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 {

    }

}