JavaTM 2 Platform
Std. Ed. v1.3.1

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

JavaTM 2 Platform
Std. Ed. v1.3.1

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For further API reference and developer documentation, see Java 2 SDK SE Developer Documentation. That documentation contains more detailed, developer-targeted descriptions, with conceptual overviews, definitions of terms, workarounds, and working code examples.

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