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

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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

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package com.baizhiedu.basic;   public interface UserService {     public void register(User user);       public void login(String name, String password); }

　　

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1	UserServiceImpl

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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

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package com.baizhiedu.basic;   public interface UserDAO {     public void save(User user);       public void queryUserByNameAndPassword(String name, String password); }

　　

UserDAOImpl

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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

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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

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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

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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

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1	userService = com.baizhiedu.basic.UserServiceImpl

　　

第二种

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1	userService = com.baizhiedu.basic.UserServiceImplNew