Springboot 属性类型不匹配

Question

我有一个常见问题，到目前为止，论坛上的所有其他类似问题 none 对我都有帮助。请耐心等待，我还在学习中。

我有一个 Spring 启动应用程序。

@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，由于从 String 到 int 的类型不匹配，我声明的第一个属性不起作用。另一个工作得很好。我的 application.properties 看起来像这样：

#file path.
filePath=

#number of documents
numberOfDocs=

我的堆栈跟踪看起来像这样：

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[=13=](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]

我在这里错过了什么？为什么我的 int 属性在 application.property 中被视为 String？我需要强制转换 int 才能工作吗？

Answer 1

问题出在 application.properties 文件中 numberOfDocs 属性的初始化。

您已将 numbeOfDocs 初始化为 ""（空字符串）并且 spring 正在尝试将此空字符串转换为整数，因为您将 numberOfDocuments 声明为 int 变量.

您的错误将通过以下三种方式之一得到修复

将 numberOfDocuments 数据类型更改为 String
用有效整数

numberOfDoc

只需从 application.properties 中删除 numberOfDoc 属性。意思是不要初始化它，所以它将采用默认值 10

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