标签:http servlet request 笔记 学习 cookie import Servlet javax
第一个servlet程序
第一种方式
package com.hz.servlet;
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("/ser01")//浏览器路径
public class servlet01 extends HttpServlet{
@Override
protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
//打印内容
System.out.println("hello servlet");
//通过流输出数据到浏览器
resp.getWriter().write("hello servlet");
}
}
第二种方式
package com.hz.servlet;
import javax.servlet.GenericServlet;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.annotation.WebServlet;
import java.io.IOException;
@WebServlet("/s2")
public class servlet02 extends GenericServlet {
@Override
public void service(ServletRequest servletRequest, ServletResponse servletResponse) throws ServletException, IOException {
System.out.println("继承GenericServlet方式...");
}
}
第三种方式
package com.hz.servlet;
import javax.servlet.*;
import javax.servlet.annotation.WebServlet;
import java.io.IOException;
@WebServlet("/s3")
public class servlet03 implements Servlet {
@Override
public void init(ServletConfig servletConfig) throws ServletException {
}
@Override
public ServletConfig getServletConfig() {
return null;
}
@Override
public void service(ServletRequest servletRequest, ServletResponse servletResponse) throws ServletException, IOException {
System.out.println("实现servlet接口....");
}
@Override
public String getServletInfo() {
return null;
}
@Override
public void destroy() {
}
}
servlet生命周期
package com.hz.servlet;
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("/s4")
public class Servlet04 extends HttpServlet {
/**
* 就绪/服务方法(处理请求数据)
* 系统方法,服务器自动调用
* 当有请求到达servlet时,就会调用该方法
* 该方法可以被多次调用
* @param req
* @param resp
* @throws ServletException
* @throws IOException
*/
@Override
protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
System.out.println("servlet被调用了");
}
/**
* 销毁方法
* 系统方法,服务器自动调用
* 当服务器关闭或应用程序停止时,调用该方法
* 这个方法也只执行一次
*/
@Override
public void destroy() {
System.out.println("servlet被销毁了");
}
//初始化方法 系统方法,服务器自动调用 当请求到达servlet容器时,servlet会判断该servlet对象是否存在,如果不存在,则创建实例并初始化
// 方法只会执行一次。
@Override
public void init() throws ServletException {
System.out.println("servlet被创建了");
}
}
常用方法
package com.hz.servlet02;
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("/s001")
public class Servlet01 extends HttpServlet {
@Override
protected void service(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
/**
* 常用方法
* 1.获取请求时的完整路径(从http开始到?前面结束)
* 2.获取请求时部分路径(从项目的站点名开始,到?前面结束)
* 3.获取请求时的参数字符串(从?后面开始,到最后的字符串)
* 4.获取请求方式(GET/POST)
* 5.获取协议版本(HTTP/1.1)
* 6.获取项目的站点名(项目的对外访问路径)
*/
String url = request.getRequestURL().toString();
System.out.println("请求时完整路径"+url);
String uri= request.getRequestURI().toString();
System.out.println("获取部分路径"+uri);
String queryString = request.getQueryString();
System.out.println("获取请求时的参数字符串"+queryString);
String method = request.getMethod();
System.out.println("获取请求方式"+method);
String protocol = request.getProtocol();
System.out.println("获取当前的协议版本"+protocol);
String contextPath = request.getContextPath();
System.out.println("获取项目的站点名"+contextPath);//上下文路径
/**
* 获取请求的参数
* 1.获取指定名称的参数值,返回字符串(!!!!!)
