1.URL的匹配规则

@WebServlet("/test")

/test就是咱们某一个资源的路径写法

用户申请了一个资源

http://localhost:8080/day41_wb/LoginServlet

1.http协议

2.localhost 本地服务器主机的名字

3.8080端口号

4.day41_wb/LoginServlet是咱们所申请的资源

day41_wb/当前应用程序目录，就是程序的绝对路径

LoginServlet 申请的资源

url匹配原则：

1.精准匹配

比如 /资源名字@WebServlet("/test.do")

2模糊匹配符

比如 @WebServlet("*.do") 以.do为后缀的资源都可以进行访问

比如@WebServlet("/*") 所有资源都可以访问

package com.javacoffee.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("*.do")
public class TestServlet extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        doGet(request, response);
    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        response.setContentType("text/html;charset=utf-8");
        response.getWriter().append("这是模糊匹配，后缀名为do的");
    }
}

package com.javacoffee.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("/TestServlet2")
public class TestServlet2 extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        doGet(request, response);
    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        response.setContentType("text/html;charset=utf-8");
        response.getWriter().append("这个是精准查询");
    }
}

package com.javacoffee.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("/*")
public class TestServlet1 extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        doGet(request, response);
    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        response.setContentType("text/html;charset=utf-8");
        response.getWriter().append("这个是模糊查询所有的资源");
    }
}

2.ServletContext【重要】

ServletContext接口，实例化以后是一个对象，

是咱们当前应用程序可以使用的唯一对象。

在一个Servlet里面，需要使用另外一个Servlet的提供的数据，怎么办？咱们会想到转发，但是如果不用转发怎么办？这时候就需要使用ServletContext对象，是全局的。比如你在一个Servlet里面设置一个数据，想要在另外一个Servlet里面使用这个数据。可以通过ServletContext这个接口，这个对象是全局的。

如果你在一个Servlet里面使用servletContext 对象设置一个数据，在另外一个Servlet里面也可以通过ServletContext这个对象获取这个数据

两个Servlet依靠servletContext对象进行通信，分享一些数据

例如TestServlet2需要获取TestServlet1的资源

package com.javacoffee.servlet;

import com.javacoffee.enity.Person;

import javax.servlet.ServletContext;
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("/TestServlet1")
public class TestServlet1 extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        doGet(request, response);
    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        response.setContentType("text/html;charset=utf-8");
        request.setCharacterEncoding("utf-8");
        //1.获取servletContext对象没当前上下文对象
        ServletContext servletContext = request.getServletContext();
        //2.给当前上下文对象设置一部分数据
        servletContext.setAttribute("name","张三");
        //也可以传入对象
        servletContext.setAttribute("person",new Person(21,"李四","特别喜欢吃河南烩面"));
        String serverInfo = servletContext.getServerInfo();//返回的是当前Servlet的详细信息
        String contextPath = servletContext.getContextPath();//项目的根目录（以后出现404可以先找这个根目录然后再一点一点的找）

        System.out.println(serverInfo);
        System.out.println(contextPath);
    }
}

package com.javacoffee.servlet;

import javax.servlet.ServletContext;
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("/TestServlet2")
public class TestServlet2 extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        doGet(request, response);
    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        response.setContentType("text/html;charset=utf-8");
        request.setCharacterEncoding("utf-8");
        ServletContext servletContext = request.getServletContext();
        Object name = servletContext.getAttribute("name");

        Object person = servletContext.getAttribute("person");

        response.getWriter().println(name+";;;"+person);
    }
}

3.Request对象

ServletReuqest接口

用户访问服务器，服务器会生成一个对象包含了http所有请求头

由于使用的是http协议，HttpServletRequest

3.1RequestAPI

getRequestURL(); 获取完成的url

getRequestURI();获取资源名字

getQueryString();获取一个url参数部分

getRemoteAddr();返回的是客户端的ip地址

getRemoteUser();返回的是客户端的用户

getRemotePort();返回的是客户端的主机的端口号

getRemoteHost();返回的是客户端的主机地址

getCookie();获取CookieD对象

getSession();获取Session对象

getLocalName();获取Web服务器主机的名字

getServletContext();获取上下文对象的

setCharacterEncoding();设置编码集的

getParameter();获取前端传过来的数据的

setAttribute();将数据设置给request对象

getAttribute();获取request对象中的数据的

package com.qfedu.c_request;
?
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("/request2")
public class RequestServlet2 extends HttpServlet {
 ? ?protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
 ? ? ? ?doGet(request, response);
 ?  }
?
 ? ?protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
 ? ? ? ?String remoteAddr = request.getRemoteAddr();
 ? ? ? ?String remoteHost = request.getRemoteHost();
 ? ? ? ?String remoteUser = request.getRemoteUser();
 ? ? ? ?int remotePort = request.getRemotePort();
 ? ? ? ?System.out.println(remoteAddr);//ip地址
 ? ? ? ?System.out.println(remoteHost);//主机的地址
 ? ? ? ?System.out.println(remoteUser);//用户名字
 ? ? ? ?System.out.println(remotePort);//端口号
 ? ? ? ?//以上代码如果你们在同一个网段是可以测试的
 ?

 ? ? ? ?//发现打印的都是别人访问的东西。意味着从这地方知道，
 ? ? ? 
 ? ? ? ?//以后开发必用的！！！是以下的方法
? ? ?  String name = request.getParameter("name");//获取前段传过来的数据
 ? ? ?  request.setCharacterEncoding("utf-8");//请求设置编码集
? ? ?  request.getRequestDispatcher("index.jsp").forward(request, response);//转发的代码
 ? ? ?  request.setAttribute("name", "狗蛋");
 ? ? ?  request.getAttribute("name");
 ? ? ? ?//request.getServletContext();//获取上文对象的
 ?  }
}