技術標籤：JavaIOC

package com.chenxb.dao;

public interface UserDao {
    void getUser();
}

package com.chenxb.dao;

public class UserDaoImpl implements UserDao {

    @Override
    public void getUser() {
        System.out.println("獲取User");
    }
}

package com.chenxb.dao;

public class
 
 UserDaoMysqlImpl implements UserDao {

    @Override
    public void getUser() {
        System.out.println("Mysql 獲取User");
    }
}

package com.chenxb.dao;

public class UserDaoOracleImpl implements UserDao {

    @Override
    public void getUser() {
        System.out.println("Oracle 獲取User"
 
);
    }
}

package com.chenxb.pojo;

import lombok.Data;

@Data
public class User {
    int id;
    String name;
    String password;
}

package com.chenxb.service;

public interface UserService {
    void getUser();
}

package com.chenxb.service;

import com.chenxb.dao.UserDao;
import com.chenxb.dao.
 
UserDaoImpl;
import com.chenxb.dao.UserDaoMysqlImpl;
import com.chenxb.dao.UserDaoOracleImpl;

public class UserServiceImpl implements UserService {
    /**
     * 第一種做法
     * 普通的三層切換多個dao，只能去修改service中的new物件
     */
//    private UserDao userDao = new UserDaoImpl();
//    private UserDao userDao = new UserDaoMysqlImpl();
//    private UserDao userDao = new UserDaoOracleImpl();

    /**
     * 第二種寫法
     * 利用set進行動態注入
     */
    private UserDao userDao;

    public void setUserDao(UserDao userDao) {
        this.userDao = userDao;
    }

    @Override
    public void getUser() {
        userDao.getUser();
    }
}

import com.chenxb.dao.UserDaoOracleImpl;
import com.chenxb.pojo.User;
import com.chenxb.service.UserService;
import com.chenxb.service.UserServiceImpl;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

public class MyTest {
    public static void main(String[] args) {
        /**
         * 第一種做法
         * 普通的三層切換多個dao，只能去修改service中的new物件
         */
//        UserService userService = new UserServiceImpl();
//        userService.getUser();

        /**
         * 第二種寫法
         * 利用set進行動態注入
         */
        UserService userService = new UserServiceImpl();
        ((UserServiceImpl)userService).setUserDao(new UserDaoOracleImpl());
        userService.getUser();


//        //獲取spring上下文物件
//        ApplicationContext context = new ClassPathXmlApplicationContext("user.xml");
//        //物件都在spring上下文物件裡，要用就直接去拿就行了
//        UserServiceImpl userServiceImpl = (UserServiceImpl) context.getBean("UserServiceImpl");
//        userServiceImpl.getUser();
    }
}