This rule reports when the Spring @Value annotation injects a simple value that does not contain an expression.

Why is this an issue?

The purpose of the @Value annotation in org.springframework.beans.factory.annotation is to inject a value into a field or method based on the Spring context after it has been established.

If the annotation does not include an expression (either Spring Expression Language or a property injection), the injected value is a simple constant that does not depend on the Spring context, making the annotation replaceable with a standard field initialization statement.

This not only implies the redundant use of @Value, but could also indicate an error where the expression indicators (#, $) were omitted by mistake.

Exceptions

This rule does not raise an issue if @Value is applied to a method or method argument, because the annotation has the side effect that the method is called.

How to fix it

• If a property is to be injected, use ${propertyName} instead of propertyName.
• If a SpEL expression is to be evaluated, use #{expression} instead of expression.
• If you intend to initialize a field with a simple value or with an expression that does not depend on the Spring context, use a standard field initialization statement.

Code examples

Noncompliant code example

@Value("catalog.name") // Noncompliant, this will not inject the property
String catalog;

Compliant solution

@Value("${catalog.name}") // Compliant
String catalog;

Noncompliant code example

@Value("book.topics[0]") // Noncompliant, this will not evaluate the expression
Topic topic;

Compliant solution

@Value("#{book.topics[0]}") // Compliant
Topic topic;

Noncompliant code example

@Value("Hello, world!") // Noncompliant, this use of @Value is redundant
String greeting;

Compliant solution

String greeting = "Hello, world!"; // Compliant

Resources

Documentation

• Spring Framework API - Annotation Interface Value

Articles & blog posts

• Baeldung - A Quick Guide to Spring @Value
• DigitalOcean - Spring @Value Annotation