org.hsqldb.jdbc
Class JDBCSQLXML

java.lang.Object
  org.hsqldb.jdbc.JDBCSQLXML

All Implemented Interfaces:

SQLXML

public class JDBCSQLXML
extends Object
implements SQLXML

The mapping in the JavaTM programming language for the SQL XML type. XML is a built-in type that stores an XML value as a column value in a row of a database table. By default drivers implement an SQLXML object as a logical pointer to the XML data rather than the data itself. An SQLXML object is valid for the duration of the transaction in which it was created.

The SQLXML interface provides methods for accessing the XML value as a String, a Reader or Writer, or as a Stream. The XML value may also be accessed through a Source or set as a Result, which are used with XML Parser APIs such as DOM, SAX, and StAX, as well as with XSLT transforms and XPath evaluations.

Methods in the interfaces ResultSet, CallableStatement, and PreparedStatement, such as getSQLXML allow a programmer to access an XML value. In addition, this interface has methods for updating an XML value.

The XML value of the SQLXML instance may be obtained as a BinaryStream using

   SQLXML sqlxml = resultSet.getSQLXML(column);
   InputStream binaryStream = sqlxml.getBinaryStream();
 

For example, to parse an XML value with a DOM parser:

   DocumentBuilder parser = DocumentBuilderFactory.newInstance().newDocumentBuilder();
   Document result = parser.parse(binaryStream);
 

or to parse an XML value with a SAX parser to your handler:

   SAXParser parser = SAXParserFactory.newInstance().newSAXParser();
   parser.parse(binaryStream, myHandler);
 

or to parse an XML value with a StAX parser:

   XMLInputFactory factory = XMLInputFactory.newInstance();
   XMLStreamReader streamReader = factory.createXMLStreamReader(binaryStream);
 

Because databases may use an optimized representation for the XML, accessing the value through getSource() and setResult() can lead to improved processing performance without serializing to a stream representation and parsing the XML.

For example, to obtain a DOM Document Node:

   DOMSource domSource = sqlxml.getSource(DOMSource.class);
   Document document = (Document) domSource.getNode();
 

or to set the value to a DOM Document Node to myNode:

   DOMResult domResult = sqlxml.setResult(DOMResult.class);
   domResult.setNode(myNode);
 

or, to send SAX events to your handler:

   SAXSource saxSource = sqlxml.getSource(SAXSource.class);
   XMLReader xmlReader = saxSource.getXMLReader();
   xmlReader.setContentHandler(myHandler);
   xmlReader.parse(saxSource.getInputSource());
 

or, to set the result value from SAX events:

   SAXResult saxResult = sqlxml.setResult(SAXResult.class);
   ContentHandler contentHandler = saxResult.getXMLReader().getContentHandler();
   contentHandler.startDocument();
   // set the XML elements and attributes into the result
   contentHandler.endDocument();
 

or, to obtain StAX events:

   StAXSource staxSource = sqlxml.getSource(StAXSource.class);
   XMLStreamReader streamReader = staxSource.getXMLStreamReader();
 

or, to set the result value from StAX events:

   StAXResult staxResult = sqlxml.getResult(StAXResult.class);
   XMLStreamWriter streamWriter = staxResult.getXMLStreamWriter();
 

or, to perform XSLT transformations on the XML value using the XSLT in xsltFile output to file resultFile:

   File xsltFile = new File("a.xslt");
   File myFile = new File("result.xml");
   Transformer xslt = TransformerFactory.newInstance().newTransformer(new StreamSource(xsltFile));
   Source source = sqlxml.getSource(null);
   Result result = new StreamResult(myFile);
   xslt.transform(source, result);
 

or, to evaluate an XPath expression on the XML value:

   XPath xpath = XPathFactory.newInstance().newXPath();
   DOMSource domSource = sqlxml.getSource(DOMSource.class);
   Document document = (Document) domSource.getNode();
   String expression = "/foo/@bar";
   String barValue = xpath.evaluate(expression, document);
 

To set the XML value to be the result of an XSLT transform:

   File sourceFile = new File("source.xml");
   Transformer xslt = TransformerFactory.newInstance().newTransformer(new StreamSource(xsltFile));
   Source streamSource = new StreamSource(sourceFile);
   Result result = sqlxml.setResult(null);
   xslt.transform(streamSource, result);
 

Any Source can be transformed to a Result using the identity transform specified by calling newTransformer():

   Transformer identity = TransformerFactory.newInstance().newTransformer();
   Source source = sqlxml.getSource(null);
   File myFile = new File("result.xml");
   Result result = new StreamResult(myFile);
   identity.transform(source, result);
 

To write the contents of a Source to standard output:

   Transformer identity = TransformerFactory.newInstance().newTransformer();
   Source source = sqlxml.getSource(null);
   Result result = new StreamResult(System.out);
   identity.transform(source, result);
 

To create a DOMSource from a DOMResult:

    DOMSource domSource = new DOMSource(domResult.getNode());
 

Incomplete or invalid XML values may cause an SQLException when set or the exception may occur when execute() occurs. All streams must be closed before execute() occurs or an SQLException will be thrown.

