eb-tomcat-snakes

Tomcat application that shows the use of RDS in a Java EE web application in AWS Elastic Beanstalk. The project shows the use of Servlets, JSPs, Simple Tag Support, Tag Files, JDBC, SQL, Log4J, Bootstrap, Jackson, and Elastic Beanstalk configuration files.

INSTRUCTIONS

Install the Java 8 JDK. The java compiler is required to run the build script. If you would like to run the web app locally, install Tomcat 8 and Postgresql 9.4.

You can deploy the ROOT.war archive that build.sh generates to an AWS Elastic Beanstalk web server environment running the Tomcat 8 platform.

To download, build and deploy the project

Clone the project (SSH):

~$ git clone [email protected]:awslabs/eb-tomcat-snakes.git

Or with HTTPS:

~$ git clone https://github.com/awslabs/eb-tomcat-snakes.git

Run build.sh to compile the web app and create a WAR file (OS X or Linux):

~$ cd eb-tomcat-snakes
~/eb-tomcat-snakes$ ./build.sh

Or in Windows with Git Bash:

~/eb-tomcat-snakes$ ./build-windows.sh

IMPORTANT Always run build.sh from the root of the project directory.

The script compiles the project's classes, packs the necessary files into a web archive, and then attempts to copy the WAR file to /Library/Tomcat for local testing. If you installed Tomcat to another location, change the path in build.sh:

if [ -d "/path/to/Tomcat/webapps" ]; then
  cp ROOT.war /path/to/Tomcat/webapps

Open localhost:8080 in a web browser to view the application running locally.

You can use either the AWS Management Console or the EB CLI to launch the compiled WAR. Scroll down for EB CLI instructions.

To deploy with the AWS Management Console

1. Open the Elastic Beanstalk Management Console
2. Choose Create New Application
3. For Application Name, type tomcat-snakes. Choose Next.
4. Choose Web Server Environment
5. Set the platform to Tomcat and choose Next.
6. Choose Upload your own and Choose File.
7. Upload ROOT.war from your project directory and choose Next.
8. Type a unique Environment URL and choose Next.
9. Check Create an RDS DB Instance with this environment and choose Next.
10. Set Instance type to t2.nano and choose Next. Choose Next again to skip tag configuration.
11. Apply the following RDS settings and choose Next (leave the other settings default):
    • DB engine: postgres
    • Engine version: 9.4.5
    • Instance class: db.t2.micro
    • Master username: any username
    • Master password: any password
12. Choose Next to create and use the default role and instance profile.
13. Choose Launch.

The process takes about 15 minutes. If you want to save time during the initial environment creation, you can launch the environment without a database, and then add one after the environment is running from the Configuration page. Launching an RDS DB instance takes about 10 minutes.

To deploy with the EB CLI

The EB CLI requires Python 2.7 or 3.4 and the package manager pip. For detailed instructions on installing the EB CLI, see Install the EB CLI in the AWS Elastic Beanstalk Developer Guide.

Install the EB CLI:

~$ pip install awsebcli

Initialize the project repository:

~/eb-tomcat-snakes$ eb init

Add the following to .elasticbeanstalk/config.yml:

deploy:
  artifact: ROOT.war

Create an environment with an RDS database:

~/eb-tomcat-snakes$ eb create tomcat-snakes --sample --single --timeout 20 -i t2.micro --database.engine postgres --database.instance db.t2.micro --database.username *any username* --database.password *any password*

Deploy the project WAR to your new environment:

~/eb-tomcat-snakes$ eb deploy --staged

Open the environment in a browser:

~/eb-tomcat-snakes$ eb open

Site Functionality

The application is a simple Java EE site that uses simple tags, tag files, and an SQL database hosted in an external database in Amazon Relational Database Service (Amazon RDS).

The front page is a very basic introduction with a little bit of Javascript. All pages use a tag file for the header, and Bootstrap CSS for mobile friendly rendering.

The Browse Movies page shows a list of movies from the database generated with a simple tag.

The Add a Movie page is a form that lets a user add a movie to the database. It takes a movie name, link to IMDB or IMDB movie ID (e.g. tt0118615), and a boolean value that indicates whether the movie has snakes in it or not. Form input is validated with a regex in the movies model.

The Search page lets you perform a basic search for a movie with full name matches only.

