JavaWeb - 【Filter】敏感詞過濾

Filter - 敏感詞過濾

• 過濾器細節
  • 執行流程
  • 生命週期（專案部署）
  • 攔截路徑
  • 攔截方式
• 從檔案中獲取敏感詞清單
• 將所有敏感詞替換為***
  • 動態代理（設計模式）

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一：過濾器細節

二：從檔案中獲取敏感詞清單

List<String> sensitiveWordsList = new ArrayList<>();

@Override
public void init(FilterConfig filterConfig){
    // 1. 獲取敏感詞清單，讀取進入List
    try {
        String sensitiveFilePath = "/WEB-INF/classes/sensitiveWords.txt";
        ServletContext servletContext = filterConfig.getServletContext();
        String realPath = servletContext.getRealPath(sensitiveFilePath);
        BufferedReader br = new BufferedReader(new InputStreamReader(new FileInputStream(realPath),
                StandardCharsets.UTF_8));
        // 1.1 如何從BufferedReader中迴圈讀取每一行
        String line = null;
        while ((line = br.readLine())!=null) {
            sensitiveWordsList.add(line);
        }
        br.close();
    }catch(Exception e){
        e.printStackTrace();
    }
}

三：將所有敏感詞替換為***

@Override
public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
    // FORWARD請求轉發的的request是：org.apache.catalina.core.ApplicationHttpRequest
    //      使用動態代理強轉ServletQuest時報錯
    //          Tomcat9.0.38
    System.out.println(servletRequest);
    // 1. 增強request的getParameter方法
    ServletRequest proxyReq = (ServletRequest) Proxy.newProxyInstance(servletRequest.getClass().getClassLoader(), servletRequest.getClass().getInterfaces(), (proxy, method, args) -> {
        if ("getParameter".equals(method.getName())) {
            String res = (String) method.invoke(servletRequest, args);
            if (res != null) {
                for (String s :
                        sensitiveWordsList) {
                    if (res.contains(s)) {
                        res = res.replaceAll(s, "***");
                    }
                }
            }
            return res;
        }
        return method.invoke(servletRequest, args);
    });

    // 2. 使用代理物件放行
    filterChain.doFilter(proxyReq,servletResponse);
}