In Spring Boot, you can configure the server port by setting the server.port property in the application.properties or application.yml file.

1. Application Properties and YAML file

Here’s an example of how to configure the server port in application.properties file:

server.port=8080

In this example, the server will run on port 8080.

You can also configure the server port using the server.port property in the application.yml file

server:
  port: 8081

In this example, the server will run on port 8081.

2. Configure Port Programmatically

You can also configure the server port programmatically in a Spring Boot application.

@Value("${server.port}")
int port;

@Bean
public EmbeddedServletContainerCustomizer containerCustomizer() {
    return (container -> {
        container.setPort(port);
    });
}

In this example, the port is injected from the properties file, and a EmbeddedServletContainerCustomizer bean is defined to set the port on the EmbeddedServletContainer instance used by Spring Boot.

System.getProperties().put( "server.port", 80 );
SpringApplication.run(App.class, args);

3. Spring HTTP Port

You can also use the spring.http.port property to configure the server port, this property is also supported by Spring Boot.

spring.http.port=8082

In this example, the server will run on port 8082.

4. Through command line

Another way to configure the port is by using the command line argument while running the application like this:

-Dserver.port=8888 or --server.port=8888

java -jar myapp.jar --server.port=8888 
  or 


java -jar myapp.jar -Dserver.port=8888 

   or
mvn spring-boot:run -Dspring-boot.run.arguments=--server.port=8085

In this example, the server will run on port 8888.

You can also use the SERVER_PORT environment variable to configure the server port.

export SERVER_PORT=8084

In this example, the server will run on port 8084.