JAVA - 工厂模式

1. 简单工厂违背OCP（Open Close Principle）原则 , 即对增加开放，对修改关闭。如果要符合OCP原则，要针对接口编程。

 1 //简单工厂模式，违反了OCP原则
 2 public class DAOFactory {
 3 
 4     public static IAddressDao getAddressDao() {
 5         return new AddressDao();
 6     }
 7 
 8     public static IUserDao getUserDao() {
 9         return new UserDao();
10     }
11 
12 }

2.下一种模式的工厂进一步优化了简单工厂，但有一个缺点就是依赖于工厂的实现类

1 public interface IFactoryDao {
2     public IUserDao createUserDao();
3     public IAddressDao createAddressDao();
4 }
 1 public class MysqlDaoFactory implements IFactoryDao {
 2     private static IFactoryDao factory = new MysqlDaoFactory();
 3     private MysqlDaoFactory() {    }
 4     
 5     public static IFactoryDao getInstance() {
 6         return factory;
 7     }
 8     
 9     @Override
10     public IAddressDao createAddressDao() {
11         return new AddressDao();
12     }
13 
14     @Override
15     public IUserDao createUserDao() {
16         return new UserDao();
17     }
18 }
 1 public class OracleDaoFactory implements IFactoryDao {
 2     private static IFactoryDao f = new OracleDaoFactory();
 3     private OracleDaoFactory(){}
 4 
 5     public static IFactoryDao getInstance() {
 6         return f;
 7     }
 8     @Override
 9     public IUserDao createUserDao() {
10         return new UserOracleDao();
11     }
12 
13     @Override
14     public IAddressDao createAddressDao() {
15         return new AddressOracleDao();
16     }
17 
18 }

3.为了解决第二种工厂模式的弊端，需要使用配置文件，然后通过反射获取工厂实例

dao.properties 配置文件

factory=dawang.dao.MysqlDaoFactory
 1 package dawang.util;
 2 
 3 import dawang.dao.IFactoryDao;
 4 
 5 import java.lang.reflect.InvocationTargetException;
 6 import java.lang.reflect.Method;
 7 import java.util.Properties;
 8 
 9 public class DaoUtil {
10     public static void main(String[] args) {
11         System.out.println(createDaoFactory());
12     }
13     @SuppressWarnings({ "rawtypes", "unchecked" })
14     public static IFactoryDao createDaoFactory() {
15         IFactoryDao f = null;
16         try {
17             Properties prop = PropertiesUtil.getDaoProp();
18             String fs = prop.getProperty("factory");
19             Class clz = Class.forName(fs);
20             String mn = "getInstance";
21             Method m = clz.getMethod(mn);
22             f = (IFactoryDao)m.invoke(clz);
23         } catch (ClassNotFoundException e) {
24             e.printStackTrace();
25         } catch (SecurityException e) {
26             e.printStackTrace();
27         } catch (NoSuchMethodException e) {
28             e.printStackTrace();
29         } catch (IllegalArgumentException e) {
30             e.printStackTrace();
31         } catch (IllegalAccessException e) {
32             e.printStackTrace();
33         } catch (InvocationTargetException e) {
34             e.printStackTrace();
35         }
36         return f;
37     }
38 }

 



posted on 2017-07-05 22:22  dawangandy  阅读(90)  评论(0)    收藏  举报

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