Java接口实现类动态切换

前言

探究数据源动态切换原理, 并进行简单原理演练。

原理演练

1. dao层基本实现

public interface IDao {
    User getUser();
}

@Slf4j
public class Dao1 implements IDao{
    @Override
    public User getUser() {
        return new User("dao1", 17);
    }
}

@Slf4j
public class Dao2 implements IDao{
    @Override
    public User getUser() {
        return new User("dao2", 17);
    }
}

2. dao管理

public class DaoContextAdapter {

    private final InheritableThreadLocal<String> proxyThreadLocal = new InheritableThreadLocal<>() {
        @Override
        protected String initialValue() {
            return "dao1";
        }
    };

    public String get() {
        return proxyThreadLocal.get();
    }

    public void set(String proxy) {
        proxyThreadLocal.set(proxy);
    }

    public void clear() {
        proxyThreadLocal.remove();
    }
}

public class DaoContext {

    private static final Map<String, IDao> DAOS = new HashMap<>();
    private final DaoContextAdapter adapter;

    static {
        DAOS.put("dao1", new Dao1());
        DAOS.put("dao2", new Dao2());
    }

    public DaoContext(DaoContextAdapter adapter) {
        this.adapter = adapter;
    }

    public IDao getDao() {
        return DAOS.get(adapter.get());
    }
}

3. service层动态切换dao

public interface IService {
    User getUser();
}

public class UserService implements IService{

    private DaoContext daoContext;

    public void setDaoContext(DaoContext daoContext) {
        this.daoContext = daoContext;
    }

    @Override
    public User getUser() {
        return daoContext.getDao().getUser();
    }
}

4. 演练

@Slf4j
class ProxyTest {

    @Test
    void proxy() throws Exception {
        DaoContextAdapter adapter = new DaoContextAdapter();
        DaoContext daoContext = new DaoContext(adapter);

        UserService userService = new UserService();
        userService.setDaoContext(daoContext);

        // User(name=dao1, age=17)
        adapter.set("dao1");
        log.info(userService.getUser().toString());

        // User(name=dao2, age=17)
        adapter.set("dao2");
        log.info(userService.getUser().toString());

    }
}