方法一：可以通過實現EmbeddedServletContainerCustomizer介面來實現，程式碼：

import javafx.application.Application;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.EnableAutoConfiguration;
import org.springframework.boot.builder.SpringApplicationBuilder;
import org.springframework.boot.context.embedded.ConfigurableEmbeddedServletContainer;
import 
 
org.springframework.boot.context.embedded.EmbeddedServletContainerCustomizer;
import org.springframework.boot.context.web.SpringBootServletInitializer;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

@RestController
@EnableAutoConfiguration
 
public class TestClass extends SpringBootServletInitializer implements EmbeddedServletContainerCustomizer{
    @RequestMapping("/")
    String home() {
        return "hi...";
    }

    public static void main(String[] args) {
        SpringApplication.run(TestClass.class, args);
    }

    @Override
 
protected SpringApplicationBuilder configure(SpringApplicationBuilder builder) {
        return builder.sources(Application.class);
    }

    @Override
public void customize(ConfigurableEmbeddedServletContainer container) {
        container.setPort(8081);
    }
}

方法二：更加簡單

在src/resource下增加檔案application.properties

加入server.port=8081

即可