Docker and Java - FontConfiguration issue

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We've got a Java application that generates word documents using a 3rd party (Asposee but I don't think it matters here). The app is built from a simple Docker file:
FROM openjdk:10-jdk-slim
COPY target/*.jar /opt/
CMD $JAVA_HOME/bin/java $JAVA_OPTS -jar /opt/*.jar
When we build the application locally (mvn package then docker build) and run the application inside k8s it works well.
However, when we build the image in our CI/CD pipeline with Jenkins we get a runtime exception when running through a specific process which apparently requires additional fonts:
Caused by: java.lang.NullPointerException: null
    at java.desktop/sun.awt.FontConfiguration.getVersion(FontConfiguration.java:1288)
    at java.desktop/sun.awt.FontConfiguration.readFontConfigFile(FontConfiguration.java:225)
    at java.desktop/sun.awt.FontConfiguration.init(FontConfiguration.java:107)
    at java.desktop/sun.awt.X11FontManager.createFontConfiguration(X11FontManager.java:765)
    at java.desktop/sun.font.SunFontManager$2.run(SunFontManager.java:440)
    at java.base/java.security.AccessController.doPrivileged(Native Method)
    at java.desktop/sun.font.SunFontManager.<init>(SunFontManager.java:385)
    at java.desktop/sun.awt.FcFontManager.<init>(FcFontManager.java:35)
    at java.desktop/sun.awt.X11FontManager.<init>(X11FontManager.java:56)
In that case the project is buit in Jenkins, compiled by the docker image maven:3.5.4-jdk-10-slim.
I've checked both jar files (locally and from jenkins) and the class files are the same (as expected).
In both cases it's the same base image so I don't understand what could be the difference. Is something different in Docker when building locally vs inside another Docker container?
We've looked into both docker images and found the following difference.
Since locally built image ls -l /usr/lib returns:
drwxr-xr-x  2 root root  4096 May  3  2017 X11
drwxr-xr-x  5 root root  4096 Apr 26 00:00 apt
drwxr-xr-x  2 root root  4096 May 26 08:31 binfmt.d
drwxr-xr-x  2 root root  4096 Jun  6 01:50 cgmanager
drwxr-xr-x  2 root root  4096 Jun  6 01:50 dbus-1.0
drwxr-xr-x  2 root root  4096 Jun  6 01:51 dconf
drwxr-xr-x  3 root root  4096 Jun  6 01:51 debug
drwxr-xr-x  3 root root  4096 Apr 20 10:08 dpkg
drwxr-xr-x  2 root root  4096 Jun  6 01:50 environment.d
drwxr-xr-x  3 root root  4096 Apr 25 04:56 gcc
drwxr-xr-x  2 root root  4096 Jun  6 01:51 glib-networking
drwxr-xr-x  2 root root  4096 Apr 26 00:00 init
drwxr-xr-x  1 root root  4096 Jun  6 01:51 jvm
drwxr-xr-x  3 root root  4096 Jun  6 01:50 kernel
lrwxrwxrwx  1 root root    20 Mar  4 09:49 libnih-dbus.so.1 -> libnih-dbus.so.1.0.0
-rw-r--r--  1 root root 34824 Mar  4 09:49 libnih-dbus.so.1.0.0
lrwxrwxrwx  1 root root    15 Mar  4 09:49 libnih.so.1 -> libnih.so.1.0.0
-rw-r--r--  1 root root 92184 Mar  4 09:49 libnih.so.1.0.0
drwxr-xr-x  3 root root  4096 Mar 29 19:47 locale
drwxr-xr-x  3 root root  4096 Jun  6 01:50 lsb
drwxr-xr-x  1 root root  4096 Jul 21  2017 mime
drwxr-xr-x  2 root root  4096 Jun  6 01:50 modprobe.d
drwxr-xr-x  2 root root  4096 May 26 08:31 modules-load.d
-rw-r--r--  1 root root   198 Jan 13 23:36 os-release
drwxr-xr-x  3 root root  4096 Jun  6 01:51 ssl
drwxr-xr-x  1 root root  4096 Jun  6 01:50 systemd
drwxr-xr-x  2 root root  4096 Jun  6 01:50 sysusers.d
drwxr-xr-x  2 root root  4096 Jul 21  2017 tar
drwxr-xr-x 15 root root  4096 Feb 11 20:06 terminfo
drwxr-xr-x  1 root root  4096 Jun  6 01:50 tmpfiles.d
drwxr-xr-x  1 root root  4096 Apr 26 00:00 udev
drwxr-xr-x  1 root root 16384 Jun  6 01:51 x86_64-linux-gnu
But inside Jenkins built image ls -l /usr/lib returns:
drwxr-xr-x  5 root root 4096 Jun 25 00:00 apt
