request对象和response对象分析

深藏阁楼爱情的钟 2023-10-06 21:47 49阅读 0赞

**目录**

request对象

一个doGet小项目：

乱码问题：

请求转发

request作用域

response对象

①:response的主要方法

②:响应乱码问题

--------------------

### request对象 ###

> 是当客户端向服务器端发送请求时，服务器为本次请求创建request对象，并在调用Servlet的service方法时，将该对象传递给service方法。Request对象中封装了客户端发送过来的所有的请求数据。

![watermark_type_d3F5LXplbmhlaQ_shadow_50_text_Q1NETiBA5Y-r5oiR6ICB5Lyv_size_20_color_FFFFFF_t_70_g_se_x_16][]

**解释：**

我们在浏览器中使用，任何操作构成请求信息，发送给reuqest对象，然后发送给Servlet接口下面的service，往下传到HttpServlet。

#### **一个doGet小项目：** ####

RegisServlet.java

package com.qcby.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;
    
    import org.apache.catalina.User;
    
    @WebServlet("/regist")
    public class RegisServlet extends HttpServlet{
    
    	@Override
    	protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
    		// TODO Auto-generated method stub
    		String username = req.getParameter("username");
    		String password = req.getParameter("password");
    		
    		System.out.println(username + " " + password);
    	}
    
    }

rigist.html

<!DOCTYPE html>
    <html>
    <head>
    <meta charset="UTF-8">
    <title>Insert title here</title>
    </head>
    <body>
    	<form action="/JiuYueServices/regist" method="get"> 
    		用户名：<input type="text" name="username"/>
    		密码：<input type="text" name="password"/>
    		<input type="submit" value="注册">
    	</form>
    </body>
    </html>

> <form action="/JiuYueServices/regist" method="get">这里面的JiuYueServices是项目名

**成功:**

![watermark_type_d3F5LXplbmhlaQ_shadow_50_text_Q1NETiBA5Y-r5oiR6ICB5Lyv_size_13_color_FFFFFF_t_70_g_se_x_16][]

#### **乱码问题：** ####

> 由于request是接收来自用户的请求，服务器会根据编码格式将请求转换。服务器端默认的编码格式为ISO-8859-1(此编码不支持中文)，而我们用户浏览器默认是utf-8的编码格式，所以往往会产生乱码。要想解决乱码问题，需要设置request当中的编码格式，告诉服务器以何种形式来解析数据。或者在接收到乱码以后，通过何种编码格式进行还原

![watermark_type_d3F5LXplbmhlaQ_shadow_50_text_Q1NETiBA5Y-r5oiR6ICB5Lyv_size_20_color_FFFFFF_t_70_g_se_x_16 1][]

**解决方法：**

方式一：（所有）

request.setCharacterEncoding("UTF-8");

方式二：（借助String对象的方法，该种方式对任何请求有效，都是通用的）

new String(request.getParameter(name).getBytes("ISO-8859-1"),"UTF-8"))

#### **请求转发** ####

> 请求转发是一种服务器行为，当客户端请求到达后，服务器进行转发，此时会将请求对象进行保存，地址栏中的url地址不会发生改变，得到相应后，服务器端会将请求发送给客户端，从始至终只有一个请求发出。

request.getRequestDispatcher(url).forward(request, response);

**两个servlet：**

/**
     * 
     * @author lenovo
     *         请求转发跳转
     *                 可以让服务器端跳转到客户端(或者指定的(Servlet)
     *           特点：	
     *     1.服务器端行为      
     *     2.地址栏不会发生改变
     *     3.从始至终都是一个请求
     *     4.request当中的数据在servlet程序中共享
     */
    @WebServlet(value="/s01")
    public class Servlet01 extends HttpServlet{
    	@Override
    	protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
    		// TODO Auto-generated method stub
    		String username  = req.getParameter("username");
    		String password = req.getParameter("password");
    		System.out.println("s01="+username + " " + password);
    		// 请求跳转到Servlet02
    		//req.getRequestDispatcher("s02").forward(req, resp);
    		//请求发送到html页面
    		req.getRequestDispatcher("RegistServlet.html").forward(req, resp);
    	
    	}
    }

@WebServlet(value="/s02")
    public class Servlet02 extends HttpServlet{
          @Override
        protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        	// TODO Auto-generated method stub
                 req.setCharacterEncoding("UTF-8");
        	  String username  = req.getParameter("username");
      		String password = req.getParameter("password");
      		System.out.println("s02=" + username + " " + password);
        }
    }

