)</title>
<para>
By default Java programs shipped with Debian will use the java in PATH.  Some
of them may respect the JAVA_HOME variable (usually only if upstream supports
this) or have command line arguments to select a different java implementation.
</para>
<para>
Unfortunately not all java implementations work as well as others.  So some
times it may be necessary to change the current java and Debian provides an
easy way to change the default java in PATH by using update-java-alternatives
(from the <systemitem role="package">java-common</systemitem>).  Some examples
of how to do this are:
</para>
<screen>
# List available java implementations
$ sudo update-java-alternatives --list
# Use openjdk-7
$ sudo update-java-alternatives --set java-7-openjdk
</screen>
<para>
For more information, please read the manpage (or the --help output) of
update-java-alternatives.  Also please note that update-java-alternatives is a
frontend for update-alternatives.
</para>
</chapter>

<chapter id="ch4"><title>Java Virtual Machines (JVM)</title>
<section id="s4.1"><title>What JVMs are available in Debian?</title>
<para>
The following JVMs are currently available in Debian Jessie:
</para>
<itemizedlist>
<listitem>
<para>
<systemitem role="package">openjdk-7-jre</systemitem>
</para>
</listitem>
</itemizedlist>
<para>
The following lists JVMs available in Debian 9.0 release ('Stretch'):
</para>
<itemizedlist>
<listitem>
<para>
<systemitem role="package">openjdk-8-jre</systemitem>
</para>
</listitem>
</itemizedlist>
</section>

<section id="s4.2"><title>What Java Compilers are available in Debian?</title>
<itemizedlist>
<listitem>
<para>
<systemitem role="package">openjdk-7-jdk</systemitem>
</para>
</listitem>
<listitem>
<para>
<systemitem role="package">openjdk-8-jdk</systemitem>
</para>
</listitem>
</itemizedlist>
<para>
Compiles Java source to native code, also source to bytecode, or bytecode to
native code.  Please note that the support of the Java language is not
completed.
</para>
</section>

<section id="s4.3"><title>What API do these JVMs provide?</title>
<para>
Note that providing an API does not mean that everything is implemented, and
certainly not implemented correctly.
</para>
</section>

<section id="s4.4"><title>Are there known problems?</title>
<para>
Yes, there are.  Some of these are reported as Debian bugs.  You can look up
the bugs for a specific Debian package at the <ulink
url="https://www.debian.org/Bugs/">Debian Bug Tracking System</ulink>.  As a
quick link, here are some packages:
</para>
<itemizedlist>
<listitem>
<para>
<ulink url="https://bugs.debian.org/java-common">java-common</ulink>
</para>
</listitem>
<listitem>
<para>
<ulink url="https://bugs.debian.org/src:openjdk-7">openjdk-7</ulink>
</para>
</listitem>
<listitem>
<para>
<ulink url="https://bugs.debian.org/src:openjdk-8">openjdk-8</ulink>
</para>
</listitem>
</itemizedlist>
<para>
As common within the Debian project, the developers would appreciate good bug
reports on found problems.  These include the good description of the problem,
the command that gives the problem, the errors given when running the command,
and any other information that might be relevant.  A good tool to report bugs
is <systemitem role="package">reportbug</systemitem>.
</para>
</section>

<section id="s4.5"><title>How can I use the proprietary version of the JDK/JRE from Oracle as a Debian package?</title>
<para>
The package <ulink
url="https://packages.debian.org/wheezy/java-package/">java-package</ulink>
provides an easy way to convert an upstream installer into a Debian package.
It should be as easy as:
</para>
<screen>
make-jpkg ~/Downloads/jdk-6u31-linux-x64.bin
</screen>
<para>
For more information, see this <ulink
url="https://sylvestre.ledru.info/blog/2012/02/29/java_package_replacement_of_sun_java6">Blog
article</ulink>
</para>
</section>

<section id="s4.6"><title>Do I need a JVM to run a Java program in Debian?</title>
<para>
No, you can try to run the applications without a jvm by compiling the source
code to native code is.  However, the usage of the OpenJDK is recommended.
</para>
</section>

</chapter>

<chapter id="browser-java"><title>Java Plugins for Browsers</title>
<itemizedlist>
<listitem>
<para>
You can install the package icedtea-7-plugin or icedtea-8-plugin in
<emphasis>jessie</emphasis>
</para>
</listitem>
</itemizedlist>
</chapter>

<chapter id="ch6"><title>Java Servlets</title>
<section id="s6.1"><title>How can I make Java servlets work?</title>
<para>
You can use:
</para>
<itemizedlist>
<listitem>
<para>
Apache <systemitem role="package">tomcat7</systemitem> from <ulink
url="https://tomcat.apache.org">https://tomcat.apache.org</ulink>.
</para>
</listitem>
<listitem>
<para>
Eclipse <systemitem role="package">jetty</systemitem> from <ulink
url="https://www.eclipse.org/jetty/">https://www.eclipse.org/jetty/</ulink>.
</para>
</listitem>
</itemizedlist>
</section>

</chapter>

<chapter id="ch7"><title>Java Policy</title>
<section id="s7.1"><title>Is there a Java policy for Debian?</title>
<para>
It is still in the works.  The current policy addresses
<emphasis>some</emphasis> of the problems.  It has not been officially
released.  You can find it at <ulink
url="https://www.debian.org/doc/packaging-manuals/java-policy/">https://www.debian.org/doc/packaging-manuals/java-policy/</ulink>.
The Java Policy can also be found in the <systemitem
role="package">java-policy</systemitem> package.
</para>
</section>

<section id="s7.2"><title>Are there holes in the Java Policy?</title>
<para>
Yes, some until under discussion.  Please check out the <ulink
url="https://bugs.debian.org/java-policy">bugs against the java-policy
package</ulink>.  Thus it is <emphasis>very</emphasis> inconvenient to use
several compilers of virtual machines since there is not one CLASSPATH setting
for all of them.
</para>
</section>

</chapter>

<chapter id="ch8"><title>Other Java alternatives for Debian</title>
<para>
If the Java packages provided in Debian are not sufficient for your needs you
might need to take a look at other alternatives.  Please understand that these
alternatives are not supported by the Debian project directly, you might get
help, however, from the debian-java mailing list if you encounter issues with
them.
</para>
<para>
Some of the alternatives presented use Debian packages which is convenient,
since the user/administrator does not need to care on installation issues.
However, mixing packages that come from a source which is not the Debian
project might cause conflicts with your installation some times.  Of course,
Debian tries to integrate as many free software efforts as possible, so some of
the alternatives described below might (if license permits) be included in
Debian in the near future.
</para>
<section id="s8.1"><title>Java programs not yet available on Debian</title>
<para>
The following are programs that have not yet been packaged for Debian nor is
there an installer.  There are quite a lot Java programs out there.
</para>
<para>
A list of missing packages is maintained on the <ulink
url="https://wiki.debian.org/Java/RequestedPackages">Debian Wiki - Java
Packaging Wishlist</ulink>.
</para>
</section>

</chapter>


</book>