Guice - Injecting different value to string variable per instance - binding

Question

Using Guice,I would like create three different instances for my Color class i.e BLUE, RED, YELLOW and want to bind different color value... but I am not understanding how to bind different value per instance...
For the below sample code, if you see, I would like to use same ColorClass implementation for all three colors Instances(named as "BLUE","RED","ORANGE") by passing different color as String variable.
public interface ColorInterface {
public String getMeColor()
}
Sample implementation....
public class ColorClass implements ColorInterface {
#Inject #Named("color")
String color
public String getMeColor(){
return color
}
}
Sample binding........
public class ColorModule extends AbstractModule {
#Override
protected void configure() {
bind(ColorInterface.class).annotatedWith(Names.named("BLUE")).to(ColorClass.class);
bind(ColorInterface.class).annotatedWith(Names.named("RED")).to(ColorClass.class);
bind(ColorInterface.class).annotatedWith(Names.named("ORANGE")).to(ColorClass.class);
......
}
}
Please help me...

Answer 1

If this directly is your issue, I would suggest a slight change in the implementation to move the injected #Named("color") String into a constructor argument and the use of a custom Provider:
public class ColorClass implements ColorInterface {
String color;
ColorClass(String color) {
this.color = color;
}
public String getMeColor(){
return color;
}
public static Provider implements Provider<ColorClass> {
String color;
public Provider(String color) {
this.color = color;
}
public ColorClass get() {
return new ColorClass(color);
}
}
}
and then in your module:
public class ColorModule extends AbstractModule {
#Override
protected void configure() {
bind(ColorInterface.class).annotatedWith(Names.named("BLUE"))
.toProvider(new ColorClass.Provider("Blue"));
bind(ColorInterface.class).annotatedWith(Names.named("RED"))
.toProvider(new ColorClass.Provider("Red"));
bind(ColorInterface.class).annotatedWith(Names.named("ORANGE"))
.toProvider(new ColorClass.Provider("Orange"));
}
}
Obviously, the Provider doesn't need to be a static inner class like I did there, just something in the same package.
In case this exact problem isn't really your problem and you really do need #Named("color") String to be differently injected (say, you've actually got some really deep nested structure pulled together with guice and need a different binding deep in the hierarchy, and can't easily refactor that into a constructor parameter), then you'll need to use private modules.
However, that technique is vast overkill for the case you presented, so I'm hesitant to dive into it here. It's really a rather advanced topic you shouldn't try to tackle unless you really need to solve the problem it solves. (The problem is sometimes referred to as the "Robot Arms" problem)