假设我有一个服务接口ServiceInterface
以及实现它的几个组件的以下结构:ProductAService
和ProductBService
我还有一个RequestContext
bean,它有一个合格的财产,表示我们说目前正在处理ProductA或ProductB。然后,如何将自动装配或其他注释自动注入正确的实现(ProductAService或ProductBService)到需要它的某个服务(下面ServiceThatNeedsServiceInterface
)。
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();
}
答案 0 :(得分:11)
Spring Source在1.1.4版本中创建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);
}
您需要将以下代码段添加到applicationContext.xml
<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看起来与下面的类似:
@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spring注释,您的代码不依赖于Spring。 我为上面的
执行了以下单元测试@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();
}
}
控制台将显示
您好,A服务
您好,B服务
一句警告。 API文档说明了 “这样的服务定位器......通常用于原型bean,即用于为每个调用返回一个新实例的工厂方法......对于单例bean,最好直接设置器或构造函数注入目标bean。”
我无法理解为什么这可能会导致问题。在我的代码中,它在对serviceThatNeedsServiceInterface.useService()的两个序列调用中返回相同的服务;
您可以在GitHub
中找到我的示例的源代码答案 1 :(得分:3)
我能想到的唯一方法就是创建像FactoryBean这样的东西,它根据RequestContext属性返回相应的实现。这是我打了一个有你想要的行为的东西:
import org.springframework.beans.factory.FactoryBean;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Qualifier;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.Scope;
import org.springframework.stereotype.Component;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.ResponseBody;
import org.springframework.web.context.WebApplicationContext;
import javax.servlet.http.HttpServletRequest;
public class InjectionQualifiedByProperty {
@Controller
@Scope(WebApplicationContext.SCOPE_REQUEST)
public static class DynamicallyInjectedController {
@Autowired
@Qualifier("picker")
Dependency dependency;
@RequestMapping(value = "/sayHi", method = RequestMethod.GET)
@ResponseBody
public String sayHi() {
return dependency.sayHi();
}
}
public interface Dependency {
String sayHi();
}
@Configuration
public static class Beans {
@Bean
@Scope(WebApplicationContext.SCOPE_REQUEST)
@Qualifier("picker")
FactoryBean<Dependency> dependencyPicker(final RequestContext requestContext,
final BobDependency bob, final FredDependency fred) {
return new FactoryBean<Dependency>() {
@Override
public Dependency getObject() throws Exception {
if ("bob".equals(requestContext.getQualifierProperty())) {
return bob;
} else {
return fred;
}
}
@Override
public Class<?> getObjectType() {
return Dependency.class;
}
@Override
public boolean isSingleton() {
return false;
}
};
}
}
@Component
public static class BobDependency implements Dependency {
@Override
public String sayHi() {
return "Hi, I'm Bob";
}
}
@Component
public static class FredDependency implements Dependency {
@Override
public String sayHi() {
return "I'm not Bob";
}
}
@Component
@Scope(WebApplicationContext.SCOPE_REQUEST)
public static class RequestContext {
@Autowired HttpServletRequest request;
String getQualifierProperty() {
return request.getParameter("which");
}
}
}
我使用此代码on Github放了一个工作示例。您可以使用以下命令克隆并运行它:
git clone git://github.com/zzantozz/testbed tmp
cd tmp/spring-mvc
mvn jetty:run
然后访问http://localhost:8080/dynamicallyInjected
以查看一个依赖项的结果,并http://localhost:8080/dynamicallyInjected?which=bob
查看另一个依赖项。
答案 2 :(得分:1)
我想,你错过了注释,告诉春天,你有一个自定义服务。 所以你的解决方案是在类名之前添加这个注释:
@Service("ProductAService")
public class ProductAService implements ServiceInterface {
@Override public void someMethod() {
System.out.println("Hello, A Service");
}
}
@Service("ProductBService")
public class ProductBService implements ServiceInterface {
@Override public void someMethod() {
System.out.println("Hello, B Service");
}
}
然后您可以自动连接它,但是为了使用特定服务,您必须添加注释Qualifier(),如下所示:
@Autowired
@Qualifier("ProductBService") // or ProductAService
ServiceInterface service;
或者你可能只需要添加一个注释限定符(“你的bean名称”):)
答案 3 :(得分:1)
这可能会对您有所帮助:
使用
AutowireCapeableBeanFactory.autowireBean(Object existingBean)
OR
AutowireCapeableBeanFactory.autowireBeanProperties(Object existingBean, int autowireMode, boolean dependencyCheck)
AutowireCapeableBeanFactory.autowireBean(Object existingBean) AutowireCapeableBeanFactory.autowireBeanProperties(Object existingBean, int autowireMode, boolean dependencyCheck)
答案 4 :(得分:0)
我认为你不能用注释做到这一点,原因是你需要一个在运行时是动态的bean(可能是服务或B服务),所以在任何地方使用bean之前都会连接@Autowire 。一种解决方案是在需要时从上下文中获取bean。
@Component
public class ServiceThatNeedsServiceInterface {
ServiceInterface service;
public void useService() {
if(something is something){
service = applicationContext.getBean("Abean", ServiceInterface.class);
}else{
service = applicationContext.getBean("Bbean", ServiceInterface.class);
}
service.someMethod();
}
}
你可以把别的逻辑放在类中的某个地方作为一个单独的函数:
public void useService() {
service = findService();
service.someMethod();
}
public ServiceInterface findService() {
if(something is something){
return applicationContext.getBean("Abean", ServiceInterface.class);
}else{
return applicationContext.getBean("Bbean", ServiceInterface.class);
}
}
这是动态的,这可能就是你想要的。
答案 5 :(得分:0)
您可以将@Qualifier注释与别名结合使用。查看基于属性here如何使用它加载bean的示例。您可以修改此方法并更改requestcontext中的属性/别名...