java web登录状态保持_java web用于保持状态的4种方法

方法一：网址重写

通过在url地址后面添加若干的token作为查询字符串来实现。token的值一般为键=值

url?key1=value1&key2=value2&...&keyn=valuen

url与token之间需要用?分开，两个token之间则是需要用一个&符号隔开。

此方法适用于token不需要在多个页面中使用时使用。

缺点是

a.在某些浏览器当中url长度有限制

b.url中的信息是可见的，安全性差

c.某些字符需要进行编码

package com.SessionManage.Test;

import java.io.IOException;

import java.io.PrintWriter;

import java.util.ArrayList;

import java.util.List;

import javax.servlet.ServletException;

import javax.servlet.annotation.WebServlet;

import javax.servlet.http.HttpServlet;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

@WebServlet(name = "Top10Servlet", urlPatterns = {"/top10"})

public class Top10Servlet extends HttpServlet {

private static final long serialVersionUID = 987654321L;

private List londonAttractions;

private List parisAttractions;

@Override

public void init() throws ServletException {

londonAttractions = new ArrayList(10);

londonAttractions.add("Buckingham Palace");

londonAttractions.add("London Eye");

londonAttractions.add("British Museum");

londonAttractions.add("National Gallery");

londonAttractions.add("Big Ben");

londonAttractions.add("Tower of London");

londonAttractions.add("Natural History Museum");

londonAttractions.add("Canary Wharf");

londonAttractions.add("2012 Olympic Park");

londonAttractions.add("St Paul's Cathedral");

parisAttractions = new ArrayList(10);

parisAttractions.add("Eiffel Tower");

parisAttractions.add("Notre Dame");

parisAttractions.add("The Louvre");

parisAttractions.add("Champs Elysees");

parisAttractions.add("Arc de Triomphe");

parisAttractions.add("Sainte Chapelle Church");

parisAttractions.add("Les Invalides");

parisAttractions.add("Musee d'Orsay");

parisAttractions.add("Montmarte");

parisAttractions.add("Sacre Couer Basilica");

}

@Override

public void doGet(HttpServletRequest request,HttpServletResponse response)

throws ServletException,IOException{

String city = request.getParameter("city");

if(city!=null&&(city.equals("london")||city.equals("paris"))){

showAttractions(request,response,city);

}else{

showMainPage(request,response);

}

private void showMainPage(HttpServletRequest request,

HttpServletResponse response) throws IOException {

// TODO Auto-generated method stub

response.setContentType("text/html");

PrintWriter writer = response.getWriter();

writer.print("

+ "

Top 10 Tourist Attractions"

+ "

+"please select a city:"

+"London"

+"Paris"

+"");

}

private void showAttractions(HttpServletRequest request,

HttpServletResponse response, String city) throws ServletException,IOException {

// TODO Auto-generated method stub

int page = 1;

String pageParameter = request.getParameter("page");

if(pageParameter!=null){

try{

page = Integer.parseInt(pageParameter);

}catch(NumberFormatException e){

e.printStackTrace();

}

if(page>2){

page = 1;

}

List attractions = null;

if(city.equals("london")){

attractions = londonAttractions;

}else if(city.equals("paris")){

attractions = parisAttractions;

}

response.setContentType("text/html");

PrintWriter writer = response.getWriter();

writer.println("

Top 10 Tourist Attractions"

");

writer.println("Select City");

writer.println("

Page"+page+"

");

int start = page*5-5;

for(int i = start; i < start+5; i++){

writer.println(attractions.get(i)+"
");

}

writer.print("

+ "Page 1");

writer.print(" Page 2");

writer.println("");

}

方法二：隐藏域

主要适用于页面当中含有表单的情况，当用户提交表单时，隐藏域中的值也传送到服务器。只有当页面包含表单，或者可以在页面添加表单时，才适合使用隐藏域。

此技术胜过网址重写的地方在于可以将更多的字符传递到服务器，且不需要进行字符编码。但仅当所需传递的信息不需要跨越多个页面时，才适合使用这种技术。

package com.SessionManage.Test2;

public class Customer {

private int id;

private String name;

private String city;

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 getCity() {

return city;

}

public void setCity(String city) {

this.city = city;

}

package com.SessionManage.Test2;

import java.io.IOException;

import java.io.PrintWriter;

import java.util.ArrayList;

import java.util.List;

import javax.servlet.ServletException;

import javax.servlet.annotation.WebServlet;

import javax.servlet.http.HttpServlet;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

@WebServlet(name = "CustomerServlet",urlPatterns = {

"/customer","/editCustomer","/updateCustomer"})

public class CustomerServlet extends HttpServlet {

private static final long serialVersionUID = -20L;

private List customers = new ArrayList();

@Override

public void init() throws ServletException{

Customer customer1 = new Customer();

customer1.setId(1);

customer1.setName("Donald D.");

customer1.setCity("Miami");

customers.add(customer1);