* 2.获取指定名称的参数的所有参数值(用于复选框传值)
*/
String uname=request.getParameter("uname");
String upwd=request.getParameter("upwd");
System.out.println("uname:" +uname);
System.out.println("upwd:" +upwd);
String[] hobbys=request.getParameterValues("hobby");
//判断数组是否为空
if (hobbys!=null&&hobbys.length>0){
for (String hobby: hobbys){
System.out.println("爱好:"+hobby);
}
}
}
}
打印输出结果
请求乱码问题
package com.hz.servlet02;
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;
/**乱码原因:
* 由于在解析过程中默认使用的编码格式为ISO-8859-1(此编码不支持中文),所以解析时一定会出现乱码
* 请求乱码问题
* Tomcat 8以上版本 GET请求不会乱码
* POST请求会乱码,通过设置服务器解析编码格式
* //设置请求的编码格式 放在获取参数前面
* req.setCharacterEncoding("UTF-8");
*
* 乱码情况
* POST请求:无论什么版本的服务器,post请求中文都会乱码 解决方式 req.setCharacterEncoding("UTF-8");
* 注意:req.setCharacterEncoding("UTF-8"); 只针对POST请求乱码
*/
@WebServlet("/s002")
public class Servlet02 extends HttpServlet {
@Override
protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
//设置请求的编码格式 放在获取参数前面
req.setCharacterEncoding("UTF-8");
//获取客户端传递的参数
String uname = req.getParameter("uname");
String upwd = req.getParameter("upwd");
System.out.println("姓名:"+ uname);
System.out.println("密码:"+ upwd);
}
}
请求转发
package com.hz.servlet02;
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;
/**
*请求转发跳转 request.getRequestDispatcher(url).forward(request,response);
* 可以让请求从服务器跳转到客户端(或者转到指定的Servlet)
*
* 特点:
* 1.服务端行为
* 2.地址栏不发生改变
* 3.从始至终只有一个请求
* 4.数据可以共享
*/
@WebServlet("/s003")
public class Servlet03 extends HttpServlet {
@Override
protected void service(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
//接收参数
String uname = request.getParameter("uname");
System.out.println("Servlet03 uname" +uname);
//请求转发到servlet04
// request.getRequestDispatcher("s004").forward(request,response);
//请求转发到jsp页面
// request.getRequestDispatcher("login.jsp").forward(request,response);
//请求转发到html页面
request.getRequestDispatcher("login.html").forward(request,response);
}
}
获取域对象内容
package com.hz.servlet02;
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.ArrayList;
import java.util.List;
/**
*request作用域
* 通过该对象可以再一个请求中传递数据,作用范围:在一次请求中有效,即服务器跳转有效(请求转发跳转时有效)
*
*/
@WebServlet("/s005")
public class Servlet05 extends HttpServlet {
@Override
protected void service(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
System.out.println("servlet05..........");
//设置域对象
request.setAttribute("name","admin");
request.setAttribute("age",18);
List<String> list= new ArrayList<>();
list.add("aaaa");
list.add("bbbb");
request.setAttribute("list",list);
//请求转发跳转到servlet06
// request.getRequestDispatcher("s006").forward(request,response);
//请求转发跳转到jsp 并通过域对象传递数据
request.getRequestDispatcher("index.jsp").forward(request,response);
}
}
<%@ page import="java.util.List" %>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
<title>$Title$</title>
</head>
<body>
<h2>index页面</h2>
<%-- 若果要在jsp中写java代码,需要写在脚本段中--%>
<%
//获取域对象
//获取域对象内容
String name= (String) request.getAttribute("name");
System.out.println("name:"+name);
Integer age= (Integer) request.getAttribute("age");
System.out.println("age:"+age);
List<String> list= (List<String>) request.getAttribute("list");
System.out.println(list.get(0));
%>
</body>
</html>
HttpResponse
package com.hz.servlet;
import javax.servlet.ServletException;
import javax.servlet.ServletOutputStream;
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.io.PrintWriter;
import java.nio.charset.StandardCharsets;
/**
* 响应数据
* getWrite() 字符输出流 输出字符串
* getOutputStream() 字节输出流 输出一切数据
*
* 两种流不可同时使用,同时使用会报错
* java.lang.IllegalStateException: 已为此响应调用getWriter()
*
*/
@WebServlet("/s01")
public class Servlet01 extends HttpServlet {
@Override
protected void service(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// getWrite() 字符输出流 输出字符串
//获取字符输出流
PrintWriter writer = response.getWriter();
//输出数据
writer.write("hello");
//getOutputStream() 字节输出流
//得到字节输出流
