1.路径问题：
注意 .代表执行程序的文件夹路径，在tomcat中也就是bin目录，所以要用this.getServletContext().getRealPath("/WEB-INF/classes/db.properties");得到绝对路径；
代码练习：
package com.http.path; import java.io.File; import java.io.FileInputStream; import java.io.IOException; import java.io.PrintWriter; import java.util.Properties; import javax.servlet.ServletException; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; public class PathDemo extends HttpServlet { public PathDemo() { super(); } public void destroy() { super.destroy(); // Just puts "destroy" string in log // Put your code here } public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { response.setCharacterEncoding("utf-8"); request.setCharacterEncoding("utf-8"); //给服务器使用的： / 表示在当前web应用的根目录（webRoot下） //request.getRequestDispatcher("/target.html").forward(request, response); //给浏览器使用的： / 表示在webapps的根目录下 //response.sendRedirect("/MyWeb/target.html"); String path = this.getServletContext().getRealPath("/WEB-INF/classes/db.properties"); //this.getServletContext().getResourceAsStream("/WEB-INF/classes/db.properties"); System.out.println(path); Properties properties = new Properties(); properties.load(new FileInputStream(new File(path))); String user = properties.getProperty("user"); String passwd = properties.getProperty("passwd"); System.out.println("user = " + user + " passwd = " + passwd); } public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { response.setContentType("text/html"); PrintWriter out = response.getWriter(); out.println("<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">"); out.println("<HTML>"); out.println(" <HEAD><TITLE>A Servlet</TITLE></HEAD>"); out.println(" <BODY>"); out.print(" This is "); out.print(this.getClass()); out.println(", using the POST method"); out.println(" </BODY>"); out.println("</HTML>"); out.flush(); out.close(); } public void init() throws ServletException { // Put your code here } }
2.Cooke技术
2.1 特点
Cookie技术：会话数据保存在浏览器客户端。
2.2 Cookie技术核心
Cookie类：用于存储会话数据
1）构造Cookie对象
Cookie(java.lang.String name, java.lang.String value)
2）设置cookie
void setPath(java.lang.String uri) ：设置cookie的有效访问路径
void setMaxAge(int expiry) ： 设置cookie的有效时间
void setValue(java.lang.String newValue) ：设置cookie的值
3）发送cookie到浏览器端保存
void response.addCookie(Cookie cookie) : 发送cookie
4）服务器接收cookie
Cookie[] request.getCookies() : 接收cookie
2.3 Cookie原理
1）服务器创建cookie对象，把会话数据存储到cookie对象中。
new Cookie("name","value");
2） 服务器发送cookie信息到浏览器
response.addCookie(cookie);
举例： set-cookie: name=eric (隐藏发送了一个set-cookie名称的响应头)
3）浏览器得到服务器发送的cookie，然后保存在浏览器端。
4）浏览器在下次访问服务器时，会带着cookie信息
举例： cookie: name=eric (隐藏带着一个叫cookie名称的请求头)
5）服务器接收到浏览器带来的cookie信息
request.getCookies();
2.4 Cookie的细节
1）void setPath(java.lang.String uri) ：设置cookie的有效访问路径。有效路径指的是cookie的有效路径保存在哪里，那么浏览器在有效路径下访问服务器时就会带着cookie信息，否则不带cookie信息。
2）void setMaxAge(int expiry) ： 设置cookie的有效时间。
正整数：表示cookie数据保存浏览器的缓存目录（硬盘中），数值表示保存的时间。
负整数：表示cookie数据保存浏览器的内存中。浏览器关闭cookie就丢失了！！
零：表示删除同名的cookie数据
3）Cookie数据类型只能保存非中文字符串类型的。可以保存多个cookie，但是浏览器一般只允许存放300个Cookie，每个站点最多存放20个Cookie，每个Cookie的大小限制为4KB。
在下面查了下，cookie也可以存中文字符串，可以用URLEncoder类中的encode方法编码，然后用URLDecoder.decode方法解码
cookie的简单练习：
package com.http.cookie; import java.io.IOException; import java.io.PrintWriter; import javax.servlet.ServletException; import javax.servlet.http.Cookie; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; public class CookieDemo1 extends HttpServlet { /** * Constructor of the object. */ public CookieDemo1() { super(); } /** * Destruction of the servlet. <br> */ public void destroy() { super.destroy(); // Just puts "destroy" string in log // Put your code here } /** * The doGet method of the servlet. <br> * * This method is called when a form has its tag value method equals to get. * * @param request the request send by the client to the server * @param response the response send by the server to the client * @throws ServletException if an error occurred * @throws IOException if an error occurred */ public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { Cookie cookie = new Cookie("name", "handsomecui"); Cookie cookie2 = new Cookie("email", "handsomecui@qq.com"); cookie2.setPath("/Test"); //cookie.setMaxAge(10);//不会受到浏览器关闭的影响 