手写一个简单的工厂模式（一）

项目结构

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完成项目后，只需修改applicationContext.properties文件里的值，就可以切换实现类。（例如从实现类UserServiceImpl，切换到UserServiceImplNew，只需按下图操作）

改变前的配置

改变前的输出

query User name = name password = suns
insert into user = User{name='suns', password='123456'}

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改变后的配置

改变后的输出

UserServiceImplNew.login
UserServiceImplNew.register

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User

package com.baizhiedu.basic;

public class User {
    private String name;
    private String password;

    public User(String name, String password) {
        this.name = name;
        this.password = password;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getPassword() {
        return password;
    }

    public void setPassword(String password) {
        this.password = password;
    }

    @Override
    public String toString() {
        return "User{" +
                "name='" + name + '\'' +
                ", password='" + password + '\'' +
                '}';
    }
}

　　

UserService

package com.baizhiedu.basic;

public interface UserService {
    public void register(User user);

    public void login(String name, String password);
}

　　

UserServiceImpl 

package com.baizhiedu.basic;

public class UserServiceImpl implements UserService {
    private UserDAO userDAO = new UserDAOImpl();
    @Override
    public void register(User user) {
        userDAO.save(user);
    }

    @Override
    public void login(String name, String password) {
        userDAO.queryUserByNameAndPassword(name, password);
    }
}

　　

UserDAO

package com.baizhiedu.basic;

public interface UserDAO {
    public void save(User user);

    public void queryUserByNameAndPassword(String name, String password);
}

　　

UserDAOImpl

package com.baizhiedu.basic;

public class UserDAOImpl implements UserDAO {
    @Override
    public void save(User user) {
        System.out.println("insert into user = " + user);
    }

    @Override
    public void queryUserByNameAndPassword(String name, String password) {
        System.out.println("query User name = " + name + " password = " + password);
    }
}

　　

BeanFactory

package com.baizhiedu.basic;

import java.io.IOException;
import java.io.InputStream;
import java.util.Properties;

public class BeanFactory {
    private static Properties env = new Properties();

    static {
        try {
            //第一步 获取IO输入流
            InputStream inputStream = BeanFactory.class.getResourceAsStream("/applicationContext.properties");
            //第二步 文件内容 封装 Properties集合中 key = userService , value = com.baizhixx.UserServiceImpl
            env.load(inputStream);
            //关流
            inputStream.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    /**
     * 对象的创建方式：
     *    1.直接调用构造方法 创建对象 UserService userService = new UserServiceImpl();
     *    2.通过反射的形式 创建对象 解耦合
     *       Class clazz = Class.forName("com.baizhiedu.basic.UserServiceImpl");
     *       UserService userService = (UserService)clazz.newInstance();
     */
    public static UserService getUserService(){
//        return new UserServiceImpl();


        UserService userService = null;
        try {
            Class clazz = Class.forName(env.getProperty("userService"));
            //Object obj = clazz.newInstance();
            userService = (UserService)clazz.newInstance();
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        } catch (InstantiationException e) {
            e.printStackTrace();
        } catch (IllegalAccessException e) {
            e.printStackTrace();
        }
        return userService;
    }
}

　　

UserServiceImplNew

package com.baizhiedu.basic;

public class UserServiceImplNew implements UserService {
    @Override
    public void register(User user) {
        System.out.println("UserServiceImplNew.register");
    }

    @Override
    public void login(String name, String password) {
        System.out.println("UserServiceImplNew.login");
    }
}

　　

TestSpring

package com.baizhiedu;

import com.baizhiedu.basic.BeanFactory;
import com.baizhiedu.basic.User;
import com.baizhiedu.basic.UserService;
import com.baizhiedu.basic.UserServiceImpl;
import org.junit.Test;

public class TestSpring {
    /**
     * 用于测试：工厂类进行解耦合的操作
     */
    @Test
    public void test1(){
        //UserServiceImplNew

        //UserService userService = new UserServiceImplNew();
//        UserService userService = new UserServiceImpl();

        UserService userService = BeanFactory.getUserService();

        userService.login("name", "suns");

        User user = new User("suns", "123456");
        userService.register(user);
    }
}

　　

applicationContext.properties

第一种

userService = com.baizhiedu.basic.UserServiceImpl

　　

第二种

userService = com.baizhiedu.basic.UserServiceImplNew