@Provides MethodsWhen 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 {
@Override
protected void configure() {
...
}
@Provides
TransactionLog provideTransactionLog() {
DatabaseTransactionLog transactionLog = new DatabaseTransactionLog();
transactionLog.setJdbcUrl("jdbc:mysql://localhost/pizza");
transactionLog.setThreadPoolSize(30);
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();
processor.setApiKey(apiKey);
return processor;
}
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This only works with Guice 2.
You can also annotate the method with a scope, like @Singleton or @RequestScoped.
limpbizkit,
Excellent point, but I suggest you update the wiki document with such an example in case users skip the comments.