Spring boot：@Value 找不到值，或启动报异常

墨蓝 2022-05-12 20:12 448阅读 0赞

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：

![70][]

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

[70]: /images/20220513/8fc7c1b50a6d499f8bcaa36d44586623.png