@Value -> 无法将“java.lang.String”类型的值转换为所需类型“java.lang.Integer”

@Value -> Failed to convert value of type 'java.lang.String' to required type 'java.lang.Integer'

提问by Vojtech

Good day, I'm working on a web application using Spring 4.1.1.RELEASE. All Spring configuration is done with annotations and it works fine except one thing:

美好的一天，我正在使用 Spring 4.1.1.RELEASE 开发 Web 应用程序。所有 Spring 配置都是通过注释完成的，它工作正常，除了一件事：

• I have a config.properties file in the project with these lines

  cases.caseList.filter=test
  cases.caseList.numberOfCasesPerPage=50
  

• I have a config class

  @Configuration
  @ComponentScan(basePackageClasses={CaseConfig.class})
  @PropertySource(value = "classpath:config.properties")
  public class CasesModuleTestContextConfig { ... }
  

• And another class

  @Component
  public class HttpRequestParamsToPaginationParams extends AbstractConverter<Map<String, String>, PaginationParams> {
  
      @Value("${cases.caseList.filter}")
      private String filter;
  
      @Value("${cases.caseList.numberOfCasesPerPage}")
      private Integer count;
  
      ...
  }
  

• 我在项目中有一个 config.properties 文件，其中包含这些行

  cases.caseList.filter=test
  cases.caseList.numberOfCasesPerPage=50
  

• 我有一个配置类

  @Configuration
  @ComponentScan(basePackageClasses={CaseConfig.class})
  @PropertySource(value = "classpath:config.properties")
  public class CasesModuleTestContextConfig { ... }
  

• 还有另一堂课

  @Component
  public class HttpRequestParamsToPaginationParams extends AbstractConverter<Map<String, String>, PaginationParams> {
  
      @Value("${cases.caseList.filter}")
      private String filter;
  
      @Value("${cases.caseList.numberOfCasesPerPage}")
      private Integer count;
  
      ...
  }
  

Value of property 'filter' is successfuly injected from the property resource. But I'm getting an exception on property 'count':

属性“过滤器”的值已成功从属性资源注入。但是我在属性“count”上遇到了一个例外：

     13:58:45.274 [main] WARN  o.s.c.s.GenericApplicationContext - Exception encountered during context initialization - cancelling refresh attempt 
     org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'cz.pokus.core.test.config.ConversionServiceTestConfig': Injection of autowired dependencies failed; nested exception is org.springframework.beans.factory.BeanCreationException: Could not autowire field: private java.util.List cz.pokus.core.test.config.ConversionServiceTestConfig.converterList; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'httpRequestParamsToPaginationParams': Injection of autowired dependencies failed; nested exception is org.springframework.beans.factory.BeanCreationException: Could not autowire field: private java.lang.Integer cz.pokus.core.cases.converter.HttpRequestParamsToPaginationParams.count; nested exception is org.springframework.beans.TypeMismatchException: Failed to convert value of type 'java.lang.String' to required type 'java.lang.Integer'; nested exception is java.lang.NumberFormatException: For input string: "${cases.caseList.numberOfCasesPerPage}"
at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor.postProcessPropertyValues(AutowiredAnnotationBeanPostProcessor.java:334) ~[spring-beans-4.1.1.RELEASE.jar:4.1.1.RELEASE]
     ...
     Caused by: org.springframework.beans.TypeMismatchException: Failed to convert value of type 'java.lang.String' to required type 'java.lang.Integer'; nested exception is java.lang.NumberFormatException: For input string: "${cases.caseList.numberOfCasesPerPage}"
     ...
     Caused by: java.lang.NumberFormatException: For input string: "${cases.caseList.numberOfCasesPerPage}"
at java.lang.NumberFormatException.forInputString(NumberFormatException.java:65) ~[na:1.8.0_20]
at java.lang.Integer.parseInt(Integer.java:569) ~[na:1.8.0_20]
at java.lang.Integer.valueOf(Integer.java:766) ~[na:1.8.0_20]
     ...

When I change type of property 'count' to String it start working:

当我将属性 'count' 的类型更改为 String 时，它开始工作：

        @Value("${cases.caseList.numberOfCasesPerPage}")
        private String count;

I believe Spring is able to convert String to Integer when injecting value from property resource into a Integer property using @Value. I'v found examples where people use without complaining. Do you please have any ideas why it doesn't work for me?

我相信当使用@Value 将属性资源中的值注入到 Integer 属性中时，Spring 能够将 String 转换为 Integer。我找到了人们使用而不抱怨的例子。你有什么想法为什么它对我不起作用？

Thanks a lot in advance.

非常感谢。

采纳答案by Lovababu

If you are trying to access the property values using @Value("")annotation, you should declare PropertySourcesPlaceholderConfigurerBean.

如果您尝试使用@Value("")注释访问属性值，则应声明PropertySourcesPlaceholderConfigurerBean。

Try to add below snippet of code in your configuration class.

尝试在您的配置类中添加以下代码片段。

@Bean
public static PropertySourcesPlaceholderConfigurer propertySourcesPlaceholderConfigurer() {
    return new PropertySourcesPlaceholderConfigurer();
}

If you don't want to declare it, Try with org.springframework.core.env.Environmentclass by autowiring it in your class, to get the property values.

如果您不想声明它，请尝试org.springframework.core.env.Environment通过在您的类中自动装配类来获取属性值。

@Autowired
private Environment environment;

public void readValues() {
    System.out.println("Some Message:"
            + environment.getProperty("<Property Name>")); 

}