如何在tomcat7和JDBC jar中部署.war文件？

Question

I am trying to deploy a war file in tomcat7. I am using MySQL JDBC driver to connect to database server. The jar file of MySQL JDBC driver is copied to $CATALINA_HOME/lib/ directory and the web application works correctly.

Now, I want to deploy the .war file in Amazon Elastic BeanStalk service. By default, Amazon doesn't place the MySQL JDBC driver in $CATALINA_HOME/lib directory by default and I can't run a script which will ssh into each instance and download the jar in the directory.

Is there any way, in which I can bundle the jar file for JDBC driver , so that I don't have to download and place the jar file in $CATALINA_HOME/lib directory ?

Answer 1

You can place the jar file in an S3 bucket, and then use a EB container command to copy the file to the lib directory, like:

"copy-lib-file":
  mode: "000644"
  owner: root
  group: root
  source: https://s3.amazonaws.com/<MY_BUCKET>/<my-JDBC-driver>.jar

Answer 2

Tomcat, like many application servers, installs a variety of class loaders (implementation of java.lang.ClassLoader) that will give your application access to the JDBC jar resource.

The order is:

1. Bootstrap
2. System
3. Common - $CATALINA_BASE/lib
4. Webapp - /WEB-INF/lib

Put the jar into the WEB-INF/lib directory inside the application. Note, this JAR will be only visible to this specific application and no others.

Answer 3

In order to do so you need to use . ebextensions . With .ebextensions you can copy files from your application package to the beanstalk file system.

However keep in mind that no other application deployed in a beanstalk environment will use your driver. Your beanstalk instance is dedicated to one application. Every time you upload the application you have to upload the mysql driver in order to be deployed to the tomcat installation.

Therefore you do not gain anything in terms of upload size or memory footprint in a tomcat (shared jdbc connetion pool through jndi).

It seems that uploading your application with the jdbc driver included (non provided in your maven config) is a more beanstalk oriented solution.

However there are cases you don't want to make any changes in the way your war gets packaged, for example your application gets deployed to an on premises tomcat server containing the jdbc driver and you want to upload it to an elastic beanstalk environment. In such cases you can consider docker with elastic beanstalk as an option too.

Answer 4

No you can't bundle JDBC JARS for Tomcat7:

I've had this issue and it was a nightmare to debug. In my trials and in the documentation you can't bundle JDBC drivers inside your WAR file. Or at least you can but the classloader will ignore JDBC classes that are not in the Tomcat Lib folder. Its in the first paragraph of the Mysql section of the documentation here -> Tomcat7-JDBC I don't know of Tomcat8 or Tomcat9 beta...

Short Term Solution

What I do is exactly what you said you don't want to do and similar to Mark B's solution. I use a script that copies it from s3 but this is really easy and is only 1 line of bash if you use the aws s3 cp command. The aws s3 tool comes installed on the EC2 instance your application will be running on.

aws s3 cp s3://mybucket/mysql.jar /usr/share/tomcat7/lib/mysql.jar

*You will need to restart tomcat another reason you should see the longterm solution

Long Term Real Solution = Automate Your Build Steps

In the end you'll eventually have to run provisioning scripts if your application becomes complex, which is why I stopped using elastic beanstalk and started using AWS cloudformation which gives you a "STEP" where you can throw in all your setup scripts similar to docker build steps. It will also run those configuration steps for every new instance that gets created so there is no needed for you to ssh onto every box.

Cloudformation is all about turning your infrastructure setup into code which you could actually check into github and build without any manual intervention. You go through the headache of configuring your build scripts once then save your environment as a json or yaml file. You can include the MySQL server, tomcat version, firewalls, load balancers etc etc and build that all from a file.