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Request+Response

NicoalsNC 2023-08-19 阅读 59
javatomcatmaven

文章目录

1. 介绍

Request+Response

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@WebServlet("/demo3")
public class ServletDemo3 extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //使用request对象 获取请求数据
        String name = request.getParameter("name");//url?name=zhangsan

        //使用response对象 设置响应数据
        response.setHeader("content-type","text/html;charset=utf-8");
        response.getWriter().write("<h1>"+name+",欢迎您！</h1>");
    }

    @Override
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        System.out.println("Post...");
    }
}

2. Request对象

2.1 Request继承体系

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  • Tomcat需要解析请求数据，封装为request对象并且创建request对象传递到service方法中;

2.2 Request获取请求数据

1.获取请求行

请求行 方法说明
String getMethod()获取请求方式: GET
String getContextPath()获取虚拟目录(项目访问路径): /request-demo
StringBuffer getRequestURL()获取URL(统一资源定位符): http://localhost:8080/request-demo/req1
String getRequestURI()获取URI(统一资源标识符): /request-demo/req1
String getQueryString()获取请求参数(GET方式): username=zhangsan&password=123
//获取请求行
@WebServlet("/demo3")
public class ServletDemo3 extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        // String getMethod()：获取请求方式： GET
        String method = req.getMethod();
        System.out.println(method);//GET
        // String getContextPath()：获取虚拟目录(项目访问路径)：/request-demo
        String contextPath = req.getContextPath();
        System.out.println(contextPath);
        // StringBuffer getRequestURL(): 获取URL(统一资源定位符)：http://localhost:8080/request-demo/req1
        StringBuffer url = req.getRequestURL();
        System.out.println(url.toString());
        // String getRequestURI()：获取URI(统一资源标识符)： /request-demo/req1
        String uri = req.getRequestURI();
        System.out.println(uri);
        // String getQueryString()：获取请求参数（GET方式）： username=zhangsan
        String queryString = req.getQueryString();
        System.out.println(queryString);
    }
    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
    }

}

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2.获取请求头

请求头 方法说明
String getHeader(String name)获取指定名称的请求头

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```java
/**
 * request 获取请求数据
 */
@WebServlet("/req1")
public class RequestDemo1 extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        //获取请求头: user-agent: 浏览器的版本信息
        String agent = req.getHeader("user-agent");
		System.out.println(agent);
    }
    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
    }
}

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3.获取请求体

请求体 方法说明
ServletInputStream getInputStream()获取字节输入流，如果前端发送的是字节数据，比如传递的是文件数据，则使用该方法
BufferedReader getReader()获取字符输入流，如果前端发送的是纯文本数据，则使用该方法
package com.itheima.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.BufferedReader;
import java.io.IOException;

@WebServlet("/demo4")
public class ServletDemo4 extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
    }
    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        //获取post 请求体：请求参数
        //1. 获取字符输入流
        BufferedReader br = req.getReader();
        //2. 读取数据
        String line = br.readLine();
        System.out.println(line);
    }
}


<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>测试获取请求体信息</title>
</head>
<body>
<h5>hello</h5>
<form action="/demo4" method="post">
  <input type="text" name="username">
  <input type="password" name="password">
  <input type="submit">

</form>

</body>
</html>

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4. 请求参数的通用方式

//实现
@WebServlet("/req1")
public class RequestDemo1 extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {

        String result = req.getQueryString();
        System.out.println(result);

    }
    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        BufferedReader br = req.getReader();
        String result = br.readLine();
        System.out.println(result);
    }
}

解决方案一:

@WebServlet("/req1")
public class RequestDemo1 extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        //获取请求方式
        String method = req.getMethod();
        //获取请求参数
        String params = "";
        if("GET".equals(method)){
            params = req.getQueryString();
        }else if("POST".equals(method)){
            BufferedReader reader = req.getReader();
            params = reader.readLine();
        }
        //将请求参数进行打印控制台
        System.out.println(params);
      
    }
    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        this.doGet(req,resp);
    }
}

解决方案二:

