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PODependency Injection based on a condition
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copied!<p>I'm using Google Guice for dependency injection. Suppose I have the following:</p> <pre><code>public interface Payment { public void pay(); } public class PaymentCardImpl implements Payment { public void pay() { System.out.println("I pay with a card"); } } public class PaymentCashImpl implements Payment { public void pay() { System.out.println("I pay cash"); } } public class Order { private Payment payment; @Inject public Order(Payment payment){ this.payment=payment; } public void finishOrder(){ this.payment.pay(); } } </code></pre> <p>Following on from this, is a very simple module for binding, like so:</p> <pre><code>public class MyModule extends AbstractModule { @Override protected void configure() { bind(Payment.class).to(PaymentCashImpl.class); } } </code></pre> <p>As you can see, a <code>Payment</code> instance is injected into the Order constructor. This is done in the <code>MyModule</code> class and overall is really cool.</p> <p>My main looks like:</p> <pre><code>public static void main(String[] args) { MyModule module = new MyModule(); Injector injector = Guice.createInjector(module); Order order = injector.getInstance(Order.class); order.finishOrder(); } </code></pre> <p>What I can't see however, is how I could incorporate some way to conditionally bind either a <code>PaymentCardImpl</code> <strong><em>or</em></strong> a <code>PaymentCashImpl</code> instance to the <code>Order</code> constructor. </p> <p>Let's say for example, that the order was an 'online' order. I would then need to this:</p> <pre><code>bind(Payment.class).to(PaymentCardImpl.class); </code></pre> <p>What's the best way to do this? I'm new to dependency injection.</p>

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