@Value - >无法将'java.lang.String'类型的值转换为必需类型'java.lang.Integer'

Question

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配置都是使用注释完成的,除了一件事外它工作正常:

• 我在项目中有这些行的config.properties文件

  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 { ... }
  

• 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;
  
      ...
  }
  

属性'过滤器'的值是从属性资源中成功注入的.但我在财产'计数'上得到例外:

     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]
     ...

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;

我相信Spring能够在使用@Value将属性资源的值注入Integer属性时将String转换为Integer.我找到了人们在没有抱怨的情况下使用的例子.你有任何想法,为什么它对我不起作用？

非常感谢提前.

Answer 1

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

尝试在配置类中添加以下代码段.

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

如果您不想声明它,请通过在org.springframework.core.env.Environment类中自动装配来尝试使用类,以获取属性值.

@Autowired
private Environment environment;

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

}

Answer 2

就我而言，我忘记了注释中的 $ 符号

@Value("{cases.caseList.filter}")

代替

@Value("${cases.caseList.filter}")