You can set database properties using the DatabaseConfig
class. For each of the properties that you can set, there is a
corresponding getter method. Also, you can always retrieve the
DatabaseConfig object used by your database using
the Database.getConfig() method.
There are a large number of properties that you can set using this class (see the javadoc for a complete listing). From the perspective of this manual, some of the more interesting properties are:
DatabaseConfig.setAllowCreate()
If true, the database is created when it is
opened. If false, the database open fails if the database does not
exist. This property has no meaning if the database currently exists.
Default is false.
DatabaseConfig.setBtreeComparator()
Sets the class that is used to compare the keys found on two database records. This class is used to determine the sort order for two records in the database. By default, byte for byte comparison is used. For more information, see Setting Comparison Functions.
DatabaseConfig.setDuplicateComparator()
Sets the class that is used to compare two duplicate records in the database. For more information, see Setting Comparison Functions.
DatabaseConfig.setSortedDuplicates()
If true, duplicate records are allowed in the
database. If this value is false, then putting a duplicate record into the database
results in an error return from the put call.
Note that this property can be set only at database creation time. Default is false.
Note that your database must not support duplicates if it is to be associated with one or more secondary indices. Secondaries are described in Secondary Databases.
DatabaseConfig.setExclusiveCreate()
If true, the database open fails if the
database currently exists. That is, the open must result in the
creation of a new database. Default is false.
DatabaseConfig.setReadOnly()
If true, the database is opened for read activities only.
Default is false.
DatabaseConfig.setTruncate()
If true, the database is truncated; that is, it is emptied of all content.
DatabaseConfig.setType()
Identifies the type of database that you want to create. This
manual will exclusively use DatabaseType.BTREE.
In addition to these, there are also methods that allow you to control the IO stream used for error reporting purposes. These are described later in this manual.
For example:
package db.GettingStarted;
import com.sleepycat.db.Database;
import com.sleepycat.db.DatabaseConfig;
import com.sleepycat.db.DatabaseException;
import com.sleepycat.db.DatabaseType;
import java.io.FileNotFoundException;
...
Database myDatabase = null;
try {
DatabaseConfig dbConfig = new DatabaseConfig();
dbConfig.setAllowCreate(true);
dbConfig.setSortedDuplicates(true);
dbConfig.setType(DatabaseType.BTREE);
myDatabase = new Database("sampleDatabase.db",
null,
dbConfig);
} catch (DatabaseException dbe) {
// Exception handling goes here.
} catch (FileNotFoundException fnfe) {
// Exception handling goes here
}