1.场景问题解决
1.1 场景描述
电子账单项目遇到的问题:银行的电子账单、广告信:
特点:量大、时间要求紧,在电子账单内容生成后,快速发送成功.
1.2 OO设计
多线程实现
- EventTemplate 为公用对象
public class EventTemplate {
private String eventSubject, eventContent;
public EventTemplate(String eventSubject, String eventContent) {
this.eventSubject = eventSubject;
this.eventContent = eventContent;
}
public String geteventSubject() {
return eventSubject;
}
public String geteventContent() {
return eventContent;
}
}
- oo 为oo设计时的
-
- Mail 邮件对象
-
- MainOOTest 测试类
public class Mail {
private String receiver;
private String subject;
private String content;
private String tail;
public Mail(EventTemplate et) {
this.tail = et.geteventContent();
this.subject = et.geteventSubject();
}
public String getReceiver() {
return receiver;
}
public void setReceiver(String receiver) {
this.receiver = receiver;
}
public String getSubject() {
return subject;
}
public void setSubject(String subject) {
this.subject = subject;
}
public void setContent(String content) {
this.content = content;
}
public String getContent() {
return content;
}
public String getTail() {
return tail;
}
public void setTail(String tail) {
this.tail = tail;
}
}
public class MainOOTest {
public static void main(String[] args) {
int i = 0;
int MAX_COUNT = 10;
EventTemplate et = new EventTemplate("9月份信用卡账单", "国庆抽奖活动...");
Mail mail = new Mail(et);
while (i < MAX_COUNT) {
// 以下是每封邮件不同的地方
mail.setContent(getRandString(5) + ",先生(女士):你的信用卡账单..."
+ mail.getTail());
mail.setReceiver(getRandString(5) + "@" + getRandString(8) + ".com");
// 然后发送邮件
sendMail(mail);
i++;
}
}
public static String getRandString(int maxLength) {
String source = "abcdefghijklmnopqrskuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ";
StringBuffer sb = new StringBuffer();
Random rand = new Random();
for (int i = 0; i < maxLength; i++) {
sb.append(source.charAt(rand.nextInt(source.length())));
}
return sb.toString();
}
public static void sendMail(Mail mail) {
System.out.println("标题:" + mail.getSubject() + "\t收件人:"
+ mail.getReceiver() + "\t内容:" + mail.getContent()
+ "\t....发送成功!");
}
}
1.3 需求变动
1.4 带来问题
2.用设计模式改进
2.1 分析
2.2 重新设计
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2.3 源码
- EventTemplate 为公用对象
public class EventTemplate {
private String eventSubject, eventContent;
public EventTemplate(String eventSubject, String eventContent) {
this.eventSubject = eventSubject;
this.eventContent = eventContent;
}
public String geteventSubject() {
return eventSubject;
}
public String geteventContent() {
return eventContent;
}
}
- proto 为原型设计模式时
-
- Mail 邮件对象
-
- MainProtoTest 测试类
public class Mail implements Cloneable {
private String receiver;
private String subject;
private String content;
private String tail;
//如果有一个ArrayList
private ArrayList<String> arrayList;
public Mail(EventTemplate et) {
this.tail = et.geteventContent();
this.subject = et.geteventSubject();
}
@Override
public Mail clone() {
Mail mail = null;
try {
mail = (Mail) super.clone();
//对象的默认copy时arrayList的是引用,所以需要用下面的方式再copy才是clone的值(独立的区域)
mail.arrayList = (ArrayList<String>)this.arrayList.clone();
} catch (CloneNotSupportedException e) {
e.printStackTrace();
}
return mail;
}
public String getReceiver() {
return receiver;
}
public void setReceiver(String receiver) {
this.receiver = receiver;
}
public String getSubject() {
return subject;
}
public void setSubject(String subject) {
this.subject = subject;
}
public void setContent(String content) {
this.content = content;
}
public String getContent() {
return content;
}
public String getTail() {
return tail;
}
public void setTail(String tail) {
this.tail = tail;
}
}
public class MainProtoTest {
public static void main(String[] args) {
int i = 0;
int MAX_COUNT = 10;
EventTemplate et = new EventTemplate("9月份信用卡账单", "国庆抽奖活动...");
Mail mail = new Mail(et);
while (i < MAX_COUNT) {
// 以下是每封邮件不同的地方
Mail cloneMail = mail.clone();
cloneMail.setContent(getRandString(5) + ",先生(女士):你的信用卡账单..."
+ mail.getTail());
cloneMail.setReceiver(getRandString(5) + "@" + getRandString(8)
+ ".com");
// 然后发送邮件
sendMail(cloneMail);
i++;
}
}
public static String getRandString(int maxLength) {
String source = "abcdefghijklmnopqrskuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ";
StringBuffer sb = new StringBuffer();
Random rand = new Random();
for (int i = 0; i < maxLength; i++) {
sb.append(source.charAt(rand.nextInt(source.length())));
}
return sb.toString();
}
public static void sendMail(Mail mail) {
System.out.println("标题:" + mail.getSubject() + "\t收件人:"
+ mail.getReceiver() + "\t内容:" + mail.getContent()
+ "\t....发送成功!");
}
}
3.设计模式总结
3.1 定义
原型模式:通过复制现有实例来创建新的实例,无须知道相应类的信息
3.2 分析思路
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3.3 优缺点
- 优点:
使用原型模式创建对象比直接new一个对象更有效
隐藏制造新实例的复杂性
重复地创建相似对象时可以考虑使用原型模式 - 缺点:
每一个类必须配备一个克隆方法
深层复制比较复杂
4. 设计模式使用场景及注意
4.1 使用场景
- 复制对象的结构与数据
- 希望对目标对象的修改不影响既有的原型对象
- 创建对象成本较大的情况下
4.2 注意
- 使用原型模式复制对象不会调用类的构造方法。所以,单例模式与原型模式是冲突的,在使用时要特别注意。(单例模式不能用clone)
- 不用用final 对象
- Object类的clone方法只会拷贝对象中的基本的数据类型,对于数组、容器对象、引用对象等都不会拷贝,这就是浅拷贝。如果要实现深拷贝,必须将原型模式中的数组、容器对象、引用对象等另行拷贝。
5.参考文章
内容总计于HeadFirst设计模式及相关视频