ServletOutputStream outputStream = response.getOutputStream();
//输出数据
outputStream.write("HI".getBytes());
}
}
字符流响应数据乱码问题
package com.hz.servlet;
import javax.servlet.ServletException;
import javax.servlet.ServletOutputStream;
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.io.PrintWriter;
import java.nio.charset.StandardCharsets;
/**
* 字符流响应数据
* 乱码解决:
* 1.设置服务端的编码格式
* response.setCharacterEncoding("UTF-8");
* 2.设置客户端的编码格式
* response.setHeader("content-type","text/html;charset=UTF-8");
*
* 总结:设置服务器端和客户端的编码都支持中文,且保持一致
*
* 同时设置客户端和服务端的编码
*response.setContentType("text/html;charset=UTF-8");
*/
@WebServlet("/s02")
public class Servlet02 extends HttpServlet {
@Override
protected void service(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// getWrite() 字符输出流 输出字符串
/*//设置服务端编码格式
response.setCharacterEncoding("UTF-8");
//设置客户端的编码格式和响应的MIME类型
response.setHeader("content-type","text/html;charset=UTF-8");*/
//同时设置服务端和客户端的编码格式
response.setContentType("text/html;charset=UTF-8");
//获取字符输出流
PrintWriter writer = response.getWriter();
//输出数据
writer.write("<h2>你好呀</h2>");
}
}
字节流乱码格式解决
import javax.servlet.ServletException;
import javax.servlet.ServletOutputStream;
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.io.PrintWriter;
/**
* 字节流响应数据
*
*/
@WebServlet("/s03")
public class Servlet03 extends HttpServlet {
@Override
protected void service(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
//getOutputStream() 字节输出流
//同时设置服务端和客户端的编码格式
response.setContentType("text/html;charset=UTF-8");
//得到字节输出流
ServletOutputStream outputStream = response.getOutputStream();
//输出数据
outputStream.write("<h2>你好</h2>".getBytes());
}
}
重定向
package com.hz.servlet;
import javax.servlet.ServletException;
import javax.servlet.ServletOutputStream;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
/**
* 重定向
* 服务端指导,客户端行为
* 存在两次请求
* 地址栏会发生改变
*/
@WebServlet("/s04")
public class Servlet04 extends HttpServlet {
@Override
protected void service(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
System.out.println("Servlet04........");
//接收参数
String uname = request.getParameter("uname");
System.out.println("servlet04:"+uname);
//重定向到s05
response.sendRedirect("s05");
}
}
package com.hz.servlet;
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;
/**
* 重定向
*/
@WebServlet("/s05")
public class Servlet05 extends HttpServlet {
@Override
protected void service(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
System.out.println("Servlet05........");
//接收参数
String uname = request.getParameter("uname");
System.out.println("servlet05:"+uname);
}
}
请求转发和重定向区别
请求转发request.getRequestDispatcher().forward() | 重定向response.sendRedirect(); |
---|---|
一次请求,数据在request域中共享 | 两次请求,request域中数据不共享 |
服务器端行为 | 客户端行为 |
地址栏不会发生变化 | 地址栏发生变化 |
绝对地址定位到站点后 | 绝对地址可写到http:// |
package com.hz.servlet;
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;
/**
* 请求转发与重定向区别
* 1.请求转发地址栏不会发生改变,重定向的地址栏会发生改变
* 2.请求转发只有一次请求,重定向有两次请求
* 3.请求转发request对象可共享,重定向request不共享
* 4.请求转发是服务端行为,重定向是客户端行为
* 5.请求转发的地址只能是当前站点下(当前项目)的资源,重定向时地址可以是任何地址
*/
@WebServlet("/s06")
public class Servlet06 extends HttpServlet {
@Override
protected void service(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
System.out.println("Servlet06........");
//接收参数
String uname = request.getParameter("uname");
System.out.println(uname);
//设置request域对象
request.setAttribute("upwd","123456");
//请求转发
// request.getRequestDispatcher("index.jsp").forward(request,response);
//重定向跳转到百度
// response.sendRedirect("http://www.baidu.com");
//请求转发到百度(404找不到)
request.getRequestDispatcher("http://www.baidu.com").forward(request,response);
}
}
Cookie对象
cookie创建
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.Cookie;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
/**
* Cookie的创建和发送
*/
@WebServlet("/cook01")
public class Cookie01 extends HttpServlet {