Database Use

The application can connect to an RDS DB instance that is part of your Elastic Beanstalk environment, or an independent RDS DB instance that you launched outside of Elastic Beanstalk. To connect to an external DB instance, configure Environment Properties for each of the connection variables (RDS_HOST, etc), or store the full connection string in a JSON file in Amazon S3.

For the latter method, a configuration file is included under src/.ebextensions/inactive that you can modify to download the connection object from S3. When the configuration file is updated to point at your bucket and object, and moved into the src/.ebextensions folder, Elastic Beanstalk downloads the file to the EC2 instance running your application during deployment. When the application attempts to create a database connection, it will look for the file and use the connection string that it specifies to connect to the database prior to reading environment variables.

The application looks for a table named movies. If it doesn't find one, it creates a new table and seeds it a with a few entries read from a JSON file included in the source bundle.

DB Instance Administration

To manage the RDS DB instance, first connect to an instance in your environment with SSH. If you did not choose an SSH key during environment creation, you can assign one with the EB CLI. Run eb config and type a key name in the EC2KeyName field under settings. If you don't have an SSH key, run eb init -i and create an SSH key when prompted.

If you want to clear the Movies table or test changes to the table initialization code, connect to the DB instance from an instance in your environment to run administrator commands.

Run eb ssh to connect to an instance:

~\eb-tomcat-snakes$ eb ssh

Install the PostgreSQL client:

[ec2-user@ip-555-55-55-555 ~]$ sudo yum install postgresql94

Connect to the RDS DB instance:

[ec2-user@ip-555-55-55-555 ~]$ psql --dbname=ebdb --host=*DB_INSTANCE_HOSTNAME* --username=*DB_USERNAME*

Read Movies table:

ebdb=> SELECT * FROM movies;

Delete Movies table (WARNING: Deletes Movies table):

ebdb=> DROP TABLE Movies;

Exit psql:

ebdb=> \q

Exit SSH:

[ec2-user@ip-555-55-55-555 ~]$ exit

Log4j

The application uses Log4j to generate a log file named snakes.log. The project includes a configuration file in src/.ebextensions that configures Elastic Beanstalk to include snakes.log when you request tailed logs.

Project Contents

This project is organized as follows (some files not shown):

├── LICENSE             - License
├── README.md           - This file
├── build.sh            - Build script
└── src
    ├── .ebextensions   - Elastic Beanstalk configuration files
    ├── 404.jsp         - 404 error JSP
    ├── add.jsp         - Add a Movie JSP
    ├── default.jsp     - Home Page JSP
    ├── movies.jsp      - Movies JSP
    ├── search.jsp      - Search JSP
    ├── WEB-INF
    │   ├── lib         - Library JARs for JSP and Servlet APIs, Jasper, Log4J and PostgreSQL
    │   ├── tags        - Header tag file
    │   │   └── header.tag
    │   ├── tlds        - Tag Library Descriptor for ListMovies simple tag
    │   │   └── movies.tld
    │   ├── log4j2.xml  - Log4J configuration file
    │   └── web.xml     - Deployment descriptor
    ├── com
    │   └── snakes
    │       ├── model   - Model classes
    │       │   ├── Media.java
    │       │   └── Movie.java
    │       └── web     - Servlet and simple tag classes
    │           ├── AddMovie.java
    │           ├── ListMovies.java
    │           └── SearchMovies.java
    ├── css             - Stylesheets
    │   ├── movies.html - HTML page for testing stylesheet changes
    │   └── snakes.css  - Custom styles
    ├── images          - Some royalty free images for the header and front page
    └── js              - Bootstrap and parallax effect javascript

build.sh

The build script simply compiles each class with the Java Compiler javac and packages the compiled classes and other files into a Web ARchive named ROOT.war. ROOT indicates that the app will run at the root path of the site that Tomcat serves.

NOTE When you deploy a WAR file to an Elastic Beanstalk environment, it is extracted during the deployment process and runs at the root path regardless of the name of the file. Elastic Beanstalk only runs apps at other paths if you package multiple WAR files into a ZIP archive and deploy that.

Only files required to run the application are included in the WAR. Uncompiled java classes and configuration files in .ebextensions/inactive are excluded.

A Windows version of the build script build-windows.sh is also included. Note that the classpath arguments are separated by semicolons instead of colons.