Exception in thread "main" java.lang.IllegalArgumentException: Circular placeholder reference ‘server.port‘ in property definitions    at org.springframework.util.PropertyPlaceholderHelper.parseStringValue(PropertyPlaceholderHelper.java:141)    at org.springframework.util.PropertyPlaceholderHelper.parseStringValue(PropertyPlaceholderHelper.java:162)    at org.springframework.util.PropertyPlaceholderHelper.parseStringValue(PropertyPlaceholderHelper.java:162)    at org.springframework.util.PropertyPlaceholderHelper.parseStringValue(PropertyPlaceholderHelper.java:145)    at org.springframework.util.PropertyPlaceholderHelper.parseStringValue(PropertyPlaceholderHelper.java:145)    at org.springframework.util.PropertyPlaceholderHelper.replacePlaceholders(PropertyPlaceholderHelper.java:126)    at org.springframework.core.env.AbstractPropertyResolver.doResolvePlaceholders(AbstractPropertyResolver.java:204)    at org.springframework.core.env.AbstractPropertyResolver.resolvePlaceholders(AbstractPropertyResolver.java:170)    at org.springframework.core.env.AbstractEnvironment.resolvePlaceholders(AbstractEnvironment.java:566)    at org.springframework.boot.context.ContextIdApplicationContextInitializer.getApplicationId(ContextIdApplicationContextInitializer.java:110)    at org.springframework.boot.context.ContextIdApplicationContextInitializer.initialize(ContextIdApplicationContextInitializer.java:105)    at org.springframework.boot.SpringApplication.applyInitializers(SpringApplication.java:640)    at org.springframework.boot.SpringApplication.createAndRefreshContext(SpringApplication.java:343)    at org.springframework.boot.SpringApplication.run(SpringApplication.java:307)    at org.springframework.boot.SpringApplication.run(SpringApplication.java:1191)    at org.springframework.boot.SpringApplication.run(SpringApplication.java:1180)    at com.xiaoyi.sns.robot.Application.main(Application.java:27)    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)    at java.lang.reflect.Method.invoke(Method.java:497)    at com.intellij.rt.execution.application.AppMain.main(AppMain.java:147)