Customer customer2 = new Customer();

customer2.setId(2);

customer2.setName("Mickey M.");

customer2.setCity("Orlando");

customers.add(customer2);

}

private void sendCustomerList(HttpServletResponse response)

throws IOException {

response.setContentType("text/html");

PrintWriter writer = response.getWriter();

writer.println("

Customer"

Customers

");

writer.println("

for(Customer customer : customers){

writer.println("

"+customer.getName()

+"("+customer.getCity()+") "

+"edit");

}

writer.println("

");

writer.println("");

}

private Customer getCustomer(int customerId){

for(Customer customer : customers){

if(customer.getId()==customerId){

return customer;

}

return null;

}

private void sendEditCustomerForm(HttpServletRequest request,HttpServletResponse response)

throws IOException {

response.setContentType("text/html");

PrintWriter writer = response.getWriter();

int customerId = 0;

try{

customerId = Integer.parseInt(request.getParameter("id"));

}catch(NumberFormatException e){

e.printStackTrace();

}

Customer customer = this.getCustomer(customerId);

if(customer!=null){

writer.println("

Edit Customer"

EditCustomer

"

+"action='updateCustomer'>");

writer.println("");

writer.println("

Name:"

+"'/>

");

writer.println("

City:"

+"'/>

");

writer.println("

");

writer.println("

+"Customer List"

");

writer.println("

");

writer.println("

");

}else{

writer.println("No customer found");

}

@Override

public void doGet(HttpServletRequest request,HttpServletResponse response)

throws ServletException, IOException {

String uri = request.getRequestURI();

if(uri.endsWith("/customer")){

this.sendCustomerList(response);

}else if(uri.endsWith("/editCustomer")){

this.sendEditCustomerForm(request, response);

}

@Override

public void doPost(HttpServletRequest request,HttpServletResponse response)

throws ServletException, IOException{

int customerId = 0;

try{

customerId = Integer.parseInt(request.getParameter("id"));

}catch(NumberFormatException e){

e.printStackTrace();

}

Customer customer = this.getCustomer(customerId);

if(customer!=null){

customer.setName(request.getParameter("name"));

customer.setCity(request.getParameter("city"));

}

this.sendCustomerList(response);

}

方法三：cookie

cookie信息可以跨越多个页面，这点是采用网址重写和隐藏域所无法实现的。cookie是自动在web服务器和浏览器之间传递的一小块信息。

cookie适用于那些需要跨越许多页面的信息。因为cookie是作为http标头嵌入的，因此传输它的过程由http协议处理。此外，可以根据自

己的需要设置cookie的有效期限。对于web浏览器而言，每台web服务器最多可以支持20个cookie。

cookie的不足之处是用户可以通过修改其浏览器设置来拒绝接受cookie。

关于cookie的代码如下：

package com.SessionManage.Test3;

import java.io.IOException;

import java.io.PrintWriter;

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;

@WebServlet(name="PreferenceServlet",urlPatterns={"/preference"})

public class PreferenceServlet extends HttpServlet {

private static final long serialVersionUID = 888L;

public static final String MENU =

+"Cookie Class "

+"Cookie Info "

+"Preference"+"

@Override

public void doGet(HttpServletRequest request,HttpServletResponse response)

throws ServletException,IOException{

response.setContentType("text/html");

PrintWriter writer = response.getWriter();

writer.print("

"+"Preference"

+"background:NavajoWhite}"

+MENU

+"Please select the values below:"

Title Font Size:"

+"large"

+"x-large"

+"xx-large"

Title Style & Weight:"

+"italic"

+"bold"

Max. Records in Table: "

+"5"

+"10"

"+""+"");

}

@Override

public void doPost(HttpServletRequest request,HttpServletResponse response)

throws ServletException,IOException{

String maxRecords = request.getParameter("maxRecords");

String[] titleStyleAndWeight = request.getParameterValues("titleStyleAndWeight");

String titleFontSize = request.getParameter("titleFontSize");

response.addCookie(new Cookie("maxRecords",maxRecords));

response.addCookie(new Cookie("titleFontSize",titleFontSize));

Cookie cookie = new Cookie("titleFontWeight","");

cookie.setMaxAge(0);

response.addCookie(cookie);

cookie = new Cookie("titleFontStyle","");

cookie.setMaxAge(0);

response.addCookie(cookie);

if(titleStyleAndWeight!=null){

for(String style : titleStyleAndWeight){

if(style.equals("bold")){

response.addCookie(new Cookie("titleFontWeight","bold"));

}else if(style.equals("italic")){

response.addCookie(new Cookie("titleFontStyle","italic"));

}

response.setContentType("text/html");

PrintWriter writer = response.getWriter();

writer.println("

"+"Preference"

"+MENU

+"Your preference has been set."

