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(Troubleshooting JRE)
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= Java on Fedora =
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<div class="messagebox" style="float: right; margin-left: 10px;">__TOC__</div>
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Java is about:
 +
* Communities: the [https://www.jcp.org/ Java Comunity Process] to define the platform, but also [https://community.oracle.com/community/java/jug Java User Groups]
 +
* Platforms (JVM, JRE ...) to run applications on PC, mobiles, embedded devices https://en.wikipedia.org/wiki/Java_(software_platform)
 +
* Programming languages (Java is the most popular, but there are Scala, Groovy, Clojure ...) https://en.wikipedia.org/wiki/Java_(programming_language)
  
Fedora uses a Free software stack that consists of [http://en.wikipedia.org/wiki/Openjdk OpenJDK], GNU Compiler for Java, GNU classpath and the Eclipse Java compiler to implement Java. See our [[JavaFAQ]]  for more information on that.  Note that AOT compilation using GCJ has been deprecated (made optional) and new packages or updated ones will be built with OpenJDK in a regular Java compilation to bytecodes.
 
  
Software mentioned on this page may come in different packaging formats. Fedora's own packages (''RPM'') are easy to install (''with Yum'') and installation instructions can be found from [[Docs/Drafts/SoftwareManagementGuide]]. Third party packages may be in archive formats (.zip, tar) and then case specific instructions should be provided.
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What do you want to do:
 +
* If you came here because an '''application ask for Java''' (or JRE, JVM) '''to be installed''', then simply install {{package|java-1.8.0-openjdk}}.
 +
* If it still does not work:
 +
** Install javafx and icedtea-web packages as well.
 +
** Lastly, and if the application '''ask specifically for [http://www.oracle.com/technetwork/java/javase/index.html Oracle Java]''': See here [[#Oracle_version]].
 +
* If '''you want to develop, code, on the Java Platform''': See [[Java/Development]].  
  
= Java Runtime Environments (JRE) =
 
  
Java's history is well known to consist different JRE implementations and wide variety of combinations which work together. Different implementations can be installed simultaneously to Fedora and activated one at the time. Activation is done using the [[Alternatives]] system (''also used to change some other subsystems''). Java's subsystem name is surprisingly ''java'' and typical commands include:
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=== JRE JDK JVM JSE ... ===
<pre># alternatives --display java</pre>
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<pre># alternatives --config java</pre>
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Some vocabulary, if you are lost:
 +
 
 +
* '''JRE''' Java Runtime Environment. Required to run Java code and applications. Install {{package|java-1.8.0-openjdk}}.
 +
* '''JVM''' Java Virtual Machine. Main component of the JRE.
 +
* '''JDK''' Java Development Kit.  Required only for development, coding.
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* '''SDK''' Software Development Kit. idem JDK
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* '''JavaWS''' [https://en.wikipedia.org/wiki/Java_Web_Start Java Web Start] is a framework to start application from the Internet 
 +
* '''JavaFX''' [https://en.wikipedia.org/wiki/JavaFX JavaFX] is a plateform to create and deliver desktop and Rich Internet Apps.
 +
* '''OpenJFX''' is the JavaFX Open Source implementation
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* '''OpenJDK''' Open Source project behind the Java Platform http://openjdk.java.net/.
 +
* '''IcedTea''' is a support project for OpenJDK (concern only developers) http://icedtea.classpath.org/
 +
* '''IcedTea-Web''' is the Java Web Start package (It contains only JavaWS, No Applets anymore.) Install to run '''JNPL''' files.
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* '''Applets''' Obsolete techno. Not implemented in any recent package.
 +
* '''JSE''', '''J2SE''', '''JEE''' ... obsolete acronyms for '''J'''ava '''S'''tandard & '''E'''nterprise '''E'''dition.  ''JavaSE'' is like ''JRE''.
  
See alternative's own documentation for more information for usage and parts involved.
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=== What is in Java OpenJDK package ===
  
Should be noted that JRE implementations installed outside Fedora distribution, may not support alternatives and thus not be visible there. Then the symbolic links under directory ''/etc/alternatives'' must be manually fixed.
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For most users, it is just another system library. It is not an application with a GUI, but it is required by some other applications to run.
 +
You might see a ''OpenJDK Policy tool'' desktop application that comes with the package, but you should not have to use it.
  
