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這篇“Java設(shè)計模式之原型模式怎么實現(xiàn)”文章的知識點大部分人都不太理解,所以小編給大家總結(jié)了以下內(nèi)容,內(nèi)容詳細,步驟清晰,具有一定的借鑒價值,希望大家閱讀完這篇文章能有所收獲,下面我們一起來看看這篇“Java設(shè)計模式之原型模式怎么實現(xiàn)”文章吧。
用原型實例指定創(chuàng)建對象的種類,并且通過拷貝這些原型創(chuàng)建新的對象。
原型模式其實就是從一個對象在創(chuàng)建另外一個可定制的對象,不需要知道任何創(chuàng)建的細節(jié)
在運行期建立和刪除原型。
經(jīng)常用于:
類初始化消耗資源較多
構(gòu)造函數(shù)比較復(fù)雜
1.實現(xiàn)cloneable 接口,重寫Object的clone方法
2.利用已有的一個原型對象,快速地生成和原型對象一樣的實例。
淺復(fù)制:基本數(shù)據(jù)類型進行值傳遞、引用數(shù)據(jù)類型的指針仍是指向原來的對象(成員變量)。
深復(fù)制:基本數(shù)據(jù)類型進行值傳遞、引用數(shù)據(jù)類型開辟新的內(nèi)存空間。
需求:實現(xiàn)克隆羊
有一頭羊,需要經(jīng)過賦值再克隆出兩頭。
/** * 克隆羊類 * * @author Promsing(張有博) * @version 1.0.0 * @since 2022/9/3 - 14:51 */ public class Sheep { private String name; private Integer age; private String color; public String getName() { return name; } public void setName(String name) { this.name = name; } public Integer getAge() { return age; } public void setAge(Integer age) { this.age = age; } public String getColor() { return color; } public void setColor(String color) { this.color = color; } public Sheep() { } public Sheep(String name, Integer age, String color) { this.name = name; this.age = age; this.color = color; } }
Main方法
/** * * 傳統(tǒng)模式 * @author Promsing(張有博) * @version 1.0.0 * @since 2022/9/3 - 14:47 */ public class Client { public static void main(String[] args) { //小羊 Sheep sheep=new Sheep("小紅",8,"紅色"); //克隆羊 Sheep sheep2=sheep; Sheep sheep3=sheep; System.out.println("通過賦值,指針還是指向sheep"); System.out.println(sheep); System.out.println(sheep2); System.out.println(sheep3); } } //通過賦值,指針還是指向sheep //com.promsing.creational.prototype.type1.Sheep@1b6d3586 //com.promsing.creational.prototype.type1.Sheep@1b6d3586 //com.promsing.creational.prototype.type1.Sheep@1b6d3586
Cloneable是標(biāo)記型的接口,它們內(nèi)部都沒有方法和屬性,實現(xiàn) Cloneable來表示該對象能被克隆,能使用Object.clone()方法。
如果沒有實現(xiàn) Cloneable的類對象調(diào)用clone()就會拋出CloneNotSupportedException。
實現(xiàn)Cloneable默認是淺復(fù)制
/** * 克隆羊 * * @author Promsing(張有博) * @version 1.0.0 * @since 2022/9/3 - 14:53 */ public class Sheep implements Cloneable { private String name; private Integer age; private String color; /** * 羊的朋友 */ private Sheep friend; public String getName() { return name; } public void setName(String name) { this.name = name; } public Integer getAge() { return age; } public void setAge(Integer age) { this.age = age; } public String getColor() { return color; } public void setColor(String color) { this.color = color; } public Sheep() { } public Sheep getFriend() { return friend; } public void setFriend(Sheep friend) { this.friend = friend; } public Sheep(String name, Integer age, String color) { this.name = name; this.age = age; this.color = color; } /** * 克隆該實例,調(diào)用object.clone的方法 * @return */ @Override protected Sheep clone() { Sheep sheep = null; try { sheep = (Sheep) super.clone(); } catch (CloneNotSupportedException e) { System.out.println(e.getMessage()); e.printStackTrace(); } return sheep; } }
Main方法
/** * 淺復(fù)制:淺復(fù)制:基本數(shù)據(jù)類型進行值傳遞、引用數(shù)據(jù)類型的指針仍是指向原來的對象(成員變量)。 */ public class ShallowClient { public static void main(String[] args) { Sheep sheep=new Sheep("小紅",9,"紅色"); sheep.setFriend(new Sheep("小黑",10,"黑色")); Sheep sheep1 = sheep.clone();//開辟了新的空間 Sheep sheep2 = sheep.clone(); //淺復(fù)制 System.out.println("原型羊"+sheep); System.out.println("克隆羊"+sheep1+"-朋友羊-"+sheep1.getFriend()); System.out.println("克隆羊"+sheep2+"-朋友羊-"+sheep2.getFriend()); //原型羊com.promsing.creational.prototype.type3.Sheep@1b6d3586 //克隆羊com.promsing.creational.prototype.type3.Sheep@4554617c-朋友羊-com.promsing.creational.prototype.type3.Sheep@74a14482 //克隆羊com.promsing.creational.prototype.type3.Sheep@1540e19d-朋友羊-com.promsing.creational.prototype.type3.Sheep@74a14482 } }
