说我有一个服务接口ServiceInterface和一些实现它的组件的以下结构：ProductAService和ProductBService我还有一个RequestContext bean,它有一个限定属性,表示我们现在正在处理ProductA或ProductB.那么如何可以自动注入自动装配或其他注释正确的实现(ProductAService或ProductBService)到某些需要它的服务(ServiceThatNeedsServiceInterface下面).
public interface ServiceInterface {
void someMethod();
}
@Component(name="ProductAService")
public class ProductAService implements ServiceInterface {
@Override public void someMethod() {
System.out.println("Hello,A Service");
}
}
@Component(name="ProductBService")
public class ProductBService implements ServiceInterface {
@Override public void someMethod() {
System.out.println("Hello,B Service");
}
}
@Component
public class ServiceThatNeedsServiceInterface {
// What to do here???
@Autowired
ServiceInterface service;
public void useService() {
service.someMethod();
}
}
@Component
@Scope( value = WebApplicationContext.SCOPE_REQUEST )
public class RequestContext {
String getSomeQualifierProperty();
}
解决方法
Spring Source在版本1.1.4中创建了
ServiceLocatorFactoryBean时引用了您的问题.为了使用它,您需要添加类似于下面的界面：
public interface ServiceLocator {
//ServiceInterface service name is the one
//set by @Component
public ServiceInterface lookup(String serviceName);
}
您需要将以下代码片段添加到您的applicationContext.xml中
<bean id="serviceLocatorfactorybean" class="org.springframework.beans.factory.config.ServiceLocatorfactorybean"> <property name="serviceLocatorInterface" value="org.haim.springframwork.stackoverflow.ServiceLocator" /> </bean>
现在您的ServiceThatNeedsServiceInterface将类似于以下内容：
@Component
public class ServiceThatNeedsServiceInterface {
// What to do here???
// @Autowired
// ServiceInterface service;
/*
* ServiceLocator lookup returns the desired implementation
* (ProductAService or ProductBService)
*/
@Autowired
private ServiceLocator serviceLocatorfactorybean;
//Let’s assume we got this from the web request
public RequestContext context;
public void useService() {
ServiceInterface service =
serviceLocatorfactorybean.lookup(context.getQualifier());
service.someMethod();
}
}
ServiceLocatorfactorybean将根据RequestContext限定符返回所需的服务.
除了弹簧注释,你的代码不依赖于Spring.
我执行了以上的单元测试
@RunWith(SpringJUnit4ClassRunner.class)
@ContextConfiguration(locations = { "classpath:Meta-INF/spring/applicationContext.xml" })
public class ServiceThatNeedsServiceInterfaceTest {
@Autowired
ServiceThatNeedsServiceInterface serviceThatNeedsServiceInterface;
@Test
public void testUseService() {
//As we are not running from a web container
//so we set the context directly to the service
RequestContext context = new RequestContext();
context.setQualifier("ProductAService");
serviceThatNeedsServiceInterface.context = context;
serviceThatNeedsServiceInterface.useService();
context.setQualifier("ProductBService");
serviceThatNeedsServiceInterface.context = context;
serviceThatNeedsServiceInterface.useService();
}
}
显示控制台
你好,一个服务
你好,B服务
一句警告. API文档说明
“这样的服务定位器…通常将用于原型bean,即对于每个调用返回一个新实例的工厂方法,对于单例bean,最好是直接设置器或构造器注入目标bean.
我不明白为什么会导致一个问题.在我的代码中,它返回相同的服务在两个序列调用serviceThatNeedsServiceInterface.useService();
