java.sql.Connection

A connection (session) with a specific database. SQL statements are executed and results are returned within the context of a connection.

A Connection object's database is able to provide information describing its tables, its supported SQL grammar, its stored procedures, the capabilities of this connection, and so on. This information is obtained with the getMetaData method.

Note: By default a Connection object is in auto-commit mode, which means that it automatically commits changes after executing each statement. If auto-commit mode has been disabled, the method commit must be called explicitly in order to commit changes; otherwise, database changes will not be saved.

A new Connection object created using the JDBC 2.1 core API has an initially empty type map associated with it. A user may enter a custom mapping for a UDT in this type map. When a UDT is retrieved from a data source with the method ResultSet.getObject, the getObject method will check the connection's type map to see if there is an entry for that UDT. If so, the getObject method will map the UDT to the class indicated. If there is no entry, the UDT will be mapped using the standard mapping.

A user may create a new type map, which is a java.util.Map object, make an entry in it, and pass it to the java.sql methods that can perform custom mapping. In this case, the method will use the given type map instead of the one associated with the connection.

For example, the following code fragment specifies that the SQL type ATHLETES will be mapped to the class Athletes in the Java programming language. The code fragment retrieves the type map for the Connection object con, inserts the entry into it, and then sets the type map with the new entry as the connection's type map.

      java.util.Map map = con.getTypeMap();
      map.put("mySchemaName.ATHLETES", Class.forName("Athletes"));
      con.setTypeMap(map);

A constant indicating that transactions are not supported.

A constant indicating that dirty reads are prevented; non-repeatable reads and phantom reads can occur. This level only prohibits a transaction from reading a row with uncommitted changes in it.

A constant indicating that dirty reads, non-repeatable reads and phantom reads can occur. This level allows a row changed by one transaction to be read by another transaction before any changes in that row have been committed (a "dirty read"). If any of the changes are rolled back, the second transaction will have retrieved an invalid row.

A constant indicating that dirty reads and non-repeatable reads are prevented; phantom reads can occur. This level prohibits a transaction from reading a row with uncommitted changes in it, and it also prohibits the situation where one transaction reads a row, a second transaction alters the row, and the first transaction rereads the row, getting different values the second time (a "non-repeatable read").

A constant indicating that dirty reads, non-repeatable reads and phantom reads are prevented. This level includes the prohibitions in TRANSACTION_REPEATABLE_READ and further prohibits the situation where one transaction reads all rows that satisfy a WHERE condition, a second transaction inserts a row that satisfies that WHERE condition, and the first transaction rereads for the same condition, retrieving the additional "phantom" row in the second read.

Clears all warnings reported for this Connection object. After a call to this method, the method getWarnings returns null until a new warning is reported for this Connection object.

Throws

SQLException

if a database access error occurs

Releases this Connection object's database and JDBC resources immediately instead of waiting for them to be automatically released.

Calling the method close on a Connection object that is already closed is a no-op.

Note: A Connection object is automatically closed when it is garbage collected. Certain fatal errors also close a Connection object.

Throws

SQLException

if a database access error occurs

Makes all changes made since the previous commit/rollback permanent and releases any database locks currently held by this Connection object. This method should be used only when auto-commit mode has been disabled.

Throws

SQLException if a database access error occurs or this Connection object is in auto-commit mode

See Also

#setAutoCommit

Creates a Statement object for sending SQL statements to the database. SQL statements without parameters are normally executed using Statement objects. If the same SQL statement is executed many times, it may be more efficient to use a PreparedStatement object.

Result sets created using the returned Statement object will by default be type TYPE_FORWARD_ONLY and have a concurrency level of CONCUR_READ_ONLY.

Return

a new default Statement object

Throws

SQLException

if a database access error occurs

Creates a Statement object that will generate ResultSet objects with the given type and concurrency. This method is the same as the createStatement method above, but it allows the default result set type and concurrency to be overridden.

