Java: Difference between revisions

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== JDK options ==

Your default choice should probably be to install <code>jdk</code>, which is an alias the latest LTS. If you're in a server environment, go for <code>jdk21_headless</code>. Java 21 is the currently-maintained LTS version of OpenJDK as of April 2024.

Your default choice should probably be to install <code>jdk</code>, which is an alias to the latest [https://en.wikipedia.org/wiki/Long-term_support LTS]. If you're in a server environment, go for <code>jdk21_headless</code>. Java 21 is the currently-maintained LTS version of OpenJDK as of April 2024.

As you might expect, though, many flavors of Java are available in NixOS.

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* JetBrains JDK (<code>jetbrains.jdk</code>), a fork of OpenJDK with modifications made by JetBrains

* Oracle's JDK (<code>oraclejdk</code>), only version 8 is available.

== VSCode + Language Support for Java (TM) by Red Hat extension ==

Unfortunately the extension contains and uses a version of the JRE which makes use of dynamically loaded libraries, which nix cannot accomodate out-of-the-box. Fortunately there's a simple solution in the use of [https://github.com/Mic92/nix-ld nix-ld]. Here's a simple <code>flake.nix</code> snippet to get you started (I'll focus on the <code>devShell</code> part for brevity):

# flake.nix

devShell = pkgs.mkShell {

buildInputs = [

pkgs.gradle

pkgs.jdk17

];

NIX_LD_LIBRARY_PATH = pkgs.lib.makeLibraryPath [

pkgs.stdenv.cc.cc

pkgs.openssl

];

NIX_LD = pkgs.lib.fileContents "${pkgs.stdenv.cc}/nix-support/dynamic-linker";

# ^--- when using direnv, this line will require the 'use flake --impure' option.

};

</syntaxhighlight>

The important lines above are the two starting with <code>NIX_LD...</code>. They will let nix-ld wrap the required, dynamically loaded libraries so that they are found when building the <code>devShell</code>.

Another solution is to use the <code>[https://github.com/redhat-developer/vscode-java?tab=readme-ov-file#supported-vs-code-settings java.jdt.ls.java.home]</code> VSCode setting to point to a nix-built Java 17. For example, using home-manager's settings: <syntaxhighlight lang="nix">

programs.vscode.enable = true;

programs.vscode.extensions = [ pkgs.vscode-extensions.redhat.java ];

programs.vscode.userSettings = {

"java.jdt.ls.java.home" = "${pkgs.jdk17}";

};

</syntaxhighlight>Note that this will still result in the extension downloading its own JRE, it just will not be used.

== Using Oracle JDK instead of Open JDK ==

Almost all Java packages in nixpkgs use Open JDK in form of a '''jre''' dependency. If you use Oracle JDK and also want other applications to use it, you can simply tweak your <code>.nixpkgs/config.nix</code> so that your desired application uses Oracles JDK or JRE.

Almost all Java packages in nixpkgs use Open JDK in form of a '''jre''' dependency. If you use Oracle JDK and also want other applications to use it, you can simply tweak your <code>nixpkgs/config.nix</code> so that your desired application uses Oracles JDK or JRE.

Example with UMLet with JRE

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To install the Oracle JRE system-wide, you need to explicitly accept the license in addition to allowing unfree modules:

# /etc/nixos/configuration.nix

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</syntaxhighlight>

Working with `requireFile` (manual downloading the tarballs and manual adding in to the nix store) might be annoying and nixops-unfriendly, so it can be overridden in overlays

Working with <code>requireFile</code> (manual downloading the tarballs and manual adding in to the nix store) might be annoying and nixops-unfriendly, so it can be overridden in overlays

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== Better font rendering==

By default java does not enable ~~antialiasing~~ for font rendering. By exporting environment variables, this can be fixed:

By default java does not enable anti-aliasing for font rendering. By exporting environment variables, this can be fixed:

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== Overriding java jks Certificate Store ==

Overriding the java certificate store may be required for adding your own Root certificates in case your company uses an internal PKI or the company utilizes an intercepting proxy.

=== jdk8 ===

Overriding the jdk8 certificate store is possible by overriding the '''cacert''' parameter of the package:

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=== jdk11 ===

JDK11 does not provide the cacert overridable and therefore it is not possible to use the same technique to override the truststore.

As an alternative solution you can either set an environment variable, <code>JAVAX_NET_SSL_TRUSTSTORE</code>, or pass an argument to your program, <code>-Djavax.net.ssl.trustStore</code>, with the location of your cacert. See [https://discourse.nixos.org/t/custom-ssl-certificates-for-jdk/18297/9 discussion].

== Building and Packaging ==

~~see~~ the [https://~~ryantm~~.~~github.io~~/nixpkgs/~~languages~~-~~frameworks/~~java/ Java section in the Nixpkgs manual]

See the [https://nixos.org/manual/nixpkgs/#sec-language-java Java section in the Nixpkgs manual].

