Class XML

java.lang.Object

org.apache.derby.iapi.types.DataType

org.apache.derby.iapi.types.XML

All Implemented Interfaces:

Externalizable, Serializable, Comparable, Formatable, Storable, StreamStorable, TypedFormat, DataValueDescriptor, Orderable, XMLDataValue

public class XML
extends DataType
implements XMLDataValue, StreamStorable

This type implements the XMLDataValue interface and thus is the type on which all XML related operations are executed. The first and simplest XML store implementation is a UTF-8 based one--all XML data is stored on disk as a UTF-8 string, just like the other Derby string types. In order to make it possible for smarter XML implementations to exist in the future, this class always writes an "XML implementation id" to disk before writing the rest of its data. When reading the data, the impl id is read first and serves as an indicator of how the rest of the data should be read. So long as there's only one implementation (UTF-8) the impl id can be ignored; but when smarter implementations are written, the impl id will be the key to figuring out how an XML value should be read, written, and processed.

See Also:

• Serialized Form

Field Summary

Fields

Modifier and Type	Field	Description
private static final int	BASE_MEMORY_USAGE
private boolean	containsTopLevelAttr
private SqlXmlUtil	tmpUtil
protected static final short	UTF8_IMPL_ID
static final int	XML_DOC_ANY
static final int	XML_SEQUENCE
private static String	xmlReqCheck
private SQLChar	xmlStringValue
static final short	XQ_EMPTY_ON_EMPTY
static final short	XQ_NULL_ON_EMPTY
static final short	XQ_PASS_BY_REF
static final short	XQ_PASS_BY_VALUE
static final short	XQ_RETURN_CONTENT
static final short	XQ_RETURN_SEQUENCE
private int	xType

Fields inherited from interface DataValueDescriptor

UNKNOWN_LOGICAL_LENGTH

Fields inherited from interface Orderable

ORDER_OP_EQUALS, ORDER_OP_GREATEROREQUALS, ORDER_OP_GREATERTHAN, ORDER_OP_LESSOREQUALS, ORDER_OP_LESSTHAN

Constructor Summary

Constructors

Modifier	Constructor	Description
	XML()	Default constructor.
private	XML(SQLChar val, int xmlType, boolean seqWithAttr, boolean materialize)	Private constructor used for the cloneValue method.

Method Summary

Modifier and Type	Method	Description
private static boolean	checkJAXPRequirement()	Check if we have a JAXP implementation installed.
static void	checkXMLRequirements()	See if the required JAXP and Xalan classes are in the user's classpath.
private static boolean	checkXPathRequirement()	Check if XPath is supported on this platform.
DataValueDescriptor	cloneValue(boolean forceMaterialization)	Clone this DataValueDescriptor.
int	compare(DataValueDescriptor other)	Compare two XML DataValueDescriptors.
int	estimateMemoryUsage()	Estimate the memory usage in bytes of the data value and the overhead of the class.
int	getLength()	Gets the length of the data value.
DataValueDescriptor	getNewNull()	Get a new null value of the same type as this data value.
String	getString()	Gets the value in the data value descriptor as a String.
int	getTypeFormatId()	Get a universally unique identifier for the type of this object.
String	getTypeName()	Get the SQL name of the datatype
int	getXType()	Retrieve this XML value's qualified type.
boolean	hasTopLevelAttr()	Return whether or not this XML value represents a sequence that has one or more top-level attribute nodes.
boolean	isNull()	Return whether the value is null or not.
void	loadStream()	Set the value by reading the stream and converting it to an object form.
void	markAsHavingTopLevelAttr()	Take note of the fact this XML value represents an XML sequence that has one or more top-level attribute nodes.
void	normalize(DataTypeDescriptor desiredType, DataValueDescriptor source)	Normalization method - this method will always be called when storing an XML value into an XML column, for example, when inserting/updating.
void	readExternal(ObjectInput in)	Read an XML value from an input stream.
void	readExternalFromArray(ArrayInputStream in)	Read the DataValueDescriptor from the stream.
void	restoreToNull()	Restore this object to its (SQL)null value.
InputStream	returnStream()	Return the on-disk stream state of the object.
protected void	setFrom(DataValueDescriptor theValue)	Set the value of this DataValueDescriptor based on the value of the specified DataValueDescriptor.
void	setStream(InputStream newStream)	sets the on-disk stream state for the object.
final void	setValueFromResultSet(ResultSet resultSet, int colNumber, boolean isNullable)	Set the value based on the value for the specified DataValueDescriptor from the specified ResultSet.
void	setXType(int xtype)	Set this XML value's qualified type.
int	typePrecedence()	Each built-in type in JSQL has a precedence.
void	writeExternal(ObjectOutput out)	Write an XML value.
BooleanDataValue	XMLExists(SqlXmlUtil sqlxUtil)	The SQL/XML XMLExists operator.
XMLDataValue	XMLParse(StringDataValue stringValue, boolean preserveWS, SqlXmlUtil sqlxUtil)	Method to parse an XML string and, if it's valid, store the _serialized_ version locally and then return this XMLDataValue.
XMLDataValue	XMLQuery(SqlXmlUtil sqlxUtil, XMLDataValue result)	Evaluate the XML query expression contained within the received util object against this XML value and store the results into the received XMLDataValue "result" param (assuming "result" is non-null; else create a new XMLDataValue).
StringDataValue	XMLSerialize(StringDataValue result, int targetType, int targetWidth, int targetCollationType)	The SQL/XML XMLSerialize operator.

