refactor(route):优化执行器路由策略实现

- 使用 StandardCharsets.UTF_8 替代手动指定 UTF-8 编码
- 移除不必要的异常捕获和抛出逻辑- 将 VIRTUAL_NODE_NUM 常量声明为 final- 优化 LFU 路由策略中的排序逻辑，使用 Map.Entry.comparingByValue()- 简化 LRU 路由策略中的元素加载逻辑
- 统一集合初始化时的泛型声明方式
-优化空集合判断逻辑，使用 isEmpty() 替代 size() 比较- 完善类字段和方法的 javadoc 注释内容

xxl-job-admin/src/main/java/com/xxl/job/admin/scheduler/route/strategy/ExecutorRouteConsistentHash.java

@@ -4,7 +4,7 @@ import com.xxl.job.admin.scheduler.route.ExecutorRouter;
 import com.xxl.job.core.biz.model.ReturnT;
 import com.xxl.job.core.biz.model.TriggerParam;
 
-import java.io.UnsupportedEncodingException;
+import java.nio.charset.StandardCharsets;
 import java.security.MessageDigest;
 import java.security.NoSuchAlgorithmException;
 import java.util.List;
@@ -15,16 +15,18 @@ import java.util.TreeMap;
  * 分组下机器地址相同，不同JOB均匀散列在不同机器上，保证分组下机器分配JOB平均；且每个JOB固定调度其中一台机器；
  *      a、virtual node：解决不均衡问题
  *      b、hash method replace hashCode：String的hashCode可能重复，需要进一步扩大hashCode的取值范围
+ *
  * Created by xuxueli on 17/3/10.
  */
 public class ExecutorRouteConsistentHash extends ExecutorRouter {
 
-    private static int VIRTUAL_NODE_NUM = 100;
+    private static final int VIRTUAL_NODE_NUM = 100;
 
     /**
      * get hash code on 2^32 ring (md5散列的方式计算hash值)
-     * @param key
-     * @return
+     *
+     * @param key key
+     * @return hash code
      */
     private static long hash(String key) {
 
@@ -37,11 +39,7 @@ public class ExecutorRouteConsistentHash extends ExecutorRouter {
         }
         md5.reset();
         byte[] keyBytes = null;
-        try {
-            keyBytes = key.getBytes("UTF-8");
-        } catch (UnsupportedEncodingException e) {
-            throw new RuntimeException("Unknown string :" + key, e);
-        }
+        keyBytes = key.getBytes(StandardCharsets.UTF_8);
 
         md5.update(keyBytes);
         byte[] digest = md5.digest();
@@ -52,10 +50,16 @@ public class ExecutorRouteConsistentHash extends ExecutorRouter {
                 | ((long) (digest[1] & 0xFF) << 8)
                 | (digest[0] & 0xFF);
 
-        long truncateHashCode = hashCode & 0xffffffffL;
-        return truncateHashCode;
+        return hashCode & 0xffffffffL;
     }
 
+    /**
+     * get address by jobId
+     *
+     * @param jobId         job id
+     * @param addressList   address list
+     * @return address
+     */
     public String hashJob(int jobId, List<String> addressList) {
 
         // ------A1------A2-------A3------

xxl-job-admin/src/main/java/com/xxl/job/admin/scheduler/route/strategy/ExecutorRouteLFU.java

@@ -17,6 +17,11 @@ import java.util.concurrent.ConcurrentMap;
  */
 public class ExecutorRouteLFU extends ExecutorRouter {
 
+    /**
+     * job lfu map
+     *
+     * <jobId, <address, count>>
+     */
     private static ConcurrentMap<Integer, HashMap<String, Integer>> jobLfuMap = new ConcurrentHashMap<Integer, HashMap<String, Integer>>();
     private static long CACHE_VALID_TIME = 0;
 
@@ -31,7 +36,7 @@ public class ExecutorRouteLFU extends ExecutorRouter {
         // lfu item init
         HashMap<String, Integer> lfuItemMap = jobLfuMap.get(jobId);     // Key排序可以用TreeMap+构造入参Compare；Value排序暂时只能通过ArrayList；
         if (lfuItemMap == null) {
-            lfuItemMap = new HashMap<String, Integer>();
+            lfuItemMap = new HashMap<>();
             jobLfuMap.putIfAbsent(jobId, lfuItemMap);   // 避免重复覆盖
         }
 
@@ -48,23 +53,17 @@ public class ExecutorRouteLFU extends ExecutorRouter {
                 delKeys.add(existKey);
             }
         }
-        if (delKeys.size() > 0) {
+        if (!delKeys.isEmpty()) {
             for (String delKey: delKeys) {
                 lfuItemMap.remove(delKey);
             }
         }
 
         // load least userd count address
-        List<Map.Entry<String, Integer>> lfuItemList = new ArrayList<Map.Entry<String, Integer>>(lfuItemMap.entrySet());
-        Collections.sort(lfuItemList, new Comparator<Map.Entry<String, Integer>>() {
-            @Override
-            public int compare(Map.Entry<String, Integer> o1, Map.Entry<String, Integer> o2) {
-                return o1.getValue().compareTo(o2.getValue());
-            }
-        });
+        List<Map.Entry<String, Integer>> lfuItemList = new ArrayList<>(lfuItemMap.entrySet());
+        lfuItemList.sort(Map.Entry.comparingByValue());     // 默认升序, 获取 Value 最小值
 
         Map.Entry<String, Integer> addressItem = lfuItemList.get(0);
-        String minAddress = addressItem.getKey();
         addressItem.setValue(addressItem.getValue() + 1);
 
         return addressItem.getKey();

xxl-job-admin/src/main/java/com/xxl/job/admin/scheduler/route/strategy/ExecutorRouteLRU.java

@@ -19,6 +19,11 @@ import java.util.concurrent.ConcurrentMap;
  */
 public class ExecutorRouteLRU extends ExecutorRouter {
 
+    /**
+     * job lru map
+     *
+     * <jobId, <address, address>>
+     */
     private static ConcurrentMap<Integer, LinkedHashMap<String, String>> jobLRUMap = new ConcurrentHashMap<Integer, LinkedHashMap<String, String>>();
     private static long CACHE_VALID_TIME = 0;
 
@@ -38,7 +43,7 @@ public class ExecutorRouteLRU extends ExecutorRouter {
              *      a、accessOrder：true=访问顺序排序（get/put时排序）；false=插入顺序排期；
              *      b、removeEldestEntry：新增元素时将会调用，返回true时会删除最老元素；可封装LinkedHashMap并重写该方法，比如定义最大容量，超出是返回true即可实现固定长度的LRU算法；
              */
-            lruItem = new LinkedHashMap<String, String>(16, 0.75f, true);
+            lruItem = new LinkedHashMap<>(16, 0.75f, true);
             jobLRUMap.putIfAbsent(jobId, lruItem);
         }
 
@@ -55,16 +60,15 @@ public class ExecutorRouteLRU extends ExecutorRouter {
                 delKeys.add(existKey);
             }
         }
-        if (delKeys.size() > 0) {
+        if (!delKeys.isEmpty()) {
             for (String delKey: delKeys) {
                 lruItem.remove(delKey);
             }
         }
 
-        // load
+        // load first elment, eldest entry
         String eldestKey = lruItem.entrySet().iterator().next().getKey();
-        String eldestValue = lruItem.get(eldestKey);
-        return eldestValue;
+        return lruItem.get(eldestKey);
     }
 
     @Override