Apache HTTP Server as Reverse Proxy with Java Back-End Application running on Tomcat

This is a simple tutorial of how to use the reverse proxy module of Apache together with back-end application.

Web Server

A web server is a system that stores and delivers content or services requested by clients over the internet.

Apache HTTP Server

Apache HTTP Server is a free and open-source cross-platform web server software. It is the most popular web server which works with Multi-Processing Modules (MPMs). These modules helps the server to extend it’s functionality. Apache supports reverse proxy with caching which is our topic in this article.

Reverse-Proxy

Proxy server is a server that acts as an intermediary for requests from clients seeking resources from other servers. A reverse proxy server is a type of proxy server that sits behind the firewall in a private network and directs client requests to the appropriate back-end server.

What we will do?

Here’s a scheme what we will do in this tutorial. When a user sends request to http://localhost/api/user it will be delivered to Apache web server. Here we will have a proxy configuration dealing with /api requests. As a back-end application we will have Java web app running on port 8080 with Tomcat. This app will accepts route “/users” and will return “Hello, user!” and this will be the respond sent to the user.

What we will need before starting?

• Linux Terminal
• IntelliJ
• Tomcat

Installing Apache

Let’s go to the terminal and update the package lists before proceeding to install our server:

$ sudo apt-get update 

Now we can install Apache 2:

$ sudo apt-get install apache2 -y

Enabling Apache Modules

As you know, Apache has many modules to extend the core functionality. For our purpose we will be using:

• mod_proxy — the main proxy module for redirecting connections
• mod_proxy_http — adds support for proxying HTTP connections

Let’s install them:

$ sudo a2enmod proxy
$ sudo a2enmod proxy_http

Now it’s time to restart Apache:

$ sudo service apache2 restart

Creating Back-end

New Maven Project

I assume you have already installed Tomcat, so let’s continue with creating a new Maven project in IntelliJ:

In pom.xml add this dependency:

In src/main create new folder, name it “java” and with right click -> “Make Directory as” -> “Sources Root”.

Creating a servlet

Let’s create a servlet! A servlet is a class which responds to a particular type of network request, in our case — a HTTP request. In java folder create new class, name it “UsersServlet” and write this:

Tomcat Configuration

Add new configuration — Tomcat-Local. Add artifact and save it.

Now we can run the application.

Enabling Reverse Proxy

We will set up the default Apache virtual host to serve as a reverse proxy for single back-end server. Open the default Apache configuration:

$ sudo nano /etc/apache2/sites-available/000-default.conf

Replace the content in VirtualHost with the following:

Let’s restart Apache:

$ sudo service apache2 restart

Result

Now, if you access http://your_server_ip/api/users in a web browser, you will see your back-end server response.

You can check my back-end app here: GitHub