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

java spring spring-mvc

2022-09-02 01:11:42

好日子，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，除了一件事之外，它工作正常：

我在项目中有一个带有这些行的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 { ... }

和另一个类

@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“filter”的值已成功从属性资源注入。但是我在属性“计数”上遇到了异常：

     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]
     ...

当我将属性类型“count”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将属性资源中的值注入Integer属性时将String转换为Integer。我发现了人们毫无怨言地使用的例子。你有什么想法，为什么它不适合我？

提前非常感谢。

答案 1

如果尝试使用注释访问属性值，则应声明 Bean。@Value("")PropertySourcesPlaceholderConfigurer

尝试在配置类中添加以下代码片段。

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

如果不想声明它，请尝试通过在类中自动连接 class 来获取属性值。org.springframework.core.env.Environment

@Autowired
private Environment environment;

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

}

答案 2

在我的情况下，我将$符号排除在注释中

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

而不是

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