先看异常信息：
org.springframework.beans.factory.UnsatisfiedDependencyException: Error creating bean with name 'ConfigReader': Unsatisfied dependency expressed through field 'driverLetter'; nested exception is org.springframework.beans.factory.BeanExpressionException: Expression parsing failed; nested exception is org.springframework.expression.spel.SpelEvaluationException: EL1008E: Property or field 'propertiesReader' cannot be found on object of type 'org.springframework.beans.factory.config.BeanExpressionContext' - maybe not public or not valid?
at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor$AutowiredFieldElement.inject(AutowiredAnnotationBeanPostProcessor.java:586) ~[spring-beans-5.0.8.RELEASE.jar:5.0.8.RELEASE]
at org.springframework.beans.factory.annotation.InjectionMetadata.inject(InjectionMetadata.java:91) ~[spring-beans-5.0.8.RELEASE.jar:5.0.8.RELEASE]
at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor.postProcessPropertyValues(AutowiredAnnotationBeanPostProcessor.java:372) ~[spring-beans-5.0.8.RELEASE.jar:5.0.8.RELEASE]
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.populateBean(AbstractAutowireCapableBeanFactory.java:1341) ~[spring-beans-5.0.8.RELEASE.jar:5.0.8.RELEASE]
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:572) ~[spring-beans-5.0.8.RELEASE.jar:5.0.8.RELEASE]
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:495) ~[spring-beans-5.0.8.RELEASE.jar:5.0.8.RELEASE]
at org.springframework.beans.factory.support.AbstractBeanFactory.lambda$doGetBean$0(AbstractBeanFactory.java:317) ~[spring-beans-5.0.8.RELEASE.jar:5.0.8.RELEASE]
at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:222) ~[spring-beans-5.0.8.RELEASE.jar:5.0.8.RELEASE]
at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:315) ~[spring-beans-5.0.8.RELEASE.jar:5.0.8.RELEASE]
at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:199) ~[spring-beans-5.0.8.RELEASE.jar:5.0.8.RELEASE]
at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:759) ~[spring-beans-5.0.8.RELEASE.jar:5.0.8.RELEASE]
at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:869) ~[spring-context-5.0.8.RELEASE.jar:5.0.8.RELEASE]
at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:550) ~[spring-context-5.0.8.RELEASE.jar:5.0.8.RELEASE]
at org.springframework.boot.web.servlet.context.ServletWebServerApplicationContext.refresh(ServletWebServerApplicationContext.java:140) ~[spring-boot-2.0.4.RELEASE.jar:2.0.4.RELEASE]
at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:762) [spring-boot-2.0.4.RELEASE.jar:2.0.4.RELEASE]
at org.springframework.boot.SpringApplication.refreshContext(SpringApplication.java:398) [spring-boot-2.0.4.RELEASE.jar:2.0.4.RELEASE]
at org.springframework.boot.SpringApplication.run(SpringApplication.java:330) [spring-boot-2.0.4.RELEASE.jar:2.0.4.RELEASE]
at org.springframework.boot.SpringApplication.run(SpringApplication.java:1258) [spring-boot-2.0.4.RELEASE.jar:2.0.4.RELEASE]
at org.springframework.boot.SpringApplication.run(SpringApplication.java:1246) [spring-boot-2.0.4.RELEASE.jar:2.0.4.RELEASE]
at com.Application.main(Application.java:10) [classes/:na]
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:1.8.0_102]
at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source) ~[na:1.8.0_102]
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source) ~[na:1.8.0_102]
at java.lang.reflect.Method.invoke(Unknown Source) ~[na:1.8.0_102]
at org.springframework.boot.devtools.restart.RestartLauncher.run(RestartLauncher.java:49) [spring-boot-devtools-2.0.4.RELEASE.jar:2.0.4.RELEASE]
Caused by: org.springframework.beans.factory.BeanExpressionException: Expression parsing failed; nested exception is org.springframework.expression.spel.SpelEvaluationException: EL1008E: Property or field 'propertiesReader' cannot be found on object of type 'org.springframework.beans.factory.config.BeanExpressionContext' - maybe not public or not valid?
