Accessing Databases Using JDBC - Java Programming: Comprehensive Concepts and Techniques - page 737

236 try

237 { // holdings deleted, now delete user

238 stmt.executeUpdate ( "DELETE FROM Users WHERE "

239 + "userID = '" +dbUserID+ "'" ) ;

240 }

241 catch ( SQLException ex )

242 {

243 throw new SQLException ( "User deletion failed: " +ex.getMessage ()) ;

244 }

245 }

246 else

247 throw new IOException ( "User not found in database - cannot delete." ) ;

248
249 try

250 {

251 con.commit () ;

252 }

253 catch ( SQLException ex )

254 {

255 throw new SQLException ( "Transaction commit failed: " +ex.getMessage ()) ;

256 }

257 }

258 catch ( SQLException ex )

259 {

260 try

261 {

262 con.rollback () ;

263 }

264 catch ( SQLException sqx )

265 {

266 throw new SQLException ( "Transaction failed then rollback failed: "

267 +sqx.getMessage ()) ;

268 }

269
270 // Transaction failed, was rolled back

271 throw new SQLException ( "Transaction failed; was rolled back: "

272 +ex.getMessage ()) ;

273 }

274
275 stmt.close () ;

276 }

277
278 // delete a record from the UserStocks table

279 public void delUserStocks ( String userID, String stockSymbol )

280 throws SQLException , IOException , ClassNotFoundException

281 {

282 Statement stmt = con.createStatement () ;

283 ResultSet rs;

284
285 stmt.executeUpdate ( "DELETE FROM UserStocks WHERE "

286 + "userID = '" +userID+ "'"

287 + "AND symbol = '" +stockSymbol+ "'" ) ;

288
289 rs = stmt.executeQuery ( "SELECT symbol FROM UserStocks "

290 + "WHERE symbol = '" +stockSymbol+ "'" ) ;

291
292 if ( !rs.next ()) // no users have this stock

293 delStock ( stockSymbol ) ;

294
295 stmt.close () ;

296
297 }

298
299

////////////////////////////////////////////////////////////////////////////

300 // Methods for listing record data from a table

301 // Ordered by:

302 // methods that obtain individual field(s),

303 // methods that obtain a complete record, and

304 // methods that obtain multiple records

305 ////////////////////////////////////////////////////////////////////////////

306
307 // Methods to access one or more individual fields

308

FIGURE 11-36

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