会话跟踪技术--session的使用

会话跟踪：

1、使用隐藏表单字段

2、URL重写

http://host/path/file.jsp?sessionid=landril

3、持久Cookie

4、会话HttpSession

一、使用session的简单步骤

获取HttpSession(request.getSession()方法)对象，查找与该会话相关的信息(session.getAttribute())，存储会话中的信息(session.setAttribute())，删除会话中的数据(session.removeAttribute())，删除当前会话(session.invalidate())

在session中，可以存储任意数量的键值对，通过键即可获取相应的值，即使用：session.getAttribute(“key”);。

二、session的常用方法

1、getAttribute()：从session中获取以前存储的值

2、getAttributeNames()：返回session中所有属性的名称

3、setAttribute()：将键与值关联起来，存储进session

4、removeAttribute()：删除session中存储的对应键的值

5、invalidate()：删除整个session及其存储的键值

6、logout()：注销当前用户

7、getId()：获取每个session对应的唯一ID

8、getCreationTime()：获取session创建的时间

9、getLastAccessedTime()：获取session最后被访问的时间

10、getMaxInactiveInterval()：在用户没有访问的情况下，会话在被自动废弃之前应该保持多长时间

三、使用session的一个例子，拥有购物车的在线商店

1、CatalogPage.java

packagecom.landril.session;

importjava.io.IOException;

importjava.io.PrintWriter;

importjavax.servlet.ServletException;

importjavax.servlet.http.HttpServlet;

importjavax.servlet.http.HttpServletRequest;

importjavax.servlet.http.HttpServletResponse;

publicclassCatalogPageextendsHttpServlet {

privateCatalogItem[]items;

privateString[]itemIds;

privateStringtitle;

protectedvoidsetItems(String[] itemIds) {

this.itemIds= itemIds;

items=newCatalogItem[itemIds.length];

for(inti = 0; i

items[i] = Catalog.getItem(itemIds[i]);

}

}

protectedvoidsetTitle(String title) {

this.title= title;

}

publicvoiddoGet(HttpServletRequest request, HttpServletResponse response)

throwsServletException, IOException {

if(items==null){

response.sendError(response.SC_NOT_FOUND,"Missing Items:");

return;

}

response.setContentType("text/html");

PrintWriter out = response.getWriter();

out.println("

"+title+"

"+title+"

");

CatalogItem item;

for(inti = 0; i

out.println("

---

");

item =items[i];

if(item ==null)

out.println("Unknow itemId: "+itemIds[i]);

else{

out.println();

String formURL = request.getContextPath()+"/orderPage";

formURL = response.encodeURL(formURL);

out.println("

");

out.println("");

out.println(newString(item.getSDesc().getBytes("utf-8"),"GBK")+"$"+item.getPrice()+item.getLDesc());

out.println("

");

}

}

}

}

2、ComputerBook.java

packagecom.landril.session;

publicclassComputerBookextendsCatalogPage{

publicvoidinit(){

String[] ids = {"book1","book2","book3","book4"};

setItems(ids);

setTitle("Japanese Book");

}

}

3、JapaneseBook.java

packagecom.landril.session;

publicclassJapaneseBookextendsCatalogPage{

publicvoidinit(){

String[] ids = {"book5","book6"};

setItems(ids);

setTitle("Computer Book");

}

}

4、OrderPage.java

packagecom.landril.session;

importjava.io.IOException;

importjava.io.PrintWriter;

importjava.util.List;

importjavax.servlet.ServletException;

importjavax.servlet.http.HttpServlet;

importjavax.servlet.http.HttpServletRequest;

importjavax.servlet.http.HttpServletResponse;

importjavax.servlet.http.HttpSession;

publicclassOrderPageextendsHttpServlet {

publicvoiddoGet(HttpServletRequest request, HttpServletResponse response)

throwsServletException, IOException {

HttpSession session = request.getSession();

ShoppingCart cart;

synchronized(session){

cart = (ShoppingCart)session.getAttribute("shop");

if(cart ==null){

cart =newShoppingCart();

session.setAttribute("shop", cart);

}

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

if(itemId !=null){

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

if(num ==null)

cart.addItem(itemId);

else{

intnumItems;

try{

numItems = Integer.parseInt(num);

}catch(NumberFormatException e) {

numItems = 1;

}

cart.setNum(itemId, numItems);

}

}

}

response.setContentType("text/html");

PrintWriter out = response.getWriter();

String title ="Your Order";

out.println("

"+title+"

"+title+"