== OpenJDK and project IcedTea ==
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Beware that JavaFX and JavaWS are packaged separately!
Fedora has shipped OpenJDK as default JRE implementation since Fedora release 9. It's based on Sun Microsystem's [http://en.wikipedia.org/wiki/JavaOne JavaOne] open source release and complemented by Red Hat's [http://en.wikipedia.org/wiki/IcedTea IcedTea] project that implements the missing third party components that Sun could not release under free License.
 
  
OpenJDK package name on Fedora is ''java-1.6.0-openjdk''.
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== Multiple implementations ==
  
== Sun Microsystems Java SE ==
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Fedora provides the Free {{package|java-1.8.0-openjdk}}. If this Open Source stack does not fulfil your requirements. Alternatives can be installed alongside or separately.
  
Original Sun Microsystem's Java SE (Standard Edition) can be downloaded directly from [http://www.java.com/en/download/ http://www.java.com/en/download/] and installed manually.
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The '''J'''ava '''C'''ommunity '''P'''rocess defines the specifications of the platform that many implements (IBM J9, Jikes, Zing, Zulu Dalvik ...). We will only focus on Oracle here.
  
== Troubleshooting JRE ==
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Multiple implementations can be installed side-by-side without interfering:
 +
* The [[alternatives system]] allows to switch from one to another.
 +
* An application can directly reference a specific Java installation
 +
* Some applications include a java platform, it is then transparent for the user. (But the package is bigger.)
  
Fedora's JRE in browser environment can be tested using the following test pages:
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=== Oracle version ===
* [http://www.java.com/en/download/help/testvm.xml http://www.java.com/en/download/help/testvm.xml]
 
* [http://java.com/en/download/installed.jsp?detect=jre&try=1 http://java.com/en/download/installed.jsp?detect=jre&try=1]
 
  
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Some applications still ask for Oracle's implementation.  It is mostly based on the OpenJDK Open Source project, but there is proprietary code and Fedora does not package non-free software.
  
'''Firefox''' detected plugin list can be seen by typing the url:
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Installing Oracle Java is fine. Just beware '''not''' to use Oracle '''RPM''', as it will kill OpenJDK default packages!
<pre>about:plugins</pre>
 
  
Firefox can be run in debug mode as follows:
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Oracle provides a tarball: https://java.com/en/download/help/linux_x64_install.xml
<pre>$ ICEDTEAPLUGIN_DEBUG=true firefox &lt;URL above&gt; 2>&1 | tee console.log
 
</pre>
 
This will write the standard output also to a file which can be attached to a bug reports.
 
  
OpenJDK does not ship the ''Java console'' anymore, but one can be found from Firefox [https://addons.mozilla.org/en-US/firefox/addon/60 Web Developer] add-on which is installed separately to the Firefox. Add-ons are installed using Firefox's own software component management system, not Fedora's RPM.
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We recommend to simply unpack the archives (tarball) to your home folder and set to path if necessary.
  
= Java Develoment Tools (SDK) =
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=== Switching alternatives ===
  
== Eclipse ==
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If you installed multiple Java implementations or version, you can configure your system to use one or another.
  
See our [[Eclipse]] page for an integrated development environment platform that itself is written in Java and has plugin support for many programming languages.
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'''Developers''': beware that javac has its own independent alternative. i.e. to change the JDK, use ''alternatives ... javac''!
  
== Maven ==
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Switching is done using the [[alternatives system]] (''also used to change some other subsystems''). Java's subsystem name is surprisingly ''java'' and typical commands include:
 +
<pre># alternatives --display java</pre>
 +
<pre># alternatives --config java</pre>
  
Fedora includes a somewhat customized version of Maven in the distribution. The customization is purely to make Maven work well in offline mode with the rest of the system. Details on how packagers can use this customized Maven are located at [[Java/JPPMavenReadme]] .  We are in the process of upgrading from maven2 2.0.4 to maven2 2.0.8 (ETA = F12).  Once that is achieved we will proceed immediately to maven2 2.0.9 and then to 2.0.10.  The reason for going by steps is that it is easier to bootstrap a maven2 release from the previous one.  Also related to maven2, a feasibility study is being performed to change the installation of Java packages to become a valid maven2 repository. We will no longer have to modify maven2 (not even with our small patch), and it wil be easier to support parallel installation of either "legacy" or "progressive" versions of Java packages.  Once some positive results are obtained, it will be discussed on the fedora-devel-java-list.
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See alternative's own documentation for more information for usage and parts involved.
  
