CODEWITHSUNDEEP
javadependency-injectionguice
Sammy Pawar
Sammy Pawar

Reputation: 1281

guice conditional module install

I have got below code in main class

public ABCImpl() {
    Injector injector = Guice.createInjector(new SomeModule());
    this.config = injector.getInstance(SomeConfig.class);

SomeModule has other modules in it installed like

public class SomeModule extends AbstractModule {

    @Override
    protected void configure() {
        install(new SomeOtherModule());
        install(new AndAnotherModule());
    }
}

SomeOtherModule module belongs to some different jar and it has a provider implementation.

@ProvidesIntoOptional(ProvidesIntoOptional.Type.DEFAULT)
public XYZ getXYZ() {
    return new XYZ();
}

Now I want to override this default inside SomeModule or create a different module to be installed based on values in config 

@ProvidesIntoOptional(ProvidesIntoOptional.Type.DEFAULT)
public XYZ getXYZDifferentWay() {
    return new XYZ(someparam);
}

How can I achieve this. My only goal is if some value on config is true then I should get different XYZ otherwise keep things as it is. This could be useful in cases where you need default resource connection but in local machine may be I can use mock resource.

Upvotes: 3

Views: 3617

Answers (1)

Andy Turner
Andy Turner

Reputation: 140554

Literally just install them conditionally:

if (condition) {
  install(new SomeOtherModule());
} else {
  install(new AndAnotherModule());
}

Or, if you want AndAnotherModule to override the bindings in SomeOtherModule, use Modules.override:

Module module = new SomeOtherModule();
if (condition) {
  module = Modules.override(module).with(new AndAnotherModule());
}
install(module);

Or, if you want to use configuration from another guice binding:

// In SomeOtherModule
@Provides @FromSomeOtherModule
public XYZ getXYZ() { ... }

// In AndAnotherModule
@Provides @FromAndAnotherModule
public XYZ getXYZ() { ... }

// In a module which "picks" between the two:
@ProvidesIntoOptional(ProvidesIntoOptional.Type.DEFAULT)
public XYZ provideBasedOnCondition(
    @SomeQualifier boolean condition,
    @FromSomeOtherModule XYZ fromSomeOtherModule,
    @FromAndAnotherModule XYZ fromAndOtherModule) {
  return condition ? fromSomeOtherModule : fromAndOtherModule;
}

where @FromSomeOtherModule, @FromAndAnotherModule and @SomeQualifier are suitable binding annotations.

Upvotes: 3

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