=== Maven ===

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<pre>mvn verify</pre>

[https://github.com/fzakaria/mvn2nix mvn2nix] ~~and~~ [https://~~github~~.~~com~~/~~NixOS~~/nixpkgs/~~blob~~/~~master/pkgs/build~~-~~support/build-maven.nix buildMaven~~] can be used to build Maven projects with Nix

[https://github.com/fzakaria/mvn2nix mvn2nix], [https://nixos.org/manual/nixpkgs/stable/#maven-buildmavenpackage buildMavenPackage] (recommended) can be used to build Maven projects with Nix

See also: [https://fzakaria.com/2020/07/20/packaging-a-maven-application-with-nix.html Packaging a Maven application with Nix]

See also: [https://fzakaria.com/2020/07/20/packaging-a-maven-application-with-nix.html Packaging a Maven application with Nix] and [https://github.com/NixOS/nixpkgs/blob/master/pkgs/by-name/ma/maven/build-maven-package.nix buildMavenPackage source]

=== Ant ===

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To fetch ivy sources in a fixed-output-derivation, see for example [https://github.com/milahu/nur-packages/blob/master/pkgs/yacy/yacy.nix yacy.nix]

~~[[Category~~:~~Applications]]~~

== JavaFX and Webkit support ==

To include support for JavaFX and Webkit, use the <code>enableJavaFX</code> and <code>withWebKit</code> options:

{ pkgs, ... }:

let

jdkWithFX = pkgs.openjdk.override {

enableJavaFX = true; # for JavaFX

# include following line if JavaFX with Webkit is needed

openjfx_jdk = pkgs.openjfx.override { withWebKit = true; };

};

in

...

</syntaxHighlight>

== Further reading ==

{{Nixpkgs manual|sec-language-java}} {{Wikipedia|Java_(programming_language)}}

[[Category:Languages]]

