/*-------------------------------------------------- * GetNpost.java * * Use GET or POST to communicate with a Java servlet. * The servlet will search a database for the balance * of an account. * * 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.io.*; import java.io.*;
public class GetNpost extends MIDlet implements CommandListener { PRivate Display display; // Reference to Display object private Form fmMain; // The main form private Alert alError; // Alert to error message private Command cmGET; // Request method GET private Command cmPOST; // Request method Post private Command cmExit; // Command to exit the MIDlet private TextField tfAcct; // Get account number private TextField tfPwd; // Get passWord private StringItem siBalance;// Show account balance private String errorMsg = null; public GetNpost() { display = Display.getDisplay(this);
// Create commands cmGET = new Command("GET", Command.SCREEN, 2); cmPOST = new Command("POST", Command.SCREEN, 3); cmExit = new Command("Exit", Command.EXIT, 1);
// Textfields tfAcct = new TextField("Account:", "", 5, TextField.NUMERIC); tfPwd = new TextField("Password:", "", 10, TextField.ANY TextField.PASSWORD);
// Balance string item siBalance = new StringItem("Balance: $", "");
public void startApp() { display.setCurrent(fmMain); }
public void pauseApp() { } public void destroyApp(boolean unconditional) { }
public void commandAction(Command c, Displayable s) { if (c == cmGET c == cmPOST) { try { if (c == cmGET) lookupBalance_withGET(); else lookupBalance_withPOST(); } catch (Exception e) { System.err.println("Msg: " + e.toString()); } } else if (c == cmExit) { destroyApp(false); notifyDestroyed(); } }
/*-------------------------------------------------- * access servlet using GET *-------------------------------------------------*/ private void lookupBalance_withGET() throws IOException { HttpConnection http = null; InputStream iStrm = null; boolean ret = false;
// Data is passed at the end of url for GET String url = "http://www.mycgiserver.com/servlet/corej2me.GetNpostServlet" + "?" + "account=" + tfAcct.getString() + "&" + "password=" + tfPwd.getString(); try { http = (HttpConnection) Connector.open(url); //---------------- // Client Request //---------------- // 1) Send request method http.setRequestMethod(HttpConnection.GET); // 2) Send header information - none // 3) Send body/data - data is at the end of URL
//---------------- // Server Response //---------------- iStrm = http.openInputStream(); // Three steps are processed in this method call ret = processServerResponse(http, iStrm); } finally { // Clean up if (iStrm != null) iStrm.close(); if (http != null) http.close(); }
// Process request failed, show alert if (ret == false) showAlert(errorMsg); }
/*-------------------------------------------------- * Access servlet using POST *-------------------------------------------------*/ private void lookupBalance_withPOST() throws IOException { HttpConnection http = null; OutputStream oStrm = null; InputStream iStrm = null; boolean ret = false; // Data is passed as a separate stream for POST (below) String url = "http://www.mycgiserver.com/servlet/corej2me.GetNpostServlet"; try { http = (HttpConnection) Connector.open(url); oStrm = http.openOutputStream(); //---------------- // Client Request //---------------- // 1) Send request type http.setRequestMethod(HttpConnection.POST); // 2) Send header information. Required for POST to work! http.setRequestProperty("Content-Type", "application/x-www-form-urlencoded");
// If you eXPerience connection/IO problems, try // removing the comment from the following line // http.setRequestProperty("Connection", "close");
// 3) Send data/body // Write account number byte data[] = ("account=" + tfAcct.getString()).getBytes(); oStrm.write(data); // Write password data = ("&password=" + tfPwd.getString()).getBytes(); oStrm.write(data); // For 1.0.3 remove flush command // See the note at the bottom of this file // oStrm.flush();
//---------------- // Server Response //---------------- iStrm = http.openInputStream(); // Three steps are processed in this method call ret = processServerResponse(http, iStrm); } finally { // Clean up if (iStrm != null) iStrm.close(); if (oStrm != null) oStrm.close(); if (http != null) http.close(); }
// Process request failed, show alert if (ret == false) showAlert(errorMsg); }
/*-------------------------------------------------- * Process a response from a server *-------------------------------------------------*/ private boolean processServerResponse(HttpConnection http, InputStream iStrm) throws IOException { //Reset error message errorMsg = null; // 1) Get status Line if (http.getResponseCode() == HttpConnection.HTTP_OK) { // 2) Get header information - none // 3) Get body (data) int length = (int) http.getLength(); String str; if (length != -1) { byte servletData[] = new byte[length]; iStrm.read(servletData); str = new String(servletData); } else // Length not available... { ByteArrayOutputStream bStrm = new ByteArrayOutputStream(); int ch; while ((ch = iStrm.read()) != -1) bStrm.write(ch);
str = new String(bStrm.toByteArray()); bStrm.close(); } // Update the string item on the display siBalance.setText(str); return true; } else // Use message from the servlet errorMsg = new String( http.getResponseMessage());
return false; }
/*-------------------------------------------------- * Show an Alert *-------------------------------------------------*/ private void showAlert(String msg) { // Create Alert, use message returned from servlet alError = new Alert("Error", msg, null, AlertType.ERROR);
// Set Alert to type Modal alError.setTimeout(Alert.FOREVER);
// Display the Alert. Once dismissed, display the form display.setCurrent(alError, fmMain); } }
/* The call to flush() uses a feature of HTTP 1.1 that allows data to be sent in smaller loads. When calling flush() or sending a large amount of data (in version 1.0.3) chunked encoding is used.
If you are using an HTTP 1.0 server or proxy server the chunked transfer may cause problems.
You can avoid the chunking behavior with small transactions by just calling close() where you were using flush(). For larger transactions you need to buffer your output so a single write() and close() are issued to the output stream. */
/*-------------------------------------------------- * GetNpostServlet.java * * Show how GET and POST from client can access and * process the same data. * Account information is maintained in a database * (connecting with jdbc) * * Table: acctInfo * Columns: * account - integer * password - varchar * balance - integer * * 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
public class GetNpostServlet extends HttpServlet { protected void doGet(HttpServletRequest req, HttpServletResponse res) throws ServletException, IOException { // Same code appears in doPost() // Shown both places to emphasize that data is received thru // different means (environment variable vs stream), // yet processed the same inside the servlet String acct = req.getParameter("account"), pwd = req.getParameter("password");
String balance = accountLookup(acct, pwd);
if (balance == null) { res.sendError(res.SC_BAD_REQUEST, "Unable to locate account."); return; }
res.setContentType("text/plain"); PrintWriter out = res.getWriter(); out.print(balance); out.close(); } protected void doPost(HttpServletRequest req, HttpServletResponse res) throws ServletException, IOException { // Same code appears in doGet() // Shown both places to emphasize that data is received thru // different means (stream vs environment variable), // yet processed the same inside the servlet String acct = req.getParameter("account"), pwd = req.getParameter("password");
String balance = accountLookup(acct, pwd);
if (balance == null) { res.sendError(res.SC_BAD_REQUEST, "Unable to locate account."); return; } res.setContentType("text/plain"); PrintWriter out = res.getWriter(); out.print(balance); out.close(); }
/*-------------------------------------------------- * Lookup bank account balance in database *-------------------------------------------------*/ private String accountLookup(String acct, String pwd) { 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 balance from acctInfo where account = " + acct + "and password = '" + pwd + "'"); if (rs.next()) return rs.getString(1); else return null; } catch (Exception e) { return e.toString(); } } /*-------------------------------------------------- * Information about servlet *-------------------------------------------------*/ public String getServletInfo() { return "GetNpostServlet 1.0 - John W. Muchow - www.corej2me.com"; } }
