钓鱼网站模板制作,做门户网站用什么服务器,许昌住房城乡建设局网站,找项目去哪个平台练习cookie做一个浏览商品记录显示#xff0c;第一次会显示浏览过的商品#xff0c;然后在浏览第二次就出现空指针异常2016-6-16 16:51:48 org.apache.catalina.core.StandardWrapperValve invoke严重: Servlet.service() for servlet [CookieDemo2] in context with path [/…练习cookie做一个浏览商品记录显示第一次会显示浏览过的商品然后在浏览第二次就出现空指针异常2016-6-16 16:51:48 org.apache.catalina.core.StandardWrapperValve invoke严重: Servlet.service() for servlet [CookieDemo2] in context with path [/testHttp] threw exceptionjava.lang.NullPointerExceptionat cn.itcast.cookie.CookieDemo2.doGet(CookieDemo2.java:43)at javax.servlet.http.HttpServlet.service(HttpServlet.java:624)at javax.servlet.http.HttpServlet.service(HttpServlet.java:731)at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:303)at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:220)at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:122)at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:505)at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:169)at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:103)at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:956)at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:116)at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:436)at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1078)at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:625)at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:316)at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886)at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908)at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)at java.lang.Thread.run(Thread.java:619)CookieDemo2.javapackage cn.itcast.cookie;import java.io.IOException;import java.io.PrintWriter;import java.util.LinkedHashMap;import java.util.Map;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 CookieDemo2 extends HttpServlet {public void doGet(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {response.setCharacterEncoding(UTF-8);response.setContentType(text/html;charsetUTF-8);PrintWriter out response.getWriter();//1.输出网站所有商品out.write(本网站有如下商品);Map map Db.getAll();for(Map.Entry entry:map.entrySet()){Book book entry.getValue();out.print(book.getName());}//2.显示用户浏览过的商品out.print(您曾经浏览过的商品);Cookie cookies[] request.getCookies();for(int i0;cookies!null iif(cookies[i].getName().equals(bookHistory)){String ids[] cookies[i].getValue().split(\\,);for(String id:ids){Book book (Book) Db.getAll().get(id);out.print(book.getName());}}}}public void doPost(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {doGet(request, response);}}class Db{private static Map map new LinkedHashMap();static{map.put(1,new Book(1,javaweb开发,老张,一本好书));map.put(2,new Book(2,jdbc开发,老张,一本好书));map.put(3,new Book(3,spring开发,老黎,一本好书));map.put(4,new Book(4,struts开发,老毕,一本好书));map.put(5,new Book(5,android开发,老黎,一本好书));}public static Map getAll(){return map;}}class Book{private String id;private String name;private String author;private String description;public Book() {super();// TODO Auto-generated constructor stub}public Book(String id, String name, String author, String description) {super();this.id id;this.name name;this.author author;this.description description;}public String getId() {return id;}public void setId(String id) {this.id id;}public String getName() {return name;}public void setName(String name) {this.name name;}public String getAuthor() {return author;}public void setAuthor(String author) {this.author author;}public String getDescription() {return description;}public void setDescription(String description) {this.description description;}}CookieDemo3.javapackage cn.itcast.cookie;import java.io.IOException;import java.io.PrintWriter;import java.util.Arrays;import java.util.LinkedList;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 CookieDemo3 extends HttpServlet {public void doGet(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {response.setCharacterEncoding(UTF-8);response.setContentType(text/html;charsetUTF-8);PrintWriter out response.getWriter();//1.根据用户带过来的id显示相应商品的详细信息String id request.getParameter(id);Book book (Book) Db.getAll().get(id);out.write(book.getId());out.write(book.getName());out.write(book.getAuthor());out.write(book.getDescription());//构建cookie回写给浏览器String cookieValue buildCookie(id,request);Cookie cookie new Cookie(bookHistory,cookieValue);cookie.setMaxAge(1*30*24*60*60);cookie.setPath(/testHttp);response.addCookie(cookie);}private String buildCookie(String id, HttpServletRequest request) {String bookHistory null;Cookie cookies[] request.getCookies();for(int i0;cookies!null iif(cookies[i].getName().equals(bookHistory)){bookHistory cookies[i].getValue();}}if(bookHistorynull){return id;}LinkedList list new LinkedList(Arrays.asList(bookHistory.split(//,)));if(list.contains(id)){list.remove(id);}else{if(list.size()3){list.removeLast();}}list.addFirst(id);StringBuffer sb new StringBuffer();for(String bid : list){sb.append(bid,);}sb.deleteCharAt(sb.length()-1).toString();return null;}public void doPost(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {doGet(request, response);}}