@@ Line 9: / Line 9: @@
 == JDK options ==
-Your default choice should probably be to install <code>jdk</code>, which is an alias the latest LTS. If you're in a server environment, go for <code>jdk21_headless</code>. Java 21 is the currently-maintained LTS version of OpenJDK as of April 2024.
+Your default choice should probably be to install <code>jdk</code>, which is an alias to the latest [https://en.wikipedia.org/wiki/Long-term_support LTS]. If you're in a server environment, go for <code>jdk21_headless</code>. Java 21 is the currently-maintained LTS version of OpenJDK as of April 2024.
 As you might expect, though, many flavors of Java are available in NixOS.
@@ Line 22: / Line 22: @@
 * JetBrains JDK (<code>jetbrains.jdk</code>), a fork of OpenJDK with modifications made by JetBrains
 * Oracle's JDK (<code>oraclejdk</code>), only version 8 is available.
+== VSCode + Language Support for Java (TM) by Red Hat extension ==
+Unfortunately the extension contains and uses a version of the JRE which makes use of dynamically loaded libraries, which nix cannot accomodate out-of-the-box. Fortunately there's a simple solution in the use of [https://github.com/Mic92/nix-ld nix-ld]. Here's a simple <code>flake.nix</code> snippet to get you started (I'll focus on the <code>devShell</code> part for brevity):
+<syntaxhighlight lang="nix" line highlight="6,10" copy>
+# flake.nix
+devShell = pkgs.mkShell {
+  buildInputs = [
+    pkgs.gradle
+    pkgs.jdk17
+  ];
+  NIX_LD_LIBRARY_PATH = pkgs.lib.makeLibraryPath [
+    pkgs.stdenv.cc.cc
+    pkgs.openssl
+  ];
+  NIX_LD = pkgs.lib.fileContents "${pkgs.stdenv.cc}/nix-support/dynamic-linker";
+  # ^--- when using direnv, this line will require the 'use flake --impure' option.
+};
+</syntaxhighlight>
+The important lines above are the two starting with <code>NIX_LD...</code>. They will let nix-ld wrap the required, dynamically loaded libraries so that they are found when building the <code>devShell</code>.
+Another solution is to use the <code>[https://github.com/redhat-developer/vscode-java?tab=readme-ov-file#supported-vs-code-settings java.jdt.ls.java.home]</code> VSCode setting to point to a nix-built Java 17. For example, using home-manager's settings: <syntaxhighlight lang="nix">
+programs.vscode.enable = true;
+programs.vscode.extensions = [ pkgs.vscode-extensions.redhat.java ];
+programs.vscode.userSettings = {
+  "java.jdt.ls.java.home" = "${pkgs.jdk17}";
+};
+</syntaxhighlight>Note that this will still result in the extension downloading its own JRE, it just will not be used.
 == Using Oracle JDK instead of Open JDK ==
-Almost all Java packages in nixpkgs use Open JDK in form of a '''jre''' dependency. If you use Oracle JDK and also want other applications to use it, you can simply tweak your <code>.nixpkgs/config.nix</code> so that your desired application uses Oracles JDK or JRE.
+Almost all Java packages in nixpkgs use Open JDK in form of a '''jre''' dependency. If you use Oracle JDK and also want other applications to use it, you can simply tweak your <code>nixpkgs/config.nix</code> so that your desired application uses Oracles JDK or JRE.
 Example with UMLet with JRE
@@ Line 39: / Line 70: @@
 To install the Oracle JRE system-wide, you need to explicitly accept the license in addition to allowing unfree modules:
 <syntaxhighlight lang="nix">
 # /etc/nixos/configuration.nix
@@ Line 47: / Line 79: @@
 </syntaxhighlight>
-Working with `requireFile` (manual downloading the tarballs and manual adding in to the nix store) might be annoying and nixops-unfriendly, so it can be overridden in overlays
+Working with <code>requireFile</code> (manual downloading the tarballs and manual adding in to the nix store) might be annoying and nixops-unfriendly, so it can be overridden in overlays
 <syntaxhighlight lang="nix">
@@ Line 76: / Line 108: @@
 == Better font rendering==
-By default java does not enable antialiasing for font rendering. By exporting environment variables, this can be fixed:
+By default java does not enable anti-aliasing for font rendering. By exporting environment variables, this can be fixed:
 <syntaxhighlight lang="console">
@@ Line 85: / Line 117: @@
 == Overriding java jks Certificate Store ==
 Overriding the java certificate store may be required for adding your own Root certificates in case your company uses an internal PKI or the company utilizes an intercepting proxy.
 === jdk8 ===
 Overriding the jdk8 certificate store is possible by overriding the '''cacert''' parameter of the package:
@@ Line 115: / Line 150: @@
 === jdk11 ===
-JDK11 does not provide the cacert overridable and therefore it is not possible to use the same technique to override the truststore.
+JDK11 does not provide the cacert overridable and therefore it is not possible to use the same technique to override the truststore.
+As an alternative solution you can either set an environment variable, <code>JAVAX_NET_SSL_TRUSTSTORE</code>, or pass an argument to your program, <code>-Djavax.net.ssl.trustStore</code>, with the location of your cacert. See [https://discourse.nixos.org/t/custom-ssl-certificates-for-jdk/18297/9 discussion].
 == Building and Packaging ==
-see the [https://ryantm.github.io/nixpkgs/languages-frameworks/java/ Java section in the Nixpkgs manual]
+See the [https://nixos.org/manual/nixpkgs/#sec-language-java Java section in the Nixpkgs manual].
 === Maven ===
@@ Line 127: / Line 165: @@
 <pre>mvn verify</pre>
-[https://github.com/fzakaria/mvn2nix mvn2nix] and [https://github.com/NixOS/nixpkgs/blob/master/pkgs/build-support/build-maven.nix buildMaven] can be used to build Maven projects with Nix
+[https://github.com/fzakaria/mvn2nix mvn2nix], [https://nixos.org/manual/nixpkgs/stable/#maven-buildmavenpackage buildMavenPackage] (recommended) can be used to build Maven projects with Nix
-See also: [https://fzakaria.com/2020/07/20/packaging-a-maven-application-with-nix.html Packaging a Maven application with Nix]
+See also: [https://fzakaria.com/2020/07/20/packaging-a-maven-application-with-nix.html Packaging a Maven application with Nix] and [https://github.com/NixOS/nixpkgs/blob/master/pkgs/by-name/ma/maven/build-maven-package.nix buildMavenPackage source]
 === Ant ===
@@ Line 149: / Line 187: @@
 To fetch ivy sources in a fixed-output-derivation, see for example [https://github.com/milahu/nur-packages/blob/master/pkgs/yacy/yacy.nix yacy.nix]
-[[Category:Applications]]
+== JavaFX and Webkit support ==
+To include support for JavaFX and Webkit, use the <code>enableJavaFX</code> and <code>withWebKit</code> options:
+<syntaxHighlight lang=nix>
+{ pkgs, ... }:
+let
+  jdkWithFX = pkgs.openjdk.override {
+    enableJavaFX = true; # for JavaFX
+    # include following line if JavaFX with Webkit is needed
+    openjfx_jdk = pkgs.openjfx.override { withWebKit = true; };
+  };
+in
+...
+</syntaxHighlight>
+== Further reading ==
+{{Nixpkgs manual|sec-language-java}}<br /><br /><br /><br /><br />{{Wikipedia|Java_(programming_language)}}
 [[Category:Languages]]