@Override
protected void service(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
//cookie的创建
Cookie cookie = new Cookie("name","admin");
//发送(响应)cookie对象
response.addCookie(cookie);
}
}
cookie获取
package com.hz.cookie;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.Cookie;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
/**
* Cookie获取
* 返回的是cookie数组
*/
@WebServlet("/cook02")
public class Cookie02 extends HttpServlet {
@Override
protected void service(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
//获取cookie数组
Cookie[] cookies= request.getCookies();
//判断cookie是否为空
if (cookies!=null&&cookies.length>0){
//遍历cookie数组
for (Cookie cookie : cookies) {
//获取cookie的名称和值
String name=cookie.getName();
String value=cookie.getValue();
System.out.println("名称:"+name);
System.out.println("值:"+value);
}
}
}
}package com.hz.cookie;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.Cookie;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
/**
* Cookie获取
* 返回的是cookie数组
*/
@WebServlet("/cook02")
public class Cookie02 extends HttpServlet {
@Override
protected void service(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
//获取cookie数组
Cookie[] cookies= request.getCookies();
//判断cookie是否为空
if (cookies!=null&&cookies.length>0){
//遍历cookie数组
for (Cookie cookie : cookies) {
//获取cookie的名称和值
String name=cookie.getName();
String value=cookie.getValue();
System.out.println("名称:"+name);
System.out.println("值:"+value);
}
}
}
}
cook到期时间
package com.hz.cookie;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.Cookie;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
/**
* cookie的到期时间
*/
@WebServlet("/cook03")
public class Cookie03 extends HttpServlet {
@Override
protected void service(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
//到期时间:负整数(默认值-1 表示只在浏览器内存中存活,关闭浏览器失效)
Cookie cookie = new Cookie("uname1","张三");
cookie.setMaxAge(-1);//关闭浏览器失效
response.addCookie(cookie);
//到期时间:正整数(表示存活指定秒数,会将数据存在磁盘中)
Cookie cookie2 = new Cookie("uname1","张三");
cookie.setMaxAge(30);//存活30秒
response.addCookie(cookie2);
//到期时间:0(表示删除cookie)
Cookie cookie3 = new Cookie("uname1","张三");
cookie.setMaxAge(0);//删除cookie
response.addCookie(cookie3);
}
}
cookie乱码问题
package com.hz.cookie;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.Cookie;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.net.URLDecoder;
import java.net.URLEncoder;
/**
* cookie的到期时间
*/
@WebServlet("/cook04")
public class Cookie04 extends HttpServlet {
@Override
protected void service(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
//cookie存中文
String name="姓名";
String value="李四";
//将中文通过编码
name= URLEncoder.encode(name);
value=URLEncoder.encode(value);
//创建cookie对象
Cookie cookie = new Cookie(name,value);
//响应cookie
response.addCookie(cookie);
//获取cookie通过解码获取
Cookie[] cookies=request.getCookies();
//判断非空
if (cookies!=null&&cookies.length>0){
//遍历
for (Cookie cookie1 : cookies) {
//解码
System.out.println(URLDecoder.decode(cookie1.getName()));
System.out.println(URLDecoder.decode(cookie1.getValue()));
}
}
}
}
cookie注意点:
- cookie只在当前浏览器中有效(不跨浏览器和电脑)
- cookie不能存中文
- 如果一定要存中文需要通过URLEncoder.encode()方法进行编码,获取时通过URLDecoder().decode()方法进行解码
- 如果出现同名的cookie对象,则会覆盖
- cookie的存储数量是有上限的,不同浏览器的
cookie的路径问题
package com.hz.cookie;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.Cookie;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.net.URLDecoder;
import java.net.URLEncoder;
/**
* cookie的路径问题
*
* 总结:只有访问的路径中包含cookie对象的path值,才可以获取到该cookie对象
*/
@WebServlet("/cook05")
public class Cookie05 extends HttpServlet {
@Override
protected void service(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
//1.当前服务器的任何项目的任意资源都可获取Cookie对象
Cookie cookie01 =new Cookie("cookie01","cookie01");
//设置路径为"/",表示在当前服务器下的任何项目都可访问到cookie对象
cookie01.setPath("/");
response.addCookie(cookie01);
