fifter常见的运用场景

　没配置过滤器　

package servlet;

import java.io.IOException;

import javax.servlet.ServletException;

import javax.servlet.annotation.WebServlet;

import javax.servlet.http.HttpServlet;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

@WebServlet("/login")

public class LoginServlet extends HttpServlet{

    @Override

    public void service(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

        String name=request.getParameter("username");

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

        System.out.println(name);

        System.out.println(password);

    }

}

加入过滤器

package servlet;

import java.io.IOException;

import javax.servlet.ServletException;

import javax.servlet.annotation.WebServlet;

import javax.servlet.http.HttpServlet;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

@WebServlet("/login")

public class LoginServlet extends HttpServlet{

    @Override

    public void service(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

        String name=request.getParameter("username");

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

        System.out.println(name);

        System.out.println(password);

    }

}

package fifter;

import java.io.IOException;

import javax.servlet.Filter;

import javax.servlet.FilterChain;

import javax.servlet.FilterConfig;

import javax.servlet.ServletException;

import javax.servlet.ServletRequest;

import javax.servlet.ServletResponse;

import javax.servlet.annotation.WebFilter;

import javax.servlet.annotation.WebServlet;

import javax.servlet.http.HttpServletRequest;

@WebFilter("/*")

public class Charseter implements Filter{

    @Override

    public void destroy() {

    }

    @Override

    public void doFilter(ServletRequest arg0, ServletResponse arg1, FilterChain arg2)

            throws IOException, ServletException {

            arg0.setCharacterEncoding("UTF-8");

            arg2.doFilter(arg0, arg1);

    }

    @Override

    public void init(FilterConfig arg0) throws ServletException {

    }

}