how to use Spring-EL in @Value when using constants to resolve a property
Solution 1
What about the simplest approach:
@Value("${" + InternalConstant.JOB_NAME_PROPERTY + "}")
private String jobName
Solution 2
You can access the property referenced by the constant using environment
directly in the SpEL expression and the correct value should be injected:
@Value("#{environment.getProperty(T(com.example.InternalConstants).JOB_NAME_PROPERTY)}")
private String jobName;
Hansjoerg Wingeier
Senior Java Software Developer Spring, SpringBatch, SpringBoot JEE
Updated on June 10, 2022Comments
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Hansjoerg Wingeier almost 2 years
I'm trying to use a constant to define a property and then resolving it with the @Value annotation.
I defined the constant in an interface:
public interface InternalConstant{ public static final String JOB_NAME_PROPERTY = "javabatch.jobName"; }
I'm using springboot and I'm adding the property as a default property to the context:
SpringApplication springApp = new SpringApplication(configs.toArray()); Properties props = new Properties(); props.setProperty(InternalConstants.JOB_NAME_PROPERTY, "MyStartableJob"); springApp.setDefaultProperties(props);
Now, I'd like to use @Value to inject the String "MyStartableJob" into a String. But instead of directly using
@Value(value="${javabatch.jobName})
, I'd like to use the defined constant.I tried
@Value(value="#{T(ch.mobi.javabatch.core.internal.InternalConstants).JOB_NAME_PROPERTY}")
But of course, this resolves only to "javabatch.jobName" and not to the value of the property named "javabatch.jobName".
So I tried to wrap it in
@Value(value="${#{T(ch.mobi.javabatch.core.internal.InternalConstants).JOB_NAME_PROPERTY}}")
, but this causes an exception.Caused by: java.lang.IllegalArgumentException: Could not resolve placeholder '#{T(ch.mobi.javabatch.core.internal.InternalConstants).JOB_NAME_PROPERTY}' in string value "${#{T(ch.mobi.javabatch.core.internal.InternalConstants).JOB_NAME_PROPERTY}}" at org.springframework.util.PropertyPlaceholderHelper.parseStringValue(PropertyPlaceholderHelper.java:174) at org.springframework.util.PropertyPlaceholderHelper.replacePlaceholders(PropertyPlaceholderHelper.java:126) at org.springframework.core.env.AbstractPropertyResolver.doResolvePlaceholders(AbstractPropertyResolver.java:204) at org.springframework.core.env.AbstractPropertyResolver.resolveRequiredPlaceholders(AbstractPropertyResolver.java:178) at org.springframework.context.support.PropertySourcesPlaceholderConfigurer$2.resolveStringValue(PropertySourcesPlaceholderConfigurer.java:175) at org.springframework.beans.factory.support.AbstractBeanFactory.resolveEmbeddedValue(AbstractBeanFactory.java:801) at org.springframework.beans.factory.support.DefaultListableBeanFactory.doResolveDependency(DefaultListableBeanFactory.java:955) at org.springframework.beans.factory.support.DefaultListableBeanFactory.resolveDependency(DefaultListableBeanFactory.java:942) at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor$AutowiredFieldElement.inject(AutowiredAnnotationBeanPostProcessor.java:533) ... 16 more
I know, that I could simply inject the Environment and using its getProperty method:
@Autowired private Environment env; public void m1() { env.getProperty(InternalConstants.JOB_NAME_PROPERTY); }
This works and serves my purpose. But I wonder, if this could also be done using SPEL in @Value.
Thanks.
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Jens almost 9 yearsShow the stacktrace please.
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Hansjoerg Wingeier almost 9 years@Jens: I added the stacktrace
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Bohuslav Burghardt almost 9 years+1 for keeping things simple. This solution also has the added benefit that rename refactoring won't break your code in less intelligent IDEs :).
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Gilles Bodart over 6 yearsBut it's not going into a class constant to use for exemple in another annotation like caching group name ...
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ASten almost 6 yearsIDEA tells me, that "attribute value must be constant" although I have a String constant as a concatenated param...