1，eureka.instance.appname

找到類 org.springframework.cloud.netflix.eureka.EurekaInstanceConfigBean.java，其中有段：

@Data
@ConfigurationProperties("eureka.instance")
public class EurekaInstanceConfigBean implements CloudEurekaInstanceConfig, EnvironmentAware {

    private static final String UNKNOWN = "unknown"
 
;

    /**
     * Get the name of the application to be registered with eureka.
     */
    private String appname = UNKNOWN;

可以看到，應用名稱 就是在這裡配置的；

2，spring.application.name

找到類 org.springframework.cloud.netflix.eureka.EurekaInstanceConfigBean，其中片段：

    @Override
    public void setEnvironment(Environment environment) {
        this
 
.environment = environment;
        // set some defaults from the environment, but allow the defaults to use relaxed binding
        RelaxedPropertyResolver springPropertyResolver = new RelaxedPropertyResolver(this.environment, "spring.application.");
        String springAppName = springPropertyResolver.getProperty("name"
 
);
        if(StringUtils.hasText(springAppName)) {
            setAppname(springAppName);
            setVirtualHostName(springAppName);
            setSecureVirtualHostName(springAppName);
        }
    }

可以看到，這裡是用 spring.application.name 配置的應用名稱；

3，結論

從以上可以看到，spring.application.name 的優先順序比 eureka.instance.appname 高，例如：

spring:
  application:
    name: jack
eureka:
  client:
    serviceUrl:
      defaultZone: http://localhost:8761/eureka/
  instance:
    appname: client

兩者都配置的時候，註冊到Eureka Server上的 appname 是 jack