at org.springframework.context.expression.StandardBeanExpressionResolver.evaluate(StandardBeanExpressionResolver.java:164) ~[spring-context-5.0.8.RELEASE.jar:5.0.8.RELEASE]
at org.springframework.beans.factory.support.AbstractBeanFactory.evaluateBeanDefinitionString(AbstractBeanFactory.java:1452) ~[spring-beans-5.0.8.RELEASE.jar:5.0.8.RELEASE]
at org.springframework.beans.factory.support.DefaultListableBeanFactory.doResolveDependency(DefaultListableBeanFactory.java:1085) ~[spring-beans-5.0.8.RELEASE.jar:5.0.8.RELEASE]
at org.springframework.beans.factory.support.DefaultListableBeanFactory.resolveDependency(DefaultListableBeanFactory.java:1062) ~[spring-beans-5.0.8.RELEASE.jar:5.0.8.RELEASE]
at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor$AutowiredFieldElement.inject(AutowiredAnnotationBeanPostProcessor.java:583) ~[spring-beans-5.0.8.RELEASE.jar:5.0.8.RELEASE]
... 24 common frames omitted
Caused by: org.springframework.expression.spel.SpelEvaluationException: EL1008E: Property or field 'propertiesReader' cannot be found on object of type 'org.springframework.beans.factory.config.BeanExpressionContext' - maybe not public or not valid?
at org.springframework.expression.spel.ast.PropertyOrFieldReference.readProperty(PropertyOrFieldReference.java:217) ~[spring-expression-5.0.8.RELEASE.jar:5.0.8.RELEASE]
at org.springframework.expression.spel.ast.PropertyOrFieldReference.getValueInternal(PropertyOrFieldReference.java:104) ~[spring-expression-5.0.8.RELEASE.jar:5.0.8.RELEASE]
at org.springframework.expression.spel.ast.PropertyOrFieldReference.getValueInternal(PropertyOrFieldReference.java:91) ~[spring-expression-5.0.8.RELEASE.jar:5.0.8.RELEASE]
at org.springframework.expression.spel.ast.CompoundExpression.getValueRef(CompoundExpression.java:52) ~[spring-expression-5.0.8.RELEASE.jar:5.0.8.RELEASE]
at org.springframework.expression.spel.ast.CompoundExpression.getValueInternal(CompoundExpression.java:88) ~[spring-expression-5.0.8.RELEASE.jar:5.0.8.RELEASE]
at org.springframework.expression.spel.ast.SpelNodeImpl.getValue(SpelNodeImpl.java:111) ~[spring-expression-5.0.8.RELEASE.jar:5.0.8.RELEASE]
at org.springframework.expression.spel.standard.SpelExpression.getValue(SpelExpression.java:270) ~[spring-expression-5.0.8.RELEASE.jar:5.0.8.RELEASE]
at org.springframework.context.expression.StandardBeanExpressionResolver.evaluate(StandardBeanExpressionResolver.java:161) ~[spring-context-5.0.8.RELEASE.jar:5.0.8.RELEASE]
... 28 common frames omitted
触发问题行为：在自定义的 文件中配置了常量，在获取的类中使用 @Value，取不到值，或报错。
报错原因： 我在配置文件中配置了图片上传的地址，其实是配置的地址找不到，遇到了错误。
解决方式：、
import org.springframework.boot.context.properties.ConfigurationProperties;
import org.springframework.context.annotation.PropertySource;
import org.springframework.stereotype.Component;
@Component
@ConfigurationProperties
@PropertySource({"classpath:properties/resourceConfig.properties"})
public class ConfigReader {
/** 本地盘符 **/
private String driverLetter;
public String getDriverLetter() {
return driverLetter;
}
public void setDriverLetter(String driverLetter) {
this.driverLetter = driverLetter;
}
}
其中配置文件中的内容为 driverLetter = xxxxxx
以上便是解决方式
重点：三个注解
@Component
@ConfigurationProperties
@PropertySource({"classpath:properties/resourceConfig.properties"})
classpath:properties/resourceConfig.propertiess意思为properties文件夹下的resourceConfig.propertiess文件
文件目录：
注意：如果您的配置文件中的key为
spring.datasource.driver-class-name= com.mysql.jdbc.Driver
spring.datasource.url =
spring.datasource.username =
spring.datasource.password =
这种格式，要获取driver-class-name、url、username、password的值，则获取值的类可以这样写：
import org.springframework.boot.context.properties.ConfigurationProperties;
import org.springframework.context.annotation.PropertySource;
import org.springframework.stereotype.Component;
@Component
@ConfigurationProperties("prefix="spring.datasource"") //意思是获取spring.datasource下的key的值
@PropertySource({"classpath:properties/resourceConfig.properties"})
public class ConfigReader {
private String url;
private String username;
private String password;
/*get，set省略*/
}
总结：解决的方式有很多，使用@value也能解决问题，这只是本人的解决方案，可能不是最优。欢迎探讨与指点。
q:1226500260