//2.当前项目下的资源可以获取cookie对象(默认不设置cookie的path)
Cookie cookie02 =new Cookie("cookie02","cookie02");
//默认不设置cookie的path或者设置为当前站点名
cookie02.setPath("/sr04");
response.addCookie(cookie02);
//3.指定项目下的资源可以获取cookie对象
Cookie cookie03 =new Cookie("cookie03","cookie03");
//默认不设置cookie的path或者设置为当前站点名
cookie03.setPath("/sr03");
response.addCookie(cookie03);
//4.指定目录下的资源可以获取cookie对象
Cookie cookie04 =new Cookie("cookie04","cookie04");
//默认不设置cookie的path或者设置为当前站点名
cookie04.setPath("/sr04/cook02");
response.addCookie(cookie04);
}
}
HttpSession对象
package com.xxxx.servlet;
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 javax.servlet.http.HttpSession;
import java.io.IOException;
/**
* session对象的获取
* request.getSession()
* 当获取session对象时,会判断session对象是否存在,如果存在,则获取session对象,如果不存在,则创建session对象
*/
@WebServlet("/ser01")
public class Session01 extends HttpServlet {
@Override
protected void service(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
//获取session
HttpSession session = request.getSession();
//获取session的会话标识符
String id = session.getId();
System.out.println(id);
//获取session的创建时间
System.out.println(session.getCreationTime());
//获取最后一次访问时间
System.out.println(session.getLastAccessedTime());
//获取是否是新的session对象
System.out.println(session.isNew());
}
}
session失效时间
package com.xxxx.servlet;
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 javax.servlet.http.HttpSession;
import java.io.IOException;
/**
*Session对象的销毁
* 1.默认到期时间是30分钟
*2.手动设置到期时间
* 3.立即销毁
* 4.关闭浏览器
* session底层依赖cookie,cookie对象默认只在浏览器内存中存活,关闭浏览器即失效
* 5.关闭服务器失效
*/
@WebServlet("/ser03")
public class Session03 extends HttpServlet {
@Override
protected void service(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
HttpSession session = request.getSession();
//对象的最大不活动时间
// System.out.println("session对象的最大不活动时间"+session.getMaxInactiveInterval());
//修改最大不活动时间
// session.setMaxInactiveInterval(15);
//立即销毁
session.invalidate();
}
}
servletContext
package com.xxxx.servlet;
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;
/**
* 获取servletContext对象
*/
@WebServlet("/s01")
public class Servlet01 extends HttpServlet {
@Override
protected void service(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
//1.通过request对象获取
ServletContext servletContext01 = request.getServletContext();
//2.通过session对象获取
ServletContext servletContext02 = request.getSession().getServletContext();
//3.通过servletConfig对象获取
ServletContext servletContext03 = getServletConfig().getServletContext();
//4.直接获取
ServletContext servletContext04 = getServletContext();
//常用方法
//1.获取当前服务器的版本信息
String serverInfo = request.getServletContext().getServerInfo();
System.out.println("版本信息:"+serverInfo);
//2.获取项目的真实路径
String realPath = request.getServletContext().getRealPath("/");
System.out.println("真实路径:"+realPath);
}
}
Servlet的三大域对象
1.request域对象
在一次请求中有效。请求转发有效,重定向失效
2.session域对象
在一次会话中有效。请求转发和重定向有效,session销毁后失效
3.servletContext域对象
在整个应用程序中有效,服务器关闭后失效
文件上传
前端页面
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>文件上传</title>
</head>
<body>
<!-- 文件上传
1.准备表单
2.设置表单的提交类型 method="post"
3.设置表单类型为文件上传表单 enctype="multipart/form-data"
4.设置文件提交的地址
5.准备表单元素
1.普通表单项 type="text"
2.文件项 type="file"
6.设置表单元素的name属性值(表单提交一定要设置表单元素的name属性值,否则后台无法接受数据)
-->
<form method="post" enctype="multipart/form-data" action="uploadServlet">
姓名:<input type="text" name="uname"><br>
文件:<input type="file" name="myfile"><br>
<!-- button默认类型是提交类型 type="submit"-->
<button>提交</button>
</form>
</body>
</html>
后台代码
package com.xxxx.servlet;
import javax.servlet.ServletException;
import javax.servlet.annotation.MultipartConfig;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.Part;
import java.io.IOException;
/**
* 文件上传
* 使用@MultipartConfig将一个servlet标识为支持文件上传
* servlet将multipart/form-data的POST请求封装成Part对象,通过Part对上传的文件进行操作
*/
@WebServlet("/uploadServlet")
@MultipartConfig//如果是文件上传,必须要设置该注解!!!!!
