[Add] 添加基于 Hashtable 的本地缓存存储容器;

[Add] HashCacheStore 添加 CacheStore 的抽象实现;
[Add] HashSingleCacheStore 添加 SingleCacheStore 的具体实现;
[Add] HashSingleCacheStoreTest 增加完整测试项(涵盖了 HashCacheStore);

ContentGrabbingJi-CacheStore-local/src/main/java/net/lamgc/cgj/bot/cache/local/HashCacheStore.java

@@ -0,0 +1,145 @@
+/*
+ * Copyright (C) 2020  LamGC
+ *
+ * ContentGrabbingJi is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as
+ * published by the Free Software Foundation, either version 3 of the
+ * License, or (at your option) any later version.
+ *
+ * ContentGrabbingJi is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+package net.lamgc.cgj.bot.cache.local;
+
+import net.lamgc.cgj.bot.cache.CacheStore;
+
+import java.util.*;
+
+/**
+ * 基于 {@link Hashtable} 的缓存存储容器.
+ * @param <V> 值类型.
+ * @author LamGC
+ * @see net.lamgc.cgj.bot.cache.CacheStore
+ * @see Hashtable
+ */
+public abstract class HashCacheStore<V> implements CacheStore<V> {
+
+    private final Map<String, CacheItem<V>> cacheMap = new Hashtable<>();
+
+    /**
+     * 获取内部 Map 对象.
+     * 仅供其他子类使用.
+     * @return 返回存储缓存项的 Map.
+     */
+    protected Map<String, CacheItem<V>> getCacheMap() {
+        return cacheMap;
+    }
+
+    @Override
+    public boolean setTimeToLive(String key, long ttl) {
+        if (!exists(key)) {
+            return false;
+        }
+        CacheItem<V> item = cacheMap.get(key);
+        item.setExpireDate(ttl < 0 ? null : new Date(System.currentTimeMillis() + ttl));
+        return true;
+    }
+
+    @Override
+    public long getTimeToLive(String key) {
+        if (!exists(key)) {
+            return -1;
+        }
+        CacheItem<V> item = cacheMap.get(key);
+        Date expireDate = item.getExpireDate();
+        if (expireDate != null) {
+            return expireDate.getTime() - System.currentTimeMillis();
+        }
+        return -1;
+    }
+
+    @Override
+    public long size() {
+        return cacheMap.size();
+    }
+
+    @Override
+    public boolean clear() {
+        cacheMap.clear();
+        return true;
+    }
+
+    @Override
+    public boolean exists(String key) {
+        if (!cacheMap.containsKey(key)) {
+            return false;
+        }
+        CacheItem<V> item = cacheMap.get(key);
+        // 在检查其过期情况后根据情况进行清理, 减轻主动清理机制的负担.
+        if (item.isExpire(new Date())) {
+            remove(key);
+            return false;
+        }
+        return true;
+    }
+
+    @Override
+    public boolean remove(String key) {
+        // 根据 Collection 说明, 删除时 key 存在映射就会返回, 只要返回 null 就代表没有.
+        return cacheMap.remove(key) != null;
+    }
+
+    @Override
+    public Set<String> keySet() {
+        return Collections.unmodifiableSet(cacheMap.keySet());
+    }
+
+    /**
+     * 缓存项.
+     * @author LamGC
+     */
+    protected final static class CacheItem<V> {
+        private final V value;
+        private Date expireDate;
+
+        CacheItem(V value) {
+            this(value, null);
+        }
+
+        CacheItem(V value, Date expireDate) {
+            this.value = value;
+            this.expireDate = expireDate;
+        }
+
+        public V getValue() {
+            return value;
+        }
+
+        public void setExpireDate(Date expireDate) {
+            this.expireDate = expireDate;
+        }
+
+        public Date getExpireDate() {
+            return expireDate;
+        }
+
+        /**
+         * 检查缓存项是否过期.
+         * @param date 当前时间.
+         * @return 如果已设置过期时间且早于提供的Date, 则该缓存项过期, 返回 true.
+         * @throws NullPointerException 当 date 传入 null 时抛出.
+         */
+        public boolean isExpire(Date date) {
+            Date expireDate = getExpireDate();
+            return expireDate != null && expireDate.before(Objects.requireNonNull(date));
+        }
+
+    }
+
+}

ContentGrabbingJi-CacheStore-local/src/main/java/net/lamgc/cgj/bot/cache/local/HashSingleCacheStore.java

@@ -0,0 +1,53 @@
+/*
+ * Copyright (C) 2020  LamGC
+ *
+ * ContentGrabbingJi is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as
+ * published by the Free Software Foundation, either version 3 of the
+ * License, or (at your option) any later version.
+ *
+ * ContentGrabbingJi is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+package net.lamgc.cgj.bot.cache.local;
+
+import net.lamgc.cgj.bot.cache.SingleCacheStore;
+
+import java.util.Objects;
+
+/**
+ * 基于 {@link java.util.Hashtable} 的 Map 缓存存储容器.
+ * @param <V> 值类型.
+ * @author LamGC
+ */
+public class HashSingleCacheStore<V> extends HashCacheStore<V> implements SingleCacheStore<V> {
+
+    @Override
+    public boolean set(String key, V value) {
+        getCacheMap().put(Objects.requireNonNull(key), new CacheItem<>(Objects.requireNonNull(value)));
+        return true;
+    }
+
+    @Override
+    public boolean setIfNotExist(String key, V value) {
+        if (exists(key)) {
+            return false;
+        }
+        return set(key, value);
+    }
+
+    @Override
+    public V get(String key) {
+        if (!exists(key)) {
+            return null;
+        }
+        return getCacheMap().get(key).getValue();
+    }
+
+}