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JSP 中的 利用Servlet的上下文环境和会话来实现聊天的程序
出处:互联网 整理: 软晨网（RuanChen.com） 发布: 2009-09-04 浏览: 88 ::
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上下文环境是针对服务器端的数据共享，例如聊天室目录，聊天信息就存在上下文环境中
会话，是针对客户端信息共享，如你登录了那个聊天室
具体代码显示如下，（参考J2EE编程指南）
/////////////////////////////////////////////////////////////
//////////////////////////////////////////
public class ChatEntry {
private String profileName;
private String message;
public ChatEntry(String profileName, String message) {
this.profileName = profileName;
this.message = message;
}
public String getProfileName() {
return profileName;
}
public void setProfileName(String profileName) {
this.profileName = profileName;
}
public String getMessage() {
return message;
}
}
/////////////////////////////////////////
///////////////
import java.util.Stack;
public class ChatRoom extends Stack {
private String name;
private String description;
public ChatRoom(String name, String description, int maxEntries) {
this.name = name;
this.description = description;
this.setSize(maxEntries);
}
public void addChatEntry(ChatEntry entry) {
push(entry);
}
public String getDescription() {
return description;
}
public String getName() {
return name;
}
}
////////////////////////////////////////////
////////////////////////////////
// Import servlet packages
import javax.servlet.ServletException;
import javax.servlet.ServletContext;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
// Import java packages
import java.io.IOException;
import java.io.PrintWriter;
import java.util.HashMap;
import java.util.Iterator;
public class ChatAdminServlet extends HttpServlet {
String chatRoomPath;
String listRoomsPath;
String chatAdminPath;
public void init() {
ServletContext context = getServletContext();
chatRoomPath = context.getInitParameter("CHATROOM_PATH");
listRoomsPath = context.getInitParameter("LISTROOMS_PATH");
chatAdminPath = context.getInitParameter("ADMIN_PATH");
}
public void doGet(HttpServletRequest req, HttpServletResponse res)
throws IOException, ServletException {
res.setContentType("text/html");
PrintWriter out = res.getWriter();
out.println("<HTML>");
out.println("<HEAD><TITLE>Chat Room Administration</TITLE></HEAD>");
out.println("<BODY>");
out.println("<H1>Chat room administration</H1>");
out.println("<FORM METHOD=\"POST\" ACTION=\"" + res.encodeURL(chatAdminPath) + "\">");
// Check for existing chat rooms
HashMap roomList = (HashMap) getServletContext().getAttribute("roomList");
if(roomList != null) {
Iterator rooms = roomList.keySet().iterator();
if(!rooms.hasNext()) {
out.println("<p>There are no rooms</p>");
} else {
out.println("<p>Check the rooms you would like to remove," + "and press Update List.</p>");
while(rooms.hasNext()) {
String roomName = (String) rooms.next();
ChatRoom room = (ChatRoom) roomList.get(roomName);
out.println("<INPUT TYPE=CHECKBOX NAME=remove VALUE='" + room.getName() + "'>" + room.getName() + "<BR>");
}
}
}
// Add fields for adding a room
out.println("<P>Enter a new room and the description<P>");
out.println("<TABLE>");
out.println("<TR><TD>Name:</TD><TD><INPUT NAME=roomname SIZE=50></TD></TR>");
out.println("<TR><TD>Description:</TD>");
out.println("<TD><TEXTAREA NAME=roomdescr COLS=40 ROWS=5>");
out.println("</TEXTAREA></TD></TR>");
out.println("</TABLE>");
// Add submit button
out.println("<P><INPUT TYPE=SUBMIT VALUE='Update List'>");
out.println("<p><A HREF=\"" + listRoomsPath + "\">Chat Now</a>");
out.println("</FORM>");
out.println("</BODY></HTML>");
out.close();
}
/**
* Processes POST request for adding new rooms, or deleting existing rooms.
