Spring Boot 2无法将属性读取为字符串

Question

在将Spring Boot应用程序从Spring Boot 1.4.0迁移到Spring Boot 2时，我开始在尝试从。properties文件读取属性时出错。

在属性文件中，属性定义为：

environment=dev

在我的一个类中，我通过@value注释导入属性，如下所示：

@Getter
@Setter
public class CustomUserFilter extends SwitchUserFilter {
    ...
    @Value("${environment}")
    private String environment;
    ...

...
@Value("${environment}")
private Environment environment;
...

Caused by: org.springframework.beans.factory.UnsatisfiedDependencyException: Error creating bean with name 'switchUserFilter': Unsatisfied dependency expressed through field 'environment'; nested exception is org.springframework.beans.ConversionNotSupportedException: Failed to convert value of type 'java.lang.String' to required type 'org.springframework.core.env.Environment'; nested exception is java.lang.IllegalStateException: Cannot convert value of type 'java.lang.String' to required type 'org.springframework.core.env.Environment': no matching editors or conversion strategy found
    at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor$AutowiredFieldElement.inject(AutowiredAnnotationBeanPostProcessor.java:584)
    at org.springframework.beans.factory.annotation.InjectionMetadata.inject(InjectionMetadata.java:90)
    at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor.postProcessPropertyValues(AutowiredAnnotationBeanPostProcessor.java:370)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.populateBean(AbstractAutowireCapableBeanFactory.java:1336)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:572)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:495)
    at org.springframework.beans.factory.support.AbstractBeanFactory.lambda$doGetBean$0(AbstractBeanFactory.java:317)
    at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:222)
    at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:315)
    at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:204)
    at org.springframework.boot.web.servlet.ServletContextInitializerBeans.getOrderedBeansOfType(ServletContextInitializerBeans.java:226)
    at org.springframework.boot.web.servlet.ServletContextInitializerBeans.addAsRegistrationBean(ServletContextInitializerBeans.java:182)
    at org.springframework.boot.web.servlet.ServletContextInitializerBeans.addAsRegistrationBean(ServletContextInitializerBeans.java:177)
    at org.springframework.boot.web.servlet.ServletContextInitializerBeans.addAdaptableBeans(ServletContextInitializerBeans.java:159)
    at org.springframework.boot.web.servlet.ServletContextInitializerBeans.<init>(ServletContextInitializerBeans.java:81)
    at org.springframework.boot.web.servlet.context.ServletWebServerApplicationContext.getServletContextInitializerBeans(ServletWebServerApplicationContext.java:261)
    at org.springframework.boot.web.servlet.context.ServletWebServerApplicationContext.selfInitialize(ServletWebServerApplicationContext.java:234)
    at org.springframework.boot.web.servlet.context.ServletWebServerApplicationContext.createWebServer(ServletWebServerApplicationContext.java:185)
    at org.springframework.boot.web.servlet.context.ServletWebServerApplicationContext.onRefresh(ServletWebServerApplicationContext.java:154)
    ... 52 more
Caused by: org.springframework.beans.ConversionNotSupportedException: Failed to convert value of type 'java.lang.String' to required type 'org.springframework.core.env.Environment'; nested exception is java.lang.IllegalStateException: Cannot convert value of type 'java.lang.String' to required type 'org.springframework.core.env.Environment': no matching editors or conversion strategy found
    at org.springframework.beans.TypeConverterSupport.doConvert(TypeConverterSupport.java:77)
    at org.springframework.beans.TypeConverterSupport.convertIfNecessary(TypeConverterSupport.java:60)
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.doResolveDependency(DefaultListableBeanFactory.java:1089)
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.resolveDependency(DefaultListableBeanFactory.java:1062)
    at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor$AutowiredFieldElement.inject(AutowiredAnnotationBeanPostProcessor.java:581)
    ... 70 more
Caused by: java.lang.IllegalStateException: Cannot convert value of type 'java.lang.String' to required type 'org.springframework.core.env.Environment': no matching editors or conversion strategy found
    at org.springframework.beans.TypeConverterDelegate.convertIfNecessary(TypeConverterDelegate.java:299)
    at org.springframework.beans.TypeConverterDelegate.convertIfNecessary(TypeConverterDelegate.java:117)
    at org.springframework.beans.TypeConverterSupport.doConvert(TypeConverterSupport.java:70)
    ... 74 more

有什么线索知道哪里会出错吗？我使用的是Spring Boot2.0、Spring5、Java11和Tomcat8.5.35。谢了！

Answer 1

这个问题与Spring靴无关。上面的类扩展了org.springframework.security.web.authentication.switchuser.switchuserfilter，它进一步扩展了org.springframework.web.filter.genericfilterbean。这个GenericFilterBean类还有一个属性Private Environment Environment；。此外，这个类在Spring5版本中进行了修改，在这个属性上包含了一个getter方法。Spring 5在类GenericFilterBean中引入了返回类型Environment的GetEnvironment()，这与返回类型String的冲突。

为了避免这种冲突，我简单地将属性的名称从environment更改为env，在此之后就可以工作了。