Reading and writing XML values to or from an SQLXML object can happen at most once. The conceptual states of readable and not readable determine if one of the reading APIs will return a value or throw an exception. The conceptual states of writable and not writable determine if one of the writing APIs will set a value or throw an exception.

The state moves from readable to not readable once free() or any of the reading APIs are called: getBinaryStream(), getCharacterStream(), getSource(), and getString(). Implementations may also change the state to not writable when this occurs.

The state moves from writable to not writeable once free() or any of the writing APIs are called: setBinaryStream(), setCharacterStream(), setResult(), and setString(). Implementations may also change the state to not readable when this occurs.

All methods on the SQLXML interface must be fully implemented if the JDBC driver supports the data type.

HSQLDB-Specific Information:

Starting with HSQLDB 2.0, a rudimentary client-side SQLXML interface implementation (this class) is supported for local use when the product is built and run under JDK 1.6+ and the SQLXML instance is constructed as the result of calling JDBCConnection.createSQLXML().

SQLXML instances retrieved in such a fashion are initially write-only, with the lifecycle of read and write availability constrained in accordance with the documentation of the interface methods.

When build and run under JDK 1.6+, it is also possible to retrieve read-only SQLXML instances from JDBCResultSet.getSQLXML(...), given that the underlying data can be converted to an XML Document Object Model (DOM).

However, at the time of this writing (2007-06-12) it is not yet possible to store SQLXML objects directly into an HSQLDB database or to use them directly for HSQLDB statement parameterization purposes. This is because the SQLXML data type is not yet natively supported by the HSQLDB engine. Instead, a JDBCSQLXML instance must first be read as a string, binary input stream, character input stream and so on, which can then be used for such purposes.

Here is the current read/write availability lifecycle for JDBCSQLXML:

Origin	Initially	After 1st Write	After 1st Read	After 1st Free
org.hsqldb.jdbc.JDBCConnection.createSQLXML()	Write-only	Read-only	Not readable or writable	Not readable or writable
org.hsqldb.jdbc.JDBCResultSet.getSQLXML(...)	Read-only	N/A	Not readable or writable	Not readable or writable

Since:

JDK 1.6, HSQLDB 2.0

Author:

boucherb@users

See Also:

javax.xml.parsers, javax.xml.stream, javax.xml.transform, javax.xml.xpath

Nested Class Summary

static class

JDBCSQLXML.SAX2XMLStreamWriter Writes to a XMLStreamWriter from SAX events.

Constructor Summary

JDBCSQLXML(Source source)
Constructs a new read-only JDBCSQLXML object from the given Source object.

Method Summary

void	free() This method closes this object and releases the resources that it held.
InputStream	getBinaryStream() Retrieves the XML value designated by this SQLXML instance as a stream.
Reader	getCharacterStream() Retrieves the XML value designated by this SQLXML instance as a java.io.Reader object.
<T extends Source> T	getSource(Class<T> sourceClass) Returns a Source for reading the XML value designated by this SQLXML instance.
String	getString() Returns a string representation of the XML value designated by this SQLXML instance.
boolean	isReadable() Retrieves the object's readability status.
boolean	isWritable() Retrieves the object's readability status.
OutputStream	setBinaryStream() Retrieves a stream that can be used to write the XML value that this SQLXML instance represents.
Writer	setCharacterStream() Retrieves a stream to be used to write the XML value that this SQLXML instance represents.
<T extends Result> T	setResult(Class<T> resultClass) Returns a Result for setting the XML value designated by this SQLXML instance.
void	setString(String value) Sets the XML value designated by this SQLXML instance to the given String representation.

Methods inherited from class java.lang.Object

equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

JDBCSQLXML

public JDBCSQLXML(Source source)
           throws SQLException

Constructs a new read-only JDBCSQLXML object from the given Source object.

Parameters:

source - a Source representing an SQLXML value

Throws:

SQLException - if the argument does not represent a valid SQLXML value

Method Detail

free

public void free()
          throws SQLException

This method closes this object and releases the resources that it held. The SQL XML object becomes invalid and neither readable or writeable when this method is called. After free has been called, any attempt to invoke a method other than free will result in a SQLException being thrown. If free is called multiple times, the subsequent calls to free are treated as a no-op.

