Java设计模式学习之工厂模式

工厂模式是创造型模式的一种，在java框架如Spring,struts2被广泛运用

该模式运用于：当程序中有一父类和一堆子类，子类的创建是根据输入的不同返回不同的子类
实例。此时只要实现一个工厂类负责不同子类的返回，代替客户端程序来返回实例。

下面例子使用Computer的类来说明工厂模式的实现机制

超类

Computer.java

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package com.walterlife.dp.FactoryDP;

public abstract class Computer {
    public abstract String getRam();
    public abstract String getHdd();
    public abstract String getCpu();
    
    public String toString() {
        return "RAM: " + getRam() 
            + " HDD: " + getHdd()
            + " CPU: " + getCpu();
    } 
}

子类

PC.java

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package com.walterlife.dp.FactoryDP;

public class PC extends Computer {
    public String ram;
    public String hdd;
    public String cpu;

    public PC(String ram, String hdd, String cpu) {
        this.ram = ram;
        this.hdd = hdd;
        this.cpu = cpu;
    } 

    /**
     * @return the ram
     */
    public String getRam() {
        return ram;
    }

    /**
     * @param ram the ram to set
     */
    public void setRam(String ram) {
        this.ram = ram;
    }

    /**
     * @return the hdd
     */
    public String getHdd() {
        return hdd;
    }

    /**
     * @param hdd the hdd to set
     */
    public void setHdd(String hdd) {
        this.hdd = hdd;
    }

    /**
     * @return the cpu
     */
    public String getCpu() {
        return cpu;
    }

    /**
     * @param cpu the cpu to set
     */
    public void setCpu(String cpu) {
        this.cpu = cpu;
    }
}

Server.java

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package com.walterlife.dp.FactoryDP;

public class Server extends Computer {
    public String ram;
    public String hdd;
    public String cpu;

    public Server(String ram, String hdd, String cpu) {
        this.ram = ram;
        this.hdd = hdd;
        this.cpu = cpu;
    } 

    /**
     * @return the ram
     */
    public String getRam() {
        return ram;
    }

    /**
     * @param ram the ram to set
     */
    public void setRam(String ram) {
        this.ram = ram;
    }

    /**
     * @return the hdd
     */
    public String getHdd() {
        return hdd;
    }

    /**
     * @param hdd the hdd to set
     */
    public void setHdd(String hdd) {
        this.hdd = hdd;
    }

    /**
     * @return the cpu
     */
    public String getCpu() {
        return cpu;
    }

    /**
     * @param cpu the cpu to set
     */
    public void setCpu(String cpu) {
        this.cpu = cpu;
    }
}

工厂类

ComputerFactory.java, 是一个工厂类，根据不同的电脑类型产出不同类型的电脑

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package  com.walterlife.dp.FactoryDP;

import org.apache.log4j.Logger;

public class ComputerFactory {
    static Logger logger = Logger.getLogger(ComputerFactory.class);

    public static Computer getComputer(String type, String ram, String hdd, String cpu) {
        Computer computer = null;
        if("pc".equalsIgnoreCase(type)) {
            computer = new PC(ram, hdd, cpu);
        } else if("server".equalsIgnoreCase(type)) {
            computer = new Server(ram, hdd, cpu);
        } else {
            logger.warn("type: " + type + " is not exist!!!");
        }
        return computer;
    } 
}

测试代码

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public static void testFactoryDP() {
    Computer pc = ComputerFactory.getComputer("pc", "2.GB", "500GB", "2.4 GHz");
    Computer server = ComputerFactory.getComputer("server", "16GB", "1TB", "4 GHz");

    if(pc != null) {
        logger.info("PC config :" + pc.toString());
    } else {
        logger.warn("PC instace is null!!!");
    } 

    if(server != null) {
        logger.info("Server config :" + server.toString());
    } else {
        logger.warn("Server instace is null!!!");
    } 
}

输出

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2015-08-23 18:14:06 INFO  com.walterlife.dp.App testFactoryDP:26 -> PC config :RAM: 2.GB HDD: 500GB CPU: 2.4 GHz
2015-08-23 18:14:06 INFO  com.walterlife.dp.App testFactoryDP:32 -> Server config :RAM: 16GB HDD: 1TB CPU: 4 GHz

使用工厂模式的好处

  1. 工厂模式是面向接口的，而不是面向实现的
  2. 工厂模式将具体子类的创建从客户端代码分离，实现了松耦合，易于扩展

留言

Jul 6 2015
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