 +
Should be noted that JRE implementations installed outside Fedora distribution, may not support alternatives and thus not be visible there. Then the symbolic links under directory ''/etc/alternatives'' must be manually fixed.
  
= Java Server Side Environments =  
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= Java packages in Fedora =
  
== Apache Tomcat ==
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There are many aliases for OpenJDK package, see http://pkgs.fedoraproject.org/cgit/rpms/java-1.8.0-openjdk.git/tree/java-1.8.0-openjdk.spec or do "dnf repoquery --provides java-1.8.0-openjdk".
Fedora ships [http://en.wikipedia.org/wiki/Apache_Tomcat Apache Tomcat] as part of standard distribution.
 
  
Apache Tomcat package name on Fedora is ''tomcat6''.
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You can use any of the following names:
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* java
 +
* java-1.8.0
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* java-1.8.0-openjdk
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* java-openjdk
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* jre
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* jre-1.8.0
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* jre-1.8.0-openjdk
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* jre-openjdk
  
  
= Teaching and Learning Java =
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<pre>dnf install java-1.8.0-openjdk</pre> might be the most safe (until 1.8 is EOL.)
  
As part of planning and implementing new 100% FLOSS Java components into Fedora, this draft document has been opened to give developers a place to teach each other about best practices, patterns, etc.
 
  
[[Docs/Drafts/JavaProgramming]]
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'''Note''' that Java Web Start ('''JavaWS''') and '''JavaFX''' are packaged separately 'icedtea-web' and 'javafx' respectively.
[[Category:Language-specific_SIGs]]
 
  
 +
Typically, without JavaFX, you may have error like:
 +
<pre>java -jar scram.jar   
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Error: Could not find or load main class com.frequal.scram.designer.jfx.Main</pre>
  
 +
<pre>dnf install icedtea-web javafx</pre>
  
 
= Communicate =
 
= Communicate =
  
You can subscribe to [https://www.redhat.com/mailman/listinfo/fedora-devel-java-list fedora-devel-java-list] or talk to us in [irc://irc.freenode.net/fedora-java #fedora-java] Freenode IRC channel. Read [[Communicate]]  page for more information.
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You can subscribe to [https://admin.fedoraproject.org/mailman/listinfo/java-devel java-devel list] or talk to us in [irc://irc.freenode.net/fedora-java #fedora-java] Freenode IRC channel. Read [[Communicate]]  page for more information.
  
 
= See Also =  
 
= See Also =  
* [[JavaFAQ]]
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* [[Java/FAQ]]
 +
* [[Java/Troubleshooting]]
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* [https://Ask.FedoraProject.org/en/questions/scope:all/sort:activity-desc/tags:java/page:1/ Ask Fedora about Java]
 +
 
 +
 
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* [https://bugzilla.redhat.com/buglist.cgi?component=java-1.8.0-openjdk&product=Fedora&bug_status=NEW&bug_status=ASSIGNED&bug_status=MODIFIED&bug_status=ON_DEV&bug_status=ON_QA&order=bugs.votes,bugs.bug_id Java-1.8.0-OpenJDK bugs]
 +
 
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* [[SIGs/Java]]
  
 
= References =
 
= References =
* [http://openjdk.java.net/ OpenJDK Home]
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* [http://openjdk.java.net/ OpenJDK Home]
* [https://bugzilla.redhat.com/buglist.cgi?component=java-1.6.0-openjdk&product=Fedora&bug_status=NEW&bug_status=ASSIGNED&bug_status=MODIFIED&bug_status=ON_DEV&bug_status=ON_QA Open openjdk-1.6.0 tickets for Fedora]
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* [https://wiki.openjdk.java.net/ OpenJDK Wiki]
* [https://bugs.openjdk.java.net/ OpenJDK Bug tracking system]
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* [http://jpackage.org/ Jpackage.org]
* [http://tomcat.apache.org/ Apache Tomcat]
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* [http://java-source.net/open-source/web-servers Java web servers]
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[[Category:Java]]
* [http://en.wikipedia.org/wiki/JBoss_application_server JBoss application server]
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[[Category:Language-specific_SIGs]]

Latest revision as of 19:05, 19 October 2017

Java is about:


What do you want to do:

  • If you came here because an application ask for Java (or JRE, JVM) to be installed, then simply install Package-x-generic-16.pngjava-1.8.0-openjdk.
  • If it still does not work:
    • Install javafx and icedtea-web packages as well.
    • Lastly, and if the application ask specifically for Oracle Java: See here #Oracle_version.
  • If you want to develop, code, on the Java Platform: See Java/Development.


