大家能把session的用法发出来让我学习么

没有什么呀就是设置,存取,移除,设置session过期时间 ! 你的书上应该也有吧!

你去下载一个DreamweaverMX，你用它来开发JSP，它和JBuilder一样，你敲入session.它会把可以用的方法全部列出来的。很方便。下面是两个最基本用法。session.setAttribute("Username",user);//给一个Session变量Username赋值，值为usersession.removeAttribute("Username");//把这个Session变量清空

/**
     *
     * Returns the time when this session was created, measured
     * in milliseconds since midnight January 1, 1970 GMT.
     *
     * @return a <code>long</code> specifying
     * when this session was created,
     * expressed in
     * milliseconds since 1/1/1970 GMT
     *
     * @exception IllegalStateException if this method is called on an
     * invalidated session
     *
     */    public long getCreationTime();
    /**
     *
     * Returns a string containing the unique identifier assigned
     * to this session. The identifier is assigned
     * by the servlet container and is implementation dependent.
     *
     * @return a string specifying the identifier
     * assigned to this session
     *
     * @exeption IllegalStateException if this method is called on an
     * invalidated session
     *
     */    public String getId();
        /**
     *
     * Returns the last time the client sent a request associated with
     * this session, as the number of milliseconds since midnight
     * January 1, 1970 GMT, and ed by the time the container recieved the request.
     *
     * <p>Actions that your application takes, such as getting or setting
     * a value associated with the session, do not affect the access
     * time.
     *
     * @return a <code>long</code>
     * representing the last time
     * the client sent a request associated
     * with this session, expressed in
     * milliseconds since 1/1/1970 GMT
     *
     * @exeption IllegalStateException if this method is called on an
     * invalidated session
     *
     */    public long getLastAccessedTime();    /**
    * Returns the ServletContext to which this session belongs.
    *
    * @return The ServletContext object for the web application
    * @since 2.3
    */    public ServletContext getServletContext();    /**
     *
     * Specifies the time, in seconds, between client requests before the
     * servlet container will invalidate this session.  A negative time
     * indicates the session should never timeout.
     *
     * @param interval An integer specifying the number
     * of seconds
     *
     */

    public void setMaxInactiveInterval(int interval);

/**
    *
    * @deprecated As of Version 2.1, this method is
    * deprecated and has no replacement.
    * It will be removed in a future
    * version of the Java Servlet API.
    *
    */    public HttpSessionContext getSessionContext();    /**
     *
     * Returns the object bound with the specified name in this session, or
     * <code>null</code> if no object is bound under the name.
     *
     * @param name a string specifying the name of the object
     *
     * @return the object with the specified name
     *
     * @exception IllegalStateException if this method is called on an
     * invalidated session
     *
     */

    public Object getAttribute(String name);

    /**
     *
     * @deprecated As of Version 2.2, this method is
     * replaced by {@link #getAttribute}.
     *
     * @param name a string specifying the name of the object
     *
     * @return the object with the specified name
     *
     * @exception IllegalStateException if this method is called on an
     * invalidated session
     *
     */

    public Object getValue(String name);   /**
     *
     * Returns an <code>Enumeration</code> of <code>String</code> objects
     * containing the names of all the objects bound to this session.
     *
     * @return an <code>Enumeration</code> of
     * <code>String</code> objects specifying the
     * names of all the objects bound to
     * this session
     *
     * @exception IllegalStateException if this method is called on an
     * invalidated session
     *
     */

    public Enumeration getAttributeNames();

    /**
     *
     * @deprecated As of Version 2.2, this method is
     * replaced by {@link #getAttributeNames}
     *
     * @return an array of <code>String</code>
     * objects specifying the
     * names of all the objects bound to
     * this session
     *
     * @exception IllegalStateException if this method is called on an
     * invalidated session
     *
     */

    public String[] getValueNames();

    /**
     * Binds an object to this session, using the name specified.
     * If an object of the same name is already bound to the session,
     * the object is replaced.
     *
     * <p>After this method executes, and if the new object
     * implements <code>HttpSessionBindingListener</code>,
     * the container calls
     * <code>HttpSessionBindingListener.valueBound</code>. The container then
     * notifies any <code>HttpSessionAttributeListener</code>s in the web
     * application.

