JavaWeb入门:HttpResponse和HttpRequest详解

JavaWeb入门:HttpResponse和HttpRequest详解

目录HttpResponse 讲解HttpServletResponse概述:Response运行流程设置响应行设置响应头一个小demo 实现刷新 页面累加设置字符编码 解决中文乱码问题重定向 redirectrequest转发重定向和转发的区别文件下载HttpRequest 讲解HttpServletRequest概述Request 运行流程获取请求携带的参数获取多个参数的值获得请求行的信息request实现转发request是一个域对象ServletContext 作用域：request作用域：总结

HttpResponse 讲解

HttpServletResponse概述:

​ 在创建Servlet时会覆盖service()方法，或doGet()/doPost(),这些方法都有两个参数，一个为代表请求的request和代表响应response。service方法中的response的类http://型是ServletResponse，而doGet/doPost方法的response的类型是HttpServletResponse，HttpServletResponse是ServletResponse的子接口，功能和方法更加强大。

Response运行流程

响应头有很多这里只介绍常用的。

在浏览器可以按F12 抓包看响应头、请求头、具体的可以再查。

设置响应行

设置响应的状态码

/**

* @Author: crush

* @Date: 2021-05-09 19:35

* version 1.0

*/

@WebServlet("/test3")

public class HttpResponseTest3 extends HttpServlet {

@Override

protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {

System.out.println("设置状态码,前台通过判断状态码，来判断请求是否成功");

resp.setStatus(404);

}

@Override

protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {

doGet(req, resp);

}

}

测试

设置响应头

刷新 跳转页面

/**

* @Author: crush

* @Date: 2021-05-09 19:35

* version 1.0

*/

@WebServlet("/test4")

public class HttpResponseTest4 extends HttpServlet {

@Override

protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {

// 设置响应头 每1秒自动刷新

System.out.println("设置响应头 每1秒自动刷新");

resp.setHeader("Refresh", "1");

//定时跳转 3秒后将自动跳转

// resp.setHeader("Refresh","3;URL=hello.jsp");

}

@Override

protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {

doGet(req, resp);

}

}

测试

一个小demo 实现刷新 页面累加

/**

* response

* @author Adimi

*/

@WebServlet("/test4")

public class ResponseTest4 extends HttpServlet {

private static Integer id=1;

@Override

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

response.setHeader("Refresh","1");

PrintWriter writer = response.getWriter();

id++;

writer.print("id==>"+id);

}

@Override

protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {

doGet(req, resp);

}

}

设置字符编码 解决中文乱码问题

/**

* @Author: crush

* @Date: 2021-05-09 19:35

* version 1.0

*/

@WebServlet("/test1")

public class HttpResponseTest1 extends HttpServlet {

@Override

protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {

// 解决中文乱码问题

// 设置响应头

// 设置字符编码 resp.setCharacterEncoding("UTF-8");

// 设置响应内容以什么格式展示到页面 什么编码格式 包含了设置字符编码

resp.setContentType("text/html;charset=utf-8");

PrintWriter writer = resp.getWriter();

writer.print("中国,你好！！！");

}

@Override

protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {

doGet(req, resp);

}

}

测试

重定向 redirect

/**

* 重定向

* @Author: crush

* @Date: 2021-05-09 19:35

* version 1.0

*/

@WebServlet("/test5")

public class HttpResponseTest5 extends HttpServlet {

@Override

protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {

resp.sendRedirect("hello.jsp");

// resp.setHeader("location","baidu.com"); 通过设置响应头转发

}

@Override

protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {

doGet(req, resp);

}

}

request转发

/**

* 重定向

* @Author: crush

* @Date: 2021-05-09 19:35

* version 1.0

*/

@WebServlet("/test5")

public class HttpResponseTest5 extends HttpServlet {

@Override

protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {

// resp.sendRedirect("hello.jsp");

req.getRequestDispatcher("hello.jsp").forward(req,resp);

}

@Override

protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {

doGet(req, resp);

}

}

重定向和转发的区别

文件下载

获取路径资源

String path=this.getServletContext().getRealPath("WEB-INF\\classes\\8.jpg");

读取资源

FileInputStream fileInputStream=new FileInputStream(path);

获取到文件名，路径在电脑上保存的形式是 \ \

String fileName=path.substring(path.lastIndexOf("\\")+1);

设置消息头告诉浏览器，我要下载1.png这个图片 设置编码

resp.setHeader("Content-Disposition", "attachment; filename=" + URLEncoder.encode(fileName, "UTF-8"));

把读取到的内容回送给浏览器

int len=0;

byte[] bytes=new byte[1024];

