hallazzang/README.md

## README.md

      
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    Docker + Apache Tomcat + JSP

This article describes how to deploy a JSP website using Docker, Apache Tomcat.
Directory structure

I found a way to make a minimal JSP web application from scratch, without any IDE.
(ref: https://www.youtube.com/watch?v=JEBR_KJdzSk)
First, organize your working directory like this:
yourproject/
    Dockerfile
    webapp/
        WEB-INF/
          classes/
          lib/
          web.xml
        index.jsp

Right now, just leave every folders and files empty.
This is the skeleton of our Dockerized web application.
Web application

First, we should fill some content for our web application.
Take your favorite editor and edit these files:
yourproject/webapp/WEB-INF/web.xml

<web-app>
</web-app>
It can be empty. Later, you can edit this file as you want.
yourproject/webapp/index.jsp

<!doctype html>
<h1>It works!</h1>
<%
  for (int i = 0; i < 5; ++i) {
      out.println("<p>Hello, world!</p>");
  }
%>
This is just an example; it will produce:
<h1>It works!</h1>
<p>Hello, world!</p><p>Hello, world!</p><p>Hello, world!</p><p>Hello, world!</p><p>Hello, world!</p>
And that's all for our website. Not too complicated, right?
Dockerfile

And let's make our Dockerfile. Open yourproject/Dockerfile and copy&paste these:
FROM tomcat:9.0.1-jre8-alpine

ADD ./webapp /usr/local/tomcat/webapps/webapp

CMD ["catalina.sh", "run"]
That's everything we need. Let me explain each line:
Apache Tomcat Image

FROM tomcat:9.0.1-jre8-alpine
We use official tomcat:9.0.1-jre8-alpine image for our base image.
You can choose any other images you want, like tomcat:8.5.23-jre8.
But tomcat:9.0.1-jre8-alpine is the latest release of Apache Tomcat image on Docker Hub now
and has much smaller(~113MB) size than tomcat:9.0.1-jre8(~557MB) so I'll stick to use it.
Copying Website and Start up Tomcat

ADD ./webapp /usr/local/tomcat/webapps/webapp
The ADD instruction copies our local files(in our case, yourproject/webapp folder)
to container's file system(/usr/local/tomcat/webapps/webapp).
I tried to use a WAR file instead of plain source codes, but it didn't work for me for some reason.
If someone knows how to pre-compile all the JSP files and copy it into image, please leave a comment.
CMD ["catalina.sh", "run"]
Finally, the CMD instruction will start up Apache Tomcat, which runs our web application.
Build Docker Image and Run

Go to yourproject/ in terminal, and type it to build a Docker image:
$ docker build -t mywebapp .
And then run:
$ docker run --rm -it -p 8888:8080 mywebapp
Visit http://localhost:8888/webapp to see if your website is running!