模板方法模式实现封装jdbc

骑猪看日落 2023-02-11 10:29 9阅读 0赞

### 文章目录 ###

*  模板方法模式
 *   *  类图
     *  实践1：各个课程流程 求同存异 写法
     *  实践2：使用模板方法模式封装jdbc
     *  好莱坞法则
     *  模板方法模式的本质
     *  什么时候用到模板方法模式
     *  相关模式对比说明

# 模板方法模式 #

## 类图 ##

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2JhaWR1XzIxMzQ5NjM1_size_16_color_FFFFFF_t_70]  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2JhaWR1XzIxMzQ5NjM1_size_16_color_FFFFFF_t_70 1]

## 实践1：各个课程流程 求同存异 写法 ##

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2JhaWR1XzIxMzQ5NjM1_size_16_color_FFFFFF_t_70 2]

/** * 模板会有一个或者多个未现实方法， * 而且这几个未实现方法有固定的执行顺序 */
    public abstract class NetWorkCourse { 
    
        protected final void createCourse() { 
            //1、发布预习资料
            this.postPreResource();
    
            //2、制作PPT课件
            this.createPPT();
    
            //3、在线直播
            this.liveVideo();
    
            //4、提交课件、课堂笔记
            this.postNote();
    
            //5、提交源码
            this.postSource();
    
            //6、布置作业，有些课是没有作业，有些课是有作业的
            //如果有作业的话，检查作业，如果没作业，完成了
            if (needHomework()) { 
                checkHomework();
            }
        }
    
        abstract void checkHomework();
    
        //钩子方法：实现流程的微调
        protected boolean needHomework() { 
            return false;
        }
    
        final void postSource() { 
            System.out.println("提交源代码");
        }
    
        final void postNote() { 
            System.out.println("提交课件和笔记");
        }
    
        final void liveVideo() { 
            System.out.println("直播授课");
        }
    
        final void createPPT() { 
            System.out.println("创建备课PPT");
        }
    
        final void postPreResource() { 
            System.out.println("分发预习资料");
        }

public class BigDataCource extends NetWorkCourse { 
        private boolean needHomeworkFlag = false;
    
        public BigDataCource(boolean needHomeworkFlag) { 
            this.needHomeworkFlag = needHomeworkFlag;
        }
    
        @Override
        void checkHomework() { 
            System.out.println("检查大数据的课后作业");
        }
    
        @Override
        protected boolean needHomework() { 
            return this.needHomeworkFlag;
        }
    }

public class JavaCourse extends NetWorkCourse { 
        @Override
        void checkHomework() { 
            System.out.println("检查Java的架构课件");
        }
    }

测试NetWorkCourseTest

public class NetWorkCourseTest { 
        public static void main(String[] args) { 
            System.out.println("---检查java作业--");
            NetWorkCourse javaCourse = new JavaCourse();
            javaCourse.createCourse();
            System.out.println("---检查大数据作业--");
            BigDataCource bigDataCource = new BigDataCource(true);
            bigDataCource.createCourse();
        }
    }

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2JhaWR1XzIxMzQ5NjM1_size_16_color_FFFFFF_t_70 3]  
可以看到java课程和大数据课程不同的作业，选择实现。相同的逻辑，父类给 实现了。

## 实践2：使用模板方法模式封装jdbc ##

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2JhaWR1XzIxMzQ5NjM1_size_16_color_FFFFFF_t_70 4]

public abstract class JdbcTemplate { 
        private DataSource dataSource;
    
        public JdbcTemplate(DataSource dataSource) { 
            this.dataSource = dataSource;
        }
        public List<?> executeQuery(String sql, RowMapper<?> rowMapper, Object[] values) { 
            try { 
                //1、获取连接
                Connection conn = this.getConnection();
                //2、创建语句集
                PreparedStatement pstm = this.createPrepareStatement(conn, sql);
                //3、执行语句集
                ResultSet rs = this.executeQuery(pstm, values);
                //4、处理结果集
                List<?> result = this.paresResultSet(rs, rowMapper);
                //5、关闭结果集
                this.closeResultSet(rs);
                //6、关闭语句集
                this.closeStatement(pstm);
                //7、关闭连接
                this.closeConnection(conn);
                return result;
            } catch (Exception e) { 
                e.printStackTrace();
            }
            return null;
        }
    