Methods inherited from class DataType

checkHostVariable, cloneHolder, coalesce, compare, compare, compare, compareTo, dataTypeConversion, equals, equals, flip, genericSetObject, getBoolean, getByte, getBytes, getDate, getDouble, getFloat, getInt, getLong, getObject, getShort, getStream, getTime, getTimestamp, getTraceString, getTypeName, greaterOrEquals, greaterThan, hasStream, in, invalidFormat, isNotNull, isNullOp, lessOrEquals, lessThan, notEquals, outOfRange, recycle, setBigDecimal, setInto, setInto, setObject, setObjectForCast, setToNull, setValue, setValue, setValue, setValue, setValue, setValue, setValue, setValue, setValue, setValue, setValue, setValue, setValue, setValue, setValue, setValue, setValue, setValue, setValue, setValue, throwLangSetMismatch, throwLangSetMismatch, typeToBigDecimal

Methods inherited from class Object

clone, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Methods inherited from interface DataValueDescriptor

checkHostVariable, cloneHolder, coalesce, compare, compare, compare, equals, getBoolean, getByte, getBytes, getDate, getDouble, getFloat, getInt, getLong, getObject, getShort, getStream, getTime, getTimestamp, getTraceString, greaterOrEquals, greaterThan, hasStream, in, isNotNull, isNullOp, lessOrEquals, lessThan, notEquals, recycle, setBigDecimal, setInto, setInto, setObjectForCast, setToNull, setValue, setValue, setValue, setValue, setValue, setValue, setValue, setValue, setValue, setValue, setValue, setValue, setValue, setValue, setValue, setValue, setValue, setValue, setValue, setValue, typeToBigDecimal

Field Details

UTF8_IMPL_ID

protected static final short UTF8_IMPL_ID

See Also:

• Constant Field Values

BASE_MEMORY_USAGE

private static final int BASE_MEMORY_USAGE

XQ_PASS_BY_REF

public static final short XQ_PASS_BY_REF

See Also:

• Constant Field Values

XQ_PASS_BY_VALUE

public static final short XQ_PASS_BY_VALUE

See Also:

• Constant Field Values

XQ_RETURN_SEQUENCE

public static final short XQ_RETURN_SEQUENCE

See Also:

• Constant Field Values

XQ_RETURN_CONTENT

public static final short XQ_RETURN_CONTENT

See Also:

• Constant Field Values

XQ_EMPTY_ON_EMPTY

public static final short XQ_EMPTY_ON_EMPTY

See Also:

• Constant Field Values

XQ_NULL_ON_EMPTY

public static final short XQ_NULL_ON_EMPTY

See Also:

• Constant Field Values

XML_DOC_ANY

public static final int XML_DOC_ANY

See Also:

• Constant Field Values

XML_SEQUENCE

public static final int XML_SEQUENCE

See Also:

• Constant Field Values

xType

private int xType

xmlStringValue

private SQLChar xmlStringValue

xmlReqCheck

private static String xmlReqCheck

containsTopLevelAttr

private boolean containsTopLevelAttr

tmpUtil

private SqlXmlUtil tmpUtil

Constructor Details

XML

public XML()

Default constructor.

