<dependency>
		<groupId>org.springframework.boot</groupId>
		<artifactId>spring-boot-starter-aop</artifactId>
</dependency>

<dependency>
		<groupId>org.springframework.boot</groupId>
		<artifactId>spring-boot-starter-thymeleaf</artifactId>
</dependency>

<dependency>
		<groupId>org.springframework.boot</groupId>
		<artifactId>spring-boot-starter-web</artifactId>
</dependency>

<dependency>
		<groupId>org.springframework.boot</groupId>
		<artifactId>spring-boot-devtools</artifactId>
		<scope>runtime</scope>
</dependency>

<dependency>
		<groupId>org.springframework.boot</groupId>
		<artifactId>spring-boot-starter-test</artifactId>
		<scope>test</scope>
</dependency>

<dependency>
		<groupId>org.apache.commons</groupId>
		<artifactId>commons-lang3</artifactId>
		<version>3.9</version>
</dependency>

 //前綴樹
    private class TrieNode{
        //關鍵詞結束標識
        private boolean isKeywordEnd = false;

        //子節(jié)點
        private Map<Character,TrieNode> subNodes = new HashMap<>();
		
		//isKeywordEnd的get、set方法
        public boolean isKeywordEnd() {
            return isKeywordEnd;
        }

        public void setKeywordEnd(boolean keywordEnd) {
            isKeywordEnd = keywordEnd;
        }

        //添加子節(jié)點
        public void addSubNode(Character c,TrieNode node){
            subNodes.put(c,node);
        }

        //獲取子節(jié)點
        public TrieNode getSubNode(Character c){
            return subNodes.get(c);
        }
    }

@Component
public class SensitiveFilter {
    // 替換符
    private static final String REPLACEMENT = "***";

    //根節(jié)點
    private TrieNode rootNode = new TrieNode();

    //bean的初始化方法，服務一啟動，容器自動給bean執(zhí)行此方法完成初始化
    //此方法的目的是讀取敏感詞文件，構建敏感詞前綴樹
    @PostConstruct
    public void init(){
        try(
                InputStream is = this.getClass().getClassLoader().getResourceAsStream("sensitive-words.txt");
                BufferedReader reader = new BufferedReader(new InputStreamReader(is));
                ){
            String keyword;
            while((keyword=reader.readLine())!=null){
                this.addKeyword(keyword);
            }
        }catch (IOException e){
            logger.error("加載敏感詞文件失敗: " + e.getMessage());
        }
    }
    
    //將一個敏感詞添加到前綴樹
    private void addKeyword(String keyword){
        TrieNode tempNode = rootNode;
        for (int i = 0; i <keyword.length() ; i++) {
            char c = keyword.charAt(i);
            TrieNode subNode = tempNode.getSubNode(c);
            if(subNode==null){
                //初始化子節(jié)點
                subNode = new TrieNode();
                tempNode.addSubNode(c,subNode);
            }
            //指向子節(jié)點，進入下一輪循環(huán)
            tempNode = subNode;

            //設置結束標志
            if(i==keyword.length()-1){
                tempNode.setKeywordEnd(true);
            }
        }
    }


    /**
     * 過濾敏感詞
     *
     * @param text 待過濾的文本
     * @return 過濾后的文本
     */
    public String filter(String text){
        if(StringUtils.isBlank(text)){
            return null;
        }
        //指針1
        TrieNode tempNode = rootNode;
        //指針2
        int begin = 0;
        //指針3
        int position = 0;
        //結果
        StringBuilder sb = new StringBuilder();
        while(position<text.length()){
            char c = text.charAt(position);
            /*
            	跳過符號
            	情況一：符號在敏感詞前面，將符號寫入結果，如 ☆敏感詞
            	情況二：符號在敏感詞中間，則將符號與敏感詞一起替換，如敏☆感☆詞
            */
            if(isSymbol(c)){
                //若指針1處于根節(jié)點，對應情況一，將符號計入結果，讓指針2向下走一步
                if(tempNode==rootNode){
                    sb.append(c);
                    begin++;
                }
                //無論符號在開頭還是敏感詞中間，指針3都向下走一步
                position++;
                continue;
            }
            //檢查下級節(jié)點
            tempNode = tempNode.getSubNode(c);
            if(tempNode==null){
                //以begin開頭的的字符串不是敏感詞
                sb.append(text.charAt(begin));
                //指針2和指針3共同指向指針2的下一個位置
                position = ++begin;
                //指針1重新指向根節(jié)點
                tempNode = rootNode;
            }else if(tempNode.isKeywordEnd()){
                //發(fā)現(xiàn)敏感詞，將begin~position字符串替換
                sb.append(REPLACEMENT);
                //進入下一個位置
                begin = ++position;
                //指針1重新指向根節(jié)點
                tempNode = rootNode;
            }else {
                //檢查下一個字符
                position++;
            }
        }
        //將最后一批字符計入結果
        sb.append(text.substring(begin));
        return sb.toString();
    }
    //判斷是否為符號
    private boolean isSymbol(Character c){
        // 0x2E80~0x9FFF 是東亞文字范圍
        return !CharUtils.isAsciiAlphanumeric(c) && (c < 0x2E80 || c > 0x9FFF);
    }
}