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Building a J2EE app using IntelliJ Idea and deploying on Heroku

·827 words·4 mins·
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Let’s see how to build a basic Java Enterprise (fondly known as J2EE) application, made up of a Servlet and a JSP file, with the help of the popular IDE by Jetbrains, IntelliJ Idea. Finally, we will have a look at how to deploy the same on the Heroku cloud. 🌧

In the first place, I’m writing this blog because I couldn’t find a full-fledged write-up on how to do this myself initially and I had to try and err to find out the right way to do it.

Requirements #

  • Java Development Kit, which can be downloaded from here.
  • IntelliJ Idea Ultimate Edition, download it here. The ultimate edition is paid, but comes with a 30-day trial license. However, as long as you are a student, you can claim an educational license for free. More about it here.
  • Heroku account. If you don’t have, create one for free here.
  • Heroku CLI. Find the instructions here.
  • Tomcat server. You need to download the same from this link, under Binary Distributions > Core > zip. After downloading, make sure to extract the contents to any folder of your wish.
    • If you’re on Linux/macOS, you’ll need to enable executable permission for the tomcat binaries by running the following command on your terminal.
    • sudo chmod -R +x <path-to-tomcat-extracted-folder>/bin

Let’s start engineering! #

  • Open IntelliJ Idea Ultimate and create a new project.
    IntelliJ Idea home
  • Create a Java Enterprise project, with Maven as the build tool, JUnit as the test runner, and Java as the language.
    Creating J2EE project
  • In the next window, under Specifications, mark the checkbox for Servlet and ignore the rest.
    Creating J2EE project
  • Regarding the project name and properties, you can fill in as you wish, and click on Finish!
    Project Properties
  • Now, the creation of the project is complete and the IDE might take sometime to load all the necessary plugins/dependencies.
  • If you look at the project directory, there will be a pom.xml at the root of the file. This is the file which Maven uses to maintain the dependencies of your project. Essentially, it’s similar to a package.json in NodeJS (or) composer.json in PHP.

Incase you ever want to add a library, say MySQL connector, you’ll need to get its dependency XML tag from here and paste inside your pom.xml. After which, you’ll see a tiny dialog on your top-right with a refresh button which on clicking will install the newly added package.

JSP #

  • Let’s create a JSP file. Right click on Project Folder > src > main > webapp from the sidebar, and create a JSP file named hello.jsp, and fill in some JSP content.
    Creating JSP file
  • Click on Add configuration at the center top. After the window opens, click on the + button as instructed, and choose Tomcat server > Local.
  • Give it a name as you wish, and near the Application server input box, click on the configure button. Now, enter the folder path where you extracted the zip of the Tomcat server.
    Setting up tomcat
  • If you see a warning at the bottom saying No artifacts marked for deployment, click the Fix button near the warning and choose ProjectName:war exploded. Then, click Okay.
  • Now, you’ll see a neat Run button at the top. Click on it and wait until Java compiles your web app and opens your default browser.
  • Your browser would have opened the URL of your application context, similar to localhost:8080/J2EEDemo_war_exploded. This is the root of your web application. Append /hello.jsp to your current URL (it becomes http://localhost:8080/J2EEDemo_war_exploded/hello.jsp) and enter. You’ll see the contents you wrote in your hello.jsp.

Servlet #

  • Let’s create a Servlet now. Right-click on Project Folder > src > main > java from the sidebar and create a new Java Servlet. Enter the name and package as you wish.
    Creating servlet
    Creating servlet
  • Under the doGet() method, paste the following code :
@WebServlet(name = "LoginServlet")
public class LoginServlet extends HttpServlet {
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        PrintWriter out = response.getWriter();
        out.println("You are at login page");
    }
}
  • Next thing to do is assign an URL to this servlet. Open src/main/webapp/WEB-INF/web.xml and paste the following :

Make sure you change the servlet-class according to your package and class name.

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns="http://xmlns.jcp.org/xml/ns/javaee"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_4_0.xsd"
         version="4.0">
    <servlet>
        <servlet-name>LoginServlet</servlet-name>
        <servlet-class>in.co.rajkumaar.LoginServlet</servlet-class>
    </servlet>
    <servlet-mapping>
        <servlet-name>LoginServlet</servlet-name>
        <url-pattern>/login</url-pattern>
    </servlet-mapping>
</web-app>

Heroku #

  • Visit https://dashboard.heroku.com/new-app and create a new app.

    Creating new Heroku app

  • On your IntelliJ Idea Ultimate, open the Build menu and click on Build artifacts. Choose AppName:war > Build.

  • You’ll be able to see a J2EEDemo-1.0-SNAPSHOT.war file inside the target/ directory of your application. Right-click on the file and copy > Absolute Path.

    Target directory with WAR file

  • Open up your terminal/command prompt, and run heroku login.

  • Authorize on the website it opens up for you.

  • Come back to the terminal, and run heroku plugins:install java.

  • Then, run the following command. Make sure you replace the path for the WAR file and your application name.

heroku war:deploy "/Users/rajkumar/Projects/J2EEDemo/target/J2EEDemo-1.0-SNAPSHOT.war" -a j2ee-test-raj