507day45重定向、转发、url匹配原则、Context资源共享、请求和响应的一些方法 - 《zhuzhiwei》

1.重定向：跳转页面
2.转发：请求资源a，显示转发资源b
3.url的匹配原则【重点】
- 精准匹配
- 模糊匹配
4.ServletContext对象，资源共享【重点】
- Context1
- Context2
5.request的一些方法
- 获取访问的主机信息
6.response的一些方法

1.重定向：跳转页面

设置重定向，让其跳转到主页面 target.html

重定向是浏览器的行为，response下面的方法

当代码进入LoginServlet资源后，跳转到target.html目标网页

响应.getParameter（“name”）

响应.sendRedirect(“目标页面”)

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
<form action="LoginServlet" method="post">
    姓名：<input type="text" name="user"><br>
    密码：<input type="password" name="pwd"><br>
    <input type="submit" name="登录">
</form>
</body>
</html>

target.html 目标

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
    我是主页
<!-- window.history.back() 返回上一个历史页面   -->
    <button onclick="window.history.back()">返回</button>
</body>
</html>

LoginServlet.java

package com.qfedu.a_redirect; /**
 * @author wodexinhuai
 * @create 2022-05-07-14:18
 */
import javax.servlet.*;
import javax.servlet.http.*;
import javax.servlet.annotation.*;
import java.io.IOException;
@WebServlet("/LoginServlet")
public class LoginServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        doPost(request, response);
    }
    @Override
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        request.setCharacterEncoding("utf-8");//post中文乱码解决方案
        String user = request.getParameter("user");
        String pwd = request.getParameter("pwd");
        System.out.println(user + ":" + pwd);
        //设置重定向，让其跳转到主页面 target.html
        //重定向是浏览器的行为，response下面的方法
        //当代码进入LoginServlet资源后，
        response.sendRedirect("target.html");
//        response.sendRedirect("http://www.baidu.com");
    }
}

2.转发：请求资源a，显示转发资源b

转发是服务器的行为 request请求

请求的test1的资源，显示的是转发后的资源（Test2）

Test1

package com.qfedu.b_zhuanfa; /**
 * @author wodexinhuai
 * @create 2022-05-07-14:37
 */
import javax.servlet.*;
import javax.servlet.http.*;
import javax.servlet.annotation.*;
import java.io.IOException;
@WebServlet(name = "Test1Servlet", value = "/Test1Servlet")
public class Test1Servlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        doPost(request, response);
    }
    @Override
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        System.out.println("用户请求Test1Servlet资源");
        //转发会带着数据（request对象）到另外一个资源中
        //request带有数据 键值对 name：呼叫博儿
        request.setAttribute("name","呼叫博儿");
        //转发是服务器的行为
        request.getRequestDispatcher("Test2Servlet").forward(request,response);
    }
}

Test2

package com.qfedu.b_zhuanfa; /**
 * @author wodexinhuai
 * @create 2022-05-07-14:41
 */
import javax.servlet.*;
import javax.servlet.http.*;
import javax.servlet.annotation.*;
import java.io.IOException;
@WebServlet(name = "Test2Servlet", value = "/Test2Servlet")
public class Test2Servlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        doPost(request, response);
    }
    @Override
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //把Test1Servlet里面转发到Test2Servlet里面的数据取出来
        //通过键取出来 在Test1中键是name
        Object name = request.getAttribute("name");
        response.setContentType("text/html;charset=utf-8");
        response.getWriter().append((String)name);
    }
}

3.url的匹配原则【重点】

url对于服务器开发很重要，因为要通过url来访问资源

URL：统一资源定位符

用户在浏览器中申请的资源

http://localhost:8080/day45_507a/Test1Servlet

精准匹配

用注解写法，是精准匹配

value = "/Test1Servlet"

模糊匹配

value = “*.do” 以.do结尾的都可以访问到这个资源

value = “/*” 写任何资源都可以匹配到这个资源

4.ServletContext对象，资源共享【重点】

可以实现资源和资源之间的共享，但仅限于servlet和jsp

Context1

package com.qfedu.d_servletcontext; /**
 * @author wodexinhuai
 * @create 2022-05-07-15:47
 */
import javax.servlet.*;
import javax.servlet.http.*;
import javax.servlet.annotation.*;
import java.io.IOException;
@WebServlet(name = "ServletContext1", value = "/text1")
public class ServletContext1 extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        doPost(request, response);
    }
    @Override
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //获取当前上下文对象
        ServletContext servletContext = request.getServletContext();
        //给当前上下文对象设置值
        servletContext.setAttribute("name","海贼王onepiece");
        Object name = servletContext.getAttribute("name");
        response.setContentType("text/html;charset=utf-8");
        response.getWriter().append("共享的数据" + name);
        response.getWriter().append("<br>");//浏览器换行
        //上下文Context对象的几个方法
        //获取当前项目的实际路径
        String realPath = servletContext.getRealPath("/");
        response.getWriter().append(realPath);
        response.getWriter().append("<br>");//浏览器换行
        //获取服务器的信息
        String serverInfo = servletContext.getServerInfo();
        response.getWriter().append(serverInfo);
        response.getWriter().append("<br>");//浏览器换行
        //获取当前项目的根路径
        String contextPath = servletContext.getContextPath();
        response.getWriter().append(contextPath);
    }
}

