What happens behind the scenes of deploying a Spring MVC application to tomcat outside of eclipse?

Question

I guess a drawback of using such an awesome IDE like eclipse is that you miss the point for what happens behind the scenes of an application. I'm a ruby developer so not a java veteran. So I've been coding a project in java and using the spring framework for IOC and MVC. Can someone explain to me what is going on when I select run on server in eclipse? Because eventually I will be deploying this masterpiece of an application to a Linux server. Here is my setup. I am using Spring MVC 3 and the maven plugin in eclipse. In the pom.xml file, I have stuff like latest spring release version, log4j, spring mvc, spring context etc.

I have been testing my application on localhost using the handy option of run on server in the eclipse IDE. The server configuration in eclipse is pointing to the tomcat directory location for where I have installed tomcat 7. Please demystify what happens behind the scenes and what I will need to do if I want to deploy this application on a production server. The more detail the better. Thanks a ton in advance.

Sotirios Delimanolis · Accepted Answer · 2013-10-02T16:01:52.500

1

Deploying a web application to Tomcat is as simple as this (assuming Tomcat is installed)

Bundle your application in a .war with the correct format.
Move the generated .war file to the /webapps directory of your Tomcat installation folder.
Run the /bin/startup.[sh|bat] script in the Tomcat installation folder.

Note that there are intermediate steps you can do to configure the deployment, like changing your context path. Go through the Tomcat documentation for details.

In step 3, Tomcat will extract the .war contents to a directory in the /webapps folder with the same name as your .war file. It will use this as the context path. The script itself launches a java process by putting the WEB-INF/[class|lib|...] onto the classpath along with some Tomcat libraries.

So Eclipse basically does all the steps above for you.

edited Oct 02 '13 at 16:01

answered Oct 02 '13 at 15:45

Sotirios Delimanolis

274,122
60
696
724

Does it have to be a war? – Horse Voice Oct 02 '13 at 15:47
@ImtiazAhmad `war` stands for "Web Archive" so in short, yes; it does. – Boris the Spider Oct 02 '13 at 15:48
@ImtiazAhmad Tomcat will extract the war and create an entry in its `server.xml` file. You can do that manually if you wanted to. – Sotirios Delimanolis Oct 02 '13 at 15:48
@SotiriosDelimanolis not in its `server.xml` methinks. It creates a file in `conf/Catalina//.xml`. – Boris the Spider Oct 02 '13 at 15:49
@BoristheSpider It probably puts stuff in many places. The `server.xml` entry just describes the context `docBase` and `path`. The safe way is to let Tomcat do it. – Sotirios Delimanolis Oct 02 '13 at 15:51
I'm confused. Can you please elaborate on the details of this step? – Horse Voice Oct 02 '13 at 15:51
Where is the war in eclipse? I don't see the war – Horse Voice Oct 02 '13 at 15:52
@ImtiazAhmad Tomcat notices you have a `.war` file. It'll extract its contents (it's just a glorified `zip`) to a folder in the `/webapps` directory. To identify it as a web application, Tomcat needs to set some additional configuration parameters in its configuration files. These are in `/conf` folder. – Sotirios Delimanolis Oct 02 '13 at 15:52
@ImtiazAhmad It might not necessarily be using the `.war` just the contents directly. The source should be in `/bin`. You can normally see this by going into project `Properties > Deployment Assembly`. – Sotirios Delimanolis Oct 02 '13 at 15:53
So What are the steps that I would need to take to deploy this by hand? – Horse Voice Oct 02 '13 at 16:00
@ImtiazAhmad The 3 steps in my answer. – Sotirios Delimanolis Oct 02 '13 at 16:01
What do you mean by context path in step 3? – Horse Voice Oct 02 '13 at 17:41
@ImtiazAhmad When you create a webapp project in Eclipse, it usually makes your application accessible at `http://localhost/projectName`. The `projectName` is the context path. You can change this to whatever (almost) you like. Maybe you want `http://localhost/some/webapp/of/my/choice` or even root `http://localhost/`. You can set that in the `server.xml`. Follow the instructions in the Tomcat document I linked. – Sotirios Delimanolis Oct 02 '13 at 17:44
alright, my mvc app is not being deployed properly. I am getting a 404. When I navigate to the tomcat folder, I dont see my project copied over to the webapps directory. – Horse Voice Oct 02 '13 at 23:04
@ImtiazAhmad Please start a new question with all the details. – Sotirios Delimanolis Oct 02 '13 at 23:20

score 0 · Answer 2 · answered Oct 02 '13 at 15:53

Ultimately you are deploying an web application that means you are deploying a war file to the server. Regardless of using frameworks like spring, struts anything.

SO a web application request starts from web.xml file. SO for spring mvc application, you are mapping all request coming from browser to DispatcherServlet and then this guy is responsible to manage whole life cycle of your application. For more details of how MVC works please see http://docs.spring.io/spring/docs/3.2.x/spring-framework-reference/html/mvc.html

So in order to deploy your application (a war) on server first of all you have to create a war from your source code. You can go to traditional approach to use java given utility like using jar from command prompt or you can use ANT, GRADLE, MAVEN and such build tool that creates war for you in automated way. Spring is not doing anything extra for you. I believe you to research a bit more on how these tools works. Once a war is ready for you, you can simply go to tomcat UI and there you will find options to deploy your war.

I hope it helps you.

What tomcat web UI are you referring to? – Horse Voice Oct 02 '13 at 17:51 — Horse Voice, Oct 02 '13 at 17:51
Tomcat UI I meant tomcat Admin console. – Mohammad Adnan Oct 03 '13 at 09:49 — Mohammad Adnan, Oct 03 '13 at 09:49

score 0 · Answer 3 · answered Oct 02 '13 at 15:54

All the majic happens in two places.

The first is your 'Servers' directory in the root of your Eclipse Package Explorer. These are your server configuration files that Eclipse will use (mostly) when it creates a new server instance.

The second is in the ./metadata/.plugins/org.eclipse.wst.server.core/ file system directory in your Eclipse workspace. This is where the tomcat application is actually deployed by eclipse.

The Tomcat Documentation is pretty good actually and helps explain how to do deployments. FYI, I do not know many people that use the Manager, from my experience most people deploy their applications by hand.

What happens behind the scenes of deploying a Spring MVC application to tomcat outside of eclipse?

3 Answers3

Linked