Apache Tomcat

Tomcat is a server for hosting java web applications, and its free and open-source.

It supports java technologies:

- java servlet

- javaserver pages (JSP)

- Java Expression Language (EL)

- Java WebSocket

Its also called a Servlet container.

It's developed by the Apache Software Foundation.

To install the Apache tomcat server, download the package from "https://tomcat.apache.org" and extract the files.

Run the below command to get the tomcat-10 package:

$ cd /opt
$ wget https://mirrors.estointernet.in/apache/tomcat/tomcat-10/v10.0.2/bin/apache-tomcat-10.0.2.zip
$ unzip apache-tomcat-10.0.2.zip

The "/opt/apache-tomcat-10.0.2" directory will be the "CATALINA_HOME" directory.

CATALINA_HOME: Represents the root of your Tomcat installation, for example 

CATALINA_BASE: Represents the root of a runtime configuration of a specific Tomcat instance. If you want to have multiple Tomcat instances on one machine, use the CATALINA_BASE property

Note: Similar to maven Tomcat has a dependency with "java-OpenJDK", to install the JDK (Java Development Kit) run the below command:

$ sudo yum install java-1.8.0-openjdk-devel -y

Below are some of the key tomcat directories:

> /bin - It contains Startup, shutdown, and other scripts. The *.sh files (for Unix systems) are functional duplicates of the *.bat files (for Windows systems). Since the Win32 command-line lacks certain functionality, there are some additional files here.

> /conf - Configuration files and related DTDs. The most important file in here is server.xml. It is the main configuration file for the container.

> /logs - Log files are here by default.

> /webapps - This is where your web apps go.

To start the tomcat server run below command from $CATALINA_HOME/bin directory:

$ ./startup.sh

Tomcat runs on port 8080

To access the tomcat dashboard go to: http://localhost:8080

To install any web application all we need to do is copy the "application.war" file in the "webapps" directory and restart the tomcat server.

$ ./shutdown.sh && ./startup.sh

To access the application go to : http://localhost:8080/application

By default, the Tomcat manager is configured to be accessed from the same server where it’s installed. If you access the manager, you will get a 403 error.

For a manager to be accessible from any host/IP, you need to do the following :

    1. Go to Tomcat installation and then webapps/manager/META-INF

    2. Open context.xml and comment Valve section as below

<Context antiResourceLocking="false" privileged="true" >

<!--

  <Valve className="org.apache.catalina.valves.RemoteAddrValve"

         allow="127\.\d+\.\d+\.\d+|::1|0:0:0:0:0:0:0:1" />

-->

  <Manager sessionAttributeValueClassNameFilter="java\.lang\.(?:Boolean|Integer|Long|Number|String)|org\.apache\.catalina\.filters\.CsrfPreventionFilter\$LruCache(?:\$1)?|java\.util\.(?:Linked)?HashMap"/>

</Context>

    3. Save the file. Next, go to conf folder and open tomcat-users.xml to adding the following above </tomcat-users> syntax.

<role rolename="manager-gui"/>

<user username="tomcat" password="tomcat" roles="manager-gui"/>

    4.Save the configuration file and restart the Tomcat