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
实践1：各个课程流程 求同存异 写法
/**
* 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();
}
}
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
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
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
代码地址:
https://github.com/hufanglei/pattern-learn/tree/master/src/main/java/com/example/template
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