过滤器 过滤关键字

import javax.servlet.*;
import javax.servlet.annotation.WebFilter;
import javax.servlet.http.HttpServletRequest;
import java.io.*;
import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Method;
import java.lang.reflect.Proxy;
import java.util.ArrayList;
import java.util.List;

@WebFilter("/*")
public class CheckWordFilter implements Filter {
    public void destroy() {
    }

    public void doFilter(ServletRequest req, ServletResponse resp, FilterChain chain) throws ServletException, IOException {
//创建代理对象，增强getParameter方法
       ServletRequest req_proxy=(ServletRequest) Proxy.newProxyInstance(req.getClass().getClassLoader(), req.getClass().getInterfaces(), new InvocationHandler() {
            @Override
            public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
                //判断方法是否为getParameter方法
                if(method.getName().equals("getParameter")){
                   //增强getParameter方法
                    //获取返回值
                    String value = (String) method.invoke(req, args);
                    if(value!=null){
                        for (String str : list) {
                            if(value.contains(str)){
                                value=value.replaceAll(str,"***");
                            }
                        }
                    }
                    return value;
                }
                return method.invoke(req, args);
            }
        });
        chain.doFilter(req_proxy,resp);
    }
private List<String> list=new ArrayList<String>();
    public void init(FilterConfig config) throws ServletException {
        try{
            //获取文件真实路径
            ServletContext servletContext = config.getServletContext();
            String realPath = servletContext.getRealPath("/WEB-INF/classes/checkword.txt");
            //读取文件
            InputStreamReader isr = new InputStreamReader(new FileInputStream(realPath), "UTF-8");
            BufferedReader br = new BufferedReader(isr);
            //定义读取的长度
            String line=null;
            while ((line=br.readLine())!=null){
             list.add(line.trim());
            }
            br.close();
            //System.out.println(list);
            for (String s : list) {
                System.out.println(s);
            }
        } catch (Exception e){
           e.printStackTrace();
        }

    }

}