Save- und Open-Methode (Beispiel) (VJ++)

Gilt für: Access 2013, Office 2013

In diesen drei Beispielen wird veranschaulicht, wie die Methoden Save und Open gemeinsam verwendet werden können.

Angenommen, Sie gehen auf eine Geschäftsreise und möchten eine Tabelle aus einer Datenbank mitnehmen. Bevor Sie fahren, greifen Sie auf die als ein Recordset-Objekt gespeicherten Daten zu und speichern Sie in einer transportierbaren Form. Wenn Sie an Ihrem Reiseziel ankommen, greifen Sie auf das Recordset -Objekt als ein lokales, getrenntes Recordset -Objekt zu. Sie nehmen Änderungen am Recordset -Objekt vor und speichern es erneut mit Ihren Änderungen. Wenn Sie schließlich wieder zu Hause ankommen, stellen Sie eine Verbindung zur Datenbank her und aktualisieren diese mit den während Ihrer Reise vorgenommenen Änderungen.

 
// BeginSaveJ 
import com.ms.wfc.data.*; 
import java.io.* ; 
 
public class SaveX 
{ 
 // The main entry point for the application. 
 
 public static void main (String[] args) 
 { 
 SaveX1(); 
 SaveX2(); 
 SaveX3(); 
 System.exit(0); 
 } 
 
 // First, access and save the Authors table. 
 
 // SaveX1 function 
 
 static void SaveX1() 
 { 
 // Define ADO Objects. 
 Recordset rstAuthors = null; 
 
 // Declarations. 
 String strCnn = "Provider='sqloledb';Data Source='MySqlServer';" + 
 "Initial Catalog='Pubs';Integrated Security='SSPI';"; 
 BufferedReader in = 
 new BufferedReader(new InputStreamReader(System.in)); 
 File file; 
 
 try 
 { 
 rstAuthors = new Recordset(); 
 rstAuthors.setCursorLocation(AdoEnums.CursorLocation.CLIENT); 
 rstAuthors.open("SELECT * FROM Authors", 
 strCnn, 
 AdoEnums.CursorType.DYNAMIC, 
 AdoEnums.LockType.OPTIMISTIC, 
 AdoEnums.CommandType.TEXT); 
 
 // For the sake of illustration, save the recordset to a 
 //diskette in XML format. 
 file = new File("c:\\Pubs.xml"); 
 if(!file.exists()) 
 rstAuthors.save("c:\\Pubs.xml",AdoEnums.PersistFormat.XML); 
 else 
 { 
 System.out.println("\nFile already exists."); 
 System.out.println("\nPress <Enter> to continue.."); 
 in.readLine(); 
 System.exit(0); 
 } 
 } 
 catch( AdoException ae ) 
 { 
 // Notify user of any errors that result from ADO. 
 
 // As passing a Recordset, check for null pointer first. 
 if (rstAuthors != null) 
 { 
 PrintProviderError(rstAuthors.getActiveConnection()); 
 } 
 else 
 { 
 System.out.println("Exception: " + ae.getMessage()); 
 } 
 } 
 // System read requires this catch. 
 catch( java.io.IOException je) 
 { 
 PrintIOError(je); 
 } 
 
 finally 
 { 
 // Cleanup objects before exit. 
 if (rstAuthors != null) 
 if (rstAuthors.getState() == 1) 
 rstAuthors.close(); 
 } 
 } 
 
 // At this point, you have arrived at your destination. You will 
 // access the Authors table as a local, disconnected Recordset. 
 // Don't forget you must have the MSPersist provider on the machine 
 // you are using in order to access the saved file, a:\Pubs.xml. 
 
