war.md

Code examples: jetty-war, tomcat-war, tomcat-war-ssl

Learn how to run and deploy a Ktor application inside a servlet container using a WAR archive.

A Ktor application can be run and deployed inside servlet containers that include Tomcat and Jetty. To deploy inside a servlet container, you need to generate a WAR archive and then deploy it to a server or a cloud service that supports WARs.

Ktor supports Jetty up to the 9.4.x version and Tomcat up to 9.0.x.

In this topic, we'll show you how to:

• configure Ktor to use it in a servlet application;
• apply Gretty and War plugins for running and packaging WAR applications;
• run a Ktor servlet application;
• generate and deploy a WAR archive.

Configure Ktor in a servlet application {id="configure-ktor"}

Ktor allows you to create and start a server with the desired engine (such as Netty, Jetty, or Tomcat) right in the application. In this case, your application has control over engine settings, connection, and SSL options.

In contrast to the approach above, a servlet container should control the application lifecycle and connection settings. Ktor provides a special ServletApplicationEngine engine that delegates control over your application to a servlet container.

Note that connection and SSL settings are not in effect when a Ktor application is deployed inside a servlet container. The tomcat-war-ssl sample demonstrates how to configure SSL in Tomcat.

Add dependencies {id="add-dependencies"}

To use Ktor in a servlet application, you need to include the ktor-server-servlet artifact in the build script:

Note that you don't need the separate Jetty or Tomcat artifacts when a Ktor application is deployed inside a servlet container.

Configure a servlet {id="configure-servlet"}

To register a Ktor servlet in your application, open the WEB-INF/web.xml file and assign ServletApplicationEngine to the servlet-class attribute:

{src="snippets/jetty-war/src/main/webapp/WEB-INF/web.xml" include-lines="7-16"}

Then, configure the URL pattern for this servlet:

{src="snippets/jetty-war/src/main/webapp/WEB-INF/web.xml" include-lines="18-21"}

Configure Gretty {id="configure-gretty"}

The Gretty plugin allows you to run a servlet application on Jetty and Tomcat. To install this plugin, open the build.gradle.kts file and add the following code to the plugins block:

{src="snippets/jetty-war/build.gradle.kts" include-lines="5,8,10"}

Then, you can configure it in a gretty block as follows:

{src="snippets/jetty-war/build.gradle.kts" include-lines="12-15"}

{src="snippets/tomcat-war/build.gradle.kts" include-lines="12-16"}

Note that if you want to use Tomcat, you need to specify servletContainer explicitly.

Finally, configure the run task:

{src="snippets/jetty-war/build.gradle.kts" include-lines="29-33"}

Configure War {id="configure-war"}

The War plugin allows you to generate WAR archives. You can install it by adding the following line to the plugins block in your build.gradle.kts file:

{src="snippets/jetty-war/build.gradle.kts" include-lines="5,9-10"}

Run an application {id="run"}

You can run a servlet application with the configured Gretty plugin by using the run task. For example, the following command runs the jetty-war example:

./gradlew :jetty-war:run

Generate and deploy a WAR archive {id="generate-war"}

To generate a WAR file with your application using the War plugin, execute the war task. For the jetty-war example, a command looks as follows:

./gradlew :jetty-war:war

The jetty-war.war is created in the build/libs directory. You can deploy the generated archive inside a servlet container by copying it to the jetty/webapps directory. For instance, a Dockerfile below shows how to run the created WAR inside a Jetty or Tomcat servlet container:

{src="snippets/jetty-war/Dockerfile"}

{src="snippets/tomcat-war/Dockerfile"}

You can find the complete examples here: jetty-war and tomcat-war.