5. Replacing tomcat with jetty

By default when we run spring boot application, it runs a tomcat server. I have personally found tomcat too heavyweight and I prefer to use Jetty for writing a webservices backend.

2018-12-19 10:54:08.403  INFO 16029 --- [           main] o.s.b.w.embedded.tomcat.TomcatWebServer  : Tomcat initialized with port(s): 8080 (http)

2018-12-19 10:54:08.424  INFO 16029 --- [           main] o.apache.catalina.core.StandardService   : Starting service [Tomcat]

2018-12-19 10:54:08.424  INFO 16029 --- [           main] org.apache.catalina.core.StandardEngine  : Starting Servlet Engine: Apache Tomcat/9.0.12

To replace tomcat with Jetty, we need to make a couple of changes.  The first step is to add Jetty dependencies in the pom.xml.

  
  <dependency>
   <groupId>org.springframework.boot</groupId>
   <artifactId>spring-boot-starter-data-jpa</artifactId>
  </dependency>
  <dependency>
   <groupId>org.springframework.boot</groupId>
   <artifactId>spring-boot-starter-jetty</artifactId>
  </dependency>
  <dependency>
   <groupId>org.eclipse.jetty</groupId>
   <artifactId>jetty-deploy</artifactId>
  </dependency>
  <dependency>
   <groupId>org.eclipse.jetty</groupId>
   <artifactId>jetty-rewrite</artifactId>
  </dependency>
  <dependency>
   <groupId>org.eclipse.jetty</groupId>
   <artifactId>jetty-util</artifactId>
  </dependency>

Since springframework boot bom automatically includes a dependency on tomcat in spring-boot-starter-web, we specifically need to exclude it. So we change

  <dependency>
   <groupId>org.springframework.boot</groupId>
   <artifactId>spring-boot-starter-web</artifactId>
  </dependency>

to

  <dependency>
   <groupId>org.springframework.boot</groupId>
   <artifactId>spring-boot-starter-web</artifactId>
   <exclusions>
    <exclusion>
     <groupId>org.springframework.boot</groupId>
     <artifactId>spring-boot-starter-tomcat</artifactId>
    </exclusion>
   </exclusions>
  </dependency>

The next step is to add a customizer for jetty which will allow us to set some parameters related to Jetty.
As we can see the customizer uses a set of variables that we can override in application.properties file to modify the behavior of the server.

2018-12-19 11:06:44.577  INFO 16219 --- [           main] o.e.jetty.server.AbstractConnector       : Started ServerConnector@42ebece0{HTTP/1.1,[http/1.1]}{0.0.0.0:8081}
2018-12-19 11:06:44.580  INFO 16219 --- [           main] o.s.b.web.embedded.jetty.JettyWebServer  : Jetty started on port(s) 8081 (http/1.1) with context path ''

Now the logs clearly show that in place of tomcat, it is running jetty.