天若有情

舉兩個(gè)例子以快速明白Java中的簡(jiǎn)單工廠模式：

女?huà)z摶土造人
話說(shuō)：“天地開(kāi)辟，未有人民，女?huà)z摶土為人。”女?huà)z需要用土造出一個(gè)個(gè)的人，但在女?huà)z造出人之前，人的概念只存在于女?huà)z的思想里面。
女?huà)z造人，這就是簡(jiǎn)單工廠模式的應(yīng)用。

　　首先，在這個(gè)造人的思想里面，有幾個(gè)重要的角色：女?huà)z本身、抽象的人的概念和女?huà)z所造出的一個(gè)個(gè)具體的人。
　　1.）女?huà)z是一個(gè)工廠類，也就是簡(jiǎn)單工廠模式的核心角色。

????????2.）具休的一個(gè)個(gè)的人，包括張三，李四等。這些人便是簡(jiǎn)單工廠模式里面的具體產(chǎn)品角色
　　3.）抽象的人是最早只存在于女?huà)z的頭腦里的一個(gè)想法，女?huà)z按照這個(gè)想法造出的一個(gè)個(gè)具體的人，便都符合這個(gè)抽象的人的定義。換言之，這個(gè)抽象的想法規(guī)定了所有具體的人必須都有的接口（特征或者功能）
　　　其UML類圖出下所示：
　　　　
理解了上面的這些東西，再來(lái)理解下面的例子，對(duì)照理解，相信看完這篇文章，便對(duì)java簡(jiǎn)單工廠模式有一個(gè)很好的理解：


有一個(gè)農(nóng)場(chǎng)公司，專門向市場(chǎng)銷售各類水果，在這個(gè)系統(tǒng)里需要描述下列水果：
　　　　　葡萄　Grape
　　　　　草莓　Stuawberry
　　　　　蘋(píng)果　Apple
水果與其他植物不同，最終可以采摘食用，那么一個(gè)自然的做法是建立一個(gè)各種水果都適用的接口，以便與其他農(nóng)場(chǎng)里的植物區(qū)分開(kāi)來(lái)，

此時(shí)，則是為水果類聲明了一個(gè)接口，表現(xiàn)在代碼上：

?1 public ? interface ?Fruit {
?2 ???? // 生長(zhǎng)
?3 ????? void ?grow();
?4 ????? // 收獲
?5 ????? void ?harvest();
?6 ????? // 種植
?7 ????? void ?plant();
?8 }
?9
10

package ?fac;

public ? class ?Apple? implements ?Fruit { // 通過(guò)implements實(shí)現(xiàn)接口Fruit
???? private ? int ?treeAge;
????
???? public ? void ?grow() {
????????log( " Apple?is?growing " );
????}
????
???? public ? void ?harvest() {
????????log( " Apple?has?been?harvested " );
????}
????
???? public ? void ?plant() {
????????log( " Apple?ha?been?planted " );
????}
????
???? public ? static ? void ?log(String?msg) {
????????System.out.println(msg);
????}
????
???? public ? int ?getTreeAge() {
???????? return ?treeAge;
????}
????
???? public ? void ?setTreeAge( int ?treeAge) {
???????? this .treeAge = treeAge;
????}
}

package?fac;

public?class?Grape?implements?Fruit{
????private?boolean?seedless;
????public?void?grow(){
????????log("Grape?is?growing.");
????}
????
????public?void?harvest(){
????????log("Grape?has?been?harvested");
????}
????
????public?void?plant(){
????????log("Grape?ha?been?planted");
????}
????
????public?static?void?log(String?msg){
????????System.out.println(msg);
????}

????public?boolean?isSeedless()?{
????????return?seedless;
????}

????public?void?setSeedless(boolean?seedless)?{
????????this.seedless?=?seedless;
????}
????

}

package?fac;

public?class?Strawberry?implements?Fruit{
????public?void?grow(){
????????log("Strawberry?is?growing");
????}
????
????public?void?harvest(){
????????log("Strawberry?has?been?harvested");
????}
????
????public?void?plant(){
????????log("Strawberry?has?been?planted");
????}
????
????public?static?void?log(String?msg){
????????System.out.println(msg);
????}
}

package?fac;

public?class?FruitGardener{
????public?static?Fruit?factory(String?which)throws?Exception{
????????if(which.equalsIgnoreCase("apple")){
????????????return?new?Apple();
????????}else?if(which.equalsIgnoreCase("strawberry")){
????????????return?new?Strawberry();
????????}else?if?(which.equalsIgnoreCase("grape")){
????????????return?new?Grape();
????????}else{
????????????throw?new?Exception("Bad?fruit?request");
????????}
????}
}

package?fac;

public?class?People?{

????public?static?void?main(String[]?args)?throws?Exception?{
????????FruitGardener?fg=new?FruitGardener();
????????Fruit?ap=fg.factory("Apple");
????????ap.grow();
????????Fruit?gp=fg.factory("Grape");
????????gp.plant();
????????
????????Fruit?dd=fg.factory("ddd");//拋出Bad?fruit?request異常
????}????