一定要實現(xiàn)接口cloneable 否則報錯:
Exception in thread "main" java.lang.CloneNotSupportedException: com.promsing.creational.prototype.type4.Sheep
at java.lang.Object.clone(Native Method)
at com.promsing.creational.prototype.type4.Sheep.clone(Sheep.java:76)
at com.promsing.creational.prototype.type4.DeepClient.main(DeepClient.java:14)
羊類、房子類都需要實現(xiàn)Cloneable接口
房子類
/** * 房子類 * * @author Promsing(張有博) * @version 1.0.0 * @since 2022/9/3 - 15:27 */ public class House implements Cloneable { //地址 private String address; //尺寸 private Integer size; public String getAddress() { return address; } public void setAddress(String address) { this.address = address; } public Integer getSize() { return size; } public void setSize(Integer size) { this.size = size; } /** * 克隆的方法 * @return * @throws CloneNotSupportedException */ @Override protected Object clone() throws CloneNotSupportedException { return super.clone(); } }
羊類
/** * 克隆羊-深拷貝 * * @author Promsing(張有博) * @version 1.0.0 * @since 2022/9/3 - 15:26 */ public class Sheep implements Cloneable { private String name; private Integer age; private String color; /** * 羊的房子:引用類型 */ private House house; public House getHouse() { return house; } public void setHouse(House house) { this.house = house; } public String getName() { return name; } public void setName(String name) { this.name = name; } public Integer getAge() { return age; } public void setAge(Integer age) { this.age = age; } public String getColor() { return color; } public void setColor(String color) { this.color = color; } public Sheep() { } public Sheep(String name, Integer age, String color) { this.name = name; this.age = age; this.color = color; } /** * 克隆該實例,調(diào)用object,clone的方法 * * @return * @throws CloneNotSupportedException */ @Override protected Object clone() throws CloneNotSupportedException { //對基本數(shù)據(jù)類型進行處理 Sheep deep = null; deep = (Sheep) super.clone(); //對引用類型進行處理 //進行再次克隆 House clone = (House) deep.getHouse().clone(); deep.setHouse(clone); return deep; } }
Main
/** * 深復(fù)制:羊類、房子類都需要重寫clone的接口,比較麻煩。不符合開閉 * * @author Promsing(張有博) * @version 1.0.0 * @since 2022/9/3 - 15:38 */ public class DeepClient { public static void main(String[] args) throws CloneNotSupportedException { Sheep sheep=new Sheep("黑",90,"heisee"); sheep.setHouse(new House()); Sheep clone = (Sheep)sheep.clone(); System.out.println("原本的對象"); System.out.println(sheep); System.out.println(sheep.getHouse()); System.out.println("克隆的對象"); System.out.println(clone); System.out.println(clone.getHouse()); //開辟了新的內(nèi)存空間 //原本的對象 //com.promsing.creational.prototype.type4.Sheep@1b6d3586 //com.promsing.creational.prototype.type4.House@4554617c //克隆的對象 //com.promsing.creational.prototype.type4.Sheep@74a14482 //com.promsing.creational.prototype.type4.House@1540e19d } }
羊類、房子類都需要實現(xiàn)Serializable接口。注意這里可以不實現(xiàn)Cloneable了。
房子類
/** * 房子類 * * @author Promsing(張有博) * @version 1.0.0 * @since 2022/9/3 - 15:27 */ public class House implements Serializable{ //地址 private String address; //尺寸 private Integer size; public String getAddress() { return address; } public void setAddress(String address) { this.address = address; } public Integer getSize() { return size; } public void setSize(Integer size) { this.size = size; } }
羊類
