Java tutorial
/* * Copyright (c) 1997-2018 Oracle and/or its affiliates. All rights reserved. * Copyright 2004 The Apache Software Foundation * * Licensed under the Apache License, Version 2.0 (the "License"); * you may not use this file except in compliance with the License. * You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */ package javax.servlet.http; import java.util.Enumeration; import javax.servlet.ServletContext; /** * * Provides a way to identify a user across more than one page * request or visit to a Web site and to store information about that user. * * <p>The servlet container uses this interface to create a session * between an HTTP client and an HTTP server. The session persists * for a specified time period, across more than one connection or * page request from the user. A session usually corresponds to one * user, who may visit a site many times. The server can maintain a * session in many ways such as using cookies or rewriting URLs. * * <p>This interface allows servlets to * <ul> * <li>View and manipulate information about a session, such as * the session identifier, creation time, and last accessed time * <li>Bind objects to sessions, allowing user information to persist * across multiple user connections * </ul> * * <p>When an application stores an object in or removes an object from a * session, the session checks whether the object implements * {@link HttpSessionBindingListener}. If it does, * the servlet notifies the object that it has been bound to or unbound * from the session. Notifications are sent after the binding methods complete. * For session that are invalidated or expire, notifications are sent after * the session has been invalidated or expired. * * <p> When container migrates a session between VMs in a distributed container * setting, all session attributes implementing the {@link HttpSessionActivationListener} * interface are notified. * * <p>A servlet should be able to handle cases in which * the client does not choose to join a session, such as when cookies are * intentionally turned off. Until the client joins the session, * <code>isNew</code> returns <code>true</code>. If the client chooses * not to join * the session, <code>getSession</code> will return a different session * on each request, and <code>isNew</code> will always return * <code>true</code>. * * <p>Session information is scoped only to the current web application * (<code>ServletContext</code>), so information stored in one context * will not be directly visible in another. * * @author Various * * @see HttpSessionBindingListener * @see HttpSessionContext */ public interface HttpSession { /** * * 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 */ 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 marked by the time the container received 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 * * @exception 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 Servlet 2.3 */ public ServletContext getServletContext(); /** * Specifies the time, in seconds, between client requests before the * servlet container will invalidate this session. * * <p>An <tt>interval</tt> value of zero or less indicates that the * session should never timeout. * * @param interval An integer specifying the number * of seconds */ public void setMaxInactiveInterval(int interval); /** * Returns the maximum time interval, in seconds, that * the servlet container will keep this session open between * client accesses. After this interval, the servlet container * will invalidate the session. The maximum time interval can be set * with the <code>setMaxInactiveInterval</code> method. * * <p>A return value of zero or less indicates that the * session will never timeout. * * @return an integer specifying the number of * seconds this session remains open * between client requests * * @see #setMaxInactiveInterval */ public int getMaxInactiveInterval(); /** * * @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. * * @return the {@link HttpSessionContext} for this session. */ @Deprecated 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 */ @Deprecated 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<String> 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 */ @Deprecated 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 */ @Deprecated 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 */ @Deprecated 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(); }