Parameters

resultSetType	a result set type; one of `ResultSet.TYPE_FORWARD_ONLY`, `ResultSet.TYPE_SCROLL_INSENSITIVE`, or `ResultSet.TYPE_SCROLL_SENSITIVE`
resultSetConcurrency	a concurrency type; one of `ResultSet.CONCUR_READ_ONLY` or `ResultSet.CONCUR_UPDATABLE`

Return

a new Statement object that will generate ResultSet objects with the given type and concurrency

Throws

SQLException if a database access error occurs or the given parameters are not ResultSet constants indicating type and concurrency

@since

1.2

Creates a Statement object that will generate ResultSet objects with the given type, concurrency, and holdability. This method is the same as the createStatement method above, but it allows the default result set type, concurrency, and holdability to be overridden.

Parameters

resultSetType	one of the following `ResultSet` constants: `ResultSet.TYPE_FORWARD_ONLY`, `ResultSet.TYPE_SCROLL_INSENSITIVE`, or `ResultSet.TYPE_SCROLL_SENSITIVE`
resultSetConcurrency	one of the following `ResultSet` constants: `ResultSet.CONCUR_READ_ONLY` or `ResultSet.CONCUR_UPDATABLE`
resultSetHoldability	one of the following `ResultSet` constants: `ResultSet.HOLD_CURSORS_OVER_COMMIT` or `ResultSet.CLOSE_CURSORS_AT_COMMIT`

Return

a new Statement object that will generate ResultSet objects with the given type, concurrency, and holdability

Throws

SQLException if a database access error occurs or the given parameters are not ResultSet constants indicating type, concurrency, and holdability

@since

1.4

See Also

ResultSet

Retrieves the current auto-commit mode for this Connection object.

Return

the current state of this Connection object's auto-commit mode

Throws

SQLException

if a database access error occurs

See Also

#setAutoCommit

Retrieves this Connection object's current catalog name.

Return

the current catalog name or null if there is none

Throws

SQLException

if a database access error occurs

See Also

#setCatalog

Retrieves the current holdability of ResultSet objects created using this Connection object.

Return

the holdability, one of ResultSet.HOLD_CURSORS_OVER_COMMIT or ResultSet.CLOSE_CURSORS_AT_COMMIT

Throws

SQLException

if a database access occurs

@since

1.4

See Also

#setHoldability , ResultSet

Retrieves a DatabaseMetaData object that contains metadata about the database to which this Connection object represents a connection. The metadata includes information about the database's tables, its supported SQL grammar, its stored procedures, the capabilities of this connection, and so on.

Return

a DatabaseMetaData object for this Connection object

Throws

SQLException

if a database access error occurs

Retrieves this Connection object's current transaction isolation level.

Return

the current transaction isolation level, which will be one of the following constants: Connection.TRANSACTION_READ_UNCOMMITTED, Connection.TRANSACTION_READ_COMMITTED, Connection.TRANSACTION_REPEATABLE_READ, Connection.TRANSACTION_SERIALIZABLE, or Connection.TRANSACTION_NONE.

Throws

SQLException

if a database access error occurs

See Also

#setTransactionIsolation

Retrieves the Map object associated with this Connection object. Unless the application has added an entry, the type map returned will be empty.

Return

the java.util.Map object associated with this Connection object

Throws

SQLException

if a database access error occurs

@since

1.2

See Also

#setTypeMap

Retrieves the first warning reported by calls on this Connection object. If there is more than one warning, subsequent warnings will be chained to the first one and can be retrieved by calling the method SQLWarning.getNextWarning on the warning that was retrieved previously.

This method may not be called on a closed connection; doing so will cause an SQLException to be thrown.

Note: Subsequent warnings will be chained to this SQLWarning.

Return

the first SQLWarning object or null if there are none

Throws

SQLException

if a database access error occurs or this method is called on a closed connection

See Also

SQLWarning

Retrieves whether this Connection object has been closed. A connection is closed if the method close has been called on it or if certain fatal errors have occurred. This method is guaranteed to return true only when it is called after the method Connection.close has been called.

This method generally cannot be called to determine whether a connection to a database is valid or invalid. A typical client can determine that a connection is invalid by catching any exceptions that might be thrown when an operation is attempted.

Return

true if this Connection object is closed; false if it is still open

Throws

SQLException

if a database access error occurs

Retrieves whether this Connection object is in read-only mode.

Return

true if this Connection object is read-only; false otherwise

Throws

SQLException

if a database access error occurs

Converts the given SQL statement into the system's native SQL grammar. A driver may convert the JDBC SQL grammar into its system's native SQL grammar prior to sending it. This method returns the native form of the statement that the driver would have sent.

