java.sql
Interface Connection

public interface Connection

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

A Connection'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 the Connection automatically commits changes after executing each statement. If auto commit has been disabled, the method commit must be called explicitly; otherwise, database changes will not be saved.

See Also:

DriverManager.getConnection(java.lang.String, java.util.Properties), Statement, ResultSet,

Methods that are new in the JDBC 2.0 API are tagged @since 1.2.

Field Summary

static int	TRANSACTION_NONE Indicates that transactions are not supported.
static int	TRANSACTION_READ_COMMITTED Dirty reads are prevented; non-repeatable reads and phantom reads can occur.
static int	TRANSACTION_READ_UNCOMMITTED Dirty reads, non-repeatable reads and phantom reads can occur.
static int	TRANSACTION_REPEATABLE_READ Dirty reads and non-repeatable reads are prevented; phantom reads can occur.
static int	TRANSACTION_SERIALIZABLE Dirty reads, non-repeatable reads and phantom reads are prevented.

Method Summary

void	clearWarnings() Clears all warnings reported for this Connection object.
void	close() Releases a Connection's database and JDBC resources immediately instead of waiting for them to be automatically released.
void	commit() Makes all changes made since the previous commit/rollback permanent and releases any database locks currently held by the Connection.
Statement	createStatement() Creates a Statement object for sending SQL statements to the database.
Statement	createStatement(int resultSetType, int resultSetConcurrency) Creates a Statement object that will generate ResultSet objects with the given type and concurrency.
boolean	getAutoCommit() Gets the current auto-commit state.
String	getCatalog() Returns the Connection's current catalog name.
DatabaseMetaData	getMetaData() Gets the metadata regarding this connection's database.
int	getTransactionIsolation() Gets this Connection's current transaction isolation level.
Map	getTypeMap() Gets the type map object associated with this connection.
SQLWarning	getWarnings() Returns the first warning reported by calls on this Connection.
boolean	isClosed() Tests to see if a Connection is closed.
boolean	isReadOnly() Tests to see if the connection is in read-only mode.
String	nativeSQL(String sql) Converts the given SQL statement into the system's native SQL grammar.
CallableStatement	prepareCall(String sql) Creates a CallableStatement object for calling database stored procedures.
CallableStatement	prepareCall(String sql, int resultSetType, int resultSetConcurrency) Creates a CallableStatement object that will generate ResultSet objects with the given type and concurrency.
PreparedStatement	prepareStatement(String sql) Creates a PreparedStatement object for sending parameterized SQL statements to the database.
PreparedStatement	prepareStatement(String sql, int resultSetType, int resultSetConcurrency) Creates a PreparedStatement object that will generate ResultSet objects with the given type and concurrency.
void	rollback() Drops all changes made since the previous commit/rollback and releases any database locks currently held by this Connection.
void	setAutoCommit(boolean autoCommit) Sets this connection's auto-commit mode.
void	setCatalog(String catalog) Sets a catalog name in order to select a subspace of this Connection's database in which to work.
void	setReadOnly(boolean readOnly) Puts this connection in read-only mode as a hint to enable database optimizations.
void	setTransactionIsolation(int level) Attempts to change the transaction isolation level to the one given.
void	setTypeMap(Map map) Installs the given type map as the type map for this connection.

Field Detail

TRANSACTION_NONE

public static final int TRANSACTION_NONE

Indicates that transactions are not supported.

TRANSACTION_READ_UNCOMMITTED

public static final int TRANSACTION_READ_UNCOMMITTED

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.

TRANSACTION_READ_COMMITTED

public static final int TRANSACTION_READ_COMMITTED

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.

TRANSACTION_REPEATABLE_READ

public static final int TRANSACTION_REPEATABLE_READ

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").

TRANSACTION_SERIALIZABLE

public static final int TRANSACTION_SERIALIZABLE

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.

Method Detail

createStatement

public Statement createStatement()
                          throws SQLException

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 is more efficient to use a PreparedStatement object.

Result sets created using the returned Statement object will by default have forward-only type and read-only concurrency.

Returns:

a new Statement object

Throws:

SQLException - if a database access error occurs

prepareStatement

public PreparedStatement prepareStatement(String sql)
                                   throws SQLException

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 is executed. This has no direct effect on users; however, it does affect which method throws certain SQLExceptions. Result sets created using the returned PreparedStatement will have forward-only type and read-only concurrency, by default.

Parameters:

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

Returns:

a new PreparedStatement object containing the pre-compiled statement

Throws:

SQLException - if a database access error occurs

prepareCall

public CallableStatement prepareCall(String sql)
                              throws SQLException

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 will have forward-only type and read-only concurrency, by default.

Parameters:

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

Returns:

a new CallableStatement object containing the pre-compiled SQL statement

Throws:

SQLException - if a database access error occurs

nativeSQL

public String nativeSQL(String sql)
                 throws SQLException

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 - a SQL statement that may contain one or more '?' parameter placeholders

Returns:

the native form of this statement

Throws:

SQLException - if a database access error occurs

setAutoCommit

public void setAutoCommit(boolean autoCommit)
                   throws SQLException

Sets this connection's auto-commit mode. 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, the statement completes when the last row of the ResultSet has been retrieved or the ResultSet 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.

