注意了！雲伺服器的一些環境配置有可能導致應用啟動失敗
嘗試用serviceComb框架跟Spring boot框架結合寫了一個測試應用，結果放到雲伺服器上啟動的時候報錯，大概錯誤如下：
Caused by: java.lang.IllegalArgumentException: Could not resolve placeholder 'HOSTNAME%%.*' in value "history -a; printf "\033]0;%[email protected]%s:%s\007" "${USER}" "${HOSTNAME%%.*}" "${PWD/#$HOME/~}""
at org.springframework.util.PropertyPlaceholderHelper.parseStringValue(PropertyPlaceholderHelper.java:174) ~[spring-core-4.3.14.RELEASE.jar:4.3.14.RELEASE]
at org.springframework.util.PropertyPlaceholderHelper.replacePlaceholders(PropertyPlaceholderHelper.java:126) ~[spring-core-4.3.14.RELEASE.jar:4.3.14.RELEASE]
at org.springframework.core.env.AbstractPropertyResolver.doResolvePlaceholders(AbstractPropertyResolver.java:236) ~[spring-core-4.3.14.RELEASE.jar:4.3.14.RELEASE]
at org.springframework.core.env.AbstractPropertyResolver.resolveRequiredPlaceholders(AbstractPropertyResolver.java:210) ~[spring-core-4.3.14.RELEASE.jar:4.3.14.RELEASE]
at org.springframework.core.env.AbstractPropertyResolver.resolveNestedPlaceholders(AbstractPropertyResolver.java:227) ~[spring-core-4.3.14.RELEASE.jar:4.3.14.RELEASE]
at org.springframework.core.env.PropertySourcesPropertyResolver.getProperty(PropertySourcesPropertyResolver.java:84) ~[spring-core-4.3.14.RELEASE.jar:4.3.14.RELEASE]
at org.springframework.core.env.PropertySourcesPropertyResolver.getProperty(PropertySourcesPropertyResolver.java:61) ~[spring-core-4.3.14.RELEASE.jar:4.3.14.RELEASE]
at org.springframework.core.env.AbstractEnvironment.getProperty(AbstractEnvironment.java:527) ~[spring-core-4.3.14.RELEASE.jar:4.3.14.RELEASE]
at org.apache.servicecomb.config.ConfigurationSpringInitializer.getProperties(ConfigurationSpringInitializer.java:141) ~[foundation-config-1.0.0.jar:1.0.0]
at org.apache.servicecomb.config.ConfigurationSpringInitializer.getAllProperties(ConfigurationSpringInitializer.java:122) ~[foundation-config-1.0.0.jar:1.0.0]
at org.apache.servicecomb.config.ConfigurationSpringInitializer.setEnvironment(ConfigurationSpringInitializer.java:61) ~[foundation-config-1.0.0.jar:1.0.0]
at org.springframework.context.support.ApplicationContextAwareProcessor.invokeAwareInterfaces(ApplicationContextAwareProcessor.java:106) ~[spring-context-4.3.16.RELEASE.jar:4.3.16.RELEASE]
at org.springframework.context.support.ApplicationContextAwareProcessor.postProcessBeforeInitialization(ApplicationContextAwareProcessor.java:97) ~[spring-context-4.3.16.RELEASE.jar:4.3.16.RELEASE]
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.applyBeanPostProcessorsBeforeInitialization(AbstractAutowireCapableBeanFactory.java:409) ~[spring-beans-4.3.16.RELEASE.jar:4.3.16.RELEASE]
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.initializeBean(AbstractAutowireCapableBeanFactory.java:1622) ~[spring-beans-4.3.16.RELEASE.jar:4.3.16.RELEASE]
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:555) ~[spring-beans-4.3.16.RELEASE.jar:4.3.16.RELEASE]
... 14 common frames omitted
配置裡面根本就不需要用到HOSTNAME%%.*，所以這下有點矇蔽，檢視相關原始碼也沒有要讀取這個HOSTNAME%%.*，不得已，用env命令看了下雲伺服器，發現了一個重要的變數：
PROMPT_COMMAND=history -a; printf "\033]0;%[email protected]%s:%s\007" "${USER}" "${HOSTNAME%%.*}" "${PWD/#$HOME/~}
明顯的，就是系統的變數讀取方法${}跟spring boot那一套衝突了，解決的辦法就是去掉這些${}，想辦法用另一種方式替換。
最後搞定!