sameb edited this page Jul 7, 2014 · 1 revision

@Provides Methods

When you need code to create an object, use an @Provides method. The method must be defined within a module, and it must have an @Provides annotation. The method's return type is the bound type. Whenever the injector needs an instance of that type, it will invoke the method.

public class BillingModule extends AbstractModule {
  protected void configure() {

  TransactionLog provideTransactionLog() {
    DatabaseTransactionLog transactionLog = new DatabaseTransactionLog();
    return transactionLog;

If the @Provides method has a binding annotation like @PayPal or @Named("Checkout"), Guice binds the annotated type. Dependencies can be passed in as parameters to the method. The injector will exercise the bindings for each of these before invoking the method.

  @Provides @PayPal
  CreditCardProcessor providePayPalCreditCardProcessor(
      @Named("PayPal API key") String apiKey) {
    PayPalCreditCardProcessor processor = new PayPalCreditCardProcessor();
    return processor;

Throwing Exceptions

Guice does not allow exceptions to be thrown from Providers. Exceptions thrown by @Provides methods will be wrapped in a ProvisionException. It is bad practice to allow any kind of exception to be thrown -- runtime or checked -- from an @Provides method. If you need to throw an exception for some reason, you may want to use the ThrowingProviders extension @CheckedProvides methods.

Clone this wiki locally
You can’t perform that action at this time.
You signed in with another tab or window. Reload to refresh your session. You signed out in another tab or window. Reload to refresh your session.
Press h to open a hovercard with more details.