Grails part 3 - database and deployment

In this, part 3 of the series on Grails, I am going to talk about how to configure our web application to use the MySQL database as our default permanent store and then how to create a war file and deploy to Tomcat.

Firstly, we're going to install MySQL. Luckily the state of Linux package management has advanced to the point where this is as simple as:

sudo apt-get install mysql-server

It should ask what you want to set the root user password to and then install the database. Once it has installed, the database server should be started. To check this, you can run the ps aux | grep mysql command. You should see a line in the output with:

mysql 1004 0.0 0.6 178908 27960 ? Ssl 21:50 0:00 /usr/sbin/mysqld

Then we need to create the database:

CREATE DATABASE Bookstore_dev;

Now that we have our database ready to go, we need to get the MySQL driver so that our grails application can connect to the database. Go to http://www.mysql.com/downloads/ and download the Connector/J package from the MySQL connectors section. Uncompress the package and copy and paste the mysql-connector-java-5.1.15-bin.jar file into the BookStore/lib folder.

Next we'll need to modify our BookStore/grails-app/conf/DataSource.groovy file to specify that we want grails to use the MySQL database instead of the typical HSQLDB that is used. The DataSource.groovy file has three different sections "development", "test" and "production", corresponding to the three different stages of the development process and the three different environments that you can work with in grails. You can define a different database for each stage/environment. There is also a default "dataSource" section at the top, which is used unless the values are overwritten in each of the different sections. To start with, we're going to specify that the development environment should use the MySQL database. We can do this by modifying the development section to look like:

development {
dataSource {
dbCreate = "create"
url = "jdbc:mysql://localhost/Bookstore_dev"
driverClassName = "com.mysql.jdbc.Driver"
username = "root"
password = "password"
}
}

Ofcourse you'll need to change the username and password to whatever you've set them to. I'll also point out that it's not good practice to use the root user to access our database, because if our application gets hacked, our whole database would be compromised. It would be best from a security standpoint to create a new user with privileges limited to the "Bookstore_dev" database. However, since this is just our development database and we're only making it available to our local computer network for the time being it should be ok.

If we now start up our application using the grails run-app command, and once it's started browse to http://localhost:8080/BookStore, we should be able to see our application. We can then add some dummy data to check that it's getting saved to the database. I've gone ahead and added the authors "Stephen King" and "Robert A. Heinlein" and the books "Pet Cemetery", "Stranger in a Strange Land", "The Moon is a Harsh Mistress" (associating them with their respective authors). If you log into the database and have a look at it's contents you can see that the values have been added:

mysql> USE Bookstore_dev;
mysql> SHOW TABLES;
+-------------------------+
| Tables_in_Bookstore_dev |
+-------------------------+
| author |
| book |
+-------------------------+
2 rows in set (0.01 sec)

mysql> SELECT * FROM author;
+----+---------+--------------------+
| id | version | name |
+----+---------+--------------------+
| 1 | 0 | Stephen King |
| 2 | 0 | Robert A. Heinlein |
+----+---------+--------------------+
2 rows in set (0.01 sec)

mysql> SELECT * FROM book;
+----+---------+-----------+----------------------------+
| id | version | author_id | title |
+----+---------+-----------+----------------------------+
| 1 | 0 | 1 | Pet Cemetery |
| 3 | 0 | 2 | Starship Troopers |
| 4 | 0 | 2 | Stranger in a Strange Land |
+----+---------+-----------+----------------------------+
3 rows in set (0.00 sec)
So, we can see that the data is being saved to the database and that the association between the Author and Book object is represented with the 'author_id' field in the Book table. It's also worth noting the "version" field which is updated by grails every time any of the fields in the row are modified.

So now that we've got an application which uses a database it's time to deploy it to our *production* server. We're going to modify our DataSource.groovy file to ensure that the production environment (the one we're going to deploy) also uses the MySQL database:

production {
dataSource {
dbCreate = "update"
url = "jdbc:mysql://localhost/Bookstore_dev"
driverClassName = "com.mysql.jdbc.Driver"
username = "root"
password = "password"
}
}

Make sure you've executed the run-app command with dbCreate set to "create" before deploying this production code as dbCreate = "update" expects the tables to already be created in the database.

Now we can create the war file which we're going to upload to Tomcat through the manager web-app by running the command grails prod war. This generates a production environment war file. The production environment is optimized for code efficiency, while the development and testing environments are optimized for developer productivity. Once the command finishes executing we should have our war file under BookStore/target/BookStore-0.1.war. The 0.1 is the application version number and can be changed in the BookStore/application.properties file.

Now we can log into our Tomcat manager application (found at http://localhost:8080/manager/html if you've setup Tomcat according to the previous post), go to the Deploy section, select our WAR file and hit 'Deploy'. Once the page refreshes we should see our BookStore app in the list of applications and the column "Running" should be set to "true". We can now click on the link in the Path column to go to our web-app and start using it.

As an alternative way to deploy your application, you can also make use of the tomcat grails plugin. In order to do this you need to add a few variables to the BookStore/grails-app/conf/Config.groovy file, namely:

tomcat.deploy.username = "[tomcat manager user]"
tomcat.deploy.password = "[tomcat manager password]"
tomcat.deploy.url = "http://localhost:8080/manager"

Deploying the application is now achieved from the command line with:

grails prod tomcat deploy

This code essentially does the same thing that we did, makes a war file and deploys it, but might be preferable as it is only one step instead of two.

So there you have it, we've taken our simple web application, configured it to use a permanent datastore and deployed it to our Tomcat webserver.

NOTE: If you need to update your deployed application, the way to do it is to first "undeploy" the application from Tomcat, which can be done with "grails prod tomcat undeploy"