Setup Java ZK Framework on Tomcat

Introduction

Table of Contents

Prerequisites

Step 1: Install JDK

1. Install the JDK
Open a terminal on your RHEL machine, then update the yum package index.

sudo yum update -y

Install the JDK (OpenJDK 11 in this guide).

sudo yum install java-11-openjdk-devel-11.0.20.1.1-2.el9.x86_64

2. Configure Environment Variable
You may want to set the JAVA_HOME environment variable. Open your .bashrc or .bash_profile file:

vim ~/.bashrc

Add the following line at the end of the file:

export JAVA_HOME=$(dirname $(dirname $(readlink -f $(which java))))

Save the file and apply the changes:

source ~/.bashrc

3. Verify the Installation and Configuration

echo $JAVA_HOME
java -version

You should see the output indicating the version of Java installed like below.

Step 2: Install Apache Maven

1. Install Maven using Yum

sudo yum install maven

2. Configure Environment Variables
Set the MAVEN_HOME environment variable in the same way as for JDK.

vim ~/.bashrc

Add the following lines.

export MAVEN_HOME=/usr/share/maven
export PATH=$MAVEN_HOME/bin:$PATH

Save the file and apply the changes:

source ~/.bashrc

3. Verify the Maven Installation

echo $MAVEN_HOME
mvn -v

You should see the output indicating the version Maven look like below.

Step 3: Install Apache Tomcat

1. Download and Extract Tomcat
Navigate to the Tomcat download page at Apache Tomcat and copy the link to the latest version of Tomcat tar file. You can use the following command to download the current latest version (9.0.96) or replace it with version available.

wget https://downloads.apache.org/tomcat/tomcat-9/v9.0.96/bin/apache-tomcat-9.0.96.tar.gz

Extract the downloaded archive.

tar -xvzf apache-tomcat-9.0.96.tar.gz

Move the extracted directory to /opt :

sudo mv apache-tomcat-9.0.96 /opt/tomcat

2. Set the appropriate permissions for the Tomcat directory.

sudo chown -R tomcat:tomcat /opt/tomcat

3. Navigate to the Tomcat bin directory and start Tomcat:

cd /opt/tomcat/apache-tomcat-9.0.96/bin
./startup.sh

Then, verify the installation by accessing Tomcat in your web browser.

http://localhost:8080

You should see the Tomcat welcome page.

4. Create the Service File
Create symbolic link on /opt/tomcat . This way we can keep multiple version of Tomcat available on the system and refer to active on using /opt/tomcat/updated directory link.

sudo ln -s /opt/tomcat/apache-tomcat-9.0.96 /opt/tomcat/updated

Open a new service file for Tomcat in the /etc/systemd/system/ directory.

sudo vim /etc/systemd/system/tomcat.service

Add the following configuration to the file:

[Unit]
Description=Apache Tomcat Web Application Container
After=network.target

[Service]
Type=forking

Environment=JAVA_HOME=/usr/lib/jvm/java-11-openjdk-11.0.20.1.1-2.el9.x86_64
Environment=CATALINA_PID=/opt/tomcat/updated/temp/tomcat.pid
Environment=CATALINA_Home=/opt/tomcat/updated
Environment=CATALINA_BASE=/opt/tomcat/updated
Environment=’CATALINA_OPTS=-Xms512M -Xmx1024M -server -XX:+UseParallelGC’
Environment=’JAVA_OPTS.awt.headless=true -Djava.security.egd=file:/dev/v/urandom’

ExecStart=/opt/tomcat/updated/bin/startup.sh
ExecStop=/opt/tomcat/updated/bin/shutdown.sh

User=tomcat
Group=tomcat
UMask=0007
RestartSec=10
Restart=always

[Install]

WantedBy=multi-user.target

Reload the systemd daemon to recognize the new service:

sudo systemctl daemon-reload

Start the Tomcat service

sudo systemctl start tomcat

If all works correctly, you should see the service status to be active (running) and you can test again to localhost:8080 .





❗
If your the Tomcat not running, you can check the logs on /opt/tomcat/updated/logs/catalina.out .
❗
If you encounter BindExeption: Address already in use, consider kill the process that already use the port 8080 or change the Tomcat port.
For killing the process run:
sudo ss -lptn 'sport = :8080'
sudo kill -9 <pid>
For changing the Tomcat port, open /opt/tomcat/updated/conf/server.xml and find this part:
    <Connector port="8080" protocol="HTTP/1.1"
               connectionTimeout="20000"
               redirectPort="8443"
               maxParameterCount="1000"
               />
Change the default port 8080 to any other that not being use.

Step 4: Create a ZK Project

1. Create a New ZK Project
Navigate to your preferred workspace directory:

cd ~

Use Maven to create a new ZK project:

mvn archetype:generate   -DgroupId=com.example.zk   -DartifactId=my-zk-app   -DarchetypeGroupId=org.zkoss   -DarchetypeArtifactId=zk-archetype-webapp   -DarchetypeVersion=9.6.0   -DinteractiveMode=false

Change into the project directory:

cd my-zk-app

Build the project.

mvn clean package

This will create a my-zk-app.war file in the target directory.

Step 5: Deploy the ZK Application

1. Copy the WAR file to the tomcat webapps directory

cp target/my-zk-app.war /opt/tomcat/updated/webapps

2. Start Tomcat

sudo systemctl start tomcat 

3. Verify the Tomcat is running

sudo systemctl status tomcat

4. View Tomcat Logs
If you encounter issues, view the logs:

cat cat /opt/tomcat/updated/logs/catalina.out

Step 6: Access Your ZK Application

http://localhost:8080/my-zk-app

Conclusion