Parameters

sql	an SQL statement that may contain one or more '?' parameter placeholders

Return

the native form of this statement

Throws

SQLException

if a database access error occurs

Creates a CallableStatement object for calling database stored procedures. The CallableStatement object provides methods for setting up its IN and OUT parameters, and methods for executing the call to a stored procedure.

Note: This method is optimized for handling stored procedure call statements. Some drivers may send the call statement to the database when the method prepareCall is done; others may wait until the CallableStatement object is executed. This has no direct effect on users; however, it does affect which method throws certain SQLExceptions.

Result sets created using the returned CallableStatement object will by default be type TYPE_FORWARD_ONLY and have a concurrency level of CONCUR_READ_ONLY.

Parameters

sql	an SQL statement that may contain one or more '?' parameter placeholders. Typically this statement is a JDBC function call escape string.

Return

a new default CallableStatement object containing the pre-compiled SQL statement

Throws

SQLException

if a database access error occurs

Creates a CallableStatement object that will generate ResultSet objects with the given type and concurrency. This method is the same as the prepareCall method above, but it allows the default result set type and concurrency to be overridden.

Parameters

sql	a `String` object that is the SQL statement to be sent to the database; may contain on or more ? parameters
resultSetType	a result set type; one of `ResultSet.TYPE_FORWARD_ONLY`, `ResultSet.TYPE_SCROLL_INSENSITIVE`, or `ResultSet.TYPE_SCROLL_SENSITIVE`
resultSetConcurrency	a concurrency type; one of `ResultSet.CONCUR_READ_ONLY` or `ResultSet.CONCUR_UPDATABLE`

Return

a new CallableStatement object containing the pre-compiled SQL statement that will produce ResultSet objects with the given type and concurrency

Throws

SQLException if a database access error occurs or the given parameters are not ResultSet constants indicating type and concurrency

@since

1.2

Parameters

sql	a `String` object that is the SQL statement to be sent to the database; may contain on or more ? parameters
resultSetType	one of the following `ResultSet` constants: `ResultSet.TYPE_FORWARD_ONLY`, `ResultSet.TYPE_SCROLL_INSENSITIVE`, or `ResultSet.TYPE_SCROLL_SENSITIVE`
resultSetConcurrency	one of the following `ResultSet` constants: `ResultSet.CONCUR_READ_ONLY` or `ResultSet.CONCUR_UPDATABLE`
resultSetHoldability	one of the following `ResultSet` constants: `ResultSet.HOLD_CURSORS_OVER_COMMIT` or `ResultSet.CLOSE_CURSORS_AT_COMMIT`

Return

a new CallableStatement object, containing the pre-compiled SQL statement, that will generate ResultSet objects with the given type, concurrency, and holdability

Throws

SQLException if a database access error occurs or the given parameters are not ResultSet constants indicating type, concurrency, and holdability

@since

1.4

See Also

ResultSet

Creates a PreparedStatement object for sending parameterized SQL statements to the database.

A SQL statement with or without IN parameters can be pre-compiled and stored in a PreparedStatement object. This object can then be used to efficiently execute this statement multiple times.

Note: This method is optimized for handling parametric SQL statements that benefit from precompilation. If the driver supports precompilation, the method prepareStatement will send the statement to the database for precompilation. Some drivers may not support precompilation. In this case, the statement may not be sent to the database until the PreparedStatement object is executed. This has no direct effect on users; however, it does affect which methods throw certain SQLException objects.

Result sets created using the returned PreparedStatement object will by default be type TYPE_FORWARD_ONLY and have a concurrency level of CONCUR_READ_ONLY.

Parameters

sql	an SQL statement that may contain one or more '?' IN parameter placeholders

Return

a new default PreparedStatement object containing the pre-compiled SQL statement

Throws

SQLException

if a database access error occurs

Creates a default PreparedStatement object that has the capability to retrieve auto-generated keys. The given constant tells the driver whether it should make auto-generated keys available for retrieval. This parameter is ignored if the SQL statement is not an INSERT statement.

Result sets created using the returned PreparedStatement object will by default be type TYPE_FORWARD_ONLY and have a concurrency level of CONCUR_READ_ONLY.

