Midlet与Servlet传递Cookie
Cookie在Java ME平台中没有得到支持，因此要想维持客户端和服务器端的状态则必须要使用URL重写的方式.
Cookie的工作原理如图：
浏览器根据 域（domain） 和 路径（path） 检查是否有匹配的cookie，如果有则把cookie 以“名称 = 值” 的形式发送给服务器
获取(客户端) cookie 的方式：
J2ME中得到服务器端的cookie并保存到RMS中，下文代码的实现思路是：
1.打开RMS并读取RMS中是否存有cookie；
2.连接服务器，采用get请求，如果RMS中有cookie，那么设置
3.如果RMS中没有记录（cookie），那么将服务器端通过
J2ME中的核心代码：
服务器端的核心代码：
在J2ME中代码URL为我公司的URL，地址可能有变，希望大家在测试的时候，更改成自己服务器的地址就可以了。
程序运行成功后的部分截图：
手机模拟器第一次运行时出现上图所示，服务器端的截图如下：
第一次手机访问服务器时，服务器产生一个随机数（100以内的整数，当然也可以采用uuid）返回客户端。
手机模拟器第二次访问和服务器的截图：
Cookie的工作原理如图：
浏览器根据 域（domain） 和 路径（path） 检查是否有匹配的cookie，如果有则把cookie 以“名称 = 值” 的形式发送给服务器
获取(客户端) cookie 的方式：
HttpConnection.getHeaderField("set-cookie");
J2ME中得到服务器端的cookie并保存到RMS中，下文代码的实现思路是：
1.打开RMS并读取RMS中是否存有cookie；
2.连接服务器，采用get请求，如果RMS中有cookie，那么设置
http.setRequestProperty("cookie", cookie);，
3.如果RMS中没有记录（cookie），那么将服务器端通过
http.getHeaderField("set-cookie");得到的cookie保存到RMS中。
J2ME中的核心代码：
package com.easymorse;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.InputStream;
import javax.microedition.io.Connector;
import javax.microedition.io.HttpConnection;
import javax.microedition.lcdui.Command;
import javax.microedition.lcdui.CommandListener;
import javax.microedition.lcdui.Display;
import javax.microedition.lcdui.Displayable;
import javax.microedition.lcdui.Form;
import javax.microedition.lcdui.TextBox;
import javax.microedition.midlet.MIDlet;
import javax.microedition.rms.RecordStore;
public class Cookie extends MIDlet implements CommandListener,Runnable{
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://dev.mopietek.net:8080/cookieServer/cookieServlet"; //连接公司服务器地址
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);
/*rs.getRecord(arg0,arg1,arg2); //返回值是所复制的数据的字节数
第一个参数是读取数据库中的第几条，第二个参数是保存读取的数据(recData)，第三个参数是指定数据写入（recData）中的起始位置索引
*/
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
{
Thread t = new Thread(this);
t.start();
}
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);
}
public void run() {
try {
connect();
} catch (IOException e) {
e.printStackTrace();
db("connect " + e.toString());
}
}
}
服务器端的核心代码：
package com.easymorse;
import java.io.IOException;
import java.io.PrintWriter;
import java.util.Random;
import javax.servlet.ServletException;
import javax.servlet.http.Cookie;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
public class CookieServlet extends HttpServlet {
/**
* Constructor of the object.
*/
public CookieServlet() {
super();
}
/**
* Destruction of the servlet. <br>
*/
public void destroy() {
super.destroy(); // Just puts "destroy" string in log
// Put your code here
}
private static int[] clientIDs = {123,456,789,901,225,701};
private static final Random rand = new Random();
/**
* The doGet method of the servlet. <br>
*
* This method is called when a form has its tag value method equals to get.
*
* @param request the request send by the client to the server
* @param response the response send by the server to the client
* @throws ServletException if an error occurred
* @throws IOException if an error occurred
*/
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
System.out.println("--------------------------------------------------------------------");
Cookie[] cookies = request.getCookies();
System.out.println("cookies=====>"+cookies);
if(cookies != null){
Cookie theCookie = cookies[0];
System.out.println("theCookie------------->"+theCookie);
String id = theCookie.getValue();
System.out.println("id=====>"+id);
PrintWriter out = response.getWriter();
out.print("Cookie passwed in was: " + id);
out.close();
}else{
System.out.println("没有cookie");
int random = rand.nextInt(100);
Cookie cookie = new Cookie("ID",Integer.toString(random));
response.addCookie(cookie);
}
}
public String getServletInfo(){
return "CookieTest";
}
/**
* The doPost method of the servlet. <br>
*
* This method is called when a form has its tag value method equals to post.
*
* @param request the request send by the client to the server
* @param response the response send by the server to the client
* @throws ServletException if an error occurred
* @throws IOException if an error occurred
*/
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
this.doGet(request, response);
}
/**
* Initialization of the servlet. <br>
*
* @throws ServletException if an error occurs
*/
public void init() throws ServletException {
// Put your code here
}
}
在J2ME中代码URL为我公司的URL，地址可能有变，希望大家在测试的时候，更改成自己服务器的地址就可以了。
程序运行成功后的部分截图：
手机模拟器第一次运行时出现上图所示，服务器端的截图如下：
第一次手机访问服务器时，服务器产生一个随机数（100以内的整数，当然也可以采用uuid）返回客户端。
手机模拟器第二次访问和服务器的截图：