Cookie是用于维持客户端和服务器端状态的一小段数据，在Java ME平台上并不支持Cookie。但是你可以按照HTTP协议相关的定义自己实现Cookie特性。本例给出了不错的参考。
/*--------------------------------------------------
* Cookie.java
*
* Pass a cookie (stored in rms) between the MIDlet
* and a Java servlet. The cookie is generated
* by the servlet on the first visit.
*
* Example from the book: Core J2ME Technology
* Copyright John W. Muchow http://www.CoreJ2ME.com
* You may use/modify for any non-commercial purpose
*-------------------------------------------------*/
import javax.microedition.midlet.*;
import javax.microedition.lcdui.*;
import javax.microedition.rms.*;
import javax.microedition.io.*;
import java.io.*;
public class Cookie extends MIDlet implements CommandListener
{
private Display display;
private TextBox tbMain;
private Form fmMain;
private Command cmExit;
private Command cmLogon;
private String cookie = null;
private RecordStore rs = null;
static final String REC_STORE = "rms_cookie";
private String url = "http://www.mycgiserver.com/servlet/corej2me.
CookieServlet";
public Cookie()
{
display = Display.getDisplay(this);
// Create commands
cmExit = new Command("Exit", Command.EXIT, 1);
cmLogon = new Command("Logon", Command.SCREEN, 2);
// Create the form, add commands, listen for events
fmMain = new Form("");
fmMain.addCommand(cmExit);
fmMain.addCommand(cmLogon);
fmMain.setCommandListener(this);
// Read cookie if available
openRecStore();
readCookie();
// System.out.println("Client cookie: " + cookie);
}
public void startApp()
{
display.setCurrent(fmMain);
}
public void pauseApp()
{ }
public void destroyApp(boolean unconditional)
{
closeRecStore(); // Close record store
}
public void openRecStore()
{
try
{
// The second parameter indicates that the record store
// should be created if it does not exist
rs = RecordStore.openRecordStore(REC_STORE, true);
}
catch (Exception e)
{
db("open " + e.toString());
}
}
public void closeRecStore()
{
try
{
rs.closeRecordStore();
}
catch (Exception e)
{
db("close " + e.toString());
}
}
/*--------------------------------------------------
* Write cookie to rms
*-------------------------------------------------*/
public void writeRecord(String str)
{
byte[] rec = str.getBytes();
try
{
rs.addRecord(rec, 0, rec.length);
}
catch (Exception e)
{
db("write " + e.toString());
}
}
/*--------------------------------------------------
* Read cookie from rms
*-------------------------------------------------*/
public void readCookie()
{
try
{
byte[] recData = new byte[25];
int len;
if (rs.getNumRecords() > 0)
{
// Only one record will ever be written, safe to use '1'
if (rs.getRecordSize(1) > recData.length)
recData = new byte[rs.getRecordSize(1)];
len = rs.getRecord(1, recData, 0);
cookie = new String(recData);
}
}
catch (Exception e) {
db("read " + e.toString());
}
}
/*--------------------------------------------------
* Send client request and recieve server response
*
* Client: If cookie exists, send it to the server
*
* Server: If cookie is sent back, this is the
* clients first request to the server. In
* that case, save the cookie. If no cookie
* sent, display server body (which indicates
* the last time the MIDlet contacted server).
*-------------------------------------------------*/
private void connect() throws IOException
{
InputStream iStrm = null;
ByteArrayOutputStream bStrm = null;
HttpConnection http = null;
try
{
// Create the connection
http = (HttpConnection) Connector.open(url);
//----------------
// Client Request
//----------------
// 1) Send request method
http.setRequestMethod(HttpConnection.GET);
// If you experience connection/IO problems, try
// removing the comment from the following line
//http.setRequestProperty("Connection", "close");
// 2) Send header information
if (cookie != null)
http.setRequestProperty("cookie", cookie);
System.out.println("Client cookie: " + cookie);
// 3) Send body/data - No data for this request
//----------------
// Server Response
//----------------
// 1) Get status Line
if (http.getResponseCode() == HttpConnection.HTTP_OK)
{
// 2) Get header information
String tmpCookie = http.getHeaderField("set-cookie");
System.out.println("server cookie: " + tmpCookie);
// Cookie will only be sent back from server only if
// client (us) did not send a cookie in the first place.
// If a cookie is returned, we need to save it to rms
if (tmpCookie != null)
{
writeRecord(tmpCookie);
// Update the MIDlet cookie variable
cookie = tmpCookie;
fmMain.append("First visit\n");
fmMain.append("Client : " + cookie + "\n");
}
else // No cookie sent from server
{
// 3) Get data, which is the last time of access
iStrm = http.openInputStream();
int length = (int) http.getLength();
String str;
if (length != -1)
{
byte serverData[] = new byte[length];
iStrm.read(serverData);
str = new String(serverData);
}
else // Length not available...