输出：
共享的数据海贼王onepiece
E:\idea_workspace\day45_507a\out\artifacts\day45_507a_war_exploded
Apache Tomcat/9.0.33
/day45_507a

Context2

package com.qfedu.d_servletcontext; /**
 * @author wodexinhuai
 * @create 2022-05-07-15:47
 */
import javax.servlet.*;
import javax.servlet.http.*;
import javax.servlet.annotation.*;
import java.io.IOException;
@WebServlet(name = "ServletContext2", value = "/text2")
public class ServletContext2 extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        doPost(request, response);
    }
    @Override
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //获取上下文对象
        ServletContext servletContext = request.getServletContext();
        //取值
        Object name = servletContext.getAttribute("name");
        response.setContentType("text/html;charset=utf-8");
        response.getWriter().append("这个是共享的数据" + name);
    }
}

先访问资源text1，之后输出：这个是共享的数据海贼王onepiece

如果没有先访问设置值之后，输出：这个是共享的数据null

5.request的一些方法

package com.qfedu.e_request; /**
 * @author wodexinhuai
 * @create 2022-05-07-16:06
 */
import javax.servlet.*;
import javax.servlet.http.*;
import javax.servlet.annotation.*;
import java.io.IOException;
import java.util.Arrays;
import java.util.Map;
import java.util.Set;
@WebServlet(name = "RequestServlet", value = "/RequestServlet")
public class RequestServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        response.setContentType("text/html;charset=utf-8");
        //获取当前的请求方式
        String method = request.getMethod();
        response.getWriter().append(method);//get
        response.getWriter().append("<br>");//浏览器换行
        //获取当前的完整的url 返回值是StringBuffer
        StringBuffer requestURL = request.getRequestURL();
        response.getWriter().append(requestURL);
        response.getWriter().append("<br>");//浏览器换行
        //获取url的已备份 uri 统一资源的标识符 返回值是String
        String requestURI = request.getRequestURI();
        response.getWriter().append(requestURI);
        response.getWriter().append("<br>");//浏览器换行
        //获取请求参数
        String queryString = request.getQueryString();
        response.getWriter().append(queryString);
        response.getWriter().append("<br>");//浏览器换行
        //获取请求的参数，以map集合展示的
        Map<String, String[]> parameterMap = request.getParameterMap();
        Set<Map.Entry<String,String[]>> set = parameterMap.entrySet();
        for (Map.Entry<String, String[]> stringEntry : set) {
            response.getWriter().append(stringEntry.getKey());//获取键
            response.getWriter().append(Arrays.toString(stringEntry.getValue()));//获取值
        }
        response.getWriter().append("<br>");//浏览器换行
    }
    @Override
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        doGet(request, response);
    }
}

http://localhost:8080/day45_507a/RequestServlet?user=boer&pwd=123

输出：
GET
http://localhost:8080/day45_507a/RequestServlet
/day45_507a/RequestServlet
user=boer&pwd=123
user[boer]pwd[123]

获取访问的主机信息

package com.qfedu.e_request; /**
 * @author wodexinhuai
 * @create 2022-05-07-16:21
 */
import javax.servlet.*;
import javax.servlet.http.*;
import javax.servlet.annotation.*;
import java.io.IOException;
@WebServlet(name = "RequestServlet2", value = "/RequestServlet2")
public class RequestServlet2 extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //获取访问我的网站的的ip地址
        String remoteAddr = request.getRemoteAddr();
        System.out.println(remoteAddr);
        //获取访问我的网站的的主机地址
        String remoteHost = request.getRemoteHost();
        System.out.println(remoteHost);
        //获取访问我的网站的的主机端口
        int remotePort = request.getRemotePort();
        System.out.println(remotePort);
        response.setContentType("text/html;charset=utf-8");
        response.getWriter().append("呼叫博儿");
    }
    @Override
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        doGet(request, response);
    }
}

用同一局域网的电脑或者手机访问：

192.168.2.232:8080/day45_507a/RequestServlet2

会显示访问的电脑的ip地址和端口号

6.response的一些方法

package com.qfedu.f_response; /**
 * @author wodexinhuai
 * @create 2022-05-07-16:36
 */
import javax.servlet.*;
import javax.servlet.http.*;
import javax.servlet.annotation.*;
import java.io.IOException;
import java.io.PrintWriter;
@WebServlet(name = "ResponseServlet", value = "/ResponseServlet")
public class ResponseServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //设置响应乱码
        response.setContentType("text/html;charset=utf-8");
        //打印字符流 并写到浏览器上
        PrintWriter writer = response.getWriter();
        writer.append("博儿");
        writer.write("is a dog");
    }
    @Override
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        doGet(request, response);
    }
}