*/
public void doPost(HttpServletRequest req, HttpServletResponse res)
throws IOException, ServletException {
HashMap roomList = null;
// Check for existing chat rooms
synchronized(getServletContext()) {
roomList = (HashMap) getServletContext().getAttribute("roomList");
if(roomList == null) {
roomList = new HashMap();
getServletContext().setAttribute("roomList", roomList);
}
}
// Update the room list
String[] removeList = req.getParameterValues("remove");
synchronized(roomList) {
if(removeList != null) {
for(int i = 0; i < removeList.length; i++) {
roomList.remove(removeList[i]);
}
}
}
String roomName = req.getParameter("roomname");
String roomDescr = req.getParameter("roomdescr");
if(roomName != null && roomName.length() > 0) {
synchronized(roomList) {
roomList.put(roomName, new ChatRoom(roomName, roomDescr, 4));
}
}
doGet(req, res);
}
}
/////////////////////////////////////////
///////////////////////////////////
// Import servlet packages
import javax.servlet.ServletException;
import javax.servlet.ServletContext;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpSession;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
// Import java packages
import java.io.IOException;
import java.io.PrintWriter;
import java.util.HashMap;
import java.util.Iterator;
import java.net.URLEncoder;
public class ListRoomsServlet extends HttpServlet {
String chatAdminPath;
String listRoomsPath;
String chatRoomPath;
public void init() {
ServletContext context = getServletContext();
chatAdminPath = context.getInitParameter("ADMIN_PATH");
listRoomsPath = context.getInitParameter("LISTROOMS_PATH");
chatRoomPath = context.getInitParameter("CHATROOM_PATH");
}
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws IOException {
response.setContentType("text/html");
PrintWriter out = response.getWriter();
String expand = request.getParameter("expand");
HttpSession session = request.getSession();
String profileName = (String) session.getAttribute("profileName");
if(profileName == null) {
profileName = "";
}
out.println("<HTML>");
out.println("<HEAD><TITLE>Chat rooms</TITLE></HEAD>");
out.println("<BODY>");
out.println("<H1>Chat rooms</H1>");
out.println("<FORM METHOD=POST ACTION=\"" + chatRoomPath + "\">");
out.println("<p><a href=\"" + chatAdminPath + "\">Create Rooms</a></p>");
// Get the list of rooms
HashMap roomList = (HashMap) getServletContext().getAttribute("roomList");
if(roomList == null) {
out.println("<p>There are no rooms available right now.</p>");
} else {
// Add radio boxes for selecting a room
out.println("Select the room you like to enter " + "or click on a name to see the description:<P>");
Iterator rooms = roomList.keySet().iterator();
boolean isFirst = true;
while(rooms.hasNext()) {
String roomName = (String) rooms.next();
ChatRoom room = (ChatRoom) roomList.get(roomName);
String listRoomsURL = listRoomsPath + "/?expand=" + URLEncoder.encode(roomName);
listRoomsURL = response.encodeURL(listRoomsURL);
out.println("<INPUT TYPE=RADIO NAME=roomName VALUE=\"" + roomName + "\"" +
(isFirst ? " CHECKED" : "") + ">" + "<A HREF=\"" + listRoomsURL + "\">" +
roomName + "</A><BR>");
isFirst = false;
// Show description if requested
if (expand != null && expand.equals(roomName)) {
out.println("<BLOCKQUOTE>");
if(room.getDescription().length() == 0) {
out.println("No description available.");
} else {
out.println(room.getDescription());
}
out.println("</BLOCKQUOTE><BR>");
}
}
// Add a field for the profile name
out.println("<P>Enter your name: ");
out.println("<INPUT NAME=profileName VALUE='" + profileName + "' SIZE=30>");
