设计模式-观察者模式

Author: dolyw

DesignPattern/src/main/java/com/design/observer/v1/Main.java

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+package com.design.observer.v1;
+
+import com.design.observer.v1.observer.SubscribeConcreteObserver;
+import com.design.observer.v1.subject.BlogConcreteSubject;
+
+/**
+ * 观察者模式，使用JDK的提供的类完成
+ *
+ * @author wliduo[i@dolyw.com]
+ * @date 2022/1/20 14:02
+ */
+public class Main {
+
+    public static void main(String[] args) {
+        // 构建具体目标
+        BlogConcreteSubject blogConcreteSubject = new BlogConcreteSubject("dolyw.com");
+        // 添加观察者
+        blogConcreteSubject.addObserver(new SubscribeConcreteObserver("王明"));
+        blogConcreteSubject.addObserver(new SubscribeConcreteObserver("王美丽"));
+        // 具体目标发送变化，发布新博客
+        blogConcreteSubject.publish("母猪的产后护理");
+    }
+
+}

DesignPattern/src/main/java/com/design/observer/v1/observer/SubscribeConcreteObserver.java

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+package com.design.observer.v1.observer;
+
+import com.design.observer.v1.subject.BlogConcreteSubject;
+
+import java.util.Observable;
+import java.util.Observer;
+
+/**
+ * 具体观察者，使用JDK提供的Observable类抽象观察者Observer
+ *
+ * @author wliduo[i@dolyw.com]
+ * @date 2022/1/20 14:21
+ */
+public class SubscribeConcreteObserver implements Observer {
+
+    private String name;
+
+    public SubscribeConcreteObserver(String name) {
+        this.name = name;
+    }
+
+    /**
+     * 发布新博客后，订阅者接收到消息
+     *
+     * @param o
+     * @param arg
+     */
+    @Override
+    public void update(Observable o, Object arg) {
+        BlogConcreteSubject blog = (BlogConcreteSubject) o;
+        String title = (String) arg;
+        System.out.println(name + "订阅的博客[" + blog.getName() + "]又发布了新文章-" + title);
+    }
+}

DesignPattern/src/main/java/com/design/observer/v1/subject/BlogConcreteSubject.java

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+package com.design.observer.v1.subject;
+
+import java.util.Observable;
+
+/**
+ * 具体目标，使用JDK提供的Observable类抽象目标
+ *
+ * @author wliduo[i@dolyw.com]
+ * @date 2022/1/20 14:13
+ */
+public class BlogConcreteSubject extends Observable {
+
+    private String name;
+
+    public BlogConcreteSubject(String name) {
+        this.name = name;
+    }
+
+    public String getName() {
+        return name;
+    }
+
+    /**
+     * 发布新文章，通知所有订阅了博客的人
+     *
+     * @param title
+     * @return void
+     * @throws
+     * @author wliduo[i@dolyw.com]
+     * @date 2022/1/20 14:17
+     */
+    public void publish(String title) {
+        // 设置标识位 changed = true，表示被观察者发生了改变
+        setChanged();
+        // 通知观察者，可以给观察者传递数据
+        notifyObservers(title);
+    }
+
+}

DesignPattern/src/main/java/com/design/observer/v2/Main.java

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+package com.design.observer.v2;
+
+import com.design.observer.v2.observer.SubscribeConcreteObserver;
+import com.design.observer.v2.subject.AbstractSubject;
+import com.design.observer.v2.subject.BlogConcreteSubject;
+
+/**
+ * 观察者模式，使用原生方式完成
+ *
+ * @author wliduo[i@dolyw.com]
+ * @date 2022/1/20 14:02
+ */
+public class Main {
+
+    public static void main(String[] args) {
+        // 构建具体目标
+        AbstractSubject blogConcreteSubject = new BlogConcreteSubject("dolyw.com");
+        // 添加观察者
+        blogConcreteSubject.addObserver(new SubscribeConcreteObserver("王明"));
+        blogConcreteSubject.addObserver(new SubscribeConcreteObserver("王美丽"));
+        // 具体目标发送变化，发布新博客
+        blogConcreteSubject.publish("Java入门到放弃");
+    }
+
+}

