敏感词校验DFA算法

　　为什么需要过滤
　　在Web系统中，用户需要进行评论/回复，或者发布一些观点，服务器需要对用户发布的内容进行过滤（如果想被请去喝茶的话可以选择不过滤），过滤的内容当然包括色情、暴力、政府相关等
　　在分析需求后，google 相关的其他系统是如何实现的. DFA 算法，可以比较高效的进行匹配 。如果使用 for 循环逐个匹配效率肯定是不行的  什么是DFA算法
　　Deterministic Finite Automaton ,也就是确定有穷自动机 ，通过 event 与 state 得到下一个 state ,即状态的转换
　　DFA 算法的实现  构建存储结构（构建类似树型结构匹配）  关键词匹配
　　通过加载数据库数据关键词，判断内容是否合法/**  *  修改为每次都读取一次 ，也可以系统启动读取一次（不实时）  */ @Component public class SensitiveWordFilter {      private final SensitiveWordDao sensitiveWordDao;      @SuppressWarnings(＂rawtypes＂)     private Map sensitiveWordMap = null;     public static int minMatchTYpe = 1;     public static int maxMatchType = 2;       public SensitiveWordFilter(SensitiveWordDao sensitiveWordDao){         this.sensitiveWordDao = sensitiveWordDao; //        Set keyWordSet  = sensitiveWordDao.list(); //        addSensitiveWordToHashMap(keyWordSet);     }      @SuppressWarnings({ ＂rawtypes＂, ＂unchecked＂ })     private void addSensitiveWordToHashMap(Set keyWordSet) {         sensitiveWordMap = new HashMap(keyWordSet.size());         String key = null;         Map nowMap = null;         Map newWorMap = null;         Iterator iterator = keyWordSet.iterator();         while(iterator.hasNext()){             key = iterator.next();             nowMap = sensitiveWordMap;             for(int i = 0 ; i < key.length() ; i++){                 char keyChar = key.charAt(i);                 Object wordMap = nowMap.get(keyChar);                  if(wordMap != null){                     nowMap = (Map) wordMap;                 }                 else{                     newWorMap = new HashMap();                     newWorMap.put(＂isEnd＂, ＂0＂);                     nowMap.put(keyChar, newWorMap);                     nowMap = newWorMap;                 }                  if(i == key.length() - 1){                     nowMap.put(＂isEnd＂, ＂1＂);                 }             }         }     }        public boolean isContainSensitiveWord(String txt, int matchType){         boolean flag = false;         for(int i = 0 ; i < txt.length() ; i++){             int matchFlag = this.CheckSensitiveWord(txt, i, matchType);             if(matchFlag > 0){                 flag = true;             }         }         return flag;     }       public Set getSensitiveWord(String txt , int matchType){         Set sensitiveWordList = new HashSet();          for(int i = 0 ; i < txt.length() ; i++){             int length = CheckSensitiveWord(txt, i, matchType);             if(length > 0){                 sensitiveWordList.add(txt.substring(i, i+length));                 i = i + length - 1;             }         }          return sensitiveWordList;     }       public String replaceSensitiveWord(String txt,int matchType,String replaceChar){         String resultTxt = txt;         Set set = getSensitiveWord(txt, matchType);         Iterator iterator = set.iterator();         String word = null;         String replaceString = null;         while (iterator.hasNext()) {             word = iterator.next();             replaceString = getReplaceChars(replaceChar, word.length());             resultTxt = resultTxt.replaceAll(word, replaceString);         }          return resultTxt;     }       private String getReplaceChars(String replaceChar,int length){         String resultReplace = replaceChar;         for(int i = 1 ; i < length ; i++){             resultReplace += replaceChar;         }          return resultReplace;     }       @SuppressWarnings({ ＂rawtypes＂})     public int CheckSensitiveWord(String txt,int beginIndex,int matchType){         Set keyWordSet  = sensitiveWordDao.list();         addSensitiveWordToHashMap(keyWordSet);         boolean  flag = false;         int matchFlag = 0;         char word = 0;         Map nowMap = sensitiveWordMap;         for(int i = beginIndex; i < txt.length() ; i++){             word = txt.charAt(i);             nowMap = (Map) nowMap.get(word);             if(nowMap != null){                 matchFlag++;                 if(＂1＂.equals(nowMap.get(＂isEnd＂))){                     flag = true;                     if(SensitiveWordFilter.minMatchTYpe == matchType){                         break;                     }                 }             }             else{                 break;             }         }         if(matchFlag < 2 || !flag){             matchFlag = 0;         }         return matchFlag;     } }
　　参考：
　　https://blog.csdn.net/weixin_43378396/article/details/105910145
　　https://blog.csdn.net/chenssy/article/details/26961957
　　https://www.cnblogs.com/twoheads/p/11349541.html
　　分类: java