/** * 克隆羊-深拷貝 * * @author Promsing(張有博) * @version 1.0.0 * @since 2022/9/3 - 15:26 */ public class Sheep implements Serializable { private String name; private Integer age; private String color; /** * 羊的房子:引用類型 */ private House house; public House getHouse() { return house; } public void setHouse(House house) { this.house = house; } public String getName() { return name; } public void setName(String name) { this.name = name; } public Integer getAge() { return age; } public void setAge(Integer age) { this.age = age; } public String getColor() { return color; } public void setColor(String color) { this.color = color; } public Sheep() { } public Sheep(String name, Integer age, String color) { this.name = name; this.age = age; this.color = color; } /** * 序列化的方式:進行深復(fù)制 * 寫著麻煩:用著簡單。支持開閉原則 * @return */ public Object deepClone() { //創(chuàng)建流對象 ByteArrayOutputStream bos = null; ObjectOutputStream oos = null; ByteArrayInputStream bis = null; ObjectInputStream ois = null; try { //序列化 bos = new ByteArrayOutputStream(); oos = new ObjectOutputStream(bos); oos.writeObject(this); //當(dāng)前這個對象以對象流的方式輸出 //反序列化 bis = new ByteArrayInputStream(bos.toByteArray()); ois = new ObjectInputStream(bis); Sheep copyObj = (Sheep) ois.readObject(); return copyObj; } catch (Exception e) { // TODO: handle exception e.printStackTrace(); return null; } finally { //關(guān)閉流 try { bos.close(); oos.close(); bis.close(); ois.close(); } catch (Exception e2) { // TODO: handle exception System.out.println(e2.getMessage()); } } } }
Main
/** * 深復(fù)制 * * @author Promsing(張有博) * @version 1.0.0 * @since 2022/9/3 - 15:38 */ public class DeepClient { public static void main(String[] args) throws CloneNotSupportedException { Sheep sheep=new Sheep("黑",90,"heisee"); sheep.setHouse(new House()); Sheep clone = (Sheep)sheep.deepClone(); System.out.println("原本的對象"); System.out.println(sheep); System.out.println(sheep.getHouse()); System.out.println("克隆的對象"); System.out.println(clone); System.out.println(clone.getHouse()); } }
Spring使用原型模式:@scope(“prototype”)
public static void main(String[] args) throws IOException { //new一個容器 AnnotationConfigWebApplicationContext context = new AnnotationConfigWebApplicationContext(); System.out.println("run success"); OrderService bean = context.getBean(OrderService.class); } //根據(jù)getBean點進去 public <T> T getBean(Class<T> requiredType) throws BeansException { assertBeanFactoryActive(); return getBeanFactory().getBean(requiredType); } public Object getBean(String name) throws BeansException { return doGetBean(name, null, null, false); }
后續(xù)走到了。AbstractBeanFactory類中的doGetBean方法中里邊代碼做判斷mbd.isPrototype()
protected <T> T doGetBean( String name, @Nullable Class<T> requiredType, @Nullable Object[] args, boolean typeCheckOnly) throws BeansException { String beanName = transformedBeanName(name); Object bean; // Eagerly check singleton cache for manually registered singletons. Object sharedInstance = getSingleton(beanName); if (sharedInstance != null && args == null) { //代碼省略~~~~ } else { //代碼省略~~~~ try { //代碼省略~~~~ // Create bean instance. //判斷是否是單例 if (mbd.isSingleton()) { sharedInstance = getSingleton(beanName, () -> { try { return createBean(beanName, mbd, args); } catch (BeansException ex) { destroySingleton(beanName); throw ex; } }); bean = getObjectForBeanInstance(sharedInstance, name, beanName, mbd); } //判斷是否是多例(原型) //這里會創(chuàng)建一個新的對象 else if (mbd.isPrototype()) { // It's a prototype -> create a new instance. Object prototypeInstance = null; try { beforePrototypeCreation(beanName); prototypeInstance = createBean(beanName, mbd, args); } finally { afterPrototypeCreation(beanName); } bean = getObjectForBeanInstance(prototypeInstance, name, beanName, mbd); } else { //代碼省略~~~~ } } catch (BeansException ex) { cleanupAfterBeanCreationFailure(beanName); throw ex; } } //代碼省略~~~~ } return (T) bean; }
ArrayList實現(xiàn)了Cloneable接口
public Object clone() { try { ArrayList<?> v = (ArrayList<?>) super.clone(); v.elementData = Arrays.copyOf(elementData, size); v.modCount = 0; return v; } catch (CloneNotSupportedException e) { // this shouldn't happen, since we are Cloneable throw new InternalError(e); } }
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