cookie.setMaxAge(-1);//cookie保存在浏览器内存，关闭移除 //cookie.setMaxAge(0);//删除同名cookie response.addCookie(cookie); response.addCookie(cookie2); System.out.println(request.getHeader("cookie")); Cookie[] cookies = request.getCookies(); if(cookies == null){ System.out.println("没有cookie"); } else{ for(Cookie acookie : cookies){ System.out.println(acookie.getName() + "是" + acookie.getValue()); } } } /** * The doPost method of the servlet. <br> * * This method is called when a form has its tag value method equals to post. * * @param request the request send by the client to the server * @param response the response send by the server to the client * @throws ServletException if an error occurred * @throws IOException if an error occurred */ public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { response.setContentType("text/html"); PrintWriter out = response.getWriter(); out.println("<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">"); out.println("<HTML>"); out.println(" <HEAD><TITLE>A Servlet</TITLE></HEAD>"); out.println(" <BODY>"); out.print(" This is "); out.print(this.getClass()); out.println(", using the POST method"); out.println(" </BODY>"); out.println("</HTML>"); out.flush(); out.close(); } /** * Initialization of the servlet. <br> * * @throws ServletException if an error occurs */ public void init() throws ServletException { // Put your code here } }
2.5 案例- 显示用户上次访问的时间
代码：
package com.http.cookie; import java.io.IOException; import java.io.PrintWriter; import java.sql.Time; import java.text.SimpleDateFormat; import java.util.Date; import javax.servlet.ServletException; import javax.servlet.http.Cookie; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; public class ShowTime extends HttpServlet { /** * Constructor of the object. */ private int cnt = 0; public ShowTime() { super(); } /** * Destruction of the servlet. <br> */ public void destroy() { super.destroy(); // Just puts "destroy" string in log // Put your code here } private String Isexist(HttpServletRequest request){ Cookie[] cookies = request.getCookies(); if(cookies == null){ return null; } for(Cookie acookie:cookies){ if("lasttime".equals(acookie.getName())){ return acookie.getValue(); } } return null; } public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { cnt++; response.setCharacterEncoding("gb2312"); request.setCharacterEncoding("gb2312"); response.getWriter().write("您好，这是您第" + cnt + "次访问本站 "); SimpleDateFormat format = new SimpleDateFormat("yyyy-MM-dd hh:mm:ss"); String str = format.format(new Date()); Cookie cookie = new Cookie("lasttime", str); response.addCookie(cookie); String lasttime = Isexist(request); if(lasttime != null){ response.getWriter().write("您上次访问的时间是：" + lasttime + " "); }else{ } response.getWriter().write("当前时间是：" + str + " "); } /** * The doPost method of the servlet. <br> * * This method is called when a form has its tag value method equals to post. * * @param request the request send by the client to the server * @param response the response send by the server to the client * @throws ServletException if an error occurred * @throws IOException if an error occurred */ public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { response.setContentType("text/html"); PrintWriter out = response.getWriter(); out.println("<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">"); out.println("<HTML>"); out.println(" <HEAD><TITLE>A Servlet</TITLE></HEAD>"); out.println(" <BODY>"); out.print(" This is "); out.print(this.getClass()); out.println(", using the POST method"); out.println(" </BODY>"); out.println("</HTML>"); out.flush(); out.close(); } /** * Initialization of the servlet. <br> * * @throws ServletException if an error occurs */ public void init() throws ServletException { // Put your code here } }
2.6 案例-查看用户浏览器过的商品
思路：ListServlet展示商品列表，Detailservlet展示商品的详细信息，最近浏览的商品，用一个hashset存储MySet类，取出前三个不重复的即可，cookie存放最近浏览的商品编号，用逗号隔开；
product类:
