TomEE

Apache TomEE a.k.a Tommy, is the Java Enterprise Edition of Apache Tomcat, an open-source implementation of the Java Servlet, JavaServer Pages, Java Expression Language and WebSocket technologies. Tomcat provides a Java HTTP web server environment in which Java code can run.

The webprofile version of TomEE is optimized for JEE [1] web applications, which is the case of the app developed in Spring

Deployment

First I tried using TomEE in a CentOS 8 container but there was some errors due to container privileges and the way CentOS works. In this case I used Debian which also runs pretty smooth since the Proxmox OS is Debian as well.

The first TomEE requirement is installing Java. In this case I considered using the AdoptOpenJDK8 version of the Java Development Kit and Java Runtime Environment.

The installation and set up was done as it follows.

cd mkdir /usr/lib/jvm/open-jdk-11
wget https://github.com/AdoptOpenJDK/openjdk8-binaries/releases/download/jdk8u252-b09/OpenJDK8U-jdk_x64_linux_hotspot_8u252b09.tar.gz
wget https://github.com/AdoptOpenJDK/openjdk8-binaries/releases/download/jdk8u252-b09/OpenJDK8U-jre_x64_linux_hotspot_8u252b09.tar.gz
tar -xf OpenJDK8U-jdk_x64_linux_hotspot_8u252b09.tar.gz
tar -xf OpenJDK8U-jre_x64_linux_hotspot_8u252b09.tar.gz
export PATH=$PWD/jdk8u252-b09/bin:$PATH
export PATH=$PWD/jdk8u252-b09-jre/bin:$PATH

After the JRE and JDK were installed, then I installed TomEE.

sudo groupadd tomcat
sudo useradd -s /bin/false -g tomcat -d /opt/tomee tomcat
wget https://apache.brunneis.com/tomee/tomee-8.0.1/apache-tomee-8.0.1-webprofile.tar.gz
sudo mkdir /opt/tomee
sudo tar xzvf apache-tomee-8.0.1-webprofile.tar.gz -C /opt/tomee --strip-components=1
sudo chgrp -R tomcat /opt/tomee
sudo chmod -R g+r conf
sudo chmod g+x conf
sudo chown -R tomee webapps/ work/ temp/ logs/
sudo nano /etc/systemd/system/tomcat.service

Edit the tomcat.service file as it follows.

[Unit]
Description=Tomee 8 servlet container
After=network.target

[Service]
Type=forking

User=tomcat
Group=tomcat

Environment="JAVA_HOME=/usr/lib/jvm/jdk8u252-b09"
Environment="JAVA_OPTS=-Djava.security.egd=file:///dev/urandom"

Environment="CATALINA_BASE=/opt/tomee"
Environment="CATALINA_HOME=/opt/tomee"
Environment="CATALINA_PID=/opt/tomee/temp/tomcat.pid"
Environment="CATALINA_OPTS=-Xms512M -Xmx1024M -server -XX:+UseParallelGC"

ExecStart=/opt/tomee/bin/startup.sh
ExecStop=/opt/tomee/bin/shutdown.sh

[Install]
WantedBy=multi-user.target

The CATALINA_OPTS are Java arguments to modify the Java server resources, just like the Minecraft server.

Finally reload the daemons list so systemctl can find the new service and start it.

sudo systemctl daemon-reload
sudo systemctl start tomcat

The web application must be in .war format, not as .jar. Deploying the app is easy as placing it in the webapps folder. TomEE automatically will detect it and deploy it, creating a new folder with the same name as the app name.

To access the application I just used the browser and typed the socket address. The default port for TomEE is 8080.

Footnotes

[1]	Java Enterprise Edition