+"
Max. Records in Table: "+maxRecords

+"
Title Font Size: "+titleFontSize

+"
Title Font Style & Weight: ");

if(titleStyleAndWeight!=null){

writer.println("

for(String style : titleStyleAndWeight){

writer.print("

"+style+"");

}

writer.println("

");

}

writer.println("");

}

package com.SessionManage.Test3;

import java.io.IOException;

import java.io.PrintWriter;

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;

@WebServlet(name="CookieClassServlet",urlPatterns={"/cookieClass"})

public class CookieClassServlet extends HttpServlet{

private static final long serialVersionUID = 837369L;

private String[] methods = {

"clone","getComment","getDomain",

"getMaxAge","getName","getPath",

"getSecure","getValue","getVersion",

"isHttpOnly","setComment","setDomain",

"setHttpOnly","setMaxAge","setPath",

"setSecure","setValue","setVersion"

};

public void doGet(HttpServletRequest request,HttpServletResponse response)

throws ServletException,IOException{

Cookie[] cookies = request.getCookies();

Cookie maxRecordsCookie = null;

if(cookies!=null){

for(Cookie cookie : cookies){

if(cookie.getName().equals("maxRecords")){

maxRecordsCookie = cookie;

break;

}

int maxRecords = 5;

if(maxRecordsCookie!=null){

try{

maxRecords = Integer.parseInt(maxRecordsCookie.getValue());

}catch(NumberFormatException e){

e.printStackTrace();

}

response.setContentType("text/html");

PrintWriter writer = response.getWriter();

writer.print("

"+"Cookie Class"

+PreferenceServlet.MENU

Here are some of the methods in "+

"javax.servlet.http.Cookie");

writer.print("

for(int i = 0;i < maxRecords; i++){

writer.print("

"+methods[i]+"");

}

writer.print("

");

writer.print("

");

}

package com.SessionManage.Test3;

import java.io.IOException;

import java.io.PrintWriter;

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.ws.rs.core.Cookie;

@WebServlet(name="CookieInfoServlet",urlPatterns={"/cookieInfo"})

public class CookieInfoServlet extends HttpServlet {

private static final long serialVersionUID = 3829L;

@Override

public void doGet(HttpServletRequest request,HttpServletResponse response)

throws ServletException,IOException{

javax.servlet.http.Cookie[] cookies = request.getCookies();

StringBuilder styles = new StringBuilder();

styles.append(".title{");

if(cookies!=null){

for(javax.servlet.http.Cookie cookie : cookies){

String name = cookie.getName();

String value = cookie.getValue();

if(name.equals("titleFontSize")){

styles.append("font-size:"+value+";");

}else if(name.equals("titleFontWeight")){

styles.append("font-weight:"+value+";");

}else if(name.equals("titleFontStyle")){

styles.append("font-style:"+value+";");

}

styles.append("}");

response.setContentType("text/html");

PrintWriter writer = response.getWriter();

writer.print("

"+"Cookie Info"

+""

"+PreferenceServlet.MENU

+"Session Management with Cookies:

");

writer.print("

");

if(cookies==null){

writer.print("No cookie in this Http response");

}else{

writer.println("
Cookie in this Http response");

for(javax.servlet.http.Cookie cookie : cookies){

writer.println("
"+cookie.getName()+":"+cookie.getValue());

}

writer.print("

");

writer.print("");

}

方法四：HttpSession对象

用户可以没有或者有一个HttpSession,并且只能访问自己的HttpSession。HttpSession是当一个用户第一次访问某个站点时创建的。通过request中getSession()方法，可以获取用户的HttpSession。而通过HttpSession的setAttribut(name,value)方法可以将值放入到HttpSession当中。

同网址重写、隐藏域和cookie所不同的地方在于，放在HttpSession中的值是保存在内存中的。因此，你只能将尽可能小的对象放在里面，并且数量不能太多。

添加到HttpSession当中的值不一定是String，可以为任意的java对象，只要它的类实现了java.io.Serializable接口即可，以便当Servlet容器认为有必要的时候，保存的对象可以序列化成一个文件或者保存到数据库中。

setAttribute方法要求不同的对象有不同的名称。如果传递一个之前用过的属性名称，那么该名称将与旧值无关联，而与新值关联。

通过HttpSession的getAttribute(name)属性可以获取HttpSession中保存的对象。其另外一个方法getAttributeNames()返回一个Enumeration，迭代一个HttpSession中的

所有属性。

注：HttpSession中保存的值不发送到客户端，这与其它的Session管理方法不同。而是Servlet容器为它所创建的每一个HttpSession生成一个唯一标示符，并将这个标示符作为一个token发送给浏览器，一般是作为一个名为JSESSIONID的cookie，或者作为一个jsessionid参数添加到url后面。在后续的请求中，浏览器会将这个token发送回服务器，使服务器知道是哪个用户在发出请求。