Interface java.sql.Connection - JDK 5 Documentation v1.1.8, Java 2 SDK 英文文档

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Interface java.sql.Connection

public interface Connection

A Connection represents a 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, etc. 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, an explicit commit must be done or database changes will not be saved.

See Also:: getConnection, Statement, ResultSet, DatabaseMetaData

TRANSACTION_NONE: Transactions are not supported.
TRANSACTION_READ_COMMITTED: Dirty reads are prevented; non-repeatable reads and phantom reads can occur.
TRANSACTION_READ_UNCOMMITTED: Dirty reads, non-repeatable reads and phantom reads can occur.
TRANSACTION_REPEATABLE_READ: Dirty reads and non-repeatable reads are prevented; phantom reads can occur.
TRANSACTION_SERIALIZABLE: Dirty reads, non-repeatable reads and phantom reads are prevented.

clearWarnings(): After this call, getWarnings returns null until a new warning is reported for this Connection.
close(): In some cases, it is desirable to immediately release a Connection's database and JDBC resources instead of waiting for them to be automatically released; the close method provides this immediate release.
commit(): Commit makes all changes made since the previous commit/rollback permanent and releases any database locks currently held by the Connection.
createStatement(): SQL statements without parameters are normally executed using Statement objects.
getAutoCommit(): Get the current auto-commit state.
getCatalog(): Return the Connection's current catalog name.
getMetaData(): A Connection's database is able to provide information describing its tables, its supported SQL grammar, its stored procedures, the capabilities of this connection, etc.
getTransactionIsolation(): Get this Connection's current transaction isolation mode.
getWarnings(): The first warning reported by calls on this Connection is returned.
isClosed(): Tests to see if a Connection is closed.
isReadOnly(): Tests to see if the connection is in read-only mode.
nativeSQL(String): A driver may convert the JDBC sql grammar into its system's native SQL grammar prior to sending it; nativeSQL returns the native form of the statement that the driver would have sent.
prepareCall(String): A SQL stored procedure call statement is handled by creating a CallableStatement for it.
prepareStatement(String): A SQL statement with or without IN parameters can be pre-compiled and stored in a PreparedStatement object.
rollback(): Rollback drops all changes made since the previous commit/rollback and releases any database locks currently held by the Connection.
setAutoCommit(boolean): If a connection is in auto-commit mode, then all its SQL statements will be executed and committed as individual transactions.
setCatalog(String): A sub-space of this Connection's database may be selected by setting a catalog name.
setReadOnly(boolean): You can put a connection in read-only mode as a hint to enable database optimizations.
setTransactionIsolation(int): You can call this method to try to change the transaction isolation level using one of the TRANSACTION_* values.

TRANSACTION_NONE

 public static final int TRANSACTION_NONE

Transactions are not supported.

TRANSACTION_READ_UNCOMMITTED

 public static final int TRANSACTION_READ_UNCOMMITTED

Dirty reads, non-repeatable reads and phantom reads can occur.

TRANSACTION_READ_COMMITTED

 public static final int TRANSACTION_READ_COMMITTED

Dirty reads are prevented; non-repeatable reads and phantom reads can occur.

TRANSACTION_REPEATABLE_READ

 public static final int TRANSACTION_REPEATABLE_READ

Dirty reads and non-repeatable reads are prevented; phantom reads can occur.

TRANSACTION_SERIALIZABLE

 public static final int TRANSACTION_SERIALIZABLE

Dirty reads, non-repeatable reads and phantom reads are prevented.

createStatement

 public abstract Statement createStatement() throws SQLException

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

Returns:: a new Statement object
Throws: SQLException: if a database-access error occurs.

prepareStatement

 public abstract PreparedStatement prepareStatement(String sql) throws SQLException

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, 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 affect on users; however, it does affect which method throws certain SQLExceptions.

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 abstract CallableStatement prepareCall(String sql) throws SQLException

A SQL stored procedure call statement is handled by creating a CallableStatement for it. The CallableStatement provides methods for setting up its IN and OUT parameters, and methods for executing it.

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

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 abstract String nativeSQL(String sql) throws SQLException

A driver may convert the JDBC sql grammar into its system's native SQL grammar prior to sending it; nativeSQL 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 abstract void setAutoCommit(boolean autoCommit) throws SQLException

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 either commit() or 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. Here the commit occurs when all results and output param values have been retrieved.

Parameters:: autoCommit - true enables auto-commit; false disables auto-commit.
Throws: SQLException: if a database-access error occurs.

getAutoCommit

 public abstract boolean getAutoCommit() throws SQLException

Get the current auto-commit state.

Returns:: Current state of auto-commit mode.
Throws: SQLException: if a database-access error occurs.
See Also:: setAutoCommit

commit

 public abstract void commit() throws SQLException

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

Throws: SQLException: if a database-access error occurs.
See Also:: setAutoCommit

rollback

 public abstract void rollback() throws SQLException

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

Throws: SQLException: if a database-access error occurs.
See Also:: setAutoCommit

close

 public abstract void close() throws SQLException

In some cases, it is desirable to immediately release a Connection's database and JDBC resources instead of waiting for them to be automatically released; the close method provides this immediate release.

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 abstract 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 abstract DatabaseMetaData getMetaData() throws SQLException

Returns:: a DatabaseMetaData object for this Connection
Throws: SQLException: if a database-access error occurs.

setReadOnly

 public abstract void setReadOnly(boolean readOnly) throws SQLException

You can put a connection in read-only mode as a hint to enable database optimizations.

Note: setReadOnly 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 abstract boolean isReadOnly() throws SQLException

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

Returns:: true if connection is read-only
Throws: SQLException: if a database-access error occurs.

setCatalog

 public abstract void setCatalog(String catalog) throws SQLException

A sub-space of this Connection's database may be selected by setting a catalog name. If the driver does not support catalogs it will silently ignore this request.

Throws: SQLException: if a database-access error occurs.

getCatalog

 public abstract String getCatalog() throws SQLException

Return the Connection's current catalog name.

Returns:: the current catalog name or null
Throws: SQLException: if a database-access error occurs.

setTransactionIsolation

 public abstract void setTransactionIsolation(int level) throws SQLException

You can call this method to try to change the transaction isolation level using one of the TRANSACTION_* values.

Note: setTransactionIsolation 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:: supportsTransactionIsolationLevel

getTransactionIsolation

 public abstract int getTransactionIsolation() throws SQLException

Get this Connection's current transaction isolation mode.

Returns:: the current TRANSACTION_* mode value
Throws: SQLException: if a database-access error occurs.

getWarnings

 public abstract SQLWarning getWarnings() throws SQLException

The first warning reported by calls on this Connection is returned.

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 abstract void clearWarnings() throws SQLException

After this call, getWarnings returns null until a new warning is reported for this Connection.

Throws: SQLException: if a database-access error occurs.

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