 // SaveX2 function 
 
 static void SaveX2() 
 { 
 // Define ADO Objects. 
 Recordset rstAuthors = null; 
 
 // Declarations. 
 BufferedReader in = 
 new BufferedReader(new InputStreamReader(System.in)); 
 
 try 
 { 
 rstAuthors = new Recordset(); 
 
 // For sake of illustration, we specify all parameters. 
 rstAuthors.open("c:\\Pubs.xml", 
 "Provider=MSPersist;", 
 AdoEnums.CursorType.FORWARDONLY, 
 AdoEnums.LockType.BATCHOPTIMISTIC, 
 AdoEnums.CommandType.FILE); 
 
 // Now you have a local, disconnected recordset. 
 // Edit it as you desire. 
 // (In this example, the change makes no difference). 
 rstAuthors.find("au_lname = 'Carson'"); 
 if(rstAuthors.getEOF()) 
 { 
 System.out.println("Name not found."); 
 System.out.println("\nPress <Enter> to continue.."); 
 in.readLine(); 
 return; 
 } 
 rstAuthors.getField("city").setString("Berkeley"); 
 rstAuthors.update(); 
 
 // Save changes in ADTG format this time, for illustration. 
 // Note that previous version on the diskette, as a:\Pubs.xml. 
 rstAuthors.save("c:\\Pubs.adtg",AdoEnums.PersistFormat.ADTG); 
 
 } 
 catch( AdoException ae ) 
 { 
 // Notify user of any errors that result from ADO. 
 
 // As passing a Recordset, check for null pointer first. 
 if (rstAuthors != null) 
 { 
 PrintProviderError(rstAuthors.getActiveConnection()); 
 } 
 else 
 { 
 System.out.println("Exception: " + ae.getMessage()); 
 } 
 } 
 
 // System read requires this catch. 
 catch( java.io.IOException je) 
 { 
 PrintIOError(je); 
 } 
 
 finally 
 { 
 // Cleanup objects before exit. 
 if (rstAuthors != null) 
 if (rstAuthors.getState() == 1) 
 rstAuthors.close(); 
 } 
 } 
 
 // Finally, update the database with your changes. 
 
 // SaveX3 function 
 
 static void SaveX3() 
 { 
 // Define ADO Objects. 
 Connection cnConn1 = null; 
 Recordset rstAuthors = null; 
 
 // Declarations. 
 String strCnn = "Provider='sqloledb';Data Source='MySqlServer';" + 
 "Initial Catalog='Pubs';Integrated Security='SSPI';"; 
 
 try 
 { 
 // If there is no ActiveConnection, you can open with defaults. 
 rstAuthors = new Recordset(); 
 rstAuthors.open("c:\\Pubs.adtg"); 
 
 // Connect to the database, associate the Recordset with 
 // connection, then update the database table with the changed 
 // Recordset. 
 cnConn1 = new Connection(); 
 cnConn1.open(strCnn); 
 rstAuthors.setActiveConnection(cnConn1); 
 rstAuthors.updateBatch(); 
 } 
 catch( AdoException ae ) 
 { 
 // Notify user of any errors that result from ADO. 
 
 // As passing a Recordset, check for null pointer first. 
 if (rstAuthors != null) 
 { 
 PrintProviderError(rstAuthors.getActiveConnection()); 
 } 
 else 
 { 
 System.out.println("Exception: " + ae.getMessage()); 
 } 
 } 
 
 finally 
 { 
 // Cleanup objects before exit. 
 if (rstAuthors != null) 
 if (rstAuthors.getState() == 1) 
 rstAuthors.close(); 
 if (cnConn1 != null) 
 if (cnConn1.getState() == 1) 
 cnConn1.close(); 
 } 
 } 
 
 // PrintProviderError Function 
 
 static void PrintProviderError( Connection Cnn1 ) 
 { 
 // Print Provider errors from Connection object. 
 // ErrItem is an item object in the Connections Errors collection. 
 com.ms.wfc.data.Error ErrItem = null; 
 long nCount = 0; 
 int i = 0; 
 
 nCount = Cnn1.getErrors().getCount(); 
 
 // If there are any errors in the collection, print them. 
 if( nCount > 0); 
 { 
 // Collection ranges from 0 to nCount - 1 
 for (i = 0; i< nCount; i++) 
 { 
 ErrItem = Cnn1.getErrors().getItem(i); 
 System.out.println("\t Error number: " + ErrItem.getNumber() 
 + "\t" + ErrItem.getDescription() ); 
 } 
 } 
 
 } 
 
 // PrintIOError Function 
 
 static void PrintIOError( java.io.IOException je) 
 { 
 System.out.println("Error \n"); 
 System.out.println("\tSource = " + je.getClass() + "\n"); 
 System.out.println("\tDescription = " + je.getMessage() + "\n"); 
 } 
} 
// EndSaveJ