package com.common.product; import java.util.ArrayList; public class Product { private static ArrayList<Product>arrayList; private int id; private String name; private String type; private double price; static{ arrayList = new ArrayList<Product>(); for(int i = 0; i < 10; i++){ Product product = new Product(i + 1, "笔记本"+(i + 1), "LN00"+(i+1), 35+i); arrayList.add(product); } } public static ArrayList<Product> getArrayList() { return arrayList; } @Override public String toString() { return "id=" + id + ", name=" + name + ", type=" + type + ", price=" + price ; } public Product(int id, String name, String type, double price) { super(); this.id = id; this.name = name; this.type = type; this.price = price; } public Product() { super(); } public int getId() { return id; } public void setId(int id) { this.id = id; } public String getName() { return name; } public void setName(String name) { this.name = name; } public String getType() { return type; } public void setType(String type) { this.type = type; } public double getPrice() { return price; } public void setPrice(double price) { this.price = price; } public Product getValueById(int p) { for(int i = 0; i < arrayList.size(); i++){ if(arrayList.get(i).getId() == p){ return arrayList.get(i); } } return null; } }
MySet类：由编号和商品名构成，主要是为了hashset的去重与排序；
package com.common.tool; import java.util.HashSet; public class MySet{ private int id; private String name; public int getId() { return id; } @Override public boolean equals(Object o) { // TODO Auto-generated method stub MySet myset = (MySet)o; return myset.getName().equals(this.getName()); } @Override public int hashCode() { // TODO Auto-generated method stub return id; } public void setId(int id) { this.id = id; } public String getName() { return name; } public void setName(String name) { this.name = name; } public MySet(int id, String name) { super(); this.id = id; this.name = name; } public MySet() { super(); } }
ListServlet：
package com.http.servlet; import java.io.IOException; import java.io.PrintWriter; import java.net.URLDecoder; import java.net.URLEncoder; import java.util.ArrayList; import javax.servlet.ServletException; import javax.servlet.http.Cookie; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import com.common.product.Product; public class ListServlet extends HttpServlet { /** * Constructor of the object. */ public ListServlet() { super(); } /** * Destruction of the servlet. <br> */ public void destroy() { super.destroy(); // Just puts "destroy" string in log // Put your code here } /** * The doGet method of the servlet. <br> * * This method is called when a form has its tag value method equals to get. * * @param request the request send by the client to the server * @param response the response send by the server to the client * @throws ServletException if an error occurred * @throws IOException if an error occurred */ public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { request.setCharacterEncoding("utf-8"); response.setCharacterEncoding("utf-8"); Product product = new Product(); String html = ""; html+=("<html>"); html+=("<head>"); html+=("<meta charset='utf-8'/>"); html+=("<title>"); html+=("商品列表"); html+=("</title>"); html+=("</head>"); html+=("<body>"); html+=("<table align='center' border='1'>"); html+=("<tr>"); html+=("<th>"); html+=("编号"); html+=("</th>"); html+=("<th>"); html+=("商品名称"); html+=("</th>"); html+=("<th>"); html+=("商品型号"); html+=("</th>"); html+=("<th>"); html+=("商品价格"); html+=("</th>"); html+=("</tr>"); ArrayList<Product> list = new Product().getArrayList(); for(int i = 0; i < list.size(); i++){ html+=("<tr>"); html+=("<td>"); html+=("" + list.get(i).getId()); html+=("</td>"); html+=("<td>"); html+=("<a href = '"+ request.getContextPath() +"/DetailServlet"+"?id="+list.get(i).getId()+"'>" + list.get(i).getName() + "</a>"); html+=("</td>"); html+=("<td>"); html+=(list.get(i).getType()); html+=("</td>"); html+=("<td>"); html+=("" + list.get(i).getPrice()); html+=("</td>"); html+=("</tr>"); } html+=("</table>"); html+=("最近浏览过的商品: " + "<br/>"); String recentview = null; Cookie[] cookies = request.getCookies(); if(cookies != null){ for(Cookie cookie : cookies){ if("RecentProduct".equals(cookie.getName())){ recentview = cookie.getValue(); break; } } } if(recentview != null){ recentview = URLDecoder.decode(recentview, "UTF-8"); String[] splits = recentview.split(","); for(String p : splits){ html += (product.getValueById(Integer.parseInt(p)) + "<br/>"); } } html+=("</body>"); html+=("</html>"); response.getWriter().write(html); } /** * The doPost method of the servlet. <br> * * This method is called when a form has its tag value method equals to post. * * @param request the request send by the client to the server * @param response the response send by the server to the client * @throws ServletException if an error occurred * @throws IOException if an error occurred */ public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { response.setContentType("text/html"); PrintWriter out = response.getWriter(); out.println("<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">"); out.println("<HTML>"); out.println(" <HEAD><TITLE>A Servlet</TITLE></HEAD>"); out.println(" <BODY>"); out.print(" This is "); out.print(this.getClass()); out.println(", using the POST method"); out.println(" </BODY>"); out.println("</HTML>"); out.flush(); out.close(); } /** * Initialization of the servlet. <br> * * @throws ServletException if an error occurs */ public void init() throws ServletException { // Put your code here } }
DetailServlet
package com.http.servlet; import java.io.IOException; import java.io.PrintWriter; import java.net.URLEncoder; import java.util.HashSet; import java.util.Iterator; import java.util.Set; import java.util.Stack; import java.net.URLEncoder; import javax.servlet.ServletException; import javax.servlet.http.Cookie; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import com.common.product.Product; import com.common.tool.MySet; @SuppressWarnings("unused") public class DetailServlet extends HttpServlet { /** * Constructor of the object. */ public DetailServlet() { super(); } /** * Destruction of the servlet. <br> */ public void destroy() { super.destroy(); // Just puts "destroy" string in log // Put your code here } /** * The doGet method of the servlet. <br> * * This method is called when a form has its tag value method equals to get. * * @param request the request send by the client to the server * @param response the response send by the server to the client * @throws ServletException if an error occurred * @throws IOException if an error occurred */ public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { request.setCharacterEncoding("utf-8"); response.setCharacterEncoding("utf-8"); int id = Integer.parseInt(request.getParameter("id")); System.out.println(id); Product product = new Product().getValueById(id); String html = ""; html+=("<html>"); html+=("<head>"); html+=("<meta charset='utf-8'/>"); html+=("<title>"); html+=("商品信息"); html+=("</title>"); html+=("</head>"); html+=("<body>"); html+=("<table align='center' border='1'>"); html+=("<tr>"); html+=("<th>"); html+=("编号"); html+=("</th>"); html+=("<td>"); html+=(id); html+=("</td>"); html+=("</tr>"); html+=("<tr>"); html+=("<th>"); html+=("商品名称"); html+=("</th>"); html+=("<td>"); html+=(product.getName()); html+=("</td>"); html+=("</tr>"); html+=("<tr>"); html+=("<th>"); html+=("商品型号"); html+=("</th>"); html+=("<td>"); html+=(product.getType()); html+=("</td>"); html+=("</tr>"); html+=("<tr>"); html+=("<th>"); html+=("商品价格"); html+=("</th>"); html+=("<td>"); html+=(product.getPrice()); html+=("</td>"); html+=("</tr>"); html+=("</body>"); html+=("</html>"); Cookie acookie = null; Cookie[] cookies = request.getCookies(); if(cookies != null){ for(Cookie cookie : cookies){ if("RecentProduct".equals(cookie.getName())){ acookie = cookie; break; } } } System.out.println(product.getName()); if(acookie == null){ acookie = new Cookie("RecentProduct", product.getId()+""); response.addCookie(acookie); }else{ String[] splits = acookie.getValue().split(","); HashSet<MySet> set = new HashSet<MySet>(); set.add(new MySet(0, product.getId()+"")); for(int i = 0, j = 0; i < splits.length;i++){ if((product.getId()+"").equals(splits[i])) continue; j++; set.add(new MySet(j, splits[i])); } String value = ""; Iterator<MySet> iterator = set.iterator(); for(int i = 0; iterator.hasNext()&& i < 3; i++){ MySet mySet = iterator.next(); value += (mySet.getName() + ","); } acookie = new Cookie("RecentProduct", value); response.addCookie(acookie); } response.getWriter().write(html); } /** * The