public class UploadServlet extends HttpServlet {
@Override
protected void service(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
System.out.println("文件上传");
//设置请求的编码格式
request.setCharacterEncoding("UTF-8");
//获取普通表单项(获取参数)
String uname=request.getParameter("uname");//表单中表单元素的name属性值
System.out.println("uanme:"+uname);
//获取Part对象
Part part=request.getPart("myfile");//表单中file文件域的name属性值
//通过Part对象得到上传的文件名
String fileName=part.getSubmittedFileName();
System.out.println("上传文件名:"+fileName);
//得到文件存放的路径
String filePath=request.getServletContext().getRealPath("/");
System.out.println("文件存放的路径"+filePath);
//上传文件到指定目录
part.write(filePath+"/"+fileName);
}
}
文件下载
超链接下载
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>文件下载</title>
</head>
<body>
<!-- 超链接下载-->
<!-- 当使用超链接(a标签)时,如果遇到浏览器能够识别的资源,则会显示内容:若果遇到浏览器不能识别的资源,则会进行下载-->
<!-- 浏览器能够识别的资源-->
<a href="download/任务书胡征.doc">文本文件</a>
<a href="download/胡征证件照.jpg">图片文件</a>
<!-- 浏览器不能识别的资源-->
<a href="download/2022届软件学院毕业设计材料模板(不要改动模板格式及日期由老师确定).zip">压缩文件</a>
<hr>
<a href="download/胡征证件照.jpg" download="证件照.jpg">图片文件</a>
</body>
</html>
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>文件下载</title>
</head>
<body>
<!-- 超链接下载-->
<!-- 当使用超链接(a标签)时,如果遇到浏览器能够识别的资源,则会显示内容:若果遇到浏览器不能识别的资源,则会进行下载-->
<!-- 浏览器能够识别的资源-->
<a href="download/任务书胡征.doc">文本文件</a>
<a href="download/胡征证件照.jpg">图片文件</a>
<!-- 浏览器不能识别的资源-->
<a href="download/2022届软件学院毕业设计材料模板(不要改动模板格式及日期由老师确定).zip">压缩文件</a>
<hr>
<a href="download/胡征证件照.jpg" download="证件照.jpg">图片文件</a>
<hr>
<form action="downloadServlet">
文件名:<input type="text" name="fileName" placeholder="请输入要下载的文件名">
<button>下载</button>
</form>
</body>
</html>
package com.xxxx.servlet;
import javax.servlet.ServletException;
import javax.servlet.ServletOutputStream;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;
/**
* 文件下载步骤
* 1.
*/
@WebServlet("/downloadServlet")
public class DownloadServlet extends HttpServlet {
@Override
protected void service(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
System.out.println("文件下载.....");
//设置请求的编码格式
request.setCharacterEncoding("UTF-8");
response.setContentType("text/html;charset=UTF-8");
//获取参数(得到要下载的文件名)
String fileName=request.getParameter("fileName");
//参数的非空判断 trim():去除字符串的前后空格
if (fileName==null||"".equals(fileName.trim())){
response.getWriter().write("请输入要下载的文件名");
response.getWriter().close();
return;
}
//得到图片存放的路径
String path=request.getServletContext().getRealPath("/download/");
//通过路径得到file对象
File file=new File(path+fileName);
//判断文件对象是否存在并且是一个标准文件
if (file.exists()&&file.isFile()){
//设置响应类型,浏览器无法使用某种方式或激活某个程序来处理MIME类型
response.setContentType("application/x-msdownload");
//设置头信息
response.setHeader("Content-Disposition","attachment;filename="+fileName);
//得到file文件的输入流
InputStream in= new FileInputStream(file);
//得到字节输出流
ServletOutputStream out=response.getOutputStream();
//定义byte数组
byte[] bytes=new byte[1024];
//定义长度
int len=0;
//循环输出
while ((len=in.read(bytes))!=-1){
//输出内容
out.write(bytes,0,len);
}
//关闭资源
out.close();
in.close();
}else {
response.getWriter().write("文件不存在,请重试");
response.getWriter().close();
}
}
}
标签:http,servlet,request,笔记,学习,cookie,import,Servlet,javax 来源: https://www.cnblogs.com/huzheng1023/p/16275505.html
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