Parameters

sql	an SQL statement that may contain one or more '?' IN parameter placeholders
autoGeneratedKeys	a flag indicating whether auto-generated keys should be returned; one of `Statement.RETURN_GENERATED_KEYS` or `Statement.NO_GENERATED_KEYS`

Return

a new PreparedStatement object, containing the pre-compiled SQL statement, that will have the capability of returning auto-generated keys

Throws

SQLException if a database access error occurs or the given parameter is not a Statement constant indicating whether auto-generated keys should be returned

@since

1.4

Creates a default PreparedStatement object capable of returning the auto-generated keys designated by the given array. This array contains the indexes of the columns in the target table that contain the auto-generated keys that should be made available. This array is ignored if the SQL statement is not an INSERT statement.

An SQL statement with or without IN parameters can be pre-compiled and stored in a PreparedStatement object. This object can then be used to efficiently execute this statement multiple times.

Result sets created using the returned PreparedStatement object will by default be type TYPE_FORWARD_ONLY and have a concurrency level of CONCUR_READ_ONLY.

Parameters

sql	an SQL statement that may contain one or more '?' IN parameter placeholders
columnIndexes	an array of column indexes indicating the columns that should be returned from the inserted row or rows

Return

a new PreparedStatement object, containing the pre-compiled statement, that is capable of returning the auto-generated keys designated by the given array of column indexes

Throws

SQLException

if a database access error occurs

@since

1.4

Creates a PreparedStatement object that will generate ResultSet objects with the given type and concurrency. This method is the same as the prepareStatement method above, but it allows the default result set type and concurrency to be overridden.

Parameters

sql	a `String` object that is the SQL statement to be sent to the database; may contain one or more ? IN parameters
resultSetType	a result set type; one of `ResultSet.TYPE_FORWARD_ONLY`, `ResultSet.TYPE_SCROLL_INSENSITIVE`, or `ResultSet.TYPE_SCROLL_SENSITIVE`
resultSetConcurrency	a concurrency type; one of `ResultSet.CONCUR_READ_ONLY` or `ResultSet.CONCUR_UPDATABLE`

Return

a new PreparedStatement object containing the pre-compiled SQL statement that will produce ResultSet objects with the given type and concurrency

Throws

SQLException if a database access error occurs or the given parameters are not ResultSet constants indicating type and concurrency

@since

1.2

Creates a PreparedStatement object that will generate ResultSet objects with the given type, concurrency, and holdability.

This method is the same as the prepareStatement method above, but it allows the default result set type, concurrency, and holdability to be overridden.

Parameters

sql	a `String` object that is the SQL statement to be sent to the database; may contain one or more ? IN parameters
resultSetType	one of the following `ResultSet` constants: `ResultSet.TYPE_FORWARD_ONLY`, `ResultSet.TYPE_SCROLL_INSENSITIVE`, or `ResultSet.TYPE_SCROLL_SENSITIVE`
resultSetConcurrency	one of the following `ResultSet` constants: `ResultSet.CONCUR_READ_ONLY` or `ResultSet.CONCUR_UPDATABLE`
resultSetHoldability	one of the following `ResultSet` constants: `ResultSet.HOLD_CURSORS_OVER_COMMIT` or `ResultSet.CLOSE_CURSORS_AT_COMMIT`

Return

a new PreparedStatement object, containing the pre-compiled SQL statement, that will generate ResultSet objects with the given type, concurrency, and holdability

Throws

SQLException if a database access error occurs or the given parameters are not ResultSet constants indicating type, concurrency, and holdability

@since

1.4

See Also

ResultSet

Creates a default PreparedStatement object capable of returning the auto-generated keys designated by the given array. This array contains the names of the columns in the target table that contain the auto-generated keys that should be returned. This array is ignored if the SQL statement is not an INSERT statement.

An SQL statement with or without IN parameters can be pre-compiled and stored in a PreparedStatement object. This object can then be used to efficiently execute this statement multiple times.

Result sets created using the returned PreparedStatement object will by default be type TYPE_FORWARD_ONLY and have a concurrency level of CONCUR_READ_ONLY.

Parameters

sql	an SQL statement that may contain one or more '?' IN parameter placeholders
columnNames	an array of column names indicating the columns that should be returned from the inserted row or rows

Return

a new PreparedStatement object, containing the pre-compiled statement, that is capable of returning the auto-generated keys designated by the given array of column names

Throws

SQLException

if a database access error occurs

@since

1.4

Removes the given Savepoint object from the current transaction. Any reference to the savepoint after it have been removed will cause an SQLException to be thrown.