方法说明
Map<String,String[]> getParameterMap()获取所有参数Map集合
String[] getParameterValues(String name)根据名称获取参数值（数组）
String getParameter(String name)根据名称获取参数值(单个值)
<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
<form action="/req" method="get">
  <input type="text" name="username"><br>
  <input type="password" name="password"><br>
  <input type="checkbox" name="hobby" value="1"> 游泳
  <input type="checkbox" name="hobby" value="2"> 爬山 <br>
  <input type="submit">

</form>
</body>
</html>

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//使用get获取请求信息
@WebServlet("/req")
public class ServletDemo5 extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        //GET请求逻辑
        System.out.println("get....");
        //1. 获取所有参数的Map集合
        Map<String, String[]> map = req.getParameterMap();
        for (String key : map.keySet()) {
            // username:zhangsan lisi
            System.out.print(key+":");

            //获取值
            String[] values = map.get(key);
            for (String value : values) {
                System.out.print(value + " ");
            }

            System.out.println();
            //2.根据key获取值
            System.out.println("------------");
            String[] hobbies = req.getParameterValues("hobby");
            for (String hobby : hobbies) {
                System.out.println(hobby);
            }

            //3.根据key获取单个参数值
            String username = req.getParameter("username");
            String password = req.getParameter("password");
            System.out.println(username);
            System.out.println(password);
        }
    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        super.doPost(req, resp);
    }
}

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IDEA模板创建Servlet：102
https://www.bilibili.com/video/BV1Qf4y1T7Hx
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5. 解决中文乱码问题

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post：

req.setCharacterEncoding("UTF-8");

解决：https://blog.csdn.net/yiqieanhaowzq/article/details/126279078

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username  = new String(username.getBytes(StandardCharsets.ISO_8859_1),
                StandardCharsets.UTF_8);

2.3 Request请求转发

方法说明
request.getRequestDispatcher(“/destination”);获取RequestDispatcher对象
dispatcher.forward(request, response);请求转发
package com.itheima.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("/demo6")
public class ServletDemo6 extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        System.out.println("demo6...get");
        //请求转发
        req.getRequestDispatcher("/demo7").forward(req,resp);
    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        super.doPost(req, resp);
    }
}


package com.itheima.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("/demo7")
public class ServletDemo7 extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        System.out.println("demo7...get");
    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        super.doPost(req, resp);
    }
}

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请求转发资源间共享数据:

需要使用request对象提供的三个方法:

方法说明
void setAttribute(String name,Object o)存储数据到request域中
Object getAttribute(String name);根据key，获取值
void removeAttribute(String name);根据key，删除该键值对
@WebServlet("/demo6")
public class ServletDemo6 extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        System.out.println("demo6...get");

        //存储数据
        req.setAttribute("msg","hello");

        //请求转发
        req.getRequestDispatcher("/demo7").forward(req,resp);
    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        super.doPost(req, resp);
    }
}


@WebServlet("/demo7")
public class ServletDemo7 extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        System.out.println("demo7...get");

        //获取数据
        Object msg = req.getAttribute("msg");
        System.out.println(msg);
    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        super.doPost(req, resp);
    }
}

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3. Response对象

3.0 Response 继承体系

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3.1 Response设置响应数据的功能介绍

1.设置响应行

方法说明
void setStatus(int sc);设置响应状态码

2.设置响应头

方法说明
void setHeader(String name,String value)设置响应头键值对

3.设置响应体

方法说明
PrintWriter getWriter();获取字符输出流
ServletOutputStream getOutputStream();获取字节输出流

3.2 Response完成重定向

resp.setStatus(302);
resp.setHeader("location","资源B的访问路径");

Q:Response重定向和Request请求转发有什么区别？
- 重定向是一种服务器响应行为，要求客户端重新发起请求。
  客户端会接收到新的URL信息，并据此发起新的请求。
- 请求转发是一种服务器内部行为，将客户端的请求转发给其他资源或处理程序来处理。
  客户端对此转发过程是不可见的。
- 重定向会向客户端发送额外的响应，通常包含重定向的状态码和新的URL信息。
  请求转发不需要额外的响应，客户端不知道请求被转发了。
- 重定向可以用于资源移动、负载均衡和认证授权等场景。
  请求转发通常用于服务器内部组织和处理请求的需要。
- 重定向浏览器地址栏会发生变化，请求转发地址栏不会发生变化


