java过滤器，实现敏感词汇过滤的示例

过滤器类

package web.filter;

import javax.servlet.*;
import javax.servlet.annotation.WebFilter;
import java.io.BufferedReader;
import java.io.FileReader;
import java.io.IOException;
import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Method;
import java.lang.reflect.Proxy;
import java.util.ArrayList;
import java.util.List;

/**
 * 敏感词汇过滤器
 */
@WebFilter("/*")
public class SensitiveWordsFilter implements Filter {


    public void doFilter(ServletRequest req, ServletResponse resp, FilterChain chain) throws ServletException, IOException {
        //1.创建代理对象，增强getParameter方法

        ServletRequest proxy_req = (ServletRequest) Proxy.newProxyInstance(req.getClass().getClassLoader(), req.getClass().getInterfaces(), new InvocationHandler() {
            @Override
            public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
                //增强getParameter方法
                //判断是否是getParameter方法
                if(method.getName().equals("getParameter")){
                    //增强返回值
                    //获取返回值
                    String value = (String) method.invoke(req,args);
                    System.out.println("method："+method.getName());
                    if(value != null){
                        for (String str : list) {
                            if(value.contains(str)){
                                value = value.replaceAll(str,"***");
                            }
        
                        }
                    }
                    
                    return  value;
                }

                //判断方法名是否是 getParameterMap

                //判断方法名是否是 getParameterValue

                return method.invoke(req,args);
            }
        });

        //2.放行
        chain.doFilter(proxy_req, resp);
    }
    private List list = new ArrayList();//敏感词汇集合
    public void init(FilterConfig config) throws ServletException {

        try{
            //1.获取文件真实路径
            ServletContext servletContext = config.getServletContext();
            String realPath = servletContext.getRealPath("/WEB-INF/classes/敏感词汇.txt");
            //2.读取文件
            BufferedReader br = new BufferedReader(new FileReader(realPath));
            //3.将文件的每一行数据添加到list中
            String line = null;
            while((line = br.readLine())!=null){
                list.add(line);
            }

            br.close();

            System.out.println(list);

        }catch (Exception e){
            e.printStackTrace();
        }

    }

    public void destroy() {
    }

}

测试类

package web.servlet;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;

@WebServlet("/testServlet")
public class TestServlet extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        String name = request.getParameter("name");
        String msg = request.getParameter("msg");

        System.out.println(name+":"+msg);
    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        this.doPost(request, response);
    }
}