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HttpServlet 会话管理（一）（URL重写表单隐藏域简单示例）

2017-02-09 17:45 253 查看

本文代码转载自
《Servlet、JSP和Spring MVC初学指南》

会话管理的目的是记录用户访问的状态，

使得之前的Http访问状态可以被之后的应用直接使用，

状态的记录即通过请求传值被记录应用的过程，所以也可以看成
不同请求方式与不同的页面跳转形式的结合。

下面先分别针对GET\POST 给出通过URL重写及隐藏域的方法进行状态传送、
会话管理的实例。

URL重写的例子如下，就是简单的GET请求页面跳转

package main.ServletStudy;

/**
* Created by ehang on 2017/2/9.
*/

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<String> londonAttractions;
private List<String> parisAttrictions;

@Override
public void init()throws ServletException{
londonAttractions = new ArrayList<String>(10);
londonAttractions.add("Buckingham Palace");
londonAttractions.add("London Eye");
londonAttractions.add("British Museum");
londonAttractions.add("Notaional 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");

parisAttrictions = new ArrayList<String>(10);
parisAttrictions.add("Eiffel Tower");
parisAttrictions.add("Notre Dame");
parisAttrictions.add("The Louvre");
parisAttrictions.add("Champs Elysees");
parisAttrictions.add("Arc de Triomphe");
parisAttrictions.add("Sainte Chapelle Church");
parisAttrictions.add("Les Invalides");
parisAttrictions.add("Musee d'Orsay");
parisAttrictions.add("Montmarte");
parisAttrictions.add("Sacre Couer Basilica");
}

@Override
public void doGet(HttpServletRequest request, HttpServletResponse response)throws IOException, ServletException{
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 ServletException, IOException{
response.setContentType("text/html");
PrintWriter writer = response.getWriter();
writer.println("<html><head><title>Top 10 Tourist Attractions</title></head><body>" +
"Please select a city:" +
"<br/><a href = '?city=london'>London</a>" +
"<br/><a href = '?city=paris'>Paris</a>" +
"</body></html>");
}

private void showAttractions(HttpServletRequest request, HttpServletResponse response, String city)throws ServletException, IOException{
int page = 1;
String pageParameter = request.getParameter("page");
if(pageParameter!= null){
try{
page = Integer.parseInt(pageParameter);
}catch(NumberFormatException e){

}
if(page > 2){
page = 1;
}

}

List<String> attractions = null;
if(city.equals("london")){
attractions = londonAttractions;
}
else if(city.equals("paris")){
attractions = parisAttrictions;
}

response.setContentType("text/html");
PrintWriter writer = response.getWriter();
writer.println("<html><head><title>Top 10 Tourist Attraction</title></head><body>" +
"<a href = 'top10'>Select City</a>");

writer.println("<hr/>Page " + page + "<hr/>");
int start = page * 5 - 5;
for(int i = start;i < start + 5;i ++){
writer.println(attractions.get(i) + "</br>");
}
writer.print("<hr style = 'color:blue'/><a href = '?city=" + city + "&page=1'>Page 1</a>");
writer.print("  <a href = '?city=" + city + "&page=2'>Page 2</.a>");

writer.println("</body></html>");

}

}

隐藏域的方式即是利用input（type = 'hidden''）的隐藏表单记录一个默认POST参数，
使得默认传值得以进行。（这种方法仅能应用于表单情形，因其需要input submit来提交请求）
下面是简单例子

package main.ServletStudy;

/**
* Created by ehang on 2017/2/9.
*/

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;
}

}

import java.io.IOException;
import java.io.PrintWriter;
import java.net.HttpRetryException;
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<Customer> customers = new ArrayList<Customer>();

@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("<html><head><title>Customers</title></head><body><h2>Customers</h2><ul>");
for(Customer customer: customers){
writer.println("<li>" + customer.getName() + "(" + customer.getCity() + ") (" +
"<a href = 'editCustomer?id=" + customer.getId() + "'>edit</a>)");
}

writer.println("</ul></body></html>");

}

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){
}
Customer customer = getCustomer(customerId);

if(customer != null){
writer.println("<html><head><title>Edit Customer</title></head><body><h2>Edit Customer</h2>" +
"<form method = 'post' action = 'updateCustomer'>" +
c491

"<input type = 'hidden' name = 'id' value = '" + customerId + "'/>" +
"<table>" +

"<tr><td>Name:</td><td>" +
"<input name = 'name' value = '" + customer.getName().replaceAll("'", "'") +
"'/></td></tr>" +

"<tr><td>City:</td><td>" +
"<input name = 'city' value = '" + customer.getCity().replaceAll("'", "'") +
"'/></td></tr>" +

"<tr><td colspan = '2' style = 'text-align:right'>" +
"<input type = 'submit' value = 'Update'></td></tr>" +

"<tr><td colspan = '2'><a href = 'customer'>Customer List</a></td></tr>" +

"</table></form></body></html>");
}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")){
sendCustomerList(response);
}else if(uri.endsWith("/editCustomer")){
sendEditCustomerForm(request, response);
}
}

@Override
public void doPost(HttpServletRequest request, HttpServletResponse response) throws HttpRetryException, IOException {
int customerId = 0;
try{
customerId = Integer.parseInt(request.getParameter("id"));
}catch(NumberFormatException e){
}

Customer customer = getCustomer(customerId);
if (customer != null){
customer.setName(request.getParameter("name"));
customer.setCity(request.getParameter("city"));
}
sendCustomerList(response);

}

}

该例与之前的例子的不同是通过request.getRequestURI()来进行URI判断进行同一个Servlet的不同页面的访问处理。
html td标签 colspan指定宽度跨多少列。

URL重写及隐藏域的方法适用于较少的页面跳转。

内容来自用户分享和网络整理，不保证内容的准确性，如有侵权内容，可联系管理员处理

标签： HttpServlet GET POST URL重写表单隐藏域

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章节导航

HttpServlet 会话管理（一）（URL重写 表单隐藏域 简单示例）

HttpServlet 会话管理（一）（URL重写表单隐藏域简单示例）