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Table of Contents
Cursors provide a mechanism by which you can iterate over the records in a database. Using cursors, you can get, put, and delete database records. If a database allows duplicate records, then cursors are the easiest way that you can access anything other than the first record for a given key.
This chapter introduces cursors. It explains how to open and close them, how to use them to modify databases, and how to use them with duplicate records.
To use a cursor, you must open it using the Database.openCursor() method. When you open a cursor, you can optionally pass it a CursorConfig object to set cursor properties.
For example:
package db.GettingStarted;
import com.sleepycat.db.Cursor;
import com.sleepycat.db.CursorConfig;
import com.sleepycat.db.Database;
import com.sleepycat.db.DatabaseException;
import java.io.FileNotFoundException;
...
Database myDatabase = null;
Cursor myCursor = null;
try {
myDatabase = new Database("myDB", null, null);
myCursor = myDatabase.openCursor(null, null);
} catch (FileNotFoundException fnfe) {
// Exception handling goes here ...
} catch (DatabaseException dbe) {
// Exception handling goes here ...
}
To close the cursor, call the Cursor.close() method. Note that if you close a database that has cursors open in it, then it will throw an exception and close any open cursors for you. For best results, close your cursors from within a finally block.
package db.GettingStarted;
import com.sleepycat.db.Cursor;
import com.sleepycat.db.Database;
...
try {
...
} catch ... {
} finally {
try {
if (myCursor != null) {
myCursor.close();
}
if (myDatabase != null) {
myDatabase.close();
}
} catch(DatabaseException dbe) {
System.err.println("Error in close: " + dbe.toString());
}
}