");

synchronized(session){

List itemOrders = cart.getItemOrders();

if(itemOrders.size() == 0)

out.println("No items");

else{

out.println("

Item ID	Short Description	Long Description	Unit Price	Number	Total Price"); ItemOrder order; for(inti = 0; i < itemOrders.size(); i++) { order = (ItemOrder)itemOrders.get(i); out.println("
"+order.getItemId()+"	"+order.getSDesc()+"	"+order.getLDesc()+"	"+order.getUnitPrice()+"	"); out.println(" "); out.println(""); out.println("	"); out.println(order.getTotalPrice()); } String checkURL = response.encodeURL(request.getContextPath()+"/check.html"); out.println("

");

out.println("

");

}

}

}

}

5、ShoppingCart.java

packagecom.landril.session;

importjava.util.ArrayList;

importjava.util.List;

publicclassShoppingCart {

privateListitemOrders;

publicShoppingCart() {

itemOrders=newArrayList();

}

publicList getItemOrders(){

returnitemOrders;

}

publicsynchronizedvoidaddItem(String itemId){

ItemOrder order;

for(inti=0;i

order = (ItemOrder)itemOrders.get(i);

if(itemId.equals(order.getItemId())){

order.addNum();

return;

}

}

ItemOrder newOrd =newItemOrder(Catalog.getItem(itemId));

itemOrders.add(newOrd);

}

publicsynchronizedvoidsetNum(String itemId,intnum){

ItemOrder order;

for(inti = 0; i

order = (ItemOrder)itemOrders.get(i);

if(itemId.equals(order.getItemId())){

if(num <=0)

itemOrders.remove(i);

else

order.setNum(num);

}

return;

}

ItemOrder newOrd =newItemOrder(Catalog.getItem(itemId));

itemOrders.add(newOrd);

}

}

6、CatalogItem.java

packagecom.landril.session;

publicclassCatalogItem {

privateStringitemId;

privateStringsDesc;

privateStringlDesc;

privatefloatprice;

publicString getItemId() {

returnitemId;

}

publicvoidsetItemId(String itemId) {

this.itemId= itemId;

}

publicString getLDesc() {

returnlDesc;

}

publicvoidsetLDesc(String desc) {

lDesc= desc;

}

publicfloatgetPrice() {

returnprice;

}

publicvoidsetPrice(floatprice) {

this.price= price;

}

publicString getSDesc() {

returnsDesc;

}

publicvoidsetSDesc(String desc) {

sDesc= desc;

}

publicCatalogItem(String itemId, String desc, String desc2,floatprice) {

super();

this.itemId= itemId;

sDesc= desc;

lDesc= desc2;

this.price= price;

}

}

7、ItemOrder.java

packagecom.landril.session;

publicclassItemOrder {

privateCatalogItemitem;

privateintnum;

publicItemOrder(CatalogItem item) {

setItem(item);

setNum(1);

}

publicCatalogItem getItem() {

returnitem;

}

publicvoidsetItem(CatalogItem item) {

this.item= item;

}

publicintgetNum() {

returnnum;

}

publicvoidsetNum(intnum) {

this.num= num;

}

publicString getItemId() {

returnitem.getItemId();

}

publicString getSDesc() {

returnitem.getSDesc();

}

publicString getLDesc() {

returnitem.getLDesc();

}

publicfloatgetUnitPrice() {

returnitem.getPrice();

}

publicvoidaddNum() {

setNum(num+ 1);

}

publicvoidcancelOrder() {

setNum(0);

}

publicfloatgetTotalPrice() {

returnnum* getUnitPrice();

}

}

8、Catalog.java

packagecom.landril.session;

publicclassCatalog {

privatestaticCatalogItem[]items= {

newCatalogItem("book1","Hibernate","Hibernate，Hibernate", 57),

newCatalogItem("book2","Spring","Spring，Spring", 36),

newCatalogItem("book3","Tomcat","Tomcat，Tomcat", 23),

newCatalogItem("book4","Jboss","Jboss，Jboss", 35),

newCatalogItem("book5","Japanese1","Japanese1，Japanese1", 35),

newCatalogItem("book6","Japanese2","Japanese2，Japanese2", 23) };

publicstaticCatalogItem getItem(String itemId) {

CatalogItem item;

if(itemId ==null)

returnnull;

for(inti = 0; i

item =items[i];

if(itemId.equals(item.getItemId()))

returnitem;

}

returnnull;

}

}

9、check.html

checking out

Checking out

posted on 2007-04-28 21:33 landril 阅读(2497) 评论(1)  编辑  收藏 所属分类: Jsp&Servlet