Java中的原型模式

原型模式简介

  • 模式属于创建型模式,它提供了一种创建对象的最佳方式。
  • 用于创建重复的对象,同时又能保证性能。
  • 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。
浅克隆
类Book实现Cloneable接口并重写clone方法
public class Book implements Cloneable { private String name; //书名 private Date publishDate; //发布日期public Book() { }public Book(String name, Date publishDate) { this.name = name; this.publishDate = publishDate; }public String getName() { return name; }public void setName(String name) { this.name = name; }public Date getPublishDate() { return publishDate; }public void setPublishDate(Date publishDate) { this.publishDate = publishDate; }@Override protected Object clone() throws CloneNotSupportedException { return super.clone(); }@Override public String toString() { return "Book{" + "name='" + name + '\'' + ", publishDate=" + publishDate + '}'; } }

测试类
public class Test { public static void main(String[] args) throws CloneNotSupportedException { String name = "Java 设计模式"; Date publishDate = new Date(); Book book = new Book(name, publishDate); //克隆出对象 Book clone = (Book) book.clone(); System.out.println(book); System.out.println(book.hashCode()); System.out.println(clone); System.out.println(clone.hashCode()); System.out.println("=================="); publishDate.setTime(publishDate.getTime() + 2000); //修改时间 System.out.println(book); System.out.println(book.hashCode()); System.out.println(clone); System.out.println(clone.hashCode()); /** * 测试结果:修改了时间,源对象和克隆的对象的时间,都发生了改变 * Book{name='Java 设计模式', publishDate=Wed Dec 29 12:17:33 CST 2021} * 2093631819 * Book{name='Java 设计模式', publishDate=Wed Dec 29 12:17:33 CST 2021} * 2074407503 * ================== * Book{name='Java 设计模式', publishDate=Wed Dec 29 12:17:35 CST 2021} * 2093631819 * Book{name='Java 设计模式', publishDate=Wed Dec 29 12:17:35 CST 2021} * 2074407503 */ } }

测试结果
Book{name='Java 设计模式', publishDate=Wed Dec 29 12:17:33 CST 2021} 2093631819 Book{name='Java 设计模式', publishDate=Wed Dec 29 12:17:33 CST 2021} 2074407503 ================== Book{name='Java 设计模式', publishDate=Wed Dec 29 12:17:35 CST 2021} 2093631819 Book{name='Java 设计模式', publishDate=Wed Dec 29 12:17:35 CST 2021} 2074407503

深克隆
类Book实现Cloneable接口并重写clone方法
public class Book implements Cloneable { private String name; //书名 private Date publishDate; //发布日期public Book() { }public Book(String name, Date publishDate) { this.name = name; this.publishDate = publishDate; }public String getName() { return name; }public void setName(String name) { this.name = name; }public Date getPublishDate() { return publishDate; }public void setPublishDate(Date publishDate) { this.publishDate = publishDate; }@Override protected Object clone() throws CloneNotSupportedException { Object obj = super.clone(); Book book = (Book) obj; //将源对象的属性也进行克隆,即深克隆 book.publishDate = (Date) book.publishDate.clone(); return obj; }@Override public String toString() { return "Book{" + "name='" + name + '\'' + ", publishDate=" + publishDate + '}'; } }

测试类
public class Test { public static void main(String[] args) throws CloneNotSupportedException { String name = "Java 设计模式"; Date publishDate = new Date(); Book book = new Book(name, publishDate); //克隆出对象 Book clone = (Book) book.clone(); System.out.println(book); System.out.println(book.hashCode()); System.out.println(clone); System.out.println(clone.hashCode()); System.out.println("=================="); publishDate.setTime(publishDate.getTime() + 2000); System.out.println(book); System.out.println(book.hashCode()); System.out.println(clone); System.out.println(clone.hashCode()); /** * 测试结果:修改了时间,源对象的时间,发生了改变,但克隆的对象的时间没有改变 * Book{name='Java 设计模式', publishDate=Wed Dec 29 12:41:47 CST 2021} * 2093631819 * Book{name='Java 设计模式', publishDate=Wed Dec 29 12:41:47 CST 2021} * 2074407503 * ================== * Book{name='Java 设计模式', publishDate=Wed Dec 29 12:41:49 CST 2021} * 2093631819 * Book{name='Java 设计模式', publishDate=Wed Dec 29 12:41:47 CST 2021} * 2074407503 */ } }

测试结果
Book{name='Java 设计模式', publishDate=Wed Dec 29 12:41:47 CST 2021} 2093631819 Book{name='Java 设计模式', publishDate=Wed Dec 29 12:41:47 CST 2021} 2074407503 ================== Book{name='Java 设计模式', publishDate=Wed Dec 29 12:41:49 CST 2021} 2093631819 Book{name='Java 设计模式', publishDate=Wed Dec 29 12:41:47 CST 2021} 2074407503

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