     * <p>If an object was already bound to this session of this name
     * that implements <code>HttpSessionBindingListener</code>, its
     * <code>HttpSessionBindingListener.valueUnbound</code> method is called.
     *
     * <p>If the value passed in is null, this has the same effect as calling
     * <code>removeAttribute()<code>.
     *
     *
     * @param name the name to which the object is bound;
     * cannot be null
     *
     * @param value the object to be bound
     *
     * @exception IllegalStateException if this method is called on an
     * invalidated session
     *
     */

    public void setAttribute(String name, Object value);

/**
     *
     * @deprecated As of Version 2.2, this method is
     * replaced by {@link #setAttribute}
     *
     * @param name the name to which the object is bound;
     * cannot be null
     *
     * @param value the object to be bound; cannot be null
     *
     * @exception IllegalStateException if this method is called on an
     * invalidated session
     *
     */

    public void putValue(String name, Object value);
    /**
     *
     * Removes the object bound with the specified name from
     * this session. If the session does not have an object
     * bound with the specified name, this method does nothing.
     *
     * <p>After this method executes, and if the object
     * implements <code>HttpSessionBindingListener</code>,
     * the container calls
     * <code>HttpSessionBindingListener.valueUnbound</code>. The container
     * then notifies any <code>HttpSessionAttributeListener</code>s in the web
     * application.
     *
     *
     *
     * @param name the name of the object to
     * remove from this session
     *
     * @exception IllegalStateException if this method is called on an
     * invalidated session
     */    public void removeAttribute(String name);
    /**
     *
     * @deprecated As of Version 2.2, this method is
     * replaced by {@link #removeAttribute}
     *
     * @param name the name of the object to
     * remove from this session
     *
     * @exception IllegalStateException if this method is called on an
     * invalidated session
     */    public void removeValue(String name);    /**
     *
     * Invalidates this session then unbinds any objects bound
     * to it.
     *
     * @exception IllegalStateException if this method is called on an
     * already invalidated session
     *
     */    public void invalidate();




    /**
     *
     * Returns <code>true</code> if the client does not yet know about the
     * session or if the client chooses not to join the session.  For
     * example, if the server used only cookie-based sessions, and
     * the client had disabled the use of cookies, then a session would
     * be new on each request.
     *
     * @return <code>true</code> if the
     * server has created a session,
     * but the client has not yet joined
     *
     * @exception IllegalStateException if this method is called on an
     * already invalidated session
     *
     */    public boolean isNew();

session对象用于在使用无状态连接协议（如HTTP）的情况下跟踪关于某个客户的信息。会话可以用于在客户请求之间存储任意信息。
每个会话应该只对应于一个客户，并且可以跨多个请求。会话通常通过URL重写或cookie来跟踪，但是跟踪进行请求的客户的方法对于session对象并不重要。
session对象是javax.servlet.http.HttpSession的实例，其行为方式与Java Servlet下的session对显完全相同。
希望对你有所帮助！！

session.putValue("tag","我是乔锋我怕谁")
String tag=(String)session.getValue("tag");
if(tag.equals("我是乔锋我怕谁")) out.println("我现在时段誉了");

Jsp中的session使用
板桥里人 jdon.comJsp的session是使用bean的一个生存期限,一般为page,session意思是在这个用户没有离开网站之前一直有效,如果无法判断用户何时离开,一般依据系统设定,tomcat中设定为30分钟.我们使用seesion功能,可以达到多个jsp程序从操作同一个java bean, 那么这个java bean可以作为我们传统意义上的"全局变量池".(在java中我们可以使用static静态化一个变量和方法,使用singleton唯一化对象.)在项目实践中,我们Jsp程序中很多参数需要从数据库中读取,有的参数实际读取一次就可以,如果设计成每个用户每产生一个页面都要读取数据库,很显然,数据库的负载很大,同时也浪费时间,虽然可能有数据库连接池优化,但是尽量少使用数据库是我们编程的原则.比如,我们的test.jsp 和test1.jsp都需要得到一个参数userdir,这个userdir是从数据库中得知,使用session将大大优化性能,程序如下:设计一个javabean 存储userdir.public class UserEnv {private String userdir = "";
private String userurl = "";public UserEnv(){
//构建方法初始化userdir,可以从数据库中读取,这里简单给值ppp
userdir="pppp";
System.out.println("init userdir, one time");
} public String getUserdir() throws Exception{
return userdir;} }test1.jsp程序:
<%@ page contentType="text/html;charset=ISO8859_1" %> <jsp:useBean id="myenv" scope="session" class="mysite.UserEnv"/>
<html>
<head>
<title>Untitled</title>
<meta http-equiv="Content-Type" content="text/html; charset=gb2312">
</head><body>this is test1.jsp:<%=myenv.getUserdir()%>
</body>
</html>
test2.jsp程序:
<%@ page contentType="text/html;charset=ISO8859_1" %> <jsp:useBean id="myenv" scope="session" class="mysite.UserEnv"/>
<html>
<head>
<title>Untitled</title>
<meta http-equiv="Content-Type" content="text/html; charset=gb2312">
</head><body>this is test2.jsp:<%=myenv.getUserdir()%>
</body>
</html> 无论用户先调用test1.jsp还是test2.jsp, java bean UserEnv总是先初始化一次, 由于这个bean存在周期是seesion,因此该用户第二次以后只要在seesion有效期内再调用,myenv.getUserdir()将直接从bean内存中读取变量,不必再初始化.这样提高速度,又减少数据库访问量.这样,我们就有了一个jsp程序之间共享变量或方法的实现办法.

