JavaWeb入门:HttpResponse和HttpRequest详解
短信预约 -IT技能 免费直播动态提醒
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。
![[外链图片转存失败,源站可能有防盗链机制,建议将图片保存下来直接上传(img-bAvaDBGw-1620739367741)(C:\Users\ASUS\Desktop\JavaWeb_study\JavaWeb\JavaWeb.assets\image-20210511163256716.png)]](/file/upload/202211/12/be4fy20jc3t.jpg)
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
@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
@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
![[外链图片转存失败,源站可能有防盗链机制,建议将图片保存下来直接上传(img-LGJQhKor-1620739367743)(C:\Users\ASUS\Desktop\JavaWeb_study\JavaWeb\JavaWeb.assets\image-20210511162434487.png)]](/file/upload/202211/12/0lpdbehidhh.jpg)
一个小demo 实现刷新 页面累加
@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
@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
![[外链图片转存失败,源站可能有防盗链机制,建议将图片保存下来直接上传(img-5VCR2LeF-1620739367746)(C:\Users\ASUS\Desktop\JavaWeb_study\JavaWeb\JavaWeb.assets\image-20210511162823603.png)]](/file/upload/202211/12/nyxyych3l54.jpg)
重定向 redirect
@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","www.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
@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
@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
获取请求携带的参数
@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("<h1>"+username+":"+password+"</h1>");
}
@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
doGet(req, resp);
}
}
![[外链图片转存失败,源站可能有防盗链机制,建议将图片保存下来直接上传(img-2zxGslkb-1620739367750)(C:\Users\ASUS\Desktop\JavaWeb_study\JavaWeb\JavaWeb.assets\image-20210511170056042.png)]](/file/upload/202211/12/ke2fow1t4os.jpg)
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<String> 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
@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
@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
本篇文章就到这里了，希望能给你带来帮助，也希望您能够多多关注编程网的更多内容！
免责声明：
① 本站未注明“稿件来源”的信息均来自网络整理。其文字、图片和音视频稿件的所属权归原作者所有。本站收集整理出于非商业性的教育和科研之目的，并不意味着本站赞同其观点或证实其内容的真实性。仅作为临时的测试数据，供内部测试之用。本站并未授权任何人以任何方式主动获取本站任何信息。
② 本站未注明“稿件来源”的临时测试数据将在测试完成后最终做删除处理。有问题或投稿请发送至: 邮箱/279061341@qq.com QQ/279061341
