原型模式
Posted abking
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原型模式（Prototype Pattern）是用于创建重复的对象，同时又能保证性能。这种类型的设计模式属于创建型模式，它提供了一种创建对象的最佳方式。
这种模式是实现了一个原型接口，该接口用于创建当前对象的克隆。当直接创建对象的代价比较大时，则采用这种模式。例如，一个对象需要在一个高代价的数据库操作之后被创建。我们可以缓存该对象，在下一个请求时返回它的克隆，在需要的时候更新数据库，以此来减少数据库调用。
定义一个Car类（浅拷贝）
1 package top.bigking.prototype; 2 3 import java.util.Date; 4 5 /** 6 * @Author ABKing 7 * @Date 2020/2/11 下午2:53 8 * 浅拷贝 9 **/ 10 public class Car implements Cloneable { 11 private String name; 12 private Date date; 13 14 @Override 15 protected Object clone() throws CloneNotSupportedException { 16 return super.clone(); 17 } 18 19 public Car() { 20 } 21 22 public Car(String name, Date date) { 23 this.name = name; 24 this.date = date; 25 } 26 27 public String getName() { 28 return name; 29 } 30 31 public void setName(String name) { 32 this.name = name; 33 } 34 35 public Date getDate() { 36 return date; 37 } 38 39 public void setDate(Date date) { 40 this.date = date; 41 } 42 }
定义一个Car2类（深拷贝）
1 package top.bigking.prototype; 2 3 import java.util.Date; 4 5 /** 6 * @Author ABKing 7 * @Date 2020/2/11 下午5:39 8 * 深拷贝 9 **/ 10 public class Car2 implements Cloneable { 11 private String name; 12 private Date date; 13 14 @Override 15 protected Object clone() throws CloneNotSupportedException { 16 Object obj = super.clone(); 17 Car2 car = (Car2) obj; 18 car.setDate((Date) this.date.clone()); 19 return obj; 20 } 21 22 public Car2() { 23 } 24 25 public Car2(String name, Date date) { 26 this.name = name; 27 this.date = date; 28 } 29 30 public String getName() { 31 return name; 32 } 33 34 public void setName(String name) { 35 this.name = name; 36 } 37 38 public Date getDate() { 39 return date; 40 } 41 42 public void setDate(Date date) { 43 this.date = date; 44 } 45 }
测试：
1 package top.bigking.prototype; 2 3 import org.junit.Test; 4 5 import java.util.Date; 6 7 /** 8 * @Author ABKing 9 * @Date 2020/2/11 下午4:40 10 **/ 11 public class TestPrototype { 12 //浅拷贝 13 @Test 14 public void testShallowCopy() throws CloneNotSupportedException { 15 Date date = new Date(11314211L); 16 Car car1 = new Car("兰博基尼", date); 17 Car car2 = (Car) car1.clone(); //拷贝 18 19 System.out.println("第一辆车：" + car1 + car1.getName() + "-----" + car1.getDate()); 20 System.out.println("第二辆车：" + car2 + car2.getName() + "-----" + car2.getDate()); 21 22 date.setTime(4444524L); 23 24 System.out.println("--------修改date后-------"); 25 26 System.out.println("第一辆车：" + car1 + car1.getName() + "-----" + car1.getDate()); 27 System.out.println("第二辆车：" + car2 + car2.getName() + "-----" + car2.getDate()); 28 } 29 //深拷贝 30 @Test 31 public void testDeepCopy() throws CloneNotSupportedException { 32 Date date = new Date(11314211L); 33 Car2 car1 = new Car2("兰博基尼", date); 34 Car2 car2 = (Car2) car1.clone(); //拷贝 35 36 System.out.println("第一辆车：" + car1 + car1.getName() + "-----" + car1.getDate()); 37 System.out.println("第二辆车：" + car2 + car2.getName() + "-----" + car2.getDate()); 38 39 date.setTime(4444524L); 40 41 System.out.println("--------修改date后-------"); 42 43 System.out.println("第一辆车：" + car1 + car1.getName() + "-----" + car1.getDate()); 44 System.out.println("第二辆车：" + car2 + car2.getName() + "-----" + car2.getDate()); 45 } 46 }
运行结果分别为：
1 /usr/local/java/jdk1.8.0_231/bin/java -ea -Didea.test.cyclic.buffer.size=1048576 -javaagent:/usr/local/bin/idea-IU-193.5662.53/lib/idea_rt.jar=37975:/usr/local/bin/idea-IU-193.5662.53/bin -Dfile.encoding=UTF-8 -classpath /usr/local/bin/idea-IU-193.5662.53/lib/idea_rt.jar:/usr/local/bin/idea-IU-193.5662.53/plugins/junit/lib/junit5-rt.jar:/usr/local/bin/idea-IU-193.5662.53/plugins/junit/lib/junit-rt.jar:/usr/local/java/jdk1.8.0_231/jre/lib/charsets.jar:/usr/local/java/jdk1.8.0_231/jre/lib/deploy.jar:/usr/local/java/jdk1.8.0_231/jre/lib/ext/cldrdata.jar:/usr/local/java/jdk1.8.0_231/jre/lib/ext/dnsns.jar:/usr/local/java/jdk1.8.0_231/jre/lib/ext/jaccess.jar:/usr/local/java/jdk1.8.0_231/jre/lib/ext/jfxrt.jar:/usr/local/java/jdk1.8.0_231/jre/lib/ext/localedata.jar:/usr/local/java/jdk1.8.0_231/jre/lib/ext/nashorn.jar:/usr/local/java/jdk1.8.0_231/jre/lib/ext/sunec.jar:/usr/local/java/jdk1.8.0_231/jre/lib/ext/sunjce_provider.jar:/usr/local/java/jdk1.8.0_231/jre/lib/ext/sunpkcs11.jar:/usr/local/java/jdk1.8.0_231/jre/lib/ext/zipfs.jar:/usr/local/java/jdk1.8.0_231/jre/lib/javaws.jar:/usr/local/java/jdk1.8.0_231/jre/lib/jce.jar:/usr/local/java/jdk1.8.0_231/jre/lib/jfr.jar:/usr/local/java/jdk1.8.0_231/jre/lib/jfxswt.jar:/usr/local/java/jdk1.8.0_231/jre/lib/jsse.jar:/usr/local/java/jdk1.8.0_231/jre/lib/management-agent.jar:/usr/local/java/jdk1.8.0_231/jre/lib/plugin.jar:/usr/local/java/jdk1.8.0_231/jre/lib/resources.jar:/usr/local/java/jdk1.8.0_231/jre/lib/rt.jar:/home/king/IdeaProjects/GOF_23/target/test-classes:/home/king/IdeaProjects/GOF_23/target/classes:/home/king/maven/repository/junit/junit/4.10/junit-4.10.jar:/home/king/maven/repository/org/hamcrest/hamcrest-core/1.1/hamcrest-core-1.1.jar com.intellij.rt.junit.JUnitStarter -ideVersion5 -junit4 top.bigking.prototype.TestPrototype,testShallowCopy 2 第一辆车：top.bigking.prototype.Car@579bb367兰博基尼-----Thu Jan 01 11:08:34 CST 1970 3 第二辆车：top.bigking.prototype.Car@255316f2兰博基尼-----Thu Jan 01 11:08:34 CST 1970 4 --------修改date后------- 5 第一辆车：top.bigking.prototype.Car@579bb367兰博基尼-----Thu Jan 01 09:14:04 CST 1970 6 第二辆车：top.bigking.prototype.Car@255316f2兰博基尼-----Thu Jan 01 09:14:04 CST 1970 7 8 Process finished with exit code 0
可以很明显的看到，修改date后，时间并没有发生改变
运行第二个JUnit测试：
1 /usr/local/java/jdk1.8.0_231/bin/java -ea -Didea.test.cyclic.buffer.size=1048576 -javaagent:/usr/local/bin/idea-IU-193.5662.53/lib/idea_rt.jar=36785:/usr/local/bin/idea-IU-193.5662.53/bin -Dfile.encoding=UTF-8 -classpath /usr/local/bin/idea-IU-193.5662.53/lib/idea_rt.jar:/usr/local/bin/idea-IU-193.5662.53/plugins/junit/lib/junit5-rt.jar:/usr/local/bin/idea-IU-193.5662.53/plugins/junit/lib/junit-rt.jar:/usr/local/java/jdk1.8.0_231/jre/lib/charsets.jar:/usr/local/java/jdk1.8.0_231/jre/lib/deploy.jar:/usr/local/java/jdk1.8.0_231/jre/lib/ext/cldrdata.jar:/usr/local/java/jdk1.8.0_231/jre/lib/ext/dnsns.jar:/usr/local/java/jdk1.8.0_231/jre/lib/ext/jaccess.jar:/usr/local/java/jdk1.8.0_231/jre/lib/ext/jfxrt.jar:/usr/local/java/jdk1.8.0_231/jre/lib/ext/localedata.jar:/usr/local/java/jdk1.8.0_231/jre/lib/ext/nashorn.jar:/usr/local/java/jdk1.8.0_231/jre/lib/ext/sunec.jar:/usr/local/java/jdk1.8.0_231/jre/lib/ext/sunjce_provider.jar:/usr/local/java/jdk1.8.0_231/jre/lib/ext/sunpkcs11.jar:/usr/local/java/jdk1.8.0_231/jre/lib/ext/zipfs.jar:/usr/local/java/jdk1.8.0_231/jre/lib/javaws.jar:/usr/local/java/jdk1.8.0_231/jre/lib/jce.jar:/usr/local/java/jdk1.8.0_231/jre/lib/jfr.jar:/usr/local/java/jdk1.8.0_231/jre/lib/jfxswt.jar:/usr/local/java/jdk1.8.0_231/jre/lib/jsse.jar:/usr/local/java/jdk1.8.0_231/jre/lib/management-agent.jar:/usr/local/java/jdk1.8.0_231/jre/lib/plugin.jar:/usr/local/java/jdk1.8.0_231/jre/lib/resources.jar:/usr/local/java/jdk1.8.0_231/jre/lib/rt.jar:/home/king/IdeaProjects/GOF_23/target/test-classes:/home/king/IdeaProjects/GOF_23/target/classes:/home/king/maven/repository/junit/junit/4.10/junit-4.10.jar:/home/king/maven/repository/org/hamcrest/hamcrest-core/1.1/hamcrest-core-1.1.jar com.intellij.rt.junit.JUnitStarter -ideVersion5 -junit4 top.bigking.prototype.TestPrototype,testDeepCopy 2 第一辆车：top.bigking.prototype.Car2@579bb367兰博基尼-----Thu Jan 01 11:08:34 CST 1970 3 第二辆车：top.bigking.prototype.Car2@255316f2兰博基尼-----Thu Jan 01 11:08:34 CST 1970 4 --------修改date后------- 5 第一辆车：top.bigking.prototype.Car2@579bb367兰博基尼-----Thu Jan 01 09:14:04 CST 1970 6 第二辆车：top.bigking.prototype.Car2@255316f2兰博基尼-----Thu Jan 01 11:08:34 CST 1970 7 8 Process finished with exit code 0
可以看到，时间已经发生了变化。
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