抽象观察者模式.

hippo4j-common/src/main/java/cn/hippo4j/common/design/observer/AbstractSubjectCenter.java

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+package cn.hippo4j.common.design.observer;
+
+import cn.hippo4j.common.toolkit.CollectionUtil;
+import cn.hippo4j.common.toolkit.StringUtil;
+import lombok.extern.slf4j.Slf4j;
+
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Map;
+import java.util.concurrent.ConcurrentHashMap;
+
+/**
+ * Send observer notification.
+ *
+ * @author chen.ma
+ * @date 2021/12/25 19:47
+ */
+@Slf4j
+public class AbstractSubjectCenter {
+
+    private static final Map<String, List<Observer>> OBSERVERS_MAP = new ConcurrentHashMap();
+
+    /**
+     * Register observer.
+     *
+     * @param observer
+     */
+    public static void register(Observer observer) {
+        register(SubjectType.SPRING_CONTENT_REFRESHED.name(), observer);
+    }
+
+    /**
+     * Register observer.
+     *
+     * @param subject
+     * @param observer
+     */
+    public static void register(String subject, Observer observer) {
+        if (StringUtil.isBlank(subject) || observer == null) {
+            log.warn("Register observer. A string whose subject or observer is empty or empty.");
+            return;
+        }
+
+        List<Observer> observers = OBSERVERS_MAP.get(subject);
+        if (CollectionUtil.isEmpty(observers)) {
+            observers = new ArrayList();
+        }
+
+        observers.add(observer);
+        OBSERVERS_MAP.put(subject, observers);
+    }
+
+    /**
+     * Remove observer.
+     *
+     * @param observer
+     */
+    public static void remove(Observer observer) {
+        remove(SubjectType.SPRING_CONTENT_REFRESHED.name(), observer);
+    }
+
+    /**
+     * Remove observer.
+     *
+     * @param subject
+     * @param observer
+     */
+    public static void remove(String subject, Observer observer) {
+        List<Observer> observers;
+        if (StringUtil.isBlank(subject) || CollectionUtil.isEmpty((observers = OBSERVERS_MAP.get(subject))) || observer == null) {
+            log.warn("Remove observer. A string whose subject or observer is empty or empty.");
+            return;
+        }
+
+        observers.remove(observer);
+    }
+
+    public static void notify(String subject, ObserverMessage observerMessage) {
+        List<Observer> observers = OBSERVERS_MAP.get(subject);
+        if (CollectionUtil.isEmpty(observers)) {
+            log.warn("Under the subject, there is no observer group.");
+            return;
+        }
+
+        observers.parallelStream().forEach(each -> {
+            try {
+                each.accept(observerMessage);
+            } catch (Exception ex) {
+                log.error("Notification subject :: {} observer exception", subject);
+            }
+        });
+    }
+
+    private enum SubjectType {
+
+        /**
+         * Spring content refreshed.
+         */
+        SPRING_CONTENT_REFRESHED
+
+    }
+
+}

hippo4j-common/src/main/java/cn/hippo4j/common/design/observer/Observer.java

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+package cn.hippo4j.common.design.observer;
+
+/**
+ * Observer.
+ *
+ * @author chen.ma
+ * @date 2021/12/25 19:46
+ */
+public interface Observer {
+
+    /**
+     * Receive notification.
+     *
+     * @param observerMessage
+     */
+    void accept(ObserverMessage observerMessage);
+
+}

hippo4j-common/src/main/java/cn/hippo4j/common/design/observer/ObserverMessage.java

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+package cn.hippo4j.common.design.observer;
+
+/**
+ * Message notifying observer.
+ *
+ * @author chen.ma
+ * @date 2021/12/25 19:54
+ */
+public interface ObserverMessage {
+
+}