Out of the box, Spring boot applications use the embedded tomcat server start at default port 8080. You can change the default embedded server port to any other port, using any one of following options.

1. Change the default port in application.properties file

This file is provided as empty file when you create a simple Spring Boot application with the inizializr application:

spring boot configure web server port

Changing the server port is just a matter of setting:

application.properties
server.port=8081

On the other hand, if you are using YAML files for your external configuration, the following will do:

application.yml
server:
  port : 8081

2. Change the server port programatically

EmbeddedServletContainerCustomizer interface is used to customize embedded tomcat configuration. Any beans of this type will get a callback with the container factory before the container itself is started, so we can set the port, address, error pages etc.

2.1. Spring boot2 – WebServerFactoryCustomizer interface

Change default server port in spring boot2 applications by implementing ConfigurableWebServerFactory interface.

AppContainerCustomizer.java
@Component
public class AppContainerCustomizer
            implements WebServerFactoryCustomizer< ConfigurableWebServerFactory > {
   
    @Override
    public void customize(ConfigurableWebServerFactory factory) {
        factory.setPort(8081);
    }
}
 

3. Use the command line

Last but not least, yu can use the command line to set the Web server port by specifying ‘server.port’ as argument during application run command.

$ java -jar -Dserver.port=8081 spring-boot-example.jar
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