{
bStrm = new ByteArrayOutputStream();
int ch;
while ((ch = iStrm.read()) != -1)
bStrm.write(ch);
str = new String(bStrm.toByteArray());
}
// Append data to the form
fmMain.append("Last access:\n" + str + "\n");
}
}
}
finally
{
// Clean up
if (iStrm != null)
iStrm.close();
if (bStrm != null)
bStrm.close();
if (http != null)
http.close();
}
}
/*--------------------------------------------------
* Process events
*-------------------------------------------------*/
public void commandAction(Command c, Displayable s)
{
// If the Command button pressed was "Exit"
if (c == cmExit)
{
destroyApp(false);
notifyDestroyed();
}
else if (c == cmLogon)
{
try
{
// Logon to the servlet
connect();
}
catch (Exception e)
{
db("connect " + e.toString());
}
}
}
/*--------------------------------------------------
* Simple message to console for debug/errors
* When used with Exceptions we should handle the
* error in a more appropriate manner.
*-------------------------------------------------*/
private void db(String str)
{
System.err.println("Msg: " + str);
}
}
/*--------------------------------------------------
* CookieServlet.java
*
* Use a cookie to identify clients
*
* Example from the book: Core J2ME Technology
* Copyright John W. Muchow http://www.CoreJ2ME.com
* You may use/modify for any non-commercial purpose
*-------------------------------------------------*/
//package corej2me; // Required for mycgiserver.com
import java.util.*;
import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;
import java.sql.*;
import java.text.*;
public class CookieServlet extends HttpServlet
{
// Pool of client ID's
private static int[] clientIDs = {123, 456, 789, 901, 225, 701};
protected void doGet(HttpServletRequest req, HttpServletResponse res)
throws ServletException, IOException
{
// Get cookie from the header
Cookie[] cookies = req.getCookies();
//-------------------------------------------
// If cookie passed in...
// 1) Lookup the client ID in the database
// and save the last access date
// 2) Update the last access date in database
// 3) Return to the client date from step 1
//-------------------------------------------
if (cookies != null)
{
// There will be only one cookie
Cookie theCookie = cookies[0];
String id = theCookie.getValue();
// Lookup client ID and get last access date
String strLastAccess = lookupLastAccessDate(Integer.parseInt(id));
// Update database with current date
updateLastAccessDate(Integer.parseInt(id));
// Send back the last access date to the client
res.setContentType("text/plain");
PrintWriter out = res.getWriter();
out.print(strLastAccess);
out.close();
}
else // No Cookie
{
//-------------------------------------------
// Generate a client ID. To keep the database
// from growing out of control, this will not
// generate a new ID for each client.
// Instead, grab a random ID from the array
// clientID's[]. The end result is the same
// as far as the client is concerned.
//-------------------------------------------
// Random value between 0 and the number of
// entries in the client list array
int random = (int) Math.round(clientIDs.length * Math.random());
// Get the client ID to send in the cookie
int ID = clientIDs[random];
// Update database with current date
updateLastAccessDate(ID);
// Create new cookie and send ID in the header
Cookie cookie = new Cookie("ID", Integer.toString(ID));
res.addCookie(cookie);
}
}
/*--------------------------------------------------
* Update database with last access date for client ID
*-------------------------------------------------*/
private void updateLastAccessDate(int ID)
{
Connection con = null;
Statement st = null;
StringBuffer msgb = new StringBuffer("");
try
{
// These will vary depending on your server/database
Class.forName("sun.jdbc.odbc.JdbcOdbcDriver");
con = DriverManager.getConnection("jdbc:odbc:acctInfo");
Statement stmt = con.createStatement();
// Create a date format
SimpleDateFormat format =
new SimpleDateFormat ("MMM dd-hh:mm aa");
String strDate = format.format(new java.util.Date());
ResultSet rs = stmt.executeQuery("UPDATE clientInfo set lastAccess = '" +
strDate + "' where clientID = " + ID);
}
catch (Exception e)
{ }
}
/*--------------------------------------------------
* Lookup the client ID in database and get the
* last access date
*-------------------------------------------------*/
private String lookupLastAccessDate(int id)
{
Connection con = null;
Statement st = null;
StringBuffer msgb = new StringBuffer("");
try
{
// These will vary depending on your server/database
Class.forName("sun.jdbc.odbc.JdbcOdbcDriver");
con = DriverManager.getConnection("jdbc:odbc:acctInfo");
Statement stmt = con.createStatement();
ResultSet rs = stmt.executeQuery("Select lastAccess from clientInfo where clientID = " + id);
if (rs.next())
return rs.getString(1);
else
return null;
}
catch (Exception e)
{
return e.toString();
}
}
/*--------------------------------------------------
* Information about servlet
*-------------------------------------------------*/
public String getServletInfo()
{
return "CookieServlet 1.0 - John W. Muchow - www.corej2me.com";
}
}