Jsp中的session管理
MHDN.net
会话状态维持是 Web 应用开发者必须面对的问题。有多种方法可以用来解决这个问题，如使用 Cookies 、隐藏的表单输入域，或直接将状态信息附加到 URL 中。 Java Servlet 提供了一个在多个请求之间持续有效的会话对象，该对象允许用户存储和提取会话状态信息。 JSP 也同样支持 Servlet 中的这个概念。
　　在 Sun 的 JSP 指南中可以看到许多有关隐含对象的说明（隐含的含义是，这些对象可以直接引用，不需要显式地声明，也不需要专门的代码创建其实例）。例如 request 对象，它是 HttpServletRequest 的一个子类。该对象包含了所有有关当前浏览器请求的信息，包括 Cookies ， HTML 表单变量等等。 session 对象也是这样一个隐含对象。这个对象在第一个 JSP 页面被装载时自动创建，并被关联到 request 对象上。与 ASP 中的会话对象相似， JSP 中的 session 对象对于那些希望通过多个页面完成一个事务的应用是非常有用的。　　为说明 session 对象的具体应用，接下来我们用三个页面模拟一个多页面的 Web 应用。第一个页面（ q1.html ）仅包含一个要求输入用户名字的 HTML 表单，代码如下：　 < HTML> 　 < BODY> 　 < FORM METHOD=POST ACTION=".jsp"> 　请输入您的姓名：　 < INPUT TYPE=TEXT NAME="thename"> 　 < INPUT TYPE=SUBMIT VALUE="SUBMIT"> 　 < /FORM> 　 < /BODY> 　 < /HTML> 　　第二个页面是一个 JSP 页面（ .jsp ），它通过 request 对象提取 q1.html 表单中的 thename 值，将它存储为 name 变量，然后将这个 name 值保存到 session 对象中。 session 对象是一个名字 / 值对的集合，在这里，名字 / 值对中的名字为“ thename ”，值即为 name 变量的值。由于 session 对象在会话期间是一直有效的，因此这里保存的变量对后继的页面也有效。 .jsp 的另外一个任务是询问第二个问题。下面是它的代码：　 < HTML> 　 < BODY> 　 < %@ page language="java" %> 　 < %! String name=""; %> 　 < % 　 name = request.getParameter("thename"); 　 session.putValue("thename", name); 　 %> 　您的姓名是： < %= name %> 　 < p> 　 < FORM METHOD=POST ACTION="q3.jsp"> 　您喜欢吃什么 ? 　 < INPUT TYPE=TEXT NAME="food"> 　 < P> 　 < INPUT TYPE=SUBMIT VALUE="SUBMIT"> 　 < /FORM> 　 < /BODY> 　 < /HTML> 　　第三个页面也是一个 JSP 页面（ q3.jsp ），主要任务是显示问答结果。它从 session 对象提取 thename 的值并显示它，以此证明虽然该值在第一个页面输入，但通过 session 对象得以保留。 q3.jsp 的另外一个任务是提取在第二个页面中的用户输入并显示它：　 < HTML> 　 < BODY> 　 < %@ page language="java" %> 　 < %! String food=""; %> 　 < % 　 food = request.getParameter("food"); 　 String name = (String) session.getValue("thename"); 　 %> 　您的姓名是： < %= name %> 　 < P> 　您喜欢吃： < %= food %> 　 < /BODY> 　 < /HTML>

调试易

大家能把session的用法发出来让我学习么

解决方案 »