Question

Just a quick and simple question. I have a program with several classes that read information off of a .properties file. Is it better practice to pass the file from class to class as an argument in the constructor, or open the file directly in each class?

Answer 1

If you’re going to do this by hand, I would recommend you create a configuration class, that takes the file via the constructor, and reads the property values into member variables. Then every other class that needs configuration takes a Configuration class via it’s constructor. However, almost no one does this, and instead uses a framework like spring, which handles property injection for you.

In spring, it would look something like this:

<!-- application context xml file -->
<context:property-placeholder location="file:///some/path/to/file" />

Then in your java classes:

public class SomeClass {
    @Value("${some.property}")
    private String someProp;

    @Value("${some.other.prop}")
    private Integer someOtherProp;

    // ...
}

At application startup the properties get injected into your class.