Configure Tomcat for Java web

In this turorial, we will find out about how to configure Tomcat in eclipse, and how to configure Tomcat to deploy web application.

Introduction to Tomcat
Configure Tomcat in Eclipse
Configure Tomcat server to deploy web application
Understanding about some configuration files in Tomcat
Some errors in Eclipse when configure Tomcat
Wrapping up

Introduction to Tomcat

Tomcat is actually composed of a number of components, including a Tomcat JSP engine and other connectors, but the main component is Catalina, which provides the implementation of the servlet specification. When starting the Tomcat server, it’s Catalina that is actually starting. The variable CATALINA_HOME is a configuration property that stores the location of the Catalina files.

These are the configuration files in Tomcat’s CATALINA_BASE/conf directory:

catalina.policy
catalina.properties
logging.properties
content.xml
server.xml
tomcat-users.xml
web.xml

Configure Tomcat in Eclipse

The first thing we have to do is to download Apache Tomcat in a link such as https://tomcat.apache.org/download-90.cgi.
Unzip this file and we have;
This step we will add Tomcat into our Eclipse:

And click Apply and Close to agree our Tomcat version.

Configure Tomcat server to deploy web application

After we unzip Tomcat file, we will do something like:

specify JDK for Tomcat.
Open startup.bat file in bin folder of Tomcat. (With Linux/Ubuntu OS, we have startup.sh file).

We will add some code into startup.bat file.

  # With Windows
  set JAVA_HOME="C:\Program Files\Java\jdk1.8.0_181"

  # With Linux/Ubuntu
  JAVA_HOME="/usr/lib/jvm/open-jdk"

Next, we will configure for account to use Tomcat. Open tomcat-users.xml in conf folder.

Tomcat was defined 4 roles:
- manager-gui - allows access to the HTML GUI and the status pages
- manager-script - allows access to the text interface and the status pages
- manager-jmx - allows access to the JMX proxy and the status pages
- manager-status - allows access to the status pages only
We can declare a user with 4 roles
```
  <role rolename="manager-gui"/>
  <role rolename="manager-script"/>
  <role rolename="manager-jmx"/>
  <role rolename="manager-status"/>
    
  <user username="tomcat"
      password="mypassword"
      roles="manager-gui,manager-script,manager-jmx,manager-status"/>
```
To run Tomcat, we double click into startup.bat file. (or startup.sh file if we use Linux/Ubuntu).
On browser, we type localhost:8080.
With Tomcat, we have authenticate username/password that we write in tomcat-users.xml file.
In Tomcat, we have /manager (Tomcat Manager Application) is the most important. It will help us to manage Tomcat, and we can access it with following path: localhost:8080/manager.
In order to deploy web application to Tomcat, we can do the following image.
After that, demo application will be deployed to Tomcat.
Run demo application, we have:

Some errors in Eclipse when configure Tomcat

WARNING: Unable to load server configuration from ... server.xml

We only need to copy a path E:\apache-tomcat-9.0.16\conf into our path where has error.
Getting 404 - Page not found error

We can solve this error that follows some steps:
- Step 1
  - Go to Eclipse IDE
  - Click on Servers Tab
  - Double click on Tomcat v9.0 Server at localhost
- Step 2
  - New Apache Tomcat configuration page will open
  - Go to Server Location section
  - Select Use Tomcat installation (takes control of Tomcat installation)
- Step 3
  - Save configuration
  - Restart Server by right clicking on tomcat server and click Restart
  - Visit http://localhost:8080 again and now you should see working tomcat page