// ServletOutputStream 提供用于将二进制数据发送到客户端的输出流

ServletOutputStream servletOutputStream=resp.getOutputStream();

while((len=fileInputStream.read(bytes))>0) {

servletOutputStream.write(bytes,0,len);

}

关闭资源

servletOutputStream.close();

fileInputStream.close();

注：8.jpg 放在我的resources 文件夹下 但是这里需要写的是编译完8.jpg存放的位置

具体代码

/**

* @Author: crush

* @Date: 2021-05-09 19:40

* version 1.0

*/

@WebServlet("/down")

public class ResponseDownFile extends HttpServlet {

@Override

protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {

//获取路径资源

String path=this.getServletContext().getRealPath("WEB-INF\\classes\\8.jpg");

//读取资源

FileInputStream fileInputStream=new FileInputStream(path);

//获取到文件名，路径在电脑上保存的形式是\\

String fileName=path.substring(path.lastIndexOf("\\")+1);

//设置消息头告诉浏览器，我要下载1.png这个图片

// 该方式文件名为中文时会乱码

//防止中文乱码

resp.setHeader("Content-Disposition", "attachment; filename=" + URLEncoder.encode(fileName, "UTF-8"));

//把读取到的内容回送给浏览器

int len=0;

byte[] bytes=new byte[1024];

ServletOutputStream servletOutputStream=resp.getOutputStream();

while((len=fileInputStream.read(bytes))>0) {

servletOutputStream.write(bytes,0,len);

}

// 关闭资源

servletOutputStream.close();

fileInputStream.close();

}

@Override

protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {

doGet(req, resp);

}

}

HttpRequest 讲解

HttpServletRequest概述

​ 我们在创建Servlet时会覆盖service()方法，或doGet()/doPost(),这些方法都有两个参数，一个为代表请求的request和代表响应response。service（）方法中写了根据请求方式的不同调用doget()和dopost().

service方法中的request的类型是ServletRequest，而doGet/doPost方法的request类型HttpServletRequest，HttpServletRequest是ServletRequest的子接口，功能和方法更加强大.

Request 运行流程

获取请求携带SpqSVM的参数

/**

* @Author: crush

* @Date: 2021-05-11 16:52

* version 1.0

*/

@WebServlet("/request1")

public class RequestTest1 extends HttpServlet {

@Override

protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {

// 这里是请求的参数名 必须是同名的

String username = req.getParameter("username");

String password = req.getParameter("password");

PrintWriter writer = resp.getWriter();

writer.print("

}

@Override

protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {

doGet(req, resp);

}

}

获取多个参数的值

@Override

protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {

// 设置请求的编码 不然会乱码

req.setCharacterEncoding("utf-8");

Enumeration names = req.getParameterNames();

while (names.hasMoreElements()) {

String name = (String) names.nextElement();

String[] values = req.getParameterValues(name);

System.out.println(name+":"+ Arrays.toString(values));

}

}

获得请求行的信息

/**

* @Author: crush

* @Date: 2021-05-11 16:52

* version 1.0

*/

@WebServlet("/request3")

public class RequestTest3 extends HttpServlet {

@Override

protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {

// 获得请求的url

StringBuffer requestURL = req.getRequestURL();

System.out.println("请求的URL===>"+requestURL);

// 获得请求的Servlet的路径

String path = req.getServletPath();

System.out.println("请求的Servlet的路径===>"+path);

//返回发出此请求的HTTP方法的名称，例如GET，POST或PUT

String method = req.getMethod();

System.out.println("返回发出此请求的HTTP方法的名称==>"+method);

//返回发送请求的客户端或最后一个代理的Internet协议（IP）地址

String remoteAddr = req.getRemoteAddr();

System.out.println("remoteAddr==>"+remoteAddr);

}

@Override

protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {

doGet(req, resp);

}

}

request实现转发

/**

* @Author: crush

* @Date: 2021-05-11 16:52

* version 1.0

*/

@WebServlet("/request2")

public class RequestTest2 extends HttpServlet {

@Override

protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {

// 访问request2 转发到 request4去

req.getRequestDispatcher("/request4").forward(req,resp);

}

@Override

protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {

doGet(req, resp);

}

}

request是一个域对象

request对象也是一个存储数据的区域对象，所以也具有如下方法：

setAttribute(String name, Object o)

getAttribute(String name)

removeAttribute(String name)

ServletContext 作用域：

创建：启动web应用程序的时候创建

销毁：关闭web应用程序的时候销毁

域的作用范围：整个web应用的启动周期

request作用域：

创建：访问时创建request

销毁：响应结束request销毁

域的作用范围：一次请求中

总结

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