場景
- 思考一下:克隆技術(shù)是怎么樣的過程?
- JavaScript語言中的,繼承怎么實現(xiàn)?那里面也有prototype
原型模式
- 通過new產(chǎn)生一個對象需要繁瑣的數(shù)據(jù)準備或訪問權(quán)限,則可以使用原型模式。
- 就是java中的克隆技術(shù)，以某個對象為原型，復制出新的對象。顯然，新的對象具備原型對象的特點。
- 優(yōu)勢有：效率高(直接克隆,避免了重新執(zhí)行構(gòu)造過程步驟)。
- 克隆類似于new，但是不同于new。new創(chuàng)建新的對象屬性采用的是默認值?？寺〕龅膶ο蟮膶傩灾低耆驮蛯ο笙嗤２⑶铱寺〕龅男聦ο蟾淖儾粫绊懺蛯ο?。然后，再修改克隆對象的值。
原型模式實現(xiàn)
- Cloneable接口和clone方法
- Prototype模式中實現(xiàn)起來最困難的地方就是內(nèi)存復制操作，所幸在Java中提供了clone()方法替我們做了絕大部分事情。
package prototype;
import java.util.Date;
public class Sheep implements Cloneable{
private String sname;
private Date birthday;
public Sheep() {
}
public Sheep(String sname, Date birthday) {
this.sname = sname;
this.birthday = birthday;
}
public String getSname() {
return sname;
}
public void setSname(String sname) {
this.sname = sname;
}
public Date getBirthday() {
return birthday;
}
public void setBirthday(Date birthday) {
this.birthday = birthday;
}
@Override
protected Object clone() throws CloneNotSupportedException {
Object obj = super.clone();
return obj;
}
}
package prototype;
import java.util.Date;
/**
* @Description: 淺克隆
*/
public class Client {
public static void main(String[] args) throws Exception {
Date date = new Date();
Sheep s1 = new Sheep("少利",date);
Sheep s2 = (Sheep) s1.clone();
System.out.println(s1);
System.out.println(s1.getSname());
System.out.println(s1.getBirthday());
date.setTime(123123123141L);
System.out.println(s1.getBirthday());
s2.setSname("多利");
System.out.println(s2);
System.out.println(s2.getSname());
System.out.println(s2.getBirthday());
}
}
輸出:
prototype.Sheep@52ab6c19
少利
Wed Apr 25 10:31:31 CST 2018
Mon Nov 26 08:52:03 CST 1973
prototype.Sheep@6929ae9b
多利
Mon Nov 26 08:52:03 CST 1973
package prototype;
import java.util.Date;
public class Sheep2 implements Cloneable{
private String sname;
private Date birthday;
public Sheep2() {
}
public Sheep2(String sname, Date birthday) {
this.sname = sname;
this.birthday = birthday;
}
public String getSname() {
return sname;
}
public void setSname(String sname) {
this.sname = sname;
}
public Date getBirthday() {
return birthday;
}
public void setBirthday(Date birthday) {
this.birthday = birthday;
}
@Override
protected Object clone() throws CloneNotSupportedException {
Object obj = super.clone();
// 深克隆實現(xiàn)
Sheep2 sheep = (Sheep2) obj;
sheep.birthday = (Date) this.birthday.clone();
return obj;
}
}
package prototype;
import java.util.Date;
/**
* @Description: 深克隆
*/
public class Client2 {
public static void main(String[] args) throws Exception{
Date date = new Date();
Sheep2 s1 = new Sheep2("少利",date);
Sheep2 s2 = (Sheep2) s1.clone();
System.out.println(s1);
System.out.println(s1.getSname());
System.out.println(s1.getBirthday());
date.setTime(123123123141L);
System.out.println(s1.getBirthday());
s2.setSname("多利");
System.out.println(s2);
System.out.println(s2.getSname());
System.out.println(s2.getBirthday());
}
}
輸出:
prototype.Sheep2@55991e21
少利
Wed Apr 25 10:33:34 CST 2018
Mon Nov 26 08:52:03 CST 1973
prototype.Sheep2@2533b5db
多利
Wed Apr 25 10:33:34 CST 2018
利用序列化和反序列化技術(shù)實現(xiàn)深克隆
package prototype;
import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.util.Date;
/**
* @Description: 利用序列化和反序列化技術(shù)實現(xiàn)深克隆
*/
public class Client3 {
public static void main(String[] args) throws Exception{
Date date = new Date();
Sheep s1 = new Sheep("少利",date);
ByteArrayOutputStream bos = new ByteArrayOutputStream();
ObjectOutputStream oos = new ObjectOutputStream(bos);
oos.writeObject(s1);
byte[] bytes = bos.toByteArray();
ByteArrayInputStream bis = new ByteArrayInputStream(bytes);
ObjectInputStream ois = new ObjectInputStream(bis);
Sheep s2 = (Sheep) ois.readObject();
System.out.println(s1);
System.out.println(s1.getSname());
System.out.println(s1.getBirthday());
date.setTime(123123123141L);
System.out.println(s1.getBirthday());
s2.setSname("多利");
System.out.println(s2);
System.out.println(s2.getSname());
System.out.println(s2.getBirthday());
}
}
輸出:
prototype.Sheep@667053be
少利
Wed Apr 25 10:47:00 CST 2018
Mon Nov 26 08:52:03 CST 1973
prototype.Sheep@528ef256
多利
Wed Apr 25 10:47:00 CST 2018
普通new方式創(chuàng)建對象和clone方式創(chuàng)建對象的效率差異
package prototype;
import java.util.concurrent.TimeUnit;
public class Client4 {
public static void testNew(int size){
long start = System.currentTimeMillis();
for (int i=0;i<size;i++){
Laptop t = new Laptop();
}
long end = System.currentTimeMillis();
System.out.println("new的方式創(chuàng)建耗時:"+(end-start));
}
public static void testClone(int size) throws CloneNotSupportedException {
long start = System.currentTimeMillis();
Laptop t = new Laptop();
for (int i=0;i<size;i++){
Laptop clone = (Laptop) t.clone();
}
long end = System.currentTimeMillis();
System.out.println("clone的方式創(chuàng)建耗時:"+(end-start));
}
public static void main(String[] args) throws Exception{
testNew(1000);
testClone(1000);
}
}
class Laptop implements Cloneable{
public Laptop(){
try {
TimeUnit.MILLISECONDS.sleep(10);
} catch (InterruptedException e) {
e.printStackTrace();
}
}
@Override
protected Object clone() throws CloneNotSupportedException {
return super.clone();
}
}
輸出:
new的方式創(chuàng)建耗時:10324
clone的方式創(chuàng)建耗時:11
如果需要段時間創(chuàng)建大量對象,并且new的過程比較耗時,則可以考慮使用原型模式。
開發(fā)中的應用場景
- 原型模式很少單獨出現(xiàn),一般是和工廠方法模式一起出現(xiàn),通過clone的方法創(chuàng)建一個對象,然后由工廠方法提供給調(diào)用者。
spring中bean的創(chuàng)建實際就兩種模式:單例模式和原型模式。(當然,原型模式需要和工廠模式搭配起來)