JRE JDK JVM JSE ...

Some vocabulary, if you are lost:

  • JRE Java Runtime Environment. Required to run Java code and applications. Install Package-x-generic-16.pngjava-1.8.0-openjdk.
  • JVM Java Virtual Machine. Main component of the JRE.
  • JDK Java Development Kit. Required only for development, coding.
  • SDK Software Development Kit. idem JDK
  • JavaWS Java Web Start is a framework to start application from the Internet
  • JavaFX JavaFX is a plateform to create and deliver desktop and Rich Internet Apps.
  • OpenJFX is the JavaFX Open Source implementation
  • OpenJDK Open Source project behind the Java Platform http://openjdk.java.net/.
  • IcedTea is a support project for OpenJDK (concern only developers) http://icedtea.classpath.org/
  • IcedTea-Web is the Java Web Start package (It contains only JavaWS, No Applets anymore.) Install to run JNPL files.
  • Applets Obsolete techno. Not implemented in any recent package.
  • JSE, J2SE, JEE ... obsolete acronyms for Java Standard & Enterprise Edition. JavaSE is like JRE.

What is in Java OpenJDK package

For most users, it is just another system library. It is not an application with a GUI, but it is required by some other applications to run. You might see a OpenJDK Policy tool desktop application that comes with the package, but you should not have to use it.

Beware that JavaFX and JavaWS are packaged separately!

Multiple implementations

Fedora provides the Free Package-x-generic-16.pngjava-1.8.0-openjdk. If this Open Source stack does not fulfil your requirements. Alternatives can be installed alongside or separately.

The Java Community Process defines the specifications of the platform that many implements (IBM J9, Jikes, Zing, Zulu Dalvik ...). We will only focus on Oracle here.

Multiple implementations can be installed side-by-side without interfering:

  • The alternatives system allows to switch from one to another.
  • An application can directly reference a specific Java installation
  • Some applications include a java platform, it is then transparent for the user. (But the package is bigger.)

Oracle version

Some applications still ask for Oracle's implementation. It is mostly based on the OpenJDK Open Source project, but there is proprietary code and Fedora does not package non-free software.

Installing Oracle Java is fine. Just beware not to use Oracle RPM, as it will kill OpenJDK default packages!

Oracle provides a tarball: https://java.com/en/download/help/linux_x64_install.xml

We recommend to simply unpack the archives (tarball) to your home folder and set to path if necessary.

Switching alternatives

If you installed multiple Java implementations or version, you can configure your system to use one or another.

Developers: beware that javac has its own independent alternative. i.e. to change the JDK, use alternatives ... javac!

Switching is done using the alternatives system (also used to change some other subsystems). Java's subsystem name is surprisingly java and typical commands include:

# alternatives --display java
# alternatives --config java

See alternative's own documentation for more information for usage and parts involved.

Should be noted that JRE implementations installed outside Fedora distribution, may not support alternatives and thus not be visible there. Then the symbolic links under directory /etc/alternatives must be manually fixed.

Java packages in Fedora

There are many aliases for OpenJDK package, see http://pkgs.fedoraproject.org/cgit/rpms/java-1.8.0-openjdk.git/tree/java-1.8.0-openjdk.spec or do "dnf repoquery --provides java-1.8.0-openjdk".

You can use any of the following names:

  • java
  • java-1.8.0
  • java-1.8.0-openjdk
  • java-openjdk
  • jre
  • jre-1.8.0
  • jre-1.8.0-openjdk
  • jre-openjdk


dnf install java-1.8.0-openjdk
might be the most safe (until 1.8 is EOL.)


Note that Java Web Start (JavaWS) and JavaFX are packaged separately 'icedtea-web' and 'javafx' respectively.

Typically, without JavaFX, you may have error like:

java -jar scram.jar    
Error: Could not find or load main class com.frequal.scram.designer.jfx.Main
dnf install icedtea-web javafx

Communicate

You can subscribe to java-devel list or talk to us in #fedora-java Freenode IRC channel. Read Communicate page for more information.

See Also


References