Is it possible to configure the spring boot server explicitly? - spring-boot

Question

I've a Spring Boot application where one of the dependencies is using spring and a embedded jetty to start an ad-hoc web server. This causes my spring boot app to start in a jetty instead of a tomcat.
My spring-boot-starter-web:
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</artifactId>
<exclusions>
<exclusion>
<groupId>org.apache.tomcat.embed</groupId>
<artifactId>tomcat-embed-websocket</artifactId>
</exclusion>
</exclusions>
</dependency>
The dependencies pom:
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-web</artifactId>
</dependency>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-webmvc</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.integration</groupId>
<artifactId>spring-integration-http</artifactId>
</dependency>
<dependency>
<groupId>org.apache.httpcomponents</groupId>
<artifactId>httpclient</artifactId>
</dependency>
<dependency>
<groupId>org.eclipse.jetty</groupId>
<artifactId>jetty-server</artifactId>
</dependency>
<dependency>
<groupId>org.eclipse.jetty</groupId>
<artifactId>jetty-servlet</artifactId>
</dependency>
Is there a possibility to configure the server to use by spring boot explicitly instead of being inferred by the dependency tree?
EDIT
I investigated the issue a little bit further and created a repo to reproduce the issue: github.com/svettwer/spring-server-test
org.eclipse.jetty.websocket:javax-websocket-server-impl causes spring to start with jetty without any other config required.
EDIT 2
The issue is not present anymore in Spring Boot 2.x
EDIT 3
I'll deleted the repo mentioned earlier, but here is the dependency setup that caused the issue:
<dependencies>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</artifactId>
<version>1.5.7.RELEASE</version>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-test</artifactId>
<version>1.5.7.RELEASE</version>
<scope>test</scope>
</dependency>
<!-- Comment that in to start spring with jetty-->
<dependency>
<groupId>org.eclipse.jetty.websocket</groupId>
<artifactId>javax-websocket-server-impl</artifactId>
<version>9.4.8.v20171121</version>
</dependency>
</dependencies>

Answer 1

Normally, if you have the spring-boot-starter-tomcat on your classpath (through spring-boot-starter-web), it should always select Tomcat since it has priority over other servlet containers. Even if you have the following dependencies, Spring boot will start with Tomcat:
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</artifactId>
</dependency>
<dependency>
<groupId>org.eclipse.jetty</groupId>
<artifactId>jetty-server</artifactId>
</dependency>
<dependency>
<groupId>org.eclipse.jetty</groupId>
<artifactId>jetty-webapp</artifactId>
</dependency>
<dependency>
<groupId>org.eclipse.jetty</groupId>
<artifactId>jetty-servlet</artifactId>
</dependency>
You can programmatically override the chosen servlet container by registering your own ServletWebServerFactory, for example:
#Bean
public ServletWebServerFactory factory() {
return new TomcatServletWebServerFactory();
}
You can choose the predefined TomcatServletWebServerFactory, JettyServletWebServerFactory or the UndertowServletWebServerFactory.

Answer 2

This guide may help you: https://docs.spring.io/spring-boot/docs/current/reference/html/howto-embedded-web-servers.html
If you run an mvn dependency:tree and search for jetty you might find that you need to exclude it, e.g:
spring-boot-starter-jetty
excluded like in the example:
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</artifactId>
<exclusions>
<!-- Exclude the Tomcat dependency -->
<exclusion>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-tomcat</artifactId>
</exclusion>
</exclusions>
</dependency>
<!-- Use Jetty instead -->
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-jetty</artifactId>
</dependency>
which is favouring jetty over tomcat - but you get the idea hopefully...
Hope this helps.