煞笔

制杖

cxk

<form action="handlerServlet" method="post">

        评论：<textarea name="comment" rows="10" cols="50"></textarea>

        <button type="submit">提交</button>

    </form>

@WebFilter("/handlerServlet")

public class HandlerFilter implements Filter {

    public void destroy() {

    }

    public void doFilter(ServletRequest req, ServletResponse resp, FilterChain chain) throws ServletException, IOException {

        //解决中文乱码

        req.setCharacterEncoding("utf-8");

        resp.setContentType("text/html;charset=utf-8");

    　 //jdk动态代理　　

        ClassLoader classLoader = req.getClass().getClassLoader();

        Class<?>[] interfaces = req.getClass().getInterfaces();

        //创建InvocationHandler接口的实例。此处使用匿名内部类来创建

        InvocationHandler invocationHandler = new InvocationHandler() {

            @Override

            public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {

                //只增强getParameter()

                if(method.getName().equals("getParameter")){

                    //调用原有的getParameter()获取参数值

                    String text = (String) method.invoke(req, args);

                    //检查是否有敏感词汇

                    Object obj = req.getServletContext().getAttribute("illegal_word_list");

                    ArrayList<String> list=(ArrayList<String>)obj;

                    for (String word : list){

                        if (text.contains(word)){

                            //用一个*替换一个字符

                            String replac="";

                            for(int i=0;i<word.length();i++){

                                replac+="*";

                            }

                            //替换所有匹配

                            text = text.replaceAll(word, replac);

                        }

                    }

                    return text;

                }

                //如果调用的是getParameter（）,执行到前面的return就结束了，不会执行到此

                //如果调用的不是getParameter()，就调用原方法，不做修改

                Object returnValue=method.invoke(req,args);  //调用目标方法

                return returnValue;

            }

        };

        //创建req的代理对象

        Object proxyInstance = Proxy.newProxyInstance(classLoader, interfaces, invocationHandler);

        //强转为ServletRequest

        ServletRequest reqProxyInstance = (ServletRequest) proxyInstance;

        //传入req的代理对象

        chain.doFilter(reqProxyInstance, resp);

    }

    public void init(FilterConfig config) throws ServletException {

        InputStream is= this.getClass().getResourceAsStream("/illegal_word.txt");

        //因为要readLine()一行一行地读，需要使用BufferedReader流，所以先转换为Reader，再加Buffer

        InputStreamReader isr = new InputStreamReader(is);

        BufferedReader br = new BufferedReader(isr);

        ArrayList<String> list=new ArrayList<>();

        String str=null;

        while (true){

            try {

                str=br.readLine();

                if (str!=null)

                    list.add(str);

                else

                    break;

            } catch (IOException e) {

                e.printStackTrace();

            }

        }

        //放到ServletContext中

        config.getServletContext().setAttribute("illegal_word_list",list);

    }

}    

@WebServlet("/handlerServlet")

public class HandlerServlet extends HttpServlet {

    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

        String comment = request.getParameter("comment");

        response.getWriter().write(comment);

    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

        doPost(request,response);

    }

}