XQConnection

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javax.xml.xquery
Interface XQConnection

All Superinterfaces:: XQDataFactory

All Known Implementing Classes:: SaxonXQConnection

public interface XQConnection
extends XQDataFactory
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
`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

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