//重定向
@WebServlet("/resp1")
public class ResponseDemo1 extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        System.out.println("resp1......");

        //重定向
        //1.设置响应状态码302
        resp.setStatus(302);

        //2. 设置响应头
        resp.setHeader("Location","/resp2");


        //简化方式重定向
        resp.sendRedirect("/resp2");

    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        super.doPost(req, resp);
    }
}



@WebServlet("/resp2")
public class ResponseDemo2 extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        System.out.println("resp2......");
    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        super.doPost(req, resp);
    }
}

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3.3 设置响应数据

方法说明
PrintWriter getWriter();获取字符输出流
ServletOutputStream getOutputStream();获取字节输出流

1. Response响应字符数据

设置响应的内容类型为text/html
 //resp.setHeader("content-type","text/html");
resp.setContentType("text/html");
resp.setContentType("text/html"；charset=utf-8);

设置响应的状态码
resp.setStatus(HttpServletResponse.SC_OK);

设置响应的字符编码：
resp.setCharacterEncoding("UTF-8");

设置响应的头部信息：
resp.setHeader("Cache-Control", "no-cache");
resp.setHeader("Expires", "0");

设置响应的重定向：
resp.sendRedirect("https://www.example.com");

设置响应的Cookie：
Cookie cookie = new Cookie("name", "value");
cookie.setMaxAge(3600); // 设置Cookie的有效期
cookie.setPath("/"); // 设置Cookie的作用路径
resp.addCookie(cookie); // 将Cookie添加到响应中

设置响应的内容长度：
resp.setContentLength(content.length());

设置响应的响应类型：
resp.setContentType("application/json");

@WebServlet("/resp3")
public class ResponseDemo3 extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        System.out.println("resp3......");
        
        //1.获取字符输出流
        PrintWriter writer = resp.getWriter();
        
        //2.设置响应的内容类型为text/html
        //resp.setHeader("content-type","text/html");
        resp.setContentType("text/html");
        
        //3.向客户端输出文本内容
        writer.write("aaa");
        
        //4.向客户端输出HTML标签
        writer.write("<h1>aaa</h1>");
        
        //5.刷新缓冲区，确保所有内容都被写入响应
        writer.flush();
        
        //6.关闭输出流
        writer.close();
    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        super.doPost(req, resp);
    }
}

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2. Response响应字节数据

//响应字节数据：设置字节数据响应体
@WebServlet("/resp4")
public class ResponseDemo4 extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        System.out.println("resp4......");

        //0.读取文件
        FileInputStream fileInputStream = new FileInputStream("C:\\Users\\11445\\Pictures\\Saved Pictures\\头像.jpg");


        //1.获取字节输出留,用于向客户端发送响应的字节数据。
        ServletOutputStream outputStream = resp.getOutputStream();

        //2.完成流的copy
        byte[] bytes = new byte[1024];  //创建一个字节数组，用于存储文件内容。
        int len = 0;  //定义一个变量 len，用于记录每次读取的字节长度。

        //循环读取文件内容，每次最多读取 1024 个字节，直到文件末尾
        while ((len = fileInputStream.read(bytes) )!= -1){
            outputStream.write(bytes,0,len);  //将读取到的字节数据写入到输出流中，发送给客户端。
        }

        fileInputStream.close();

    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        super.doPost(req, resp);
    }
}

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简化流的copy

    <dependency>
      <groupId>commons-io</groupId>
      <artifactId>commons-io</artifactId>
      <version>2.6</version>
    </dependency>

//2.完成流的copy
        IOUtils.copy(fileInputStream,outputStream);

4.案例：用户登录/用户注册

登录注册案例：https://blog.csdn.net/meini32/article/details/132305323

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