DesignPattern/src/main/java/com/design/observer/v2/observer/AbstractObserver.java

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+package com.design.observer.v2.observer;
+
+import com.design.observer.v2.subject.AbstractSubject;
+
+/**
+ * 抽象观察者
+ *
+ * @author wliduo[i@dolyw.com]
+ * @date 2022/1/20 14:05
+ */
+public abstract class AbstractObserver {
+
+    /**
+     * 观察者接收通知
+     *
+     * @param abstractSubject
+	 * @param arg
+     * @return void
+     * @throws
+     * @author wliduo[i@dolyw.com]
+     * @date 2022/1/21 15:39
+     */
+    public abstract void update(AbstractSubject abstractSubject, Object arg);
+
+}

DesignPattern/src/main/java/com/design/observer/v2/observer/SubscribeConcreteObserver.java

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+package com.design.observer.v2.observer;
+
+import com.design.observer.v2.subject.AbstractSubject;
+import com.design.observer.v2.subject.BlogConcreteSubject;
+
+/**
+ * 具体观察者，使用原生方式实现
+ *
+ * @author wliduo[i@dolyw.com]
+ * @date 2022/1/20 14:21
+ */
+public class SubscribeConcreteObserver extends AbstractObserver {
+
+    private String name;
+
+    public SubscribeConcreteObserver(String name) {
+        this.name = name;
+    }
+
+    /**
+     * 订阅目标发布新博客后，订阅者接收到消息
+     *
+     * @param abstractSubject
+     * @param arg
+     */
+    @Override
+    public void update(AbstractSubject abstractSubject, Object arg) {
+        BlogConcreteSubject blog = (BlogConcreteSubject) abstractSubject;
+        String title = (String) arg;
+        System.out.println(name + "订阅的博客[" + blog.getName() + "]又发布了新文章-" + title);
+    }
+}

DesignPattern/src/main/java/com/design/observer/v2/subject/AbstractSubject.java

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+package com.design.observer.v2.subject;
+
+import com.design.observer.v2.observer.AbstractObserver;
+
+import java.util.ArrayList;
+import java.util.List;
+
+/**
+ * 抽象目标
+ *
+ * @author wliduo[i@dolyw.com]
+ * @date 2022/1/20 14:03
+ */
+public abstract class AbstractSubject {
+
+    protected List<AbstractObserver> observerList = new ArrayList<>();
+
+    public synchronized void addObserver(AbstractObserver observer) {
+        if (observer == null) {
+            throw new NullPointerException();
+        }
+        if (!observerList.contains(observer)) {
+            observerList.add(observer);
+        }
+    }
+
+    public synchronized void deleteObserver(AbstractObserver observer) {
+        observerList.remove(observer);
+    }
+
+    /**
+     * 通知所有观察者
+     *
+     * @param arg
+     */
+    public void notifyObservers(Object arg) {
+        for (AbstractObserver abstractObserver : observerList) {
+            abstractObserver.update(this, arg);
+        }
+    }
+
+    /**
+     * 目标发生变化
+     *
+     * @param title
+     */
+    public abstract void publish(String title);
+
+}

DesignPattern/src/main/java/com/design/observer/v2/subject/BlogConcreteSubject.java

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+package com.design.observer.v2.subject;
+
+/**
+ * 具体目标，使用原生方式实现
+ *
+ * @author wliduo[i@dolyw.com]
+ * @date 2022/1/20 14:13
+ */
+public class BlogConcreteSubject extends AbstractSubject {
+
+    private String name;
+
+    public BlogConcreteSubject(String name) {
+        this.name = name;
+    }
+
+    public String getName() {
+        return name;
+    }
+
+    /**
+     * 发布新文章，通知所有订阅了博客的人
+     *
+     * @param title
+     * @return void
+     * @throws
+     * @author wliduo[i@dolyw.com]
+     * @date 2022/1/20 14:17
+     */
+    @Override
+    public void publish(String title) {
+        // 通知观察者，可以给观察者传递数据
+        notifyObservers(title);
+    }
+
+}