XML

private XML(SQLChar val,
 int xmlType,
 boolean seqWithAttr,
 boolean materialize)

Private constructor used for the cloneValue method. Returns a new instance of XML whose fields are clones of the values received.

Parameters:

val - A SQLChar instance to clone and use for this XML value.

xmlType - Qualified XML type for "val"

seqWithAttr - Whether or not "val" corresponds to sequence with one or more top-level attribute nodes.

materialize - whether or not to force materialization of the underlying source data

Method Details

cloneValue

public DataValueDescriptor cloneValue(boolean forceMaterialization)

Description copied from interface: DataValueDescriptor

Clone this DataValueDescriptor. Results in a new object that has the same value as this but can be modified independently.

Even though the objects can be modified independently regardless of the value of forceMaterialization, both the clone and the original may be dependent on the store state if forceMaterialization is set to false. An example is if you need to access the value you just read using cloneValue after the current transaction has ended, or after the source result set has been closed.

Specified by:

cloneValue in interface DataValueDescriptor

Parameters:

forceMaterialization - any streams representing the data value will be materialized if true, the data value will be kept as a stream if possible if false

Returns:

A clone of the DataValueDescriptor with the same initial value as this.

See Also:

• DataValueDescriptor.cloneValue(boolean)

getNewNull

public DataValueDescriptor getNewNull()

Description copied from interface: DataValueDescriptor

Get a new null value of the same type as this data value.

Specified by:

getNewNull in interface DataValueDescriptor

See Also:

• DataValueDescriptor.getNewNull()

getTypeName

public String getTypeName()

Description copied from interface: DataValueDescriptor

Get the SQL name of the datatype

Specified by:

getTypeName in interface DataValueDescriptor

Returns:

The SQL name of the datatype

See Also:

• DataValueDescriptor.getTypeName()

typePrecedence

public int typePrecedence()

Description copied from class: DataType

Each built-in type in JSQL has a precedence. This precedence determines how to do type promotion when using binary operators. For example, float has a higher precedence than int, so when adding an int to a float, the result type is float. The precedence for some types is arbitrary. For example, it doesn't matter what the precedence of the boolean type is, since it can't be mixed with other types. But the precedence for the number types is critical. The SQL standard requires that exact numeric types be promoted to approximate numeric when one operator uses both. Also, the precedence is arranged so that one will not lose precision when promoting a type.

Specified by:

typePrecedence in interface DataValueDescriptor

Overrides:

typePrecedence in class DataType

Returns:

The precedence of this type.

See Also:

• DataValueDescriptor.typePrecedence()

getString

public String getString()
                 throws StandardException

Description copied from interface: DataValueDescriptor

Gets the value in the data value descriptor as a String. Throws an exception if the data value is not a string.

Specified by:

getString in interface DataValueDescriptor

Returns:

The data value as a String.

Throws:

StandardException - Thrown on error

See Also:

• DataValueDescriptor.getString()

getLength

public int getLength()
              throws StandardException

Description copied from interface: DataValueDescriptor

Gets the length of the data value. The meaning of this is implementation-dependent. For string types, it is the number of characters in the string. For numeric types, it is the number of bytes used to store the number. This is the actual length of this value, not the length of the type it was defined as. For example, a VARCHAR value may be shorter than the declared VARCHAR (maximum) length.

Specified by:

getLength in interface DataValueDescriptor

Returns:

The length of the data value

Throws:

StandardException - On error

See Also:

• DataValueDescriptor.getLength()

estimateMemoryUsage

public int estimateMemoryUsage()

Description copied from interface: DataValueDescriptor

Estimate the memory usage in bytes of the data value and the overhead of the class.

Specified by:

estimateMemoryUsage in interface DataValueDescriptor

Returns:

the estimated memory usage

See Also:

• DataValueDescriptor.estimateMemoryUsage()

readExternalFromArray

public void readExternalFromArray(ArrayInputStream in)
                           throws IOException

Description copied from class: DataType

Read the DataValueDescriptor from the stream. The default implementation calls readExternal(), which accesses the ArrayInputStream as a generic stream. If sub-classes can implement it more efficiently by accessing the array, they should override this method.

Specified by:

readExternalFromArray in interface DataValueDescriptor

Overrides:

readExternalFromArray in class DataType

Parameters:

in - The array stream positioned at the beginning of the byte stream to read from.

Throws:

IOException - Usual error is if you try to read past limit on the stream.

