Injections.md

The dependency injection pattern separates behaviour from dependency resolution. Rather than looking up dependencies directly or from factories, the pattern recommends that dependencies are passed in. The process of setting dependencies into an object is called injection.

下面介绍Guice的注入方式.

构造器注入

public class RealBillingService implements BillingService {
  private final CreditCardProcessor processorProvider;
  private final TransactionLog transactionLogProvider;

  @Inject
  public RealBillingService(CreditCardProcessor processorProvider,
      TransactionLog transactionLogProvider) {
    this.processorProvider = processorProvider;
    this.transactionLogProvider = transactionLogProvider;
  }
}

方法注入

public class PayPalCreditCardProcessor implements CreditCardProcessor {

  private static final String DEFAULT_API_KEY = "development-use-only";

  private String apiKey = DEFAULT_API_KEY;

  @Inject
  public void setApiKey(@Named("PayPal API key") String apiKey) {
    this.apiKey = apiKey;
  }
}