Parameters

savepoint the Savepoint object to be removed

Throws

SQLException if a database access error occurs or the given Savepoint object is not a valid savepoint in the current transaction

@since

1.4

Undoes all changes made in the current transaction and releases any database locks currently held by this Connection object. This method should be used only when auto-commit mode has been disabled.

Throws

SQLException if a database access error occurs or this Connection object is in auto-commit mode

See Also

#setAutoCommit

Undoes all changes made after the given Savepoint object was set.

This method should be used only when auto-commit has been disabled.

Parameters

savepoint the Savepoint object to roll back to

Throws

SQLException if a database access error occurs, the Savepoint object is no longer valid, or this Connection object is currently in auto-commit mode

@since

1.4

See Also

Savepoint , #rollback

Sets this connection's auto-commit mode to the given state. If a connection is in auto-commit mode, then all its SQL statements will be executed and committed as individual transactions. Otherwise, its SQL statements are grouped into transactions that are terminated by a call to either the method commit or the method rollback. By default, new connections are in auto-commit mode.

The commit occurs when the statement completes or the next execute occurs, whichever comes first. In the case of statements returning a ResultSet object, the statement completes when the last row of the ResultSet object has been retrieved or the ResultSet object has been closed. In advanced cases, a single statement may return multiple results as well as output parameter values. In these cases, the commit occurs when all results and output parameter values have been retrieved.

NOTE: If this method is called during a transaction, the transaction is committed.

Parameters

autoCommit true to enable auto-commit mode; false to disable it

Throws

SQLException

if a database access error occurs

See Also

#getAutoCommit

Sets the given catalog name in order to select a subspace of this Connection object's database in which to work.

If the driver does not support catalogs, it will silently ignore this request.

Parameters

catalog the name of a catalog (subspace in this Connection object's database) in which to work

Throws

SQLException

if a database access error occurs

See Also

#getCatalog

Changes the holdability of ResultSet objects created using this Connection object to the given holdability.

Parameters

holdability a ResultSet holdability constant; one of ResultSet.HOLD_CURSORS_OVER_COMMIT or ResultSet.CLOSE_CURSORS_AT_COMMIT

Throws

SQLException if a database access occurs, the given parameter is not a ResultSet constant indicating holdability, or the given holdability is not supported

@since

1.4

See Also

#getHoldability , ResultSet

Puts this connection in read-only mode as a hint to the driver to enable database optimizations.

Note: This method cannot be called during a transaction.

Parameters

readOnly true enables read-only mode; false disables it

Throws

SQLException

if a database access error occurs or this method is called during a transaction

Creates an unnamed savepoint in the current transaction and returns the new Savepoint object that represents it.

Return

the new Savepoint object

Throws

SQLException if a database access error occurs or this Connection object is currently in auto-commit mode

@since

1.4

See Also

Savepoint

Creates a savepoint with the given name in the current transaction and returns the new Savepoint object that represents it.

Parameters

name	a `String` containing the name of the savepoint

Return

the new Savepoint object

Throws

SQLException if a database access error occurs or this Connection object is currently in auto-commit mode

@since

1.4

See Also

Savepoint

Attempts to change the transaction isolation level for this Connection object to the one given. The constants defined in the interface Connection are the possible transaction isolation levels.

Note: If this method is called during a transaction, the result is implementation-defined.

Parameters

level one of the following Connection constants: Connection.TRANSACTION_READ_UNCOMMITTED, Connection.TRANSACTION_READ_COMMITTED, Connection.TRANSACTION_REPEATABLE_READ, or Connection.TRANSACTION_SERIALIZABLE. (Note that Connection.TRANSACTION_NONE cannot be used because it specifies that transactions are not supported.)

Throws

SQLException if a database access error occurs or the given parameter is not one of the Connection constants

Installs the given TypeMap object as the type map for this Connection object. The type map will be used for the custom mapping of SQL structured types and distinct types.

Parameters

map	the `java.util.Map` object to install as the replacement for this `Connection` object's default type map

Throws

SQLException if a database access error occurs or the given parameter is not a java.util.Map object

@since

1.2

See Also

#getTypeMap