我們?cè)谌粘ｉ_發(fā)中，有時(shí)候會(huì)遇到需要使用接口實(shí)現(xiàn)多態(tài)的需求，那么在Spring中該如何實(shí)現(xiàn)呢？
Spring為我們提供了InitializingBean 接口，接口中的afterPropertiesSet()方法將在所有的屬性被初始化后調(diào)用，但是會(huì)在init前調(diào)用。
下面我們先來(lái)看一下該接口的定義:

public interface InitializingBean {
    /**
     * Invoked by a BeanFactory after it has set all bean properties supplied
     * (and satisfied BeanFactoryAware and ApplicationContextAware).
     * <p>This method allows the bean instance to perform initialization only
     * possible when all bean properties have been set and to throw an
     * exception in the event of misconfiguration.
     * @throws Exception in the event of misconfiguration (such
     * as failure to set an essential property) or if initialization fails.
     */
    void afterPropertiesSet() throws Exception;
}

想要實(shí)現(xiàn)接口的多態(tài)注入需要進(jìn)行如下的步驟：
首先，定義一個(gè)接口類：

public interface IService {

    Integer getType();

    void print(String str);
}

然后寫兩個(gè)實(shí)現(xiàn)類實(shí)現(xiàn)IService接口，實(shí)現(xiàn)接口中的方法：

@Service
public class IServiceAImpl implements IService{
    @Override
    public Integer getType() {
        return new Integer(1);
    }

    @Override
    public void print(String str) {
        System.out.preintln(str);
    }
}

@Service
public class IServiceBImpl implements IService{
    @Override
    public Integer getType() {
        return new Integer(2);
    }

    @Override
    public void print(String str) {
        System.out.preintln(str);
    }
}

下面是核心的代碼，實(shí)現(xiàn)路由功能：

@Component
public class ServiceRouter implements InitializingBean {

    private static final Map<Integer, IService> routerMap = Maps.newHashMap();

    @Autowired
    private List<IService> iServiceList;

    @Override
    public void afterPropertiesSet() throws Exception {
        for (IService service : iServiceList) {
            routerMap.put(service.getType(), service);
        }
    }

    public IService getService(Integer type) {
        return routerMap.get(type);
    }
}

寫一個(gè)測(cè)試類：

@RestController
public class MyController {

    @Autowired
    private ServiceRouter router;

    @RequestMapping("/test")
    public void test(@RequestParam Integer type) {
        IService service = router.getService(type);
        service.print("hello world");
    }
}

那么現(xiàn)在就可以根據(jù)傳進(jìn)來(lái)的type進(jìn)行動(dòng)態(tài)的調(diào)用實(shí)現(xiàn)類，實(shí)現(xiàn)多態(tài)了。是不是很簡(jiǎn)單。

由于本人水平有限，如有錯(cuò)誤請(qǐng)大家多多包涵~