Specified by:

free in interface SQLXML

Throws:

SQLException - if there is an error freeing the XML value.

SQLFeatureNotSupportedException - if the JDBC driver does not support this method

Since:

JDK 1.6

getBinaryStream

public InputStream getBinaryStream()
                            throws SQLException

Retrieves the XML value designated by this SQLXML instance as a stream. The bytes of the input stream are interpreted according to appendix F of the XML 1.0 specification. The behavior of this method is the same as ResultSet.getBinaryStream() when the designated column of the ResultSet has a type java.sql.Types of SQLXML.

The SQL XML object becomes not readable when this method is called and may also become not writable depending on implementation.

Specified by:

getBinaryStream in interface SQLXML

Returns:

a stream containing the XML data.

Throws:

SQLException - if there is an error processing the XML value. An exception is thrown if the state is not readable.

SQLFeatureNotSupportedException - if the JDBC driver does not support this method

Since:

JDK 1.6

setBinaryStream

public OutputStream setBinaryStream()
                             throws SQLException

Retrieves a stream that can be used to write the XML value that this SQLXML instance represents. The stream begins at position 0. The bytes of the stream are interpreted according to appendix F of the XML 1.0 specification The behavior of this method is the same as ResultSet.updateBinaryStream() when the designated column of the ResultSet has a type java.sql.Types of SQLXML.

The SQL XML object becomes not writeable when this method is called and may also become not readable depending on implementation.

Specified by:

setBinaryStream in interface SQLXML

Returns:

a stream to which data can be written.

Throws:

SQLException - if there is an error processing the XML value. An exception is thrown if the state is not writable.

SQLFeatureNotSupportedException - if the JDBC driver does not support this method

Since:

JDK 1.6

getCharacterStream

public Reader getCharacterStream()
                          throws SQLException

Retrieves the XML value designated by this SQLXML instance as a java.io.Reader object. The format of this stream is defined by org.xml.sax.InputSource, where the characters in the stream represent the unicode code points for XML according to section 2 and appendix B of the XML 1.0 specification. Although an encoding declaration other than unicode may be present, the encoding of the stream is unicode. The behavior of this method is the same as ResultSet.getCharacterStream() when the designated column of the ResultSet has a type java.sql.Types of SQLXML.

The SQL XML object becomes not readable when this method is called and may also become not writable depending on implementation.

Specified by:

getCharacterStream in interface SQLXML

Returns:

a stream containing the XML data.

Throws:

SQLException - if there is an error processing the XML value. The getCause() method of the exception may provide a more detailed exception, for example, if the stream does not contain valid characters. An exception is thrown if the state is not readable.

SQLFeatureNotSupportedException - if the JDBC driver does not support this method

Since:

JDK 1.6

setCharacterStream

public Writer setCharacterStream()
                          throws SQLException

Retrieves a stream to be used to write the XML value that this SQLXML instance represents. The format of this stream is defined by org.xml.sax.InputSource, where the characters in the stream represent the unicode code points for XML according to section 2 and appendix B of the XML 1.0 specification. Although an encoding declaration other than unicode may be present, the encoding of the stream is unicode. The behavior of this method is the same as ResultSet.updateCharacterStream() when the designated column of the ResultSet has a type java.sql.Types of SQLXML.

The SQL XML object becomes not writeable when this method is called and may also become not readable depending on implementation.

Specified by:

setCharacterStream in interface SQLXML

Returns:

a stream to which data can be written.

Throws:

SQLException - if there is an error processing the XML value. The getCause() method of the exception may provide a more detailed exception, for example, if the stream does not contain valid characters. An exception is thrown if the state is not writable.

SQLFeatureNotSupportedException - if the JDBC driver does not support this method

Since:

JDK 1.6 Build 79

getString

public String getString()
                 throws SQLException

Returns a string representation of the XML value designated by this SQLXML instance. The format of this String is defined by org.xml.sax.InputSource, where the characters in the stream represent the unicode code points for XML according to section 2 and appendix B of the XML 1.0 specification. Although an encoding declaration other than unicode may be present, the encoding of the String is unicode. The behavior of this method is the same as ResultSet.getString() when the designated column of the ResultSet has a type java.sql.Types of SQLXML.

The SQL XML object becomes not readable when this method is called and may also become not writable depending on implementation.

Specified by:

getString in interface SQLXML

Returns:

a string representation of the XML value designated by this SQLXML instance.

