如何在 Spring @Value 注解中正确指定默认值?

2022-01-13 00:00:00 annotations properties spring java

最初，我有以下规格:

@Value("#{props.isFPL}")
private boolean isFPL=false;

这可以正常从属性文件中获取值:

This works fine correctly getting the value from the property file:

isFPL = true

但是，以下带有默认值的表达式会导致错误:

However, the following expression with default results in the error:

@Value("#{props.isFPL:false}")
private boolean isFPL=false;

表达式解析失败；嵌套异常是 org.springframework.expression.spel.SpelParseException: EL1041E:(pos 28): 解析有效表达式后，表达式中还有更多数据:'colon(:)'

我也尝试使用 $ 而不是 #.

I also tried to use $ instead of #. 

@Value("${props.isFPL:true}")
private boolean isFPL=false;

然后注释中的默认值工作正常，但我没有从属性文件中得到正确的值:

Then the default value in annotation works fine but I did not get the correct value from the Properties file:

推荐答案

试试 $ 如下:

@Value("${props.isFPL:true}")
private boolean isFPL=false;

还要确保将 ignore-resource-no-found 设置为 true，这样如果缺少属性文件，default将被取值.

Also make sure you set the ignore-resource-no-found to true so that if the property file is missing, the default value will be taken.

如果使用基于 XML 的配置，请将以下内容放在上下文文件中:

Place the following in the context file if using XML based configuration: 

<context:property-placeholder ignore-resource-not-found="true"/>

如果使用 Java 配置:

If using Java configurations:

 @Bean
 public static PropertySourcesPlaceholderConfigurer   propertySourcesPlaceholderConfigurer() {
     PropertySourcesPlaceholderConfigurer p =  new PropertySourcesPlaceholderConfigurer();
     p.setIgnoreResourceNotFound(true);

    return p;
 }

相关文章