Cookie
1. 发送Cookie对象
java.util.Date date=new java.util.Date();
Cookie c=new Cookie("lastVisited",date.toString());
c.setMaxAge(60*60*24);//设置有效时间.
c.setPath(); //设置路径
response.addCookie(c);//存储Cookie文件
2.读取Cookie
Cookie[] cookies=request.getCookies();
Cookie c=null;
if(cookies!=null){
for(int i=0;i<cookies.length;i++){
c=cookies[i];
out.println("Cookie name:"+c.getName()+"<br>");
out.println("Cookie value:"+c.getValue()+"<br>");
}
}
3.修改Cookie
Cookie[] cookies=request.getCookies();
Cookie c=null;
for(int i=0;i<cookies.length;i++){
c=cookies[i];
if(c.getName().equal("lastvisited")){
c.setValue("2010-11-11");
c.setMaxValue(60*60*24);
response.addCookie(c);
}
}
4.删除Cookie
Cookie[] cookies=request.getCookies();
Cookie c=null;
for(int i=0;i<cookies.length;i++){
c=cookies[i];
if(c.getName().equal("lastvisited")){
c.setMaxValue(0);
response.addCookie(c);
}
}
使用Cookie的注意事项:
1.Cookie的大小和数量是有限制的.只能是英文字符和数字,不能是汉字.
2.Cookie的个人硬盘上所保存的文本信息以明文格式进行保存.没有任何加密措施.
3.浏览器用户可以设定不适用Cookie
例子:
web project:Cookie
编写username.html
编写SetCookieServlet.java(Servlet),映射为/servlet/setServlet
编写GetCookieServlet.java(Servlet)映射为/servlet/getServlet
编写StringUtil.java 用来过滤一些恶意代码.
username.html:
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>无标题文档</title>
</head>
<body>
<form id="form1" name="form1" method="post" action="/Cookie/servlet/setCookies">
<table width="361" border="1">
<tr>
<th colspan="2" scope="col"><div align="left">请输入用户名:</div></th>
</tr>
<tr>
<th scope="row">用户名:</th>
<td><input type="text" name="username" id="username" /></td>
</tr>
<tr>
<th scope="row"><input type="reset" name="reset" id="reset" value="重置" /></th>
<td><input type="submit" name="submit" id="submit" value="提交" /></td>
</tr>
</table>
</form>
</body>
</html>
SetCookieServlet.java:
import java.io.IOException;
import java.io.PrintWriter;
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;
import com.v512.guestbook.StringUtil;
public class SetCookiesServlet extends HttpServlet {
private static final long serialVersionUID = 1L;
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
doPost(request, response);
}
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
String username=request.getParameter("username");
String outputContent=null;
if (!StringUtil.validateNull(username)) {
Cookie cookie1=new Cookie ("username",StringUtil.filterHtml(username));
cookie1.setMaxAge(24*60*60*30);
SimpleDateFormat sdf=new SimpleDateFormat("yyyy-MM-dd");
Cookie cookie2=new Cookie("lastVisited", sdf.format(new Date()));
cookie2.setMaxAge(24*60*60*30);
response.addCookie(cookie1);
response.addCookie(cookie2);
outputContent="本次登录的用户名与时间已经写到Cookie当中.<br><a href='/Cookie/servlet/getCookies'>读取Cookie</a><br>";
}else {
outputContent="本次记录没有写到Cookie当中.<br><a href='/Cookie/username.html'>重新输入</a><br>";
}
response.setContentType("text/html;charset=utf-8");
PrintWriter out = response.getWriter();
out.println("<!DOCTYPE HTML PUBLIC \"-//W3C//DTD HTML 4.01 Transitional//EN\">");
out.println("<HTML>");
out.println(" <HEAD><TITLE>set cookie</TITLE></HEAD>");
out.println(" <BODY>");
out.println("<h2>"+outputContent+"</h2>");
out.println(" </BODY>");
out.println("</HTML>");
out.flush();
out.close();
}
}
3.GetCookieServlet.java
import java.io.IOException;
import java.io.PrintWriter;
import java.net.CookiePolicy;
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 GetCookiesServlet extends HttpServlet {
private static final long serialVersionUID = 1L;
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
doPost(request, response);
}
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
response.setContentType("text/html;charset=utf-8");
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.println("<h2>从Cookie读取的上次登录日期与用户名</h2>");
Cookie[] cookies=request.getCookies();
Cookie cookie=null;
if (cookies!=null) {
for (int i = 0; i < cookies.length; i++) {
cookie=cookies[i];
if (cookie.getName().equals("username")) {
out.println("用户名:"+cookie.getValue()+"<br>");
}
if (cookie.getName().equals("lastVisited")) {
out.println("上次登录的日期:"+cookie.getValue()+"<br>");
}
}
}
out.println(" </BODY>");
out.println("</HTML>");
out.flush();
out.close();
}
}
StringUtil.java
public class StringUtil {
public static boolean validateNull(String args) {
if (args == null || args.length() == 0) {
return true;
} else {
return false;
}
}
public static String ChangeNull(String source, String target) {
if (source == null || source.length() == 0
|| source.equalsIgnoreCase("null")) {
return target;
} else {
return source;
}
}
// 过滤一些恶意的代码
public static String filterHtml(String input) {
if (input == null) {
return null;
}
if (input.length() == 0) {
return input;
}
input = input.replaceAll("&", "&");
input = input.replaceAll("<", "<");
input = input.replaceAll(">", ">");
input = input.replaceAll(" ", " ");
input = input.replaceAll("'", "'");
input = input.replaceAll("\"", """);
input = input.replaceAll("\n", "<br>");// 空格过滤一定要放在最后面!
return input;
}
}