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/*
* MyLock.java - lock management for multiuser sessions
*
* Copyright (c) 2025 Stefano Marchetti
*
* This file is part of Jedecma - breast ultrasound examinations archiving software
*
* Jedecma is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* Jedecma is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with Jedecma. If not, see <http://www.gnu.org/licenses/>.
*
*/
/*
* Nota bene: nata per l'uso multiutente, e' comunque operativa anche in monoutenza.
* Si tratta di una gestione rudimentale basata su registrazioni
* su una tabella apposita del database.
* *** Non e' mai stata testata in un contesto d'uso reale. ***
* In caso di interruzione della sessione, i lock restano attivi e vanno
* eliminati riavviando e terminando immediatamente il programma con lo
* stesso utente.
*/
/*
* Notice: designed for a multiuser mode, is used even in single user mode.
* It is a rudimentary system based on records on a dedicated database table.
* *** Never tested in real use ***
* In case of incorrect termination of the session, locks are left active:
* to erase them restart the program with same user and terminate it immediately.
*/
package jedecma;
import java.sql.ResultSet;
import java.sql.SQLException;
public class MyLock {
final static boolean EXCL = true;
final static boolean SHARED = false;
final static int TRYMAX = 10; // n.massimo tentativi di accesso prima di
// restituire l'errore
MyLock() {
}
public static int chkLock(JDBCMgr db, String lc) { // 1^ modalita'
// verifica se esiste un lock con codice lc
// ritorna lo userid del primo lock trovato; -1 se non trovati
int rc = -1;
ResultSet rSet;
if (lc.indexOf("%") > -1) {
rSet = db
.executeQuery("SELECT lockusr FROM TBLLCKS WHERE lockcod LIKE '"
+ lc + "'");
} else {
rSet = db
.executeQuery("SELECT lockusr FROM TBLLCKS WHERE lockcod = '"
+ lc + "'");
}
try {
if (rSet.next()) {
rc = rSet.getInt(1);
}
} catch (SQLException ex) {
System.err.println(ex);
Uti1.error(Jedecma.localMessagesBundle.getString("SQL_ERROR"), true);
}
System.out.println("chkLock: rc=" + rc);
return (rc);
}
public static int chkLock(JDBCMgr db, String lc, int ui) { // 2^ modalita'
// verifica se esiste un lock con codice lc e userid ui
// ritorna lo userid del primo lock trovato; -1 se non trovati
int rc = -1;
ResultSet rSet;
if (lc.indexOf("%") > -1) {
rSet = db
.executeQuery("SELECT lockusr FROM TBLLCKS WHERE lockcod LIKE '"
+ lc + "' AND lockusr = " + ui);
} else {
rSet = db
.executeQuery("SELECT lockusr FROM TBLLCKS WHERE lockcod = '"
+ lc + "' AND lockusr = " + ui);
}
try {
if (rSet.next()) {
rc = rSet.getInt(1);
}
} catch (SQLException ex) {
System.err.println(ex);
Uti1.error(Jedecma.localMessagesBundle.getString("SQL_ERROR"), true);
}
System.out.println("chkLock: rc=" + rc);
return (rc);
}
public static int delLock(JDBCMgr db, String lc, int ui) {
// cancella il lock con codice lc e userid ui
// ritorna 0
int rc = 0;
String q;
if (lc.indexOf("%") > -1) {
q = "DELETE FROM TBLLCKS WHERE lockcod like '" + lc
+ "' AND lockusr = " + ui;
} else {
q = "DELETE FROM TBLLCKS WHERE lockcod = '" + lc
+ "' AND lockusr = " + ui;
}
int rowCount = db.executeUpdate(q);
if (rowCount > 0) {
rc = 0;
} else {
rc = -1;
}
return (rc);
}
public static int setLock(JDBCMgr db, String lc, int ui, boolean ex) {
// aggiunge un lock con codice lc per userid ui
// ritorna 0 se risulta un lock per ui; -1 in caso contrario
int iex = ui;
if (ex) {
iex = Jedecma.user.IDEXCL;
}
int rc = -1;
int lap = 0;
// Thread myThread = Thread.currentThread();
while (lap <= TRYMAX) {
System.out.println("setLock: lap #" + lap);
String q = "INSERT INTO TBLLCKS VALUES (DEFAULT, '" + lc + "', "
+ ui + ", " + iex + ")";
// Use the keyword DEFAULT to set a column explicitly to its default
// value (->auto_increment!)
if (db.executeUpdate(q) == 1) {
System.out.println("setLock: " + lc + " " + ui + " " + iex
+ " rc=" + rc);
rc = 0;
break;
}
try { // attende un tempo random
Thread.sleep((long) (Math.random() * 100));
} catch (InterruptedException e) {
}
lap++;
}
return (rc);
}
} // end MyLock Class
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