drwxr-xr-x  3 root root 4096 Jul  3 01:00 debug
drwxr-xr-x  3 root root 4096 Apr 20 10:08 dpkg
drwxr-xr-x  3 root root 4096 Jun 17 03:36 gcc
drwxr-xr-x  2 root root 4096 Jun 25 00:00 init
drwxr-xr-x  1 root root 4096 Jul  3 01:00 jvm
drwxr-xr-x  1 root root 4096 Jul 12 11:00 locale
drwxr-xr-x  3 root root 4096 Jul  3 01:00 lsb
drwxr-xr-x  1 root root 4096 May 16 07:47 mime
-rw-r--r--  1 root root  198 Jan 13 23:36 os-release
drwxr-xr-x  3 root root 4096 Jul  3 01:00 ssl
drwxr-xr-x  3 root root 4096 Apr 20 10:08 systemd
drwxr-xr-x  2 root root 4096 May 16 07:47 tar
drwxr-xr-x 15 root root 4096 May 21 08:54 terminfo
drwxr-xr-x  2 root root 4096 Jun 25 00:00 tmpfiles.d
drwxr-xr-x  3 root root 4096 Jun 25 00:00 udev
drwxr-xr-x  2 root root 4096 May  3  2017 X11
drwxr-xr-x  1 root root 4096 Jul  3 01:00 x86_64-linux-gnu
This is really puzzling as I thought Docker would always produce the same image from identical Dockerfiles
Dockerfile:
FROM openjdk:8u111-jdk-alpine
# Needed to fix 'Fontconfig warning: ignoring C.UTF-8: not a valid language tag'
ENV LANG en_GB.UTF-8
# JRE fails to load fonts if there are no standard fonts in the image; DejaVu is a good choice,
# see https://github.com/docker-library/openjdk/issues/73#issuecomment-207816707
RUN apk add --update ttf-dejavu && rm -rf /var/cache/apk/*
VOLUME /tmp
COPY /target/*.jar app.jar
ENTRYPOINT ["java","-Xmx100m","-Djava.security.egd=file:/dev/./urandom","-jar","/app.jar"]
                Worked for me using openjdk:8-jdk-alpine and without the ENV LANG en_GB.UTF-8 declaration
– batero
                Oct 20, 2020 at 17:49
I think we found the problem.
When running on Jenkins we use the docker:dind (Docker inside docker) Docker image to provide the docker command in the build. This image is based on Alpine linux. When running docker info we get the following:
On Mac:
Kernel Version: 4.9.87-linuxkit-aufs
Operating System: Docker for Mac
On Jenkins:
Kernel Version: 4.4.115-k8s
Operating System: Alpine Linux v3.7 (containerized)
Alpine linux must be missing those fonts. We fixed the problem by manually installing them in the Dockerfile:
RUN apt-get update \
 && apt-get install --assume-yes apt-utils \
 && apt-get install --assume-yes software-properties-common \
 && apt-get install --assume-yes dbus \
 && apt-get install --assume-yes cgmanager \
 && apt-get install --assume-yes glib-networking \
 && apt-get install --assume-yes libnih-dbus-dev \
 && apt-get install --assume-yes dconf-cli \
 && apt-get install --assume-yes fontconfig
Not sure this is the minimum required libraries but those did the trick :D
                Thanks for a well-explained answer :-) even though this wasn't the solution to my version of the problem.
– David Z
                Sep 8, 2020 at 4:11
If you trying to do in Java/Spring boot , adding following in Dockerfile worked for me in java 11.
# Font packages to be added for java 11
RUN apk update \
 && apk add fontconfig \
 && apk add ttf-dejavu
RUN ln -s /usr/lib/libfontconfig.so.1 /usr/lib/libfontconfig.so && \
    ln -s /lib/libuuid.so.1 /usr/lib/libuuid.so.1 && \
    ln -s /lib/libc.musl-x86_64.so.1 /usr/lib/libc.musl-x86_64.so.1
ENV LD_LIBRARY_PATH /usr/lib
Problem NullPointerException with fonts occurs when you use openjdk docker image in alpine version for example :
adoptopenjdk/openjdk11:jre-11.0.11_9-alpine.
You need change image to full version: adoptopenjdk/openjdk11:jre-11.0.11_9
If you are running it on local with Docker Desktop and using docker file to create the image.
Please make changes in Dockerfile from FROM openjdk:8-jdk-alpine to FROM adoptopenjdk/openjdk11:ubi
I also got the same issue while running below command and restart app server resolved this issue.
Yup install fontconfig
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