Parameters:

autoCommit - true enables auto-commit; false disables auto-commit.

Throws:

SQLException - if a database access error occurs

getAutoCommit

public boolean getAutoCommit()
                      throws SQLException

Gets the current auto-commit state.

Returns:

the current state of auto-commit mode

Throws:

SQLException - if a database access error occurs

See Also:

setAutoCommit(boolean)

commit

public void commit()
            throws SQLException

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

Throws:

SQLException - if a database access error occurs

See Also:

setAutoCommit(boolean)

rollback

public void rollback()
              throws SQLException

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

Throws:

SQLException - if a database access error occurs

See Also:

setAutoCommit(boolean)

close

public void close()
           throws SQLException

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

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

Throws:

SQLException - if a database access error occurs

isClosed

public boolean isClosed()
                 throws SQLException

Tests to see if a Connection is closed.

Returns:

true if the connection is closed; false if it's still open

Throws:

SQLException - if a database access error occurs

getMetaData

public DatabaseMetaData getMetaData()
                             throws SQLException

Gets the metadata regarding this connection's database. A Connection'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 made available through a DatabaseMetaData object.

Returns:

a DatabaseMetaData object for this Connection

Throws:

SQLException - if a database access error occurs

setReadOnly

public void setReadOnly(boolean readOnly)
                 throws SQLException

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

Note: This method cannot be called while in the middle of a transaction.

Parameters:

readOnly - true enables read-only mode; false disables read-only mode.

Throws:

SQLException - if a database access error occurs

isReadOnly

public boolean isReadOnly()
                   throws SQLException

Tests to see if the connection is in read-only mode.

Returns:

true if connection is read-only and false otherwise

Throws:

SQLException - if a database access error occurs

setCatalog

public void setCatalog(String catalog)
                throws SQLException

Sets a catalog name in order to select a subspace of this Connection's database in which to work. If the driver does not support catalogs, it will silently ignore this request.

Throws:

SQLException - if a database access error occurs

getCatalog

public String getCatalog()
                  throws SQLException

Returns the Connection's current catalog name.

Returns:

the current catalog name or null

Throws:

SQLException - if a database access error occurs

setTransactionIsolation

public void setTransactionIsolation(int level)
                             throws SQLException

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

Note: This method cannot be called while in the middle of a transaction.

Parameters:

level - one of the TRANSACTION_* isolation values with the exception of TRANSACTION_NONE; some databases may not support other values

Throws:

SQLException - if a database access error occurs

See Also:

DatabaseMetaData.supportsTransactionIsolationLevel(int)

getTransactionIsolation

public int getTransactionIsolation()
                            throws SQLException

Gets this Connection's current transaction isolation level.

Returns:

the current TRANSACTION_* mode value

Throws:

SQLException - if a database access error occurs

getWarnings

public SQLWarning getWarnings()
                       throws SQLException

Returns the first warning reported by calls on this Connection.

Note: Subsequent warnings will be chained to this SQLWarning.

Returns:

the first SQLWarning or null

Throws:

SQLException - if a database access error occurs

clearWarnings

public void clearWarnings()
                   throws SQLException

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.

Throws:

SQLException - if a database access error occurs

createStatement

public Statement createStatement(int resultSetType,
                                 int resultSetConcurrency)
                          throws SQLException

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 result set concurrency type to be overridden.

Parameters:

resultSetType - a result set type; see ResultSet.TYPE_XXX

resultSetConcurrency - a concurrency type; see ResultSet.CONCUR_XXX

Returns:

a new Statement object

Throws:

SQLException - if a database access error occurs

Since:

1.2

See Also:

What Is in the JDBC 2.0 API

prepareStatement

public PreparedStatement prepareStatement(String sql,
                                          int resultSetType,
                                          int resultSetConcurrency)
                                   throws SQLException

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 result set concurrency type to be overridden.

Parameters:

resultSetType - a result set type; see ResultSet.TYPE_XXX

resultSetConcurrency - a concurrency type; see ResultSet.CONCUR_XXX

Returns:

a new PreparedStatement object containing the pre-compiled SQL statement

Throws:

SQLException - if a database access error occurs

Since:

1.2

See Also:

What Is in the JDBC 2.0 API

prepareCall

public CallableStatement prepareCall(String sql,
                                     int resultSetType,
                                     int resultSetConcurrency)
                              throws SQLException

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 result set concurrency type to be overridden.

Parameters:

resultSetType - a result set type; see ResultSet.TYPE_XXX

resultSetConcurrency - a concurrency type; see ResultSet.CONCUR_XXX

Returns:

a new CallableStatement object containing the pre-compiled SQL statement

Throws:

SQLException - if a database access error occurs

Since:

1.2

See Also:

What Is in the JDBC 2.0 API

getTypeMap

public Map getTypeMap()
               throws SQLException

Gets the type map object associated with this connection. Unless the application has added an entry to the type map, the map returned will be empty.

Returns:

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

Since:

1.2

See Also:

What Is in the JDBC 2.0 API

setTypeMap

public void setTypeMap(Map map)
                throws SQLException

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

Parameters:

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

Since:

1.2

See Also:

What Is in the JDBC 2.0 API