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

问题内容：

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，除了以下几点之外，它可以正常工作：

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 { ... }

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;

        ...
    }

已成功从属性资源注入属性“过滤器”的值。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]
         ...

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;

我相信当使用@Value将值从属性资源注入到Integer属性中时，Spring能够将String转换为Integer。我找到了一些人们在抱怨的情况下使用的示例。您是否有任何想法为什么对我不起作用？

非常感谢。

问题答案：

如果尝试使用@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();
}

如果不想声明它，请尝试在org.springframework.core.env.Environment类中自动装配它，以获取属性值。

@Autowired
private Environment environment;

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

}

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

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