我有一个共同的问题，论坛上所有其他类似的问题都没有帮到我。请容忍我，我还在学习。
我有一个spring boot应用程序。

@RequiredArgsConstructor
@SpringBootApplication
public class ConsoleApp implements CommandLineRunner {

    @Value("${numberOfDocs:10}")
    private int numberOfDocuments;
    @Value("${filePath:testdoc-al.pdf}")
    private String filePath;

不幸的是，我声明的第一个属性由于从string到int的类型不匹配而不起作用，其他的就可以了。我的application.properties如下所示：

# file path.

filePath=

# number of documents

numberOfDocs=

我的stacktrace如下所示：

org.springframework.beans.factory.UnsatisfiedDependencyException: Error creating bean with name 'ConsoleApp': Unsatisfied dependency expressed through field 'numberOfDocuments'; nested exception is org.springframework.beans.TypeMismatchException: Failed to convert value of type 'java.lang.String' to required type 'int'; nested exception is java.lang.NumberFormatException: For input string: ""
at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor$AutowiredFieldElement.inject(AutowiredAnnotationBeanPostProcessor.java:598) ~[spring-beans-5.1.16.RELEASE.jar:5.1.16.RELEASE]
at org.springframework.beans.factory.annotation.InjectionMetadata.inject(InjectionMetadata.java:90) ~[spring-beans-5.1.16.RELEASE.jar:5.1.16.RELEASE]
at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor.postProcessProperties(AutowiredAnnotationBeanPostProcessor.java:376) ~[spring-beans-5.1.16.RELEASE.jar:5.1.16.RELEASE]
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.populateBean(AbstractAutowireCapableBeanFactory.java:1404) ~[spring-beans-5.1.16.RELEASE.jar:5.1.16.RELEASE]
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:592) ~[spring-beans-5.1.16.RELEASE.jar:5.1.16.RELEASE]
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:515) ~[spring-beans-5.1.16.RELEASE.jar:5.1.16.RELEASE]
at org.springframework.beans.factory.support.AbstractBeanFactory.lambda$doGetBean$0(AbstractBeanFactory.java:320) ~[spring-beans-5.1.16.RELEASE.jar:5.1.16.RELEASE]
at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:226) ~[spring-beans-5.1.16.RELEASE.jar:5.1.16.RELEASE]
at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:318) ~[spring-beans-5.1.16.RELEASE.jar:5.1.16.RELEASE]
at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:199) ~[spring-beans-5.1.16.RELEASE.jar:5.1.16.RELEASE]
at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:860) ~[spring-beans-5.1.16.RELEASE.jar:5.1.16.RELEASE]
at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:878) ~[spring-context-5.1.16.RELEASE.jar:5.1.16.RELEASE]
at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:550) ~[spring-context-5.1.16.RELEASE.jar:5.1.16.RELEASE]
at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:744) ~[spring-boot-2.1.15.RELEASE.jar:2.1.15.RELEASE]
at org.springframework.boot.SpringApplication.refreshContext(SpringApplication.java:391) ~[spring-boot-2.1.15.RELEASE.jar:2.1.15.RELEASE]
at org.springframework.boot.SpringApplication.run(SpringApplication.java:312) ~[spring-boot-2.1.15.RELEASE.jar:2.1.15.RELEASE]
at org.springframework.boot.builder.SpringApplicationBuilder.run(SpringApplicationBuilder.java:140) ~[spring-boot-2.1.15.RELEASE.jar:2.1.15.RELEASE]
at ConsoleApp.main(ConsoleApp.java:36) ~[main/:na]

我错过了什么？为什么我的int属性在application.property中被视为字符串？我需要投int才能工作吗？