doPost method of the servlet. <br> * * This method is called when a form has its tag value method equals to post. * * @param request the request send by the client to the server * @param response the response send by the server to the client * @throws ServletException if an error occurred * @throws IOException if an error occurred */ public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { response.setContentType("text/html"); PrintWriter out = response.getWriter(); out.println("<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">"); out.println("<HTML>"); out.println(" <HEAD><TITLE>A Servlet</TITLE></HEAD>"); out.println(" <BODY>"); out.print(" This is "); out.print(this.getClass()); out.println(", using the POST method"); out.println(" </BODY>"); out.println("</HTML>"); out.flush(); out.close(); } /** * Initialization of the servlet. <br> * * @throws ServletException if an error occurs */ public void init() throws ServletException { // Put your code here } }
4 Session技术
4.1 引入
Cookie的局限：
1）Cookie只能存字符串类型。不能保存对象
2）只能存非中文。
3）1个Cookie的容量不超过4KB。
如果要保存非字符串，超过4kb内容，只能使用session技术！！！
Session特点：
会话数据保存在服务器端。（内存中）
4.2 Session技术核心
HttpSession类：用于保存会话数据
1）创建或得到session对象
HttpSession getSession()
HttpSession getSession(boolean create)
2）设置session对象
void setMaxInactiveInterval(int interval) ： 设置session的有效时间
void invalidate() ： 销毁session对象
java.lang.String getId() ： 得到session编号
3）保存会话数据到session对象
void setAttribute(java.lang.String name, java.lang.Object value) ： 保存数据
java.lang.Object getAttribute(java.lang.String name) ： 获取数据
void removeAttribute(java.lang.String name) ： 清除数据
4.3 Session原理
问题： 服务器能够识别不同的浏览者！！！
现象：
前提： 在哪个session域对象保存数据，就必须从哪个域对象取出！！！！
浏览器1：(给s1分配一个唯一的标记：s001,把s001发送给浏览器)
1）创建session对象，保存会话数据
HttpSession session = request.getSession(); --保存会话数据 s1
浏览器1 的新窗口（带着s001的标记到服务器查询，s001->s1,返回s1）
1）得到session对象的会话数据
HttpSession session = request.getSession(); --可以取出 s1
新的浏览器1：(没有带s001,不能返回s1)
1）得到session对象的会话数据
HttpSession session = request.getSession(); --不可以取出 s2
浏览器2：(没有带s001,不能返回s1)
1）得到session对象的会话数据
HttpSession session = request.getSession(); --不可以取出 s3
代码解读：HttpSession session = request.getSession();
1）第一次访问创建session对象，给session对象分配一个唯一的ID，叫JSESSIONID
new HttpSession();
2）把JSESSIONID作为Cookie的值发送给浏览器保存
Cookie cookie = new Cookie("JSESSIONID", sessionID);
response.addCookie(cookie);
3）第二次访问的时候，浏览器带着JSESSIONID的cookie访问服务器
4）服务器得到JSESSIONID，在服务器的内存中搜索是否存放对应编号的session对象。
if(找到){
return map.get(sessionID);
}
Map<String,HttpSession>]
<"s001", s1>
<"s001,"s2>
5）如果找到对应编号的session对象，直接返回该对象
6）如果找不到对应编号的session对象，创建新的session对象，继续走1的流程
结论：通过JSESSION的cookie值在服务器找session对象！！！！！
4.4 Sesson细节
1）java.lang.String getId() ： 得到session编号
2）两个getSession方法：
getSession(true) / getSession() : 创建或得到session对象。没有匹配的session编号，自动创 建新的session对象。
getSession(false): 得到session对象。没有匹配的session编号，返回null
3）void setMaxInactiveInterval(int interval) ： 设置session的有效时间
session对象销毁时间：
3.1 默认情况30分服务器自动回收
3.2 修改session回收时间
3.3 全局修改session有效时间
|
<!-- 修改session全局有效时间:分钟 --> <session-config> <session-timeout>1</session-timeout> </session-config> |
3.4.手动销毁session对象
void invalidate() ： 销毁session对象
4）如何避免浏览器的JSESSIONID的cookie随着浏览器关闭而丢失的问题
|
/** * 手动发送一个硬盘保存的cookie给浏览器 */ Cookie c = new Cookie("JSESSIONID",session.getId()); c.setMaxAge(60*60); response.addCookie(c); |
代码SessionDemo1
package com.http.cookie; import java.io.IOException; import java.io.PrintWriter; import java.net.URLEncoder; import javax.servlet.ServletException; import javax.servlet.http.Cookie; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import javax.servlet.http.HttpSession; public class SessionDemo1 extends HttpServlet { /** * Constructor of the object. */ public SessionDemo1() { super(); } /** * Destruction of the servlet. <br> */ public void destroy() { super.destroy(); // Just puts "destroy" string in log // Put your code here } /** * The doGet method of the servlet. <br> * * This method is called when a form has its tag value method equals to get. * * @param request the request send by the client to the server * @param response the response send by the server to the client * @throws ServletException if an error occurred * @throws IOException