        //1、获取连接
        public Connection getConnection() throws Exception { 
            return this.dataSource.getConnection();
        }
        //2、创建语句集
        protected PreparedStatement createPrepareStatement(Connection conn, String sql) throws Exception { 
            return conn.prepareStatement(sql);
        }
        //3、执行语句集
        protected ResultSet executeQuery(PreparedStatement pstm, Object[] values) throws Exception { 
            for (int i = 0; i < values.length; i++) { 
                pstm.setObject(i,values[i]);
            }
            return pstm.executeQuery();
        }
        //4、处理结果集
        protected List<?> paresResultSet(ResultSet rs, RowMapper<?> rowMapper) throws Exception { 
            List<Object> result = new ArrayList<Object>();
            int rowNum = 1;
            while (rs.next()){ 
                result.add(rowMapper.mapRow(rs,rowNum ++));
            }
            return result;
        }
        //5、关闭结果集
        protected void closeResultSet(ResultSet rs) throws Exception { 
            rs.close();
        }
        //6、关闭语句集
        protected void closeStatement(PreparedStatement pstm) throws Exception { 
            pstm.close();
        }
        //7、关闭连接
        protected void closeConnection(Connection conn) throws Exception { 
            //数据库连接池，我们不是关闭
            conn.close();
        }
    
    }

public class Member { 
        private String username;
        private String password;
        private String nickname;
        private int age;
        private String addr;
    
        public String getUsername() { 
            return username;
        }
    
        public void setUsername(String username) { 
            this.username = username;
        }
    
        public String getPassword() { 
            return password;
        }
    
        public void setPassword(String password) { 
            this.password = password;
        }
    
        public String getNickname() { 
            return nickname;
        }
    
        public void setNickname(String nickname) { 
            this.nickname = nickname;
        }
    
        public int getAge() { 
            return age;
        }
    
        public void setAge(int age) { 
            this.age = age;
        }
    
        public String getAddr() { 
            return addr;
        }
    
        public void setAddr(String addr) { 
            this.addr = addr;
        }
    }

/** * Title: RowMapper * Description: TODO * * @author hfl * @version V1.0 * @date 2020-05-20 */
    public interface RowMapper<T> { 
        T mapRow(ResultSet rs, int rowNum)throws Exception;
    }

public class MemberDao extends JdbcTemplate { 
        public MemberDao(DataSource dataSource) { 
            super(dataSource);
        }
    
        public List<?> selectAll(){ 
            String sql = "select * from t_member";
            return super.executeQuery(sql, new RowMapper<Member>() { 
                @Override
                public Member mapRow(ResultSet rs, int rowNum) throws Exception { 
                    Member member = new Member();
                    //字段过多，原型模式
                    member.setUsername(rs.getString("username"));
                    member.setPassword(rs.getString("password"));
                    member.setAge(rs.getInt("age"));
                    member.setAddr(rs.getString("addr"));
                    return member;
                }
            },null);
    
        }
    }

public class MemberDaoTest { 
    
        public static void main(String[] args) { 
            MemberDao memberDao = new MemberDao(null);
            List<?> result = memberDao.selectAll();
            System.out.println(result);
        }
    }

继续总结下模板方法模式:

## 好莱坞法则 ##

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2JhaWR1XzIxMzQ5NjM1_size_16_color_FFFFFF_t_70 5]

## 模板方法模式的本质 ##

![在这里插入图片描述][20200523133812593.png]  
![在这里插入图片描述][20200523133825177.png]

## 什么时候用到模板方法模式 ##

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2JhaWR1XzIxMzQ5NjM1_size_16_color_FFFFFF_t_70 6]

## 相关模式对比说明 ##

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2JhaWR1XzIxMzQ5NjM1_size_16_color_FFFFFF_t_70 7]

代码地址:  
[https://github.com/hufanglei/pattern-learn/tree/master/src/main/java/com/example/template][https_github.com_hufanglei_pattern-learn_tree_master_src_main_java_com_example_template]

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![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2JhaWR1XzIxMzQ5NjM1_size_16_color_FFFFFF_t_70 8]

--------------------

完

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[20200523133812593.png]: https://img-blog.csdnimg.cn/20200523133812593.png
[20200523133825177.png]: https://img-blog.csdnimg.cn/20200523133825177.png
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[https_github.com_hufanglei_pattern-learn_tree_master_src_main_java_com_example_template]: https://github.com/hufanglei/pattern-learn/tree/master/src/main/java/com/example/template
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2JhaWR1XzIxMzQ5NjM1_size_16_color_FFFFFF_t_70 8]: https://img-blog.csdnimg.cn/20200524195802340.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2JhaWR1XzIxMzQ5NjM1,size_16,color_FFFFFF,t_70