本文參考博客：https://blog.csdn.net/henshuia/article/details/111498753?utm_medium=distribute.pc_relevant.none-task-blog-2_defaultbaidujs_title~default-0.pc_relevant_default&spm=1001.2101.3001.4242.1&utm_relevant_index=3
再次感謝作者分享！

實現敏感詞過濾，一般都是遍歷敏感詞庫然后一個一個的用敏感詞進行匹配，但是這樣效率不高并且如果敏感詞中間摻雜特殊符號或者空格就匹配不到了，其次高級點使用正則匹配，但是正則匹配效率低，所有就使用DFA算法解決。

DFA簡介
在實現文字過濾的算法中，DFA是唯一比較好的實現算法。DFA即Deterministic Finite Automaton，也就是確定有窮自動機，它是是通過event和當前的state得到下一個state，即event+state=nextstate。下圖展示了其狀態的轉換

如果我們敏感詞是：黃色、黃賭毒、黃色絲襪、絲襪，則數據結構如下所示

每次過濾文章的時候先從整片文章從第一個字開始往后過濾，如果當前這個字存在根節點下則用這個字后面字個這個節點下一個節點匹配，如果存在并且end=1則是敏感詞。
首先創建對敏感詞處理，按格式寫入

private SoftReference<Map<String, Map>> sensitiveWordReference=null;private void setWordMap(List<String> result){Map<String, Map> sensitiveWordMap=new HashMap<>(result.size());Iterator<String> iterator = result.iterator();String key = null;Map nowMap = null;while(iterator.hasNext()){nowMap=sensitiveWordMap;key = iterator.next();for(int i=0;i< key.length();i++){char keyChar = key.charAt(i);if(nowMap.containsKey(keyChar)){nowMap=(Map)nowMap.get(keyChar);}else{Map<String,String>newWorMap = new HashMap();newWorMap.put("end", "0");nowMap.put(keyChar, newWorMap);nowMap = newWorMap;}if(i==(key.length()-1)){nowMap.put("end","1");}}}log.info("敏感詞組合{}", JSONObject.toJSONString(sensitiveWordMap));sensitiveWordReference=new SoftReference<Map<String, Map>>(sensitiveWordMap);}

敏感詞是：毒品,黑色,黃色絲襪,色情,絲襪,黃色,黃賭毒

敏感詞組合 {"黑": {"色": {"end": "1"},"end": "0"},"毒": {"品": {"end": "1"},"end": "0"},"色": {"情": {"end": "1"},"end": "0"},"黃": {"色": {"end": "1","絲": {"end": "0","襪": {"end": "1"}}},"end": "0","賭": {"毒": {"end": "1"},"end": "0"}},"絲": {"end": "0","襪": {"end": "1"}} }

檢查并返回匹配到的第一個敏感詞

private String checkWords(String sensitiveWords){if(StringUtils.isEmpty(sensitiveWords)){return StringUtils.EMPTY;}Map<String, Map> sensitiveWordMap=sensitiveWordReference.get();Map nowMap = null;StringBuffer sb=new StringBuffer();for(int i =0; i < sensitiveWords.length(); i++){if(!Character.toString(sensitiveWords.charAt(i)).matches("[\\u4E00-\\u9FA5]+")) {continue;}if(!sensitiveWordMap.containsKey(sensitiveWords.charAt(i))){continue;}sb=new StringBuffer().append(sensitiveWords.charAt(i));nowMap=sensitiveWordMap.get(sensitiveWords.charAt(i));int sensitiveWordLength=i;while (sensitiveWordLength<MAX_MAP_LENGTH){sensitiveWordLength++;if(!Character.toString(sensitiveWords.charAt(sensitiveWordLength)).matches("[\\u4E00-\\u9FA5]+")) {sb.append(sensitiveWords.charAt(sensitiveWordLength));continue;}nowMap=(Map)nowMap.get(sensitiveWords.charAt(sensitiveWordLength));if(CollectionUtils.isEmpty(nowMap)){break;}sb.append(sensitiveWords.charAt(sensitiveWordLength));if(nowMap.get("end").equals("1")){return sb.toString();}}}return sb.toString();}

本文增加了對特殊字符的處理，匹配敏感詞的時候會忽略特殊字符只匹配漢字。
執行輸入檢查的文章：發 絲 0 襪送的發達色法士大夫黃 的色是打發士大 夫是
返回結果敏感詞是：絲 0 襪

總結

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