javax.xml.xquery

Interface XQConnection

All Superinterfaces:

XQDataFactory

public interface XQConnection
extends XQDataFactory

A connection (session) with a specific XQuery engine. Connections are obtained through an XQDataSource object.

XQuery expressions are executed and results are returned within the context of a connection. They are either executed through XQExpression or XQPreparedExpression objects.

  XQDataSource ds;// obtain the XQuery datasource
  ...
  XQConnection conn = ds.getConnection();

  XQPreparedExpression expr = conn.prepareExpression("for $i in ...");
  XQResultSequence result = expr.executeQuery();
  // - or -
  XQExpression expr = conn.createExpression();
  XQSequence result = expr.executeQuery("for $i in..");

  // The sequence can now be iterated
  while (result.next())
  {
     String str  = result.getItemAsString();
     System.out.println(" output "+ str);
  }
  result.close();
  expr.close();
  conn.close();  // close the connection and free all resources..

 

A connection holds also default values for XQExpression and XQPreparedExpression properties. An application can override these defaults by passing an XQStaticContext object to the setStaticContext() method.

By default a connection operates in auto-commit mode, which means that each xquery is executed and committed in an individual transaction. If auto-commit mode is disabled, a transaction must be ended explicitly by the application calling commit() or rollback().

An XQConnection object can be created on top of an existing JDBC connection. If an XQConnection is created on top of the JDBC connection, it inherits the transaction context from the JDBC connection. Also, in this case, if the auto-commit mode is changed, or a transaction is ended using commit or rollback, it also changes the underlying JDBC connection.

An XQJ driver is not required to provide finalizer methods for the connection and other objects. Hence it is strongly recommended that users call close method explicitly to free any resources. It is also recommended that they do so under a final block to ensure that the object is closed even when there are exceptions. Not closing this object explicitly might result in serious memory leaks.

When the XQConnection is closed any XQExpression and XQPreparedExpression objects obtained from it are also implicitly closed.

Method Summary

Modifier and Type	Method and Description
void	close() Closes the connection.
void	commit() Makes all changes made in the current transaction permanent and releases any locks held by the datasource.
XQExpression	createExpression() Creates a new XQExpression object that can be used to perform execute immediate operations with XQuery expressions.
XQExpression	createExpression(XQStaticContext properties) Creates a new XQExpression object that can be used to perform execute immediate operations with XQuery expressions.
boolean	getAutoCommit() Gets the auto-commit attribute of this connection
XQMetaData	getMetaData() Gets the metadata for this connection.
XQStaticContext	getStaticContext() Gets an XQStaticContext representing the default values for all expression properties.
boolean	isClosed() Checks if the connection is closed.
XQPreparedExpression	prepareExpression(InputStream xquery) Prepares an expression for execution.
XQPreparedExpression	prepareExpression(InputStream xquery, XQStaticContext properties) Prepares an expression for execution.
XQPreparedExpression	prepareExpression(Reader xquery) Prepares an expression for execution.
XQPreparedExpression	prepareExpression(Reader xquery, XQStaticContext properties) Prepares an expression for execution.
XQPreparedExpression	prepareExpression(String xquery) Prepares an expression for execution.
XQPreparedExpression	prepareExpression(String xquery, XQStaticContext properties) Prepares an expression for execution.
void	rollback() Undoes all changes made in the current transaction and releases any locks held by the datasource.
void	setAutoCommit(boolean autoCommit) Sets the auto-commit attribute to the given state.
void	setStaticContext(XQStaticContext properties) Sets the default values for all expression properties.

Methods inherited from interface javax.xml.xquery.XQDataFactory

createAtomicType, createAtomicType, createAttributeType, createAttributeType, createCommentType, createDocumentElementType, createDocumentSchemaElementType, createDocumentType, createElementType, createElementType, createItem, createItemFromAtomicValue, createItemFromBoolean, createItemFromByte, createItemFromDocument, createItemFromDocument, createItemFromDocument, createItemFromDocument, createItemFromDocument, createItemFromDouble, createItemFromFloat, createItemFromInt, createItemFromLong, createItemFromNode, createItemFromObject, createItemFromShort, createItemFromString, createItemType, createNodeType, createProcessingInstructionType, createSchemaAttributeType, createSchemaElementType, createSequence, createSequence, createSequenceType, createTextType

Method Detail

close

void close()
    throws XQException

Closes the connection. This also closes any XQExpression and XQPreparedExpression obtained from this connection. Once the connection is closed, no method other than close or the isClosed method may be called on the connection object. Calling close on an XQConnection object that is already closed has no effect. Note that an XQJ driver is not required to provide finalizer methods for the connection and other objects. Hence it is strongly recommended that users call this method explicitly to free any resources. It is also recommended that they do so under a final block to ensure that the object is closed even when there are exceptions.

Throws:

XQException - if there is an error during closing the connection.

setAutoCommit

void setAutoCommit(boolean autoCommit)
            throws XQException

Sets the auto-commit attribute to the given state. If a connection is in auto-commit mode, each xquery is executed and committed in an individual transaction. When auto-commit mode is disabled, xqueries are grouped in a transaction that must be ended explicitly by the application calling commit() or rollback().
By default, new connections are in auto-commit mode.
If the value of auto-commit is changed in the middle of a transaction, the transaction is committed. If setAutoCommit is called and the auto-commit attribute is not changed from its current value, the request is treated as a no-op.

