Servlet&HTTP&Request

2023-11-16 11:24:28

Servlet

Servlet的体系结构：
Servlet – 接口 GenericServlet – 抽象类 HttpServlet – 抽象类
GenericServlet：将Servlet接口中其他方法做了默认空实现，只将service（）方法作为抽象，将来定义Servlet类时，可以继承GenericServlet，实现service（）方法即可
HttpServlet：对http协议的一种封装，简化操作：
1，定义类继承HttpServlet
2，复写doGet/doPost方法
Servlet相关配置：
一个Servlet可以定义多个访问路径：@WebServlet({"/d4","/dd4","/ddd4"})
路径定义三种规范：
1，/xxx:路径匹配 2，/xxx/xxx:多层路径，目录结构 3，*.do:扩展名匹配

HTTP

超文本传输协议：定义了客户端和服务器端通信时发送数据的格式
特点：

  1. 基于TCP/IP高级协议
  2. 默认端口号：80
  3. 基于请求/响应模型：一次请求对应一次响应
  4. 无状态，每次请求之间相互独立，不能交互数据
    HTTP协议有7种请求方式，常用GET和POST
    GET：请求参数在请求行中，在url后，请求的url长度有限制，不太安全
    POST：请求参数在请求体中，请求的url长度没有限制，相对安全

Request

1，request和response对象是由服务器创建的。
2，request对象负责获取请求消息，response对象是来设置响应消息
request对象继承体系结构：
ServletRequest --接口 HttpServletRequest–接口org.apache.catalina.connector.RequestFacade – 类(tomcat)
获取请求行数据：

package com.wzc.web.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;
/*
演示Request对象获取数据请求行数据
* */
@WebServlet("/RequestDemo1")
public class RequestDemo1 extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
//        获取请求方式：GET
        String method = request.getMethod();
        System.out.println(method);
//        获取虚拟路径
        String contextPath = request.getContextPath();
        System.out.println(contextPath);
//        获取Servlet路径
        String queryString = request.getQueryString();
        System.out.println(queryString);
//        获取请求URI
        String requestURI = request.getRequestURI();
        System.out.println(requestURI);
//        获取URL
        StringBuffer requestURL = request.getRequestURL();
        System.out.println(requestURL);
//        获取协议以及版本
        String protocol = request.getProtocol();
        System.out.println(protocol);
//        获取客户机的IP地址
        String remoteAddr = request.getRemoteAddr();
        System.out.println(remoteAddr);
    }
}

获取请求头数据：

package com.wzc.web.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;
import java.util.Enumeration;

@WebServlet("/RequestDemo2")
public class RequestDemo2 extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
     //获取请求头数据
//        获取所有请求头名称
        Enumeration<String> headerNames = request.getHeaderNames();
//        遍历
        while(headerNames.hasMoreElements()){
            String name = headerNames.nextElement();
//            根据名称获取请求头的值
            String value = request.getHeader(name);
            System.out.println(name+"------"+value);
        }
    }
}

获取请求体数据：

package com.wzc.web.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.BufferedReader;
import java.io.IOException;

@WebServlet("/RequestDemo5")
public class RequestDemo5 extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
//        获取请求消息体--请求参数
//        获取字符流
        BufferedReader br = request.getReader();
//        读取数据
        String line = null;
        while ((line = br.readLine()) !=null){
            System.out.println(line);
        }

    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

    }
}

其他功能：
获取请求参数通用方式：不论get还是post请求方式都可以使用下列方法来获取请求参数
1. String getParameter(String name):根据参数名称获取参数值 username=zs&password=123
2. String[] getParameterValues(String name):根据参数名称获取参数值的数组 hobby=xx&hobby=game
3. Enumeration getParameterNames():获取所有请求的参数名称
4. Map<String,String[]> getParameterMap():获取所有参数的map集合
如何解决中文乱码问题：
get方式：tomcat8已经将get方式乱码问题解决了
post方式：会乱码，通过设置request的编码request.setCharacterEnconding(“utf-8”)
请求转发：一种在服务器内部的资源跳转方式
1，通过request对象获取请求转发器对象：RequestDispatcher getRequestDispatcher(String path)
2,使用RequestDispatcher对象来进行转发：forward(ServletRequest
request,ServletResponse response)
特点：
1，浏览器地址栏路径不发生变化
2，只能转发到当前服务器内部资源中
3，转发是一次请求
共享数据：
域对象：一个有作用范围的对象，可以在范围内共享数据
request域：代表一次请求范围，一般用于请求转发的多个资源*享数据

package com.wzc.web.request;

import javax.servlet.RequestDispatcher;
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;
import java.util.Enumeration;
import java.util.Map;
import java.util.Set;

@WebServlet("/RequestDemo7")
public class RequestDemo7 extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        System.out.println("demo7777被访问了");
//        转发到demo8资源
      /*  RequestDispatcher requestDispatcher = request.getRequestDispatcher("/RequestDemo8");
        requestDispatcher.forward(request,response);*/
//        存储数据到request域中
        request.setAttribute("msg","hello");
        request.getRequestDispatcher("/RequestDemo8").forward(request,response);
    }
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

        this.doPost(request,response);
    }
}


package com.wzc.web.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;
import java.util.Enumeration;
import java.util.Map;
import java.util.Set;

@WebServlet("/RequestDemo8")
public class RequestDemo8 extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
//        获取数据
        Object msg = request.getAttribute("msg");
        System.out.println(msg);
        System.out.println("demo8888被访问了");
    }
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

        this.doPost(request,response);
    }
}

获取ServletContext：

package com.wzc.web.request;

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("/RequestDemo9")
public class RequestDemo9 extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        ServletContext servletContext = request.getServletContext();
        System.out.println(servletContext);
    }
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

        this.doPost(request,response);
    }
}
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