// Add submit button
out.println("<P><INPUT TYPE=SUBMIT VALUE='Enter'>");
out.println("</FORM>");
}
out.println("</BODY></HTML>");
out.close();
}
}
/////////////////////////////////////////////////////
///////////////////////////////////////
// Import servlet packages
import javax.servlet.ServletException;
import javax.servlet.ServletContext;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpSession;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
// Import java packages
import java.io.IOException;
import java.io.PrintWriter;
import java.util.HashMap;
import java.util.Iterator;
public class ChatRoomServlet extends HttpServlet {
String chatRoomPath;
String listRoomsPath;
public void init() {
ServletContext context = getServletContext();
chatRoomPath = context.getInitParameter("CHATROOM_PATH");
listRoomsPath = context.getInitParameter("LISTROOMS_PATH");
}
public void doGet(HttpServletRequest req, HttpServletResponse res)
throws IOException, ServletException {
res.setContentType("text/html");
PrintWriter out = res.getWriter();
ChatRoom room = getRoom(req, res);
if(room == null) {
return;
}
// Check if it's a request for a message list or a form
String listPar = req.getParameter("list");
if(listPar != null && listPar.equals("true")) {
writeMessages(out, room, getProfileName(req));
} else {
out.println("<HTML>");
out.println("<BODY>");
out.println("<FORM METHOD=\"POST\" ACTION=\"" + res.encodeURL(chatRoomPath) + "\" TARGET=\"_top\">");
out.println("<p>Enter your message:</p>");
out.println("<INPUT NAME=\"msg\" SIZE=\"30\">");
// Add a Submit button
out.println("<P><INPUT TYPE=SUBMIT VALUE='Send Message'>");
// Add an Exit button
out.println("</FORM>");
out.println("<FORM ACTION=\"" + res.encodeURL(listRoomsPath) + "\" METHOD=\"GET\" TARGET=\"_top\">");
out.println("<INPUT TYPE=SUBMIT VALUE=Exit>");
out.println("</FORM>");
out.println("</BODY></HTML>");
}
out.close();
}
public void doPost(HttpServletRequest req, HttpServletResponse res)
throws IOException, ServletException {
res.setContentType("text/html");
ChatRoom room = getRoom(req, res);
if (room == null) {
return;
}
String profileName = getProfileName(req);
// Save message if any
String msg = req.getParameter("msg");
if (msg != null && msg.length() != 0) {
room.addChatEntry(new ChatEntry(profileName, msg));
}
writeFrame(res, room);
}
private String getProfileName(HttpServletRequest req) {
HttpSession session = req.getSession(true);
String profileName = (String) session.getAttribute("profileName");
if (profileName == null) {
// Entered a room for the first time?
profileName = req.getParameter("profileName");
if(profileName == null || profileName.length() == 0) {
profileName = "Anonymous";
}
session.setAttribute("profileName", profileName);
} else {
// Entered a new room with a new name?
String newName = req.getParameter("profileName");
if (newName != null && newName.length() > 0 && !newName.equals(profileName)) {
profileName = newName;
session.setAttribute("profileName", profileName);
}
}
return profileName;
}
private ChatRoom getRoom(HttpServletRequest req, HttpServletResponse res)
throws IOException {
HttpSession session = req.getSession(true);
PrintWriter out = res.getWriter();
String roomName = (String) session.getAttribute("roomName");
if(roomName == null) {
// Just entered?
roomName = req.getParameter("roomName");
if(roomName == null || roomName.length() == 0) {
writeError(out, "Room not specified");
return null;
}
session.setAttribute("roomName", roomName);
} else {
// Entered a new room?