Parameters:

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

Throws:

XQException - if (1) the connection is in a closed state, or (2) auto-commit is turned off but the implementation doesn't support transactions

getAutoCommit

boolean getAutoCommit()
               throws XQException

Gets the auto-commit attribute of this connection

Returns:

the auto-commit attribute of this connection. true if the connection operates in auto-commit mode; otherwise false

Throws:

XQException - if the connection is in a closed state

commit

void commit()
     throws XQException

Makes all changes made in the current transaction permanent and releases any locks held by the datasource. This method should be used only when auto-commit mode is disabled. Any XQResultSequence, or XQResultItem may be implicitly closed upon commit, if the holdability property of the sequence is set to XQConstants.HOLDTYPE_CLOSE_CURSORS_AT_COMMIT.

Throws:

XQException - if the connection is in a closed state or this connection is operating in auto-commit mode

createExpression

XQExpression createExpression()
                       throws XQException

Creates a new XQExpression object that can be used to perform execute immediate operations with XQuery expressions. The properties of the connection's default XQStaticContext are copied to the returned XQExpression.

Returns:

XQExpression that can be used to execute multiple expressions

Throws:

XQException - if the connection is in a closed state

createExpression

XQExpression createExpression(XQStaticContext properties)
                       throws XQException

Creates a new XQExpression object that can be used to perform execute immediate operations with XQuery expressions. The properties of the specified XQStaticContext values are copied to the returned XQExpression.

Parameters:

properties - XQStaticContext containing values of expression properties

Returns:

XQExpression that can be used to execute multiple expressions

Throws:

XQException - if (1) the connection is in a closed state, or (2) the specified argument is null

getMetaData

XQMetaData getMetaData()
                throws XQException

Gets the metadata for this connection.

Returns:

XQMetadata representing the metadata of this connection

Throws:

XQException - if the connection is in a closed state

isClosed

boolean isClosed()

Checks if the connection is closed.

Returns:

true if the connection is in a closed state, false otherwise

prepareExpression

XQPreparedExpression prepareExpression(String xquery)
                                throws XQException

Prepares an expression for execution.

The properties of the connection's default XQStaticContext are copied to the returned XQPreparedExpression.

Parameters:

xquery - the XQuery expression as a String. Cannot be null

Returns:

the prepared XQuery expression

Throws:

XQException - if (1) the connection is in a closed state, (2) there are errors preparing the expression, or (3) the xquery parameter is null

prepareExpression

XQPreparedExpression prepareExpression(String xquery,
                                       XQStaticContext properties)
                                throws XQException

Prepares an expression for execution.

The properties of the specified XQStaticContext values are copied to the returned XQPreparedExpression.

Parameters:

xquery - the XQuery expression as a String. Cannot be null

properties - XQStaticContext containing values of expression properties.

Returns:

the prepared XQuery expression

Throws:

XQException - if (1) the connection is in a closed state, or (2) the specified argument is null

prepareExpression

XQPreparedExpression prepareExpression(Reader xquery)
                                throws XQException

Prepares an expression for execution.

The properties of the connection's default XQStaticContext are copied to the returned XQPreparedExpression.

Parameters:

xquery - the XQuery expression as a Reader. Cannot be null

Returns:

the prepared XQuery expression

Throws:

XQException - if (1) the connection is in a closed state, (2) there are errors preparing the expression, or (3) the xquery parameter is null

prepareExpression

XQPreparedExpression prepareExpression(Reader xquery,
                                       XQStaticContext properties)
                                throws XQException

Prepares an expression for execution.

The properties of the specified XQStaticContext values are copied to the returned XQPreparedExpression.

Parameters:

xquery - the XQuery expression as a Reader. Cannot be null

properties - XQStaticContext containing values of expression properties

Returns:

the prepared XQuery expression

Throws:

XQException - if (1) the connection is in a closed state, or (2) the specified argument is null

prepareExpression

XQPreparedExpression prepareExpression(InputStream xquery)
                                throws XQException

Prepares an expression for execution.

The properties of the connection's default XQStaticContext are copied to the returned XQPreparedExpression.

Parameters:

xquery - the XQuery expression as an InputStream. Cannot be null

Returns:

the prepared XQuery expression

Throws:

XQException - if (1) the connection is in a closed state, (2) there are errors preparing the expression or (3) the xquery parameter is null

prepareExpression

XQPreparedExpression prepareExpression(InputStream xquery,
                                       XQStaticContext properties)
                                throws XQException

Prepares an expression for execution.

The properties of the specified XQStaticContext values are copied to the returned XQPreparedExpression.

Parameters:

xquery - the XQuery expression as an InputStream. Cannot be null

properties - XQStaticContext containing values of expression properties

Returns:

the prepared XQuery expression

Throws:

XQException - if (1) the connection is in a closed state, or (2) the specified argument is null

rollback

void rollback()
       throws XQException

Undoes all changes made in the current transaction and releases any locks held by the datasource. This method should be used only when auto-commit mode is disabled.

Throws:

XQException - if the connection is in a closed state or this connection is operating in auto-commit mode

getStaticContext

XQStaticContext getStaticContext()
                          throws XQException

Gets an XQStaticContext representing the default values for all expression properties. In order to modify the defaults, it is not sufficient to modify the values in the returned XQStaticContext object; in addition setStaticContext should be called to make those new values effective.

Returns:

XQStaticContext representing the default values for all expression properties

Throws:

XQException - if the connection is in a closed state

setStaticContext

void setStaticContext(XQStaticContext properties)
               throws XQException

Sets the default values for all expression properties. The implementation will read out all expression properties from the specified XQStaticContext and update its private copy.

Parameters:

properties - XQStaticContext containing values of expression properties

Throws:

XQException - if the connection is in a closed state