报错信息：

org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'helloController': Injection of autowired dependencies failed; nested exception is java.lang.IllegalArgumentException: Could not resolve placeholder 'name' in value "${name}"
	at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor.postProcessProperties(AutowiredAnnotationBeanPostProcessor.java:380) ~[spring-beans-5.1.9.RELEASE.jar:5.1.9.RELEASE]
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.populateBean(AbstractAutowireCapableBeanFactory.java:1411) ~[spring-beans-5.1.9.RELEASE.jar:5.1.9.RELEASE]
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:592) ~[spring-beans-5.1.9.RELEASE.jar:5.1.9.RELEASE]
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:515) ~[spring-beans-5.1.9.RELEASE.jar:5.1.9.RELEASE]
	at org.springframework.beans.factory.support.AbstractBeanFactory.lambda$doGetBean$0(AbstractBeanFactory.java:320) ~[spring-beans-5.1.9.RELEASE.jar:5.1.9.RELEASE]
	at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:222) ~[spring-beans-5.1.9.RELEASE.jar:5.1.9.RELEASE]
	at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:318) ~[spring-beans-5.1.9.RELEASE.jar:5.1.9.RELEASE]
	at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:199) ~[spring-beans-5.1.9.RELEASE.jar:5.1.9.RELEASE]
	at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:845) ~[spring-beans-5.1.9.RELEASE.jar:5.1.9.RELEASE]
	at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:877) ~[spring-context-5.1.9.RELEASE.jar:5.1.9.RELEASE]
	at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:549) ~[spring-context-5.1.9.RELEASE.jar:5.1.9.RELEASE]
	at org.springframework.boot.web.servlet.context.ServletWebServerApplicationContext.refresh(ServletWebServerApplicationContext.java:141) ~[spring-boot-2.1.8.RELEASE.jar:2.1.8.RELEASE]
	at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:744) [spring-boot-2.1.8.RELEASE.jar:2.1.8.RELEASE]
	at org.springframework.boot.SpringApplication.refreshContext(SpringApplication.java:391) [spring-boot-2.1.8.RELEASE.jar:2.1.8.RELEASE]
	at org.springframework.boot.SpringApplication.run(SpringApplication.java:312) [spring-boot-2.1.8.RELEASE.jar:2.1.8.RELEASE]
	at org.springframework.boot.SpringApplication.run(SpringApplication.java:1215) [spring-boot-2.1.8.RELEASE.jar:2.1.8.RELEASE]
	at org.springframework.boot.SpringApplication.run(SpringApplication.java:1204) [spring-boot-2.1.8.RELEASE.jar:2.1.8.RELEASE]
	at com.idheima.springbootinit.SpringbootInitApplication.main(SpringbootInitApplication.java:11) [classes/:na]
Caused by: java.lang.IllegalArgumentException: Could not resolve placeholder 'name' in value "${name}"
	at org.springframework.util.PropertyPlaceholderHelper.parseStringValue(PropertyPlaceholderHelper.java:178) ~[spring-core-5.1.9.RELEASE.jar:5.1.9.RELEASE]
	at org.springframework.util.PropertyPlaceholderHelper.replacePlaceholders(PropertyPlaceholderHelper.java:124) ~[spring-core-5.1.9.RELEASE.jar:5.1.9.RELEASE]
	at org.springframework.core.env.AbstractPropertyResolver.doResolvePlaceholders(AbstractPropertyResolver.java:237) ~[spring-core-5.1.9.RELEASE.jar:5.1.9.RELEASE]
	at org.springframework.core.env.AbstractPropertyResolver.resolveRequiredPlaceholders(AbstractPropertyResolver.java:211) ~[spring-core-5.1.9.RELEASE.jar:5.1.9.RELEASE]
	at org.springframework.context.support.PropertySourcesPlaceholderConfigurer.lambda$processProperties$0(PropertySourcesPlaceholderConfigurer.java:175) ~[spring-context-5.1.9.RELEASE.jar:5.1.9.RELEASE]
	at org.springframework.beans.factory.support.AbstractBeanFactory.resolveEmbeddedValue(AbstractBeanFactory.java:851) ~[spring-beans-5.1.9.RELEASE.jar:5.1.9.RELEASE]
	at org.springframework.beans.factory.support.DefaultListableBeanFactory.doResolveDependency(DefaultListableBeanFactory.java:1192) ~[spring-beans-5.1.9.RELEASE.jar:5.1.9.RELEASE]
	at org.springframework.beans.factory.support.DefaultListableBeanFactory.resolveDependency(DefaultListableBeanFactory.java:1171) ~[spring-beans-5.1.9.RELEASE.jar:5.1.9.RELEASE]
	at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor$AutowiredFieldElement.inject(AutowiredAnnotationBeanPostProcessor.java:593) ~[spring-beans-5.1.9.RELEASE.jar:5.1.9.RELEASE]
	at org.springframework.beans.factory.annotation.InjectionMetadata.inject(InjectionMetadata.java:90) ~[spring-beans-5.1.9.RELEASE.jar:5.1.9.RELEASE]
	at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor.postProcessProperties(AutowiredAnnotationBeanPostProcessor.java:374) ~[spring-beans-5.1.9.RELEASE.jar:5.1.9.RELEASE]
	... 17 common frames omitted

我出现的问题：

配置文件中的变量没办法被读取：

如图，name没办法被读取。

可能的原因：

1、冒号后面忘记加空格

2、对应的target文件中为空。

对第二种原因的解释：项目编译时，会将所有.class文件都放入target文件中，当项目运行时，会从target文件中选取.class文件运行。

因此，如果target文件中没有对应的配置文件，那么项目不会运行成功

我的错误是因为第二种原因，因此，将配置文件复制到target中，即可。