}

（注：以上代碼在JDK5.0，Myeclise3.2下編譯通過(guò)）

?

?類比兩個(gè)例子，園丁就相當(dāng)于女?huà)z，而水果就相當(dāng)于具體的人，接口水果類就相當(dāng)于存在于類女?huà)z思想里的人的抽象概念。

由以上兩個(gè)例子可得出，簡(jiǎn)單工廠模式需要由以下角色組成：
　　　　　　接口
????????????????????????接口的實(shí)現(xiàn)類（簡(jiǎn)單工廠模式里面的具體產(chǎn)品角色）
????????????????????????工廠

理解了以下兩個(gè)例子，再來(lái)看第三個(gè)例子：
注意對(duì)比以下三個(gè)實(shí)例的不同
實(shí)例１：

package?org.jzkangta.factorydemo01;
//定義接口
interface?Car{
????public?void?run();
????public?void?stop();
}
//具體實(shí)現(xiàn)類
class?Benz?implements?Car{
????public?void?run(){
????????System.out.println("Benz開(kāi)始啟動(dòng)了。。。。。");
????}
????public?void?stop(){
????????System.out.println("Benz停車了。。。。。");
????}
}
//具體實(shí)現(xiàn)類
class?Ford?implements?Car{
????public?void?run(){
????????System.out.println("Ford開(kāi)始啟動(dòng)了。。。");
????}
????public?void?stop(){
????????System.out.println("Ford停車了。。。。");
????}
}
//工廠
class?Factory{
????public?static?Car?getCarInstance(){
????????return?new?Ford();
????}
}
public?class?FactoryDemo01?{

????public?static?void?main(String[]?args)?{
????????Car?c=Factory.getCarInstance();
????????c.run();
????????c.stop();

????}

}

package?fac;


//定義接口
interface?Car{
????public?void?run();
????public?void?stop();
}
//具體實(shí)現(xiàn)類
class?Benz?implements?Car{
????public?void?run(){
????????System.out.println("Benz開(kāi)始啟動(dòng)了。。。。。");
????}
????public?void?stop(){
????????System.out.println("Benz停車了。。。。。");
????}
}

class?Ford?implements?Car{
????public?void?run(){
????????System.out.println("Ford開(kāi)始啟動(dòng)了。。。");
????}
????public?void?stop(){
????????System.out.println("Ford停車了。。。。");
????}
}
//工廠
class?Factory{
????public?static?Car?getCarInstance(String?type){
????????Car?c=null;
????????if("Benz".equals(type)){
????????????c=new?Benz();
????????}
????????if("Ford".equals(type)){
????????????c=new?Ford();
????????}
????????return?c;
????}
}


public?class?FactoryDemo02?{

????public?static?void?main(String[]?args)?{
????????Car?c=Factory.getCarInstance("Benz");
????????if(c!=null){
????????????c.run();
????????????c.stop();
????????}else{
????????????System.out.println("造不了這種汽車。。。");
????????}
????????

????}

}

interface?Car{
????public?void?run();
????public?void?stop();
}

class?Benz?implements?Car{
????public?void?run(){
????????System.out.println("Benz開(kāi)始啟動(dòng)了。。。。。");
????}
????public?void?stop(){
????????System.out.println("Benz停車了。。。。。");
????}
}

class?Ford?implements?Car{
????public?void?run(){
????????System.out.println("Ford開(kāi)始啟動(dòng)了。。。");
????}
????public?void?stop(){
????????System.out.println("Ford停車了。。。。");
????}
}

class?Toyota?implements?Car{
????public?void?run(){
????????System.out.println("Toyota開(kāi)始啟動(dòng)了。。。");
????}
????public?void?stop(){
????????System.out.println("Toyota停車了。。。。");
????}
}

class?Factory{
????public?static?Car?getCarInstance(String?type){
????????Car?c=null;
????????try?{
????????????c=(Car)Class.forName("org.jzkangta.factorydemo03."+type).newInstance();//利用反射得到汽車類型　
????????}?catch?(InstantiationException?e)?{
????????????//?TODO?Auto-generated?catch?block
????????????e.printStackTrace();
????????}?catch?(IllegalAccessException?e)?{
????????????//?TODO?Auto-generated?catch?block
????????????e.printStackTrace();
????????}?catch?(ClassNotFoundException?e)?{
????????????//?TODO?Auto-generated?catch?block
????????????e.printStackTrace();
????????}
????
????????return?c;
????}
}
public?class?FactoryDemo03?{

????public?static?void?main(String[]?args)?{
????????Car?c=Factory.getCarInstance("Toyota");
????????if(c!=null){
????????????c.run();
????????????c.stop();
????????}else{
????????????System.out.println("造不了這種汽車。。。");
????????}
????????

????}

}