if an error occurred */ public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { HttpSession session = request.getSession(); System.out.println("id = "+session.getId()); session.setAttribute("name", "rose"); session.setMaxInactiveInterval(60*60); Cookie cookie = new Cookie("JSESSIONID", session.getId()); cookie.setMaxAge(60*60); response.addCookie(cookie); } /** * The doPost method of the servlet. <br> * * This method is called when a form has its tag value method equals to post. * * @param request the request send by the client to the server * @param response the response send by the server to the client * @throws ServletException if an error occurred * @throws IOException if an error occurred */ public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { response.setContentType("text/html"); PrintWriter out = response.getWriter(); out.println("<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">"); out.println("<HTML>"); out.println(" <HEAD><TITLE>A Servlet</TITLE></HEAD>"); out.println(" <BODY>"); out.print(" This is "); out.print(this.getClass()); out.println(", using the POST method"); out.println(" </BODY>"); out.println("</HTML>"); out.flush(); out.close(); } /** * Initialization of the servlet. <br> * * @throws ServletException if an error occurs */ public void init() throws ServletException { // Put your code here } }
SessionDemo2:
package com.http.cookie; import java.io.IOException; import java.io.PrintWriter; import javax.servlet.ServletException; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import javax.servlet.http.HttpSession; public class SessionDemo2 extends HttpServlet { /** * Constructor of the object. */ public SessionDemo2() { super(); } /** * Destruction of the servlet. <br> */ public void destroy() { super.destroy(); // Just puts "destroy" string in log // Put your code here } /** * The doGet method of the servlet. <br> * * This method is called when a form has its tag value method equals to get. * * @param request the request send by the client to the server * @param response the response send by the server to the client * @throws ServletException if an error occurred * @throws IOException if an error occurred */ public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { HttpSession session = request.getSession(false); if(session != null){ System.out.println(session.getAttribute("name")); } } /** * The doPost method of the servlet. <br> * * This method is called when a form has its tag value method equals to post. * * @param request the request send by the client to the server * @param response the response send by the server to the client * @throws ServletException if an error occurred * @throws IOException if an error occurred */ public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { response.setContentType("text/html"); PrintWriter out = response.getWriter(); out.println("<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">"); out.println("<HTML>"); out.println(" <HEAD><TITLE>A Servlet</TITLE></HEAD>"); out.println(" <BODY>"); out.print(" This is "); out.print(this.getClass()); out.println(", using the POST method"); out.println(" </BODY>"); out.println("</HTML>"); out.flush(); out.close(); } /** * Initialization of the servlet. <br> * * @throws ServletException if an error occurs */ public void init() throws ServletException { // Put your code here } }
DeleteSession
package com.http.cookie; import java.io.IOException; import java.io.PrintWriter; import javax.servlet.ServletException; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import javax.servlet.http.HttpSession; public class DeleteSession extends HttpServlet { /** * The doGet method of the servlet. <br> * * This method is called when a form has its tag value method equals to get. * * @param request the request send by the client to the server * @param response the response send by the server to the client * @throws ServletException if an error occurred * @throws IOException if an error occurred */ public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { HttpSession session = request.getSession(false); if(session != null){ session.invalidate(); System.out.println("销毁成功"); } } }