annotation that changes the string value

Is there an annotation in spring or java that transforms a given string?

For example, Spring has the annotation @Value("some string"). What if instead of assigning "some string" to the parameter/instance variable whatever, I want to assign a transformed value of that string. Let's say the string is "foo". Every time I see this annotation I want the string returned to be "bar:foo" and not foo. All I want is to be able to place an annotation over a parameter or instance variable and for that transformation to occur automatically. Perhaps maybe even an annotation that takes a class as well as the string such that the class acts as the transformer for the given string.

Is there 开发者_如何学编程an annotation in spring or java that does this and if not what would be the best way to go about implementing such a thing?

Thanks Lauren

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You can use Spring Expression Language inside your @Value annotation.

This is how you'll use it for a static method:

@Value("#{T(fully.qualified.package.name.to.class).getFooString()}")
public void setBar(String value){
   this.bar = value;
}

If you have a bean define previously then you can simply use @Value("#{bean.method()}") or @Value("#{bean.property}")

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The @Value annotation of Spring is useful to assign a value other than a constant to a property, using the Spring expression language. For example, a value read from a properties file. If all it did was assigning a constant, you could as well use private String foo = "bar";.

So, you might use it to get the value you want from some configuration file or system property.

If what you want is to apply some transformation algorithm to a field, I don't really see the point of using an annotation. Just call a Java method:

@Value("foo") // or some EL expression which evaluates to "foo"
public void setBar(String value) {
    this.bar = someStringTransformer.transform(value);
}

That seems easy to read, test and maintain.