设计模式学习之简单工厂+反射+配置文件

川长思鸟来 2023-10-06 08:17 7阅读 0赞

用反射+配置文件的方法重新实现大话设计模式课本上15章15.7的例题

问题分析：相比抽象工厂，用DataAccess类代替了工厂接口以及工厂类，再加上使用反射+配置文件的方式，可以做到不对编译好的程序作出改变就能修改数据库种类，客户端可以只是用DateAccess进行数据库访问实例的创建，达到了解耦的目的。

UML图：  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzE1NzE5NjEz_size_16_color_FFFFFF_t_70]

package com.cmc;
    //用户数据类
    public class User {
        
    	private int id;
    	private String name;
    	public int getId() {
        
    		return id;
    	}
    	public void setId(int id) {
        
    		this.id = id;
    	}
    	public String getName() {
        
    		return name;
    	}
    	public void setName(String name) {
        
    		this.name = name;
    	}
    }
     
    package com.cmc;
    //部门数据类
    public class Department {
        
    	int id;
    	String dept_name;
    	public int getId() {
        
    		return id;
    	}
    	public void setId(int id) {
        
    		this.id = id;
    	}
    	public String getDept_name() {
        
    		return dept_name;
    	}
    	public void setDept_name(String dept_name) {
        
    		this.dept_name = dept_name;
    	}
    	
    }
    package com.cmc;
    //用户数据库操作的接口
    public interface IUser {
        
    	void insert(User user);
    	User getUser(int id);
    }
    package com.cmc;
    //部门数据库操作接口
    public interface IDepartment {
        
        void insert(Department department);
    	
    	Department getDepartment(int id);
    }
    package com.cmc;
    //在SqlServer中实现对用户数据库的操作
    public class SqlserverUser implements IUser {
        
     
    	public User getUser(int id) {
        
    		System.out.println("在SQL Server中根据ID得到一条记录");
    		return null;
    	}
     
    	public void insert(User u) {
        
    		// TODO Auto-generated method stub
    		System.out.println("在SQL Server 中给user表添加一条记录");
     
    	}
     
    }
    package com.cmc;
    //在Access中实现对用户数据库的操作
    public class AccessUser implements IUser {
        
     
    	public User getUser(int id) {
        
    		System.out.println("在Access中根据ID得到一条记录");
    		return null;
    	}
     
    	public void insert(User user) {
        
    		// TODO Auto-generated method stub
    		System.out.println("在Access中给user表添加一条记录");
     
    	}
     
    }
    package com.cmc;
     
    public class SqlserverDepartment implements IDepartment {
        
     
    	public Department getDepartment(int id) {
        
    		System.out.println("在SQL Server中根据ID得到一条记录");
    		// TODO Auto-generated method stub
    		return null;
    	}
     
    	public void insert(Department department) {
        
    		// TODO Auto-generated method stub
    		System.out.println("在SQL Server 中给Department表添加一条记录");
     
    	}
     
    }
    package com.cmc;
     
    public class AccessDepartment implements IDepartment {
        
     
    	public Department getDepartment(int id) {
        
    		System.out.println("在Access中根据ID得到一条记录");
    		// TODO Auto-generated method stub
    		return null;
    	}
     
    	public void insert(Department department) {
        
    		// TODO Auto-generated method stub
    		System.out.println("在Access中给Department表添加一条记录");
    	}
     
    }
     
    package com.cmc;
    //通过配置文件+反射对要创建的类进行切换
    import java.io.IOException;
    import java.util.Properties;
     
    import config.RunMain;
     
    public class DataAccess {
        
    	public static IUser CreatUser(){
        
    		IUser result = null;
    		Properties prop = new Properties();
    		try {
        
    			prop.load(RunMain.class.getResourceAsStream("/com/cmc/datebase.properties"));
    			Class db = Class.forName("com.cmc."+prop.getProperty("dbuser"));
    			result = (IUser)db.newInstance();
    		} catch (ClassNotFoundException e) {
        
    			e.printStackTrace();
    		} catch (InstantiationException e) {
        
    			e.printStackTrace();
    		} catch (IllegalAccessException e) {
        
    			e.printStackTrace();
    		} catch (IOException e) {
        
    			e.printStackTrace();
    		}
    		return result;
    	}
    	public static IDepartment CreatDepartment(){
        
    		IDepartment result = null;
    		Properties properties = new Properties();
    		try {
        
    			properties.load(RunMain.class.getResourceAsStream("/com/cmc/datebase.properties"));
    			Class db = Class.forName("com.cmc."+properties.getProperty("dbdepartment"));
    			result=(IDepartment)db.newInstance();
    		} catch (ClassNotFoundException e) {
        
    			e.printStackTrace();
    		} catch (InstantiationException e) {
        
    			e.printStackTrace();
    		} catch (IllegalAccessException e) {
        
    			e.printStackTrace();
    		} catch (IOException e) {
        
    			e.printStackTrace();
    		}
    		return result;
    	}
    }

优点：  
1.实现了组件的封装，然后让组件外部能真正面向接口编程。  
2.通过简单工厂，实现了客户端和具体实现类的解耦。  
缺点：不方便扩展子工厂，如果要增加oracle数据库，必须在DateAccess类中增加oracle的方法，在工厂中增加创建case，这一点不符合开闭原则。显然使用反射+配置文件可以解决后者。

[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzE1NzE5NjEz_size_16_color_FFFFFF_t_70]: https://img-blog.csdnimg.cn/20200507152112837.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzE1NzE5NjEz,size_16,color_FFFFFF,t_70