模板方法模式（上）

1.

/**
 * 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循序
 * 
 */
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 BigDataCourse extends NetworkCourse {

    private boolean needHomeworkFlag = false;

    public BigDataCourse(boolean needHomeworkFlag) {
        this.needHomeworkFlag = needHomeworkFlag;
    }

    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 {
    void checkHomework() {
        System.out.println("检查Java的架构课件");
    }
}

test

public class NetworkCourseTest {
    public static void main(String[] args) {

        System.out.println("---Java架构师课程---");
        NetworkCourse javaCourse = new JavaCourse();
        javaCourse.createCourse();

        System.out.println("---大数据课程---");
        NetworkCourse bigDataCourse = new BigDataCourse(true);
        bigDataCourse.createCourse();

    }
}

示例二：

/**
 * ORM映射定制化的接口
 * Created by Tom on 2019/3/16.
 */
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>() {
            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 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;
    }
}

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;
    }

    protected void closeConnection(Connection conn) throws Exception {
        //数据库连接池，我们不是关闭
        conn.close();
    }

    protected void closeStatement(PreparedStatement pstm) throws Exception {
        pstm.close();
    }

    protected void closeResultSet(ResultSet rs) throws Exception {
        rs.close();
    }

    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;
    }

    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();
    }

    protected PreparedStatement createPrepareStatement(Connection conn, String sql) throws Exception {
        return conn.prepareStatement(sql);
    }

    public Connection getConnection() throws Exception {
        return this.dataSource.getConnection();
    }
}

public class MemberDaoTest {

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

 三、模板方法的本质是

/**
 * 模板模式用处是复用和扩展
 * 复用骨架里共用代码模块，子类扩展骨架里的抽象方法实现
 */
public abstract class AbstractClass {

    public final void templateMethod() {
        //...
        method1();
        //...
        method2();
        //...
    }

    protected abstract void method1();
    protected abstract void method2();
}

package com.lf.pattern.template;

public class ConcreteClass1 extends AbstractClass{

    @Override
    protected void method1() {

    }

    @Override
    protected void method2() {

    }
}

package com.lf.pattern.template;

public class ConcreteClass2 extends AbstractClass{
    
    @Override
    protected void method1() {

    }

    @Override
    protected void method2() {

    }
}

package com.lf.pattern.template;

public class UserDemo {
    public static void main(String[] args) {
        AbstractClass demo = new ConcreteClass1();
        demo.templateMethod();
    }
}