ref[net]: move SingleCache to net module

net/src/main/java/com/zfoo/net/util/SingleCache.java

@@ -0,0 +1,100 @@
+/*
+ * Copyright (C) 2020 The zfoo Authors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
+ * in compliance with the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software distributed under the License is distributed
+ * on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and limitations under the License.
+ */
+
+package com.zfoo.net.util;
+
+import com.zfoo.event.manager.EventBus;
+import com.zfoo.scheduler.manager.SchedulerBus;
+import com.zfoo.scheduler.util.TimeUtils;
+
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.atomic.AtomicLong;
+import java.util.function.Supplier;
+
+/**
+ * 单值缓存，会隔一段时间在后台刷新一下缓存
+ *
+ * @author godotg
+ */
+public class SingleCache<V> {
+
+    private long refreshDuration;
+
+    private Supplier<V> supplier;
+
+
+    private volatile V cache;
+
+    private AtomicLong refreshTimeAtomic;
+
+    private SingleCache(long refreshDuration, Supplier<V> supplier) {
+        this.refreshDuration = refreshDuration;
+        this.supplier = supplier;
+        this.refreshTimeAtomic = new AtomicLong(TimeUtils.now() + refreshDuration);
+    }
+
+    /**
+     * @param refreshDuration 刷新实际那，毫秒
+     * @param supplier        缓存提供者
+     * @return 简单的缓存
+     */
+    public static <V> SingleCache<V> build(long refreshDuration, Supplier<V> supplier) {
+        var cache = new SingleCache<V>(refreshDuration, supplier);
+        cache.cache = supplier.get();
+        return cache;
+    }
+
+    public static <V> SingleCache<V> lazyBuild(long refreshDuration, Supplier<V> supplier) {
+        var cache = new SingleCache<V>(refreshDuration, supplier);
+        cache.lazyRefresh();
+        return cache;
+    }
+
+
+    public V get() {
+        var now = TimeUtils.now();
+        var refreshTime = refreshTimeAtomic.get();
+        // 使用双重检测锁的方式
+        if (now > refreshTime) {
+            if (refreshTimeAtomic.compareAndSet(refreshTime, now + refreshDuration)) {
+                cache = supplier.get();
+            }
+        }
+        return cache;
+    }
+
+    public V lazyGet() {
+        var now = TimeUtils.now();
+        var refreshTime = refreshTimeAtomic.get();
+        // 使用双重检测锁的方式
+        if (now > refreshTime) {
+            if (refreshTimeAtomic.compareAndSet(refreshTime, now + refreshDuration)) {
+                lazyRefresh();
+            }
+        }
+        return cache;
+    }
+
+    public void set(V value) {
+        cache = value;
+    }
+
+    public void lazyRefresh() {
+        EventBus.asyncExecute(this.hashCode(), () -> cache = supplier.get());
+    }
+
+    public void lazyRefreshDelay(long delay, TimeUnit unit) {
+        SchedulerBus.schedule(this::lazyRefresh, delay, unit);
+    }
+
+}