我通过带有mvn清洁安装spring-boot： run的maven在嵌入式tomcat服务器上运行spring-boot。但是每次我运行它都会收到这个错误：

 Caused by: java.lang.IllegalArgumentException: Could not resolve placeholder 'language' in string value "${language}"
    at org.springframework.util.PropertyPlaceholderHelper.parseStringValue(PropertyPlaceholderHelper.java:174) ~[spring-core-4.3.6.RELEASE.jar:4.3.6.RELEASE]
    at org.springframework.util.PropertyPlaceholderHelper.replacePlaceholders(PropertyPlaceholderHelper.java:126) ~[spring-core-4.3.6.RELEASE.jar:4.3.6.RELEASE]
    at org.springframework.core.env.AbstractPropertyResolver.doResolvePlaceholders(AbstractPropertyResolver.java:236) ~[spring-core-4.3.6.RELEASE.jar:4.3.6.RELEASE]
    at org.springframework.core.env.AbstractPropertyResolver.resolveRequiredPlaceholders(AbstractPropertyResolver.java:210) ~[spring-core-4.3.6.RELEASE.jar:4.3.6.RELEASE]
    at org.springframework.context.support.PropertySourcesPlaceholderConfigurer$2.resolveStringValue(PropertySourcesPlaceholderConfigurer.java:172) ~[spring-context-4.3.6.RELEASE.jar:4.3.6.RELEASE]
    at org.springframework.beans.factory.support.AbstractBeanFactory.resolveEmbeddedValue(AbstractBeanFactory.java:831) ~[spring-beans-4.3.6.RELEASE.jar:4.3.6.RELEASE]
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.doResolveDependency(DefaultListableBeanFactory.java:1086) ~[spring-beans-4.3.6.RELEASE.jar:4.3.6.RELEASE]
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.resolveDependency(DefaultListableBeanFactory.java:1066) ~[spring-beans-4.3.6.RELEASE.jar:4.3.6.RELEASE]
    at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor$AutowiredFieldElement.inject(AutowiredAnnotationBeanPostProcessor.java:585) ~[spring-beans-4.3.6.RELEASE.jar:4.3.6.RELEASE]
    at org.springframework.beans.factory.annotation.InjectionMetadata.inject(InjectionMetadata.java:88) ~[spring-beans-4.3.6.RELEASE.jar:4.3.6.RELEASE]
    at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor.postProcessPropertyValues(AutowiredAnnotationBeanPostProcessor.java:366) ~[spring-beans-4.3.6.RELEASE.jar:4.3.6.RELEASE]
    ... 35 common frames omitted

该错误与这两行代码有关：

@Value("${language}")
private String language;

该语言标志在我的application.properties中指定如下：

application.properties

language=java
logging.level.org.springframework=TRACE

这是令人困惑的部分：当我在没有spring-boot： run命令的情况下运行构建时，它会正确构建，我可以毫无问题地运行构建的jar。只有当我尝试在嵌入式tomcat服务器上运行时，我才会遇到这个问题。

我可以通过在我的代码中执行此操作来绕过它：

@Value("${language:java}")
private String language;

但这对我来说没有意义，因为Spring应该自动从application.properties文件中读取默认值。

编辑：正如人们所指出的，在嵌入式tomcat服务器上运行时，它根本不会读取application.properties。有什么方法可以强制它读取文件，或者为什么它可能没有读取它？当部署到外部应用服务器而不是嵌入式服务器时，它工作得很好。