设计模式的模板方式应用

如Struts2中的拦截器，简单的Demo如下：

Java代码 

package com.pattern.templateMethod; 
  
/** 
 * 抽象类,充当模板角色 
 * @author administrator 
 * 
 */  
public abstract class AbstractDisplay {  
    //由子类实现的抽象方法  
    public abstract void open();     
    public abstract void print();  
    public abstract void close();  
    //抽象类实现的方法,final可以保证在子类不会被修改  
    public final void display() {  
        open();   //先open...  
        for(int i=0; i < 5; i++) {  //反复输出5次  
            print();    
        }  
        close(); //输出完毕,close  
    }  
}  
 
  2.字符类，输出单个字符
Java代码  
package com.pattern.templateMethod;  
  
public class CharDisplay extends AbstractDisplay {  
    private char ch;     //应输出的字符  
    public CharDisplay(char ch) {  //把构造函数传递过来的字符ch,存储在字段内  
        this.ch = ch;  
    }  
    
    public void open() {  
        System.out.print("<<");   //输出"<<"作为开始字符串  
    }  
    public void close() {  
        System.out.println(">>");  //输出 ">>"作为结束字符串  
    }  
    public void print() {  
        System.out.print(ch);    //输出存储在字段的字符  
    }  
  
}  
 
   3.字符串类，输出字符串
Java代码  
package com.pattern.templateMethod;  
  
/** 
 *  
 * @author administrator 
 */  
public class StringDisplay extends AbstractDisplay {  
    private String string;  //应输出的字符串  
    private int width;      //以byte为单位所求出的字符串的"长度"  
      
    public StringDisplay(String string) {  
        this.string =string;  
        width = string.getBytes().length;  
    }  
  
    public void open() {  //打印头装饰字符串  
        printLine();  
    }  
    public void print() { //打印内容  
        System.out.println("|"+string+"|");  
    }  
    public void close() { //打印尾装饰字符串  
        printLine();  
    }  
  
    public void printLine() {  
        System.out.print("+");  //输出"+"号表示边框位置  
        for(int i=0; i < width; ++i) {  
            System.out.print("-");  //当作线段  
        }  
        System.out.println("+");  //输出"+"号表示边框位置  
    }  
}  
  4.测试类
Java代码  
package com.pattern.templateMethod;  
  
public class Main {  
    public static void main(String[] args) {  
        //建立1个有'A'的CharDisplay的对象  
        AbstractDisplay d1 = new CharDisplay('A');  
        //建立1个有"Hello world"的StringDisplay的对象  
        AbstractDisplay d2 = new StringDisplay("Hello World");  
          
        //d1,d2都是AbstractDisplay的子类对象,可以调用继承到的display()方法  
        d1.display();  
        d2.display();  
    }  
}  
 
 输出:
 
C代码  
 <<AAAAA>>  
+-----------+  
|Hello World|  
|Hello World|  
|Hello World|  
|Hello World|  
|Hello World|  
+-----------+

Demo 2

BaseDAO.

package com.test.templatemethod;

public abstract class BaseDao<T> {
    public void save(T t) {
        if (beforeSave(t)) {
            System.out.println("save T");
        }
        beforeSave(t);
    }

    protected boolean beforeSave(T t) {
        return true;
    }

    protected void afterSave(T t) {
    }
}

UserDAO:

package com.test.templatemethod;

public class UserDao extends BaseDao<User> {

    @Override
    protected void afterSave(User t) {
        System.out.println("do afterSave");
    }

    @Override
    protected boolean beforeSave(User t) {
        System.out.println("do beforeSave");
        return true;
    }

}

User 类

package com.test.templatemethod;

public class User {
    private String name;

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }
}

测试类:

package com.test.templatemethod;

public class Test {
    public static void main(String[] args) {
        User user = new User();
        user.setName("test");

        UserDao userDao = new UserDao();
        userDao.save(user);
    }
}