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I'm about to build my first website in Java with Spring Framework using Spring Boot and it's much easier to build it in jar, but I have a few questions about it.

What are the differences in general?

In jar files the views are under /resources/templates, but in war file it's under /webapp/WEB-INF/.

What are the differences? Can I deploy a jar on an online host?

Tom
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Hama Saadwn
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7 Answers7

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Spring Boot can be told to produce a 'fat JAR' which includes all of your module/service's dependencies and can be run with java -jar <your jar>. See "Create an executable JAR with Maven" here.

Spring Boot can also be told to produce a WAR file, in which case you'll likely choose to deploy it to a web container such as Tomcat or Jetty.

Plenty more details on Spring Boot deployment here.

glytching
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    and don't forget to exclude the embedded tomcat in this case; check the link in @lazyneuron's answer – P.J.Meisch Jul 18 '17 at 11:42
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    @HamaSaadwn just fyi, spring-boot application build as `war` could also be run as `java -jar xxx.war`. It could be used in some transition phase when you're making changes to your deployment infrastructure with moving to `fat jar` – rilaby Jul 18 '17 at 12:29
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    Whether it's "fat" (i.e. containing all dependencies) and executable or not, does not depend on whether it's a .jar or .war file. This currently accepted answer does not explain the difference between both (which is what was asked). – herman Mar 20 '20 at 10:28
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    What is the difference? You didn't answer the question!!! – Davoud Feb 13 '21 at 21:30
  • the real question was never answered? I thought the original question was about the difference... – lee Feb 15 '22 at 01:38
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Depends on your deployment. If you are planning to deploy your application to an existing Java EE Application Server (e.g. Tomcat), then standard approach is to perform a war build.

When you use fat jar approach, your application will be deployed on embedded application container provided by spring boot. Conduct Deploying Spring Boot Applications for more information.

lazyneuron
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    This is the proper answer (stating the difference) to the question amongst all. – Derrick Dec 11 '19 at 17:58
  • You can create an executable war file as well, in which case it works the same as a jar but with a war layout. So this isn't really the difference between both. – herman Mar 20 '20 at 10:17
  • why a person will choose to deploy on an external server ? is not that means loosing on the beauty of sprint boot which was suppose to have auto initializing the server.. – Manoj K Sardana Sep 07 '21 at 07:38
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Running spring-boot application as fat *.jar

It is possible to build so called fat JAR that is executable *.jar file with embedded application container (Tomcat as default option). There are spring-boot plugins for various build systems. Here is the one for maven: spring-boot-maven-plugin

To execute the kind of fat *.jar you could simple run command:

java -jar *.jar

Or using spring-boot-maven goal:

mvn spring-boot:run

Building spring-boot application as *.war archive

The other option is to ship your application as old-fashioned war file. It could be deployed to any servlet container out there. Here is step by step how-to list:

  1. Change packaging to war (talking about maven's pom.xml)
  2. Inherit main spring-boot application class from SpringBootServletInitializer and override SpringApplicationBuilder configure(SpringApplicationBuilder) method (see javadoc)
  3. Make sure to set the scope of spring-boot-starter-tomcat as provided

More info in spring-boot documentation

rilaby
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I was under the same problem, when I deployed my jar issue free on my local. Then I had to demo it on the server. You can create a war file by changing the pom.xml , tag 

<packaging>jar</packaging>

to

<packaging>war</packaging>

and you will have a war file in your target which you can deploy to your server(tomcat in my case)

Groot
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If you need to deploy it in an external container, you'll normally have to create a war file (which doesn't have to be executable).

If you want to use the embedded container, you can choose to create an executable .jar file or an executable .war file. AFAIK the only difference is in the layout of the archive, and therefore normally also the layout of your source repository.

E.g. using standard folder structure with Maven / Gradle, static resources for a .jar will need to be in src/main/resources/static while for a .war file they should be in src/main/webapp.

herman
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war file is a Web Application Archive which runs inside an application server while a .jar is Java Application Archive that runs a desktop application on a user's machine. A war file is a special jar file that is used to package a web application to make it easy to deploy it on an application server.

Ousama
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Simple and easy answer. Packaging type jar represented as standalone application and packaging type war represented as web application.

Abhishek Gupta
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