Package javax.xml.xquery

Interface XQConnection

All Superinterfaces:
XQDataFactory
All Known Implementing Classes:
SaxonXQConnection
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 Details

    • 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