Throws:

SQLException - if there is an error processing the XML value. The getCause() method of the exception may provide a more detailed exception, for example, if the stream does not contain valid characters. An exception is thrown if the state is not readable.

SQLFeatureNotSupportedException - if the JDBC driver does not support this method

Since:

JDK 1.6

setString

public void setString(String value)
               throws SQLException

Sets the XML value designated by this SQLXML instance to the given String representation. The format of this String is defined by org.xml.sax.InputSource, where the characters in the stream represent the unicode code points for XML according to section 2 and appendix B of the XML 1.0 specification. Although an encoding declaration other than unicode may be present, the encoding of the String is unicode. The behavior of this method is the same as ResultSet.updateString() when the designated column of the ResultSet has a type java.sql.Types of SQLXML.

The SQL XML object becomes not writeable when this method is called and may also become not readable depending on implementation.

Specified by:

setString in interface SQLXML

Parameters:

value - the XML value

Throws:

SQLException - if there is an error processing the XML value. The getCause() method of the exception may provide a more detailed exception, for example, if the stream does not contain valid characters. An exception is thrown if the state is not writable.

SQLFeatureNotSupportedException - if the JDBC driver does not support this method

Since:

JDK 1.6

getSource

public <T extends Source> T getSource(Class<T> sourceClass)
                           throws SQLException

Returns a Source for reading the XML value designated by this SQLXML instance. Sources are used as inputs to XML parsers and XSLT transformers.

Sources for XML parsers will have namespace processing on by default. The systemID of the Source is implementation dependent.

The SQL XML object becomes not readable when this method is called and may also become not writable depending on implementation.

Note that SAX is a callback architecture, so a returned SAXSource should then be set with a content handler that will receive the SAX events from parsing. The content handler will receive callbacks based on the contents of the XML.

   SAXSource saxSource = sqlxml.getSource(SAXSource.class);
   XMLReader xmlReader = saxSource.getXMLReader();
   xmlReader.setContentHandler(myHandler);
   xmlReader.parse(saxSource.getInputSource());
 

Specified by:

getSource in interface SQLXML

Parameters:

sourceClass - The class of the source, or null. If the class is null, a vendor specifc Source implementation will be returned. The following classes are supported at a minimum:

   javax.xml.transform.dom.DOMSource - returns a DOMSource
   javax.xml.transform.sax.SAXSource - returns a SAXSource
   javax.xml.transform.stax.StAXSource - returns a StAXSource
   javax.xml.transform.stream.StreamSource - returns a StreamSource
 

Returns:

a Source for reading the XML value.

Throws:

SQLException - if there is an error processing the XML value or if this feature is not supported. The getCause() method of the exception may provide a more detailed exception, for example, if an XML parser exception occurs. An exception is thrown if the state is not readable.

SQLFeatureNotSupportedException - if the JDBC driver does not support this method

Since:

JDK 1.6 Build 79

setResult

public <T extends Result> T setResult(Class<T> resultClass)
                           throws SQLException

Returns a Result for setting the XML value designated by this SQLXML instance.

The systemID of the Result is implementation dependent.

The SQL XML object becomes not writeable when this method is called and may also become not readable depending on implementation.

Note that SAX is a callback architecture and the returned SAXResult has a content handler assigned that will receive the SAX events based on the contents of the XML. Call the content handler with the contents of the XML document to assign the values.

   SAXResult saxResult = sqlxml.getResult(SAXResult.class);
   ContentHandler contentHandler = saxResult.getXMLReader().getContentHandler();
   contentHandler.startDocument();
   // set the XML elements and attributes into the result
   contentHandler.endDocument();
 

Specified by:

setResult in interface SQLXML

Parameters:

resultClass - The class of the result, or null. If resultClass is null, a vendor specific Result implementation will be returned. The following classes are supported at a minimum:

   javax.xml.transform.dom.DOMResult - returns a DOMResult
   javax.xml.transform.sax.SAXResult - returns a SAXResult
   javax.xml.transform.stax.StAXResult - returns a StAXResult
   javax.xml.transform.stream.StreamResult - returns a StreamResult
 

Returns:

Returns a Result for setting the XML value.

Throws:

SQLException - if there is an error processing the XML value or if this feature is not supported. The getCause() method of the exception may provide a more detailed exception, for example, if an XML parser exception occurs. An exception is thrown if the state is not writable.

SQLFeatureNotSupportedException - if the JDBC driver does not support this method

Since:

JDK 1.6 Build 79

isReadable

public boolean isReadable()

Retrieves the object's readability status.

Returns:

if true, then readable; else not readable

isWritable

public boolean isWritable()

Retrieves the object's readability status.

Returns:

if true, then writable; else not writable