web初级阶段及过滤器

package cn.tedu.web;

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(urlPatterns = "/d8")
public class Demo8 extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        //1.处理字节流的中文乱码问题
        resp.setContentType("text/html;charset=utf-8");
        //2.获取字节输出流,响应中文数据
        String str = "hello 字节流数据";
        //设置字节数据的编码格式
        byte[] bytes = str.getBytes("utf-8");
        //3.响应数据到浏览器
        resp.getOutputStream().write(bytes);
    }
}

package cn.tedu.web;

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(urlPatterns = "/d9")
    public class Demo9 extends HttpServlet {
        @Override
        protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
            req.setCharacterEncoding("utf-8");
            resp.setContentType("text/html;utf-8");
            String user = req.getParameter("username");
            String psw = req.getParameter("psw");
            if(user.equalsIgnoreCase("admin") && psw.equals("111")){
                String indexUrl = "http://localhost:8080/web/welcome.html";
                resp.sendRedirect(indexUrl);
            }else{
                String info = "用户名或密码错误,请重新登录";
                String loginUrl = "http://localhost:8080/web/login.html";
                info+="<br/>";
                info+="<a href='"+loginUrl+"'>点击,重新登录<a/>";
                resp.getWriter().println(info);
            }
        }
    }

过滤器 

package cn.tedu.filter;
//本类用于测试filter过滤器
import javax.servlet.*;
import javax.servlet.annotation.WebFilter;
import java.io.IOException;
@WebFilter("/*")//拦截所有请求,只要访问这个项目里的资源,全都拦截,不放行就阻塞
//导包过程中注意所导包的位置,需要用的Filter包只有doFilter方法需要重写
public class Demo1 {
    public void destroy(){}
    public void init(FilterConfig config) throws ServletException {}
    public void doFilter(ServletRequest req, ServletResponse resp, FilterChain chain) throws ServletException, IOException {
        System.out.println("filter上线....");
        chain.doFilter(req,resp);
    }
}

package cn.tedu.filter;
//本类用于测试过滤器的配置方式
/*1,具体文件: /index.jsp ,是指只有访问index.jsp这一个资源时,过滤器会被执行
* 2,匹配前缀: /user/* ,是指访问user下的所有资源时,过滤器会被执行
* 3,匹配后缀: * .jsp, 是指访问所有后缀名为jsp的文件时,过滤器会被执行
* 4,匹配所有: /* ,是指访问所有资源时,过滤器都会被执行*/
import javax.servlet.*;
import javax.servlet.annotation.WebFilter;
import java.io.IOException;
//@WebFilter("/hello1.html")//只拦截固定资源
//@WebFilter("/user/*")//按照请求前缀拦截
//@WebFilter("*.jsp")//按照请求后缀拦截
@WebFilter("/*")//啥都拦截
public class Demo2 implements Filter {
    @Override
    public void init(FilterConfig filterConfig) throws ServletException {

    }

    @Override
    public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {

    }

    @Override
    public void destroy() {

    }
}

package cn.tedu.filter;
//本类用于测试通过滤器解决中文乱码问题
import javax.servlet.*;
import javax.servlet.annotation.WebFilter;
import java.io.IOException;
@WebFilter("/user/*")
public class Demo3 implements Filter {
    @Override
    public void init(FilterConfig filterConfig) throws ServletException {
        System.out.println("initFilter");
    }
    @Override
    public void doFilter(ServletRequest req, ServletResponse resp, FilterChain chain) throws IOException, ServletException {
        System.out.println("filter1...doFilter");
        req.setAttribute("name","jack");
        req.setCharacterEncoding("utf-8");//解决请求时的中文乱码
        resp.setContentType("text/html;charset=utf8");//解决响应时的中文乱码
        chain.doFilter(req,resp);//放行请求,可以继续访问目标资源.否则就会拦截请求
    }
    @Override
    public void destroy() {
        System.out.println("destroyFilter");
    }
}