**运行起来我们发现s01和s02都会输出，且只是请求了一次**

![watermark_type_d3F5LXplbmhlaQ_shadow_50_text_Q1NETiBA5Y-r5oiR6ICB5Lyv_size_20_color_FFFFFF_t_70_g_se_x_16 2][]

![watermark_type_d3F5LXplbmhlaQ_shadow_50_text_Q1NETiBA5Y-r5oiR6ICB5Lyv_size_20_color_FFFFFF_t_70_g_se_x_16 3][]

#### request作用域 ####

request表示一个请求，只要发出一个请求就会创建一个request对象，他的作用域：仅在当前请求中有效。

用处:常用于服务器间同一请求不同页面之间的参数传递，常用于表单的控制值传递。

**常用的方法**

<table style="width:500px;"> 
 <tbody> 
  <tr> 
   <td>request.setAttribute(String name,Object value)</td> 
   <td>设置域对象内容</td> 
   <td></td> 
  </tr> 
  <tr> 
   <td>request.getAttribute(String name)</td> 
   <td>获取域对象内容</td> 
   <td></td> 
  </tr> 
  <tr> 
   <td>request.removeAttribute(String name)</td> 
   <td>删除域对象内容</td> 
   <td></td> 
  </tr> 
 </tbody> 
</table>

**两个servlet**

@WebServlet("/s03")
    public class Servlet03 extends HttpServlet{
    	
    	@Override
    	protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
    		// TODO Auto-generated method stub
    		System.out.println("我是03");
    		req.setAttribute("user", "qcby");
        	req.setAttribute("age", 18);
                    		
        	req.getRequestDispatcher("s04").forward(req, resp);
    
    	}
    
    }

@WebServlet("/s04")
    public class Servlet04 extends HttpServlet{
          @Override
        protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        	// TODO Auto-generated method stub
        	System.out.println("我是04");
        	System.out.println(req.getAttribute("user"));
        	System.out.println(req.getAttribute("age"));
        }
    }

访问：http://localhost:8080/SecondServlet/s03

![watermark_type_d3F5LXplbmhlaQ_shadow_50_text_Q1NETiBA5Y-r5oiR6ICB5Lyv_size_10_color_FFFFFF_t_70_g_se_x_16][]

### response对象 ###

![watermark_type_d3F5LXplbmhlaQ_shadow_50_text_Q1NETiBA5Y-r5oiR6ICB5Lyv_size_20_color_FFFFFF_t_70_g_se_x_16 4][]

![watermark_type_d3F5LXplbmhlaQ_shadow_50_text_Q1NETiBA5Y-r5oiR6ICB5Lyv_size_20_color_FFFFFF_t_70_g_se_x_16 5][]

#### **①:response的主要方法** ####

<table style="width:500px;"> 
 <tbody> 
  <tr> 
   <td>getWriter()</td> 
   <td>获取字符流(只能相应字符串数据)</td> 
  </tr> 
  <tr> 
   <td>getOutputStream()</td> 
   <td>获取字节流(能相应一切数据)</td> 
  </tr> 
 </tbody> 
</table>

**getWriter()**

@WebServlet("/regist")
    public class RegistServlet  extends HttpServlet{
    	
    	
    	@Override
    	protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
    		
    		
    		
    		PrintWriter printWriter = resp.getWriter();
    		printWriter.print("success");
    	
    	}
    
    }

**getOutputStream()**

@WebServlet("/regist")
    public class RegistServlet  extends HttpServlet{
    	
    	
    	@Override
    	protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
    		// TODO Auto-generated method stub
    		// PrintWriter writer = resp.getWriter();
    		// writer.print("success");
    		ServletOutputStream stream  = resp.getOutputStream();
    		stream.write("Success".getBytes());
    		
    	}
    
    }

**html**

<!DOCTYPE html>
    <html>
    <head>
    <meta charset="UTF-8">
    <title>Insert title here</title>
    </head>
    <body>
    	<form action="/SecondServlet/regist" method="post"> 
    		用户名：<input type="text" name="username"/>
    		密码：<input type="text" name="password"/>
    		<input type="submit" value="注册">
    	</form>
    </body>
    </html>

#### **②:响应乱码问题** ####

response.setCharacterEncoding("UTF-8");
    response.setHeader("content-type", "text/html;charset=UTF-8");

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