Is it “bad practice” to pass argument to guice module

问题

Checking out Guice and I love it. I currently have problem where guice solved it by injecting all the required dependencies I need. But I wonder if I am using Guice in the wrong way. What I require though is define bindings depending on specific instance. And to achieve this I passed the instance in the module.

For instance, consider the following (somewhat similar to my problem):

public class CustomerModule extends AbstractModule { 
   private Customer customer;

   public CustomerModule(Customer customer){
       this.customer = customer;
   }  

   @Override 
   public void configure() {
      bind(ReportGenerator.class).to(HtmlReportGenerator.class);
   }

   @Provides 
   Account providePurchasingAccount() { 
      return customer.getPurchasingAccount();
   }
}

I use this module to get Account dependency injected to the report generator class that needs the account of a specific customer. For example, a user chooses a specific customer and say, wants to show a generated report. I have method like

public void printReport (Customer customer){
   Injector injector = Guice.createInjector(new CustomerModule(customer));
   ReportGenerator reportGenerator  = injector.getInstance(ReportGenerator.class);

   showReport(reportGenerator.generate())
}

Once the work is done, I am done with this module.

Is this a ok use of guice?

回答1:

It is appropriate and useful to accept a constructor argument for a Module. This is an especially common pattern when making bindings for similar objects. Example:

// Installs @Named("accounts") Db to the given impl, backed with the given cache.
install(new DbModule("accounts", AccountDb.class, InMemoryCache.class));
// Same as above.
install(new DbModule("users", UserDb.class, DiskCache.class));
install(new DbModule("products", ProductDb.class, CustomProductCache.class));

That said, it is not common to create a new root Injector per action (such as printReport). Injector creation can take a long time as Guice reflectively queries classes and their dependencies. Instead, it is much more common to create the root Injector at application startup, and then create a child injector when you need to bind specific objects the way you have them.

Though it may make sense for you to temporarily create a brand new root Injector for each action, the way you have it, bear in mind that future development may make warrant singleton or application-level scope that persists beyond a single action, or your object graph may grow such that mid-action root Injector creation is no longer performant enough for your uses. If/when that happens, you may want to shift most of your Injector creation and configuration to a predictable startup flow, and only bind your Customer (and nothing else) into a child injector.

来源：https://stackoverflow.com/questions/35833660/is-it-bad-practice-to-pass-argument-to-guice-module

标签

dependency-injection

Guice