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

Question

您好，我正在使用Spring 4.1.1.RELEASE开发一个web应用程序。所有的Spring配置都是通过注释完成的，除了一点之外，它运行得很好:

>

我在项目中有一个包含这些行的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中注入。但是我在属性“计数”上得到了一个例外：

     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整数属性时，Spring能够将字符串转换为整数。我找到了人们使用而不抱怨的例子。你知道为什么它不适合我吗？

非常感谢。

Answer 1

在我的例子中，我在注释中放弃了$符号

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

而不是

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

Answer 2

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片段。

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

如果您不想声明它，请尝试使用组织.Spring框架.core.env.环境类，方法是在您的类中自动布线它，以获取属性值。

@Autowired
private Environment environment;

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

}