String newRoom = req.getParameter("roomName");
if (newRoom != null && newRoom.length() > 0 && !newRoom.equals(roomName)) {
roomName = newRoom;
session.setAttribute("roomName", roomName);
}
}
HashMap roomList = (HashMap) getServletContext().getAttribute("roomList");
ChatRoom room = (ChatRoom) roomList.get(roomName);
if(room == null) {
writeError(out, "Room " + roomName + " not found");
return null;
}
return room;
}
private void writeError(PrintWriter out, String msg) {
out.println("<HTML>");
out.println("<HEAD><TITLE>Error</TITLE></HEAD>");
out.println("<BODY>");
out.println("<H1>Error</H1>");
out.println(msg);
out.println("</BODY></HTML>");
}
private void writeFrame(HttpServletResponse res, ChatRoom room) throws IOException {
PrintWriter out = res.getWriter();
out.println("<HTML>");
out.println("<HEAD><TITLE>" + room.getName() + "</TITLE></HEAD>");
out.println("<FRAMESET ROWS='50%,50%' BORDER=0 FRAMEBORDER=NO>");
out.println("<FRAME SRC=\"" + res.encodeURL(chatRoomPath) + "?list=true\" NAME=\"list\" SCROLLING=\"AUTO\">");
out.println("<FRAME SRC=\"" + res.encodeURL(chatRoomPath) + "?list=false\" NAME=\"form\" SCROLLING=\"AUTO\">");
out.println("<NOFRAMES>");
out.println("<BODY>");
out.println("Viewing this page requires a browser capable of displaying frames.");
out.println("</BODY>");
out.println("</NOFRAMES>");
out.println("</FRAMESET>");
out.println("</HTML>");
out.close();
}
private void writeMessages(PrintWriter out, ChatRoom room, String profileName) {
StringBuffer sb = new StringBuffer();
out.println("<HTML>");
out.println("<HEAD><META http-equiv=\"refresh\" content=\"5\"></HEAD>");
out.println("<BODY>");
out.println("<B>Room: " + room.getName() + "</B><BR>" + "<B>Identity: " + profileName + "</B><BR>");
// List all messages in the room
if (room.size() == 0) {
out.println("<FONT COLOR=RED>There are no messages in this room yet</FONT>");
} else {
Iterator entries = room.iterator();
while(entries.hasNext()) {
ChatEntry entry = (ChatEntry) entries.next();
if(entry == null) continue;
String entryName = entry.getProfileName();
if(entryName.equals(profileName)) {
out.print("<FONT COLOR=BLUE>");
}
out.println(entryName + " : " + entry.getMessage() + "<BR>");
if(entryName.equals(profileName)) {
out.print("</FONT>");
}
}
}
out.println("</BODY></HTML>");
}
}
////////////////////////////////////
////////////
web.xml配置文件如下
<?xml version="1.0" ?>
<!DOCTYPE web-app PUBLIC "-//Sun Microsystems, Inc.//DTD Web Application 1.2//EN" "http://java.sun.com/j2ee/dtds/web-app_2_2.dtd">
<web-app>
<context-param>
<param-name>ADMIN_PATH</param-name>
<param-value>chatAdmin</param-value>
</context-param>
<context-param>
<param-name>LISTROOMS_PATH</param-name>
<param-value>listRooms</param-value>
</context-param>
<context-param>
<param-name>CHATROOM_PATH</param-name>
<param-value>chatRoom</param-value>
</context-param>
<servlet>
<servlet-name>chatAdmin</servlet-name>
<servlet-class>ChatAdminServlet</servlet-class>
</servlet>
<servlet>
<servlet-name>chatRoom</servlet-name>
<servlet-class>ChatRoomServlet</servlet-class>
</servlet>
<servlet>
<servlet-name>listRooms</servlet-name>
<servlet-class>ListRoomsServlet</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>chatAdmin</servlet-name>
<url-pattern>/chatAdmin/*</url-pattern>
</servlet-mapping>
<servlet-mapping>
<servlet-name>chatRoom</servlet-name>
<url-pattern>/chatRoom/*</url-pattern>
</servlet-mapping>
<servlet-mapping>
<servlet-name>listRooms</servlet-name>
<url-pattern>/listRooms/*</url-pattern>
</servlet-mapping>
</web-app>
在Weblogic下配置成功通过
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