[Fix] Issue #1 修复了ImageCache对重复缓存请求的策略(忽略并返回)导致的后续处理发生NPE的问题;

[Update] ImageCache 更新了ImageCache, 将该部分单独分离到 ImageCacheStore;
[Update] BotCommandProcess 适配新的ImageCache, 调整内容检查的时机以减少不必要的API访问;

src/main/java/net/lamgc/cgj/bot/cache/ImageCacheHandler.java

@@ -28,9 +28,9 @@ public class ImageCacheHandler implements EventHandler {
     private final static Set<ImageCacheObject> cacheQueue = Collections.synchronizedSet(new HashSet<>());
 
     @SuppressWarnings("unused")
-    public void getImageToCache(ImageCacheObject event) {
+    public void getImageToCache(ImageCacheObject event) throws Exception {
         if(cacheQueue.contains(event)) {
-            log.debug("图片 {} 已存在相同缓存任务, 跳过.", event.getStoreFile().getName());
+            log.warn("图片 {} 已存在相同缓存任务, 跳过.", event.getStoreFile().getName());
             return;
         } else {
             cacheQueue.add(event);
@@ -43,11 +43,11 @@ public class ImageCacheHandler implements EventHandler {
             try {
                 if(!storeFile.exists() && !storeFile.createNewFile()) {
                     log.error("无法创建文件(Path: {})", storeFile.getAbsolutePath());
-                    return;
+                    throw new IOException("Failed to create file");
                 }
             } catch (IOException e) {
                 log.error("无法创建文件(Path: {})", storeFile.getAbsolutePath());
-                e.printStackTrace();
+                throw e;
             }
 
             HttpGet request = new HttpGet(event.getDownloadLink());
@@ -57,11 +57,11 @@ public class ImageCacheHandler implements EventHandler {
                 response = httpClient.execute(request);
             } catch (IOException e) {
                 log.error("Http请求时发生异常", e);
-                return;
+                throw e;
             }
             if(response.getStatusLine().getStatusCode() != 200) {
                 log.warn("Http请求异常：{}", response.getStatusLine());
-                return;
+                throw new IOException("Http Response Error: " + response.getStatusLine());
             }
 
             log.debug("正在下载...(Content-Length: {}KB)", response.getEntity().getContentLength() / 1024);
@@ -69,7 +69,7 @@ public class ImageCacheHandler implements EventHandler {
                 IOUtils.copy(response.getEntity().getContent(), fos);
             } catch (IOException e) {
                 log.error("下载图片时发生异常", e);
-                return;
+                throw e;
             }
             event.getImageCache().put(URLs.getResourceName(event.getDownloadLink()), storeFile);
         } finally {

src/main/java/net/lamgc/cgj/bot/cache/ImageCacheStore.java

@@ -0,0 +1,109 @@
+package net.lamgc.cgj.bot.cache;
+
+import com.google.common.util.concurrent.ThreadFactoryBuilder;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.util.Hashtable;
+import java.util.Map;
+import java.util.concurrent.*;
+import java.util.concurrent.atomic.AtomicReference;
+import java.util.concurrent.locks.Condition;
+import java.util.concurrent.locks.ReentrantLock;
+
+public final class ImageCacheStore {
+
+    private final static Logger log = LoggerFactory.getLogger(ImageCacheStore.class.getName());
+
+    private final static Map<ImageCacheObject, Task> cacheMap = new Hashtable<>();
+
+    private final static ThreadPoolExecutor imageCacheExecutor = new ThreadPoolExecutor(
+            4, 6,
+            30L,
+            TimeUnit.SECONDS,
+            new LinkedBlockingQueue<>(100),
+            new ThreadFactoryBuilder()
+                    .setNameFormat("ImageCacheThread-%d")
+                    .build()
+    );
+
+    private final static ImageCacheHandler handler = new ImageCacheHandler();
+
+    private ImageCacheStore() {}
+
+    /**
+     * 传递图片缓存任务, 并等待缓存完成.
+     * @param cacheObject 缓存任务组
+     */
+    public static void executeCacheRequest(ImageCacheObject cacheObject) throws InterruptedException {
+        Task task = getTaskState(cacheObject);
+        if(task.taskState.get() == TaskState.COMPLETE) {
+            return;
+        }
+
+        boolean locked = false;
+        try {
+            if(task.taskState.get() == TaskState.COMPLETE) {
+                return;
+            }
+            task.lock.lock();
+            locked = true;
+            // 双重检查
+            if(task.taskState.get() == TaskState.COMPLETE) {
+                return;
+            }
+
+            // 置任务状态
+            task.taskState.set(TaskState.RUNNING);
+
+            try {
+                Throwable throwable = imageCacheExecutor.submit(() -> {
+                    try {
+                        handler.getImageToCache(cacheObject);
+                    } catch (Throwable e) {
+                        return e;
+                    }
+                    return null;
+                }).get();
+
+                if(throwable == null) {
+                    task.taskState.set(TaskState.COMPLETE);
+                } else {
+                    task.taskState.set(TaskState.ERROR);
+                }
+            } catch (ExecutionException e) {
+                log.error("执行图片缓存任务时发生异常", e);
+            }
+        } finally {
+            if(locked) {
+                task.lock.unlock();
+            }
+        }
+
+    }
+
+    private static Task getTaskState(ImageCacheObject cacheObject) {
+        if(!cacheMap.containsKey(cacheObject)) {
+            cacheMap.put(cacheObject, new Task());
+        }
+        return cacheMap.get(cacheObject);
+    }
+
+    /**
+     * 任务状态
+     */
+    private enum TaskState {
+        READY, RUNNING, COMPLETE, ERROR
+    }
+
+    private static class Task {
+
+        public final ReentrantLock lock = new ReentrantLock(true);
+
+        public final AtomicReference<TaskState> taskState = new AtomicReference<>(TaskState.READY);
+
+        public final Condition condition = lock.newCondition();
+
+    }
+
+}