See Also:

• DataValueDescriptor.readExternalFromArray(ArrayInputStream)

setFrom

protected void setFrom(DataValueDescriptor theValue)
                throws StandardException

Description copied from class: DataType

Set the value of this DataValueDescriptor based on the value of the specified DataValueDescriptor.

Overrides:

setFrom in class DataType

Parameters:

theValue - The DataValueDescriptor that holds the value to which we want to set this DataValueDescriptor's value.

Throws:

StandardException

See Also:

• DataType.setFrom(DataValueDescriptor)

setValueFromResultSet

public final void setValueFromResultSet(ResultSet resultSet,
 int colNumber,
 boolean isNullable)
                                 throws SQLException

Description copied from interface: DataValueDescriptor

Set the value based on the value for the specified DataValueDescriptor from the specified ResultSet.

Specified by:

setValueFromResultSet in interface DataValueDescriptor

Parameters:

resultSet - The specified ResultSet.

colNumber - The 1-based column # into the resultSet.

isNullable - Whether or not the column is nullable (No need to call wasNull() if not)

Throws:

SQLException - Error accessing the result set

See Also:

• DataValueDescriptor.setValueFromResultSet(ResultSet, int, boolean)

compare

public int compare(DataValueDescriptor other)
            throws StandardException

Compare two XML DataValueDescriptors. NOTE: This method should only be used by the database store for the purpose of index positioning--comparisons of XML type are not allowed from the language side of things. That said, all store wants to do is order the NULLs, so we don't actually have to do a full comparison. Just return an order value based on whether or not this XML value and the other XML value are null. As mentioned in the "compare" method of DataValueDescriptor, nulls are considered equal to other nulls and less than all other values. An example of when this method might be used is if the user executed a query like: select i from x_table where x_col is not null

Specified by:

compare in interface DataValueDescriptor

Parameters:

other - The Orderable to compare this one to.

Returns:

<0 - this Orderable is less than other. 0 - this Orderable equals other. >0 - this Orderable is greater than other. The code should not explicitly look for -1, or 1.

Throws:

StandardException - Thrown on error

See Also:

• DataValueDescriptor.compare(DataValueDescriptor)

normalize

public void normalize(DataTypeDescriptor desiredType,
 DataValueDescriptor source)
               throws StandardException

Normalization method - this method will always be called when storing an XML value into an XML column, for example, when inserting/updating. We always force normalization in this case because we need to make sure the qualified type of the value we're trying to store is XML_DOC_ANY--we don't allow anything else.

Specified by:

normalize in interface DataValueDescriptor

Overrides:

normalize in class DataType

Parameters:

desiredType - The type to normalize the source column to

source - The value to normalize

Throws:

StandardException - Thrown if source is not XML_DOC_ANY.

getTypeFormatId

public int getTypeFormatId()

Description copied from interface: TypedFormat

Get a universally unique identifier for the type of this object.

Specified by:

getTypeFormatId in interface TypedFormat

Returns:

The identifier. (A UUID stuffed in an array of 16 bytes).

See Also:

• From the engine's perspective, all XML implementations share the same format id.

isNull

public boolean isNull()

Description copied from interface: Storable

Return whether the value is null or not.

Specified by:

isNull in interface Storable

Returns:

true if the value is null and false otherwise.

See Also:

• Storable.isNull()

restoreToNull

public void restoreToNull()

Description copied from interface: Storable

Restore this object to its (SQL)null value.

Specified by:

restoreToNull in interface Storable

See Also:

• Storable.restoreToNull()

readExternal

public void readExternal(ObjectInput in)
                  throws IOException

Read an XML value from an input stream.

Specified by:

readExternal in interface Externalizable

Parameters:

in - The stream from which we're reading.

Throws:

IOException

writeExternal

public void writeExternal(ObjectOutput out)
                   throws IOException

Write an XML value.

Specified by:

writeExternal in interface Externalizable

Parameters:

out - The stream to which we're writing.

Throws:

IOException

returnStream

public InputStream returnStream()

Description copied from interface: StreamStorable

Return the on-disk stream state of the object.

Specified by:

returnStream in interface StreamStorable

See Also:

• StreamStorable.returnStream()

setStream

public void setStream(InputStream newStream)

Description copied from interface: StreamStorable

sets the on-disk stream state for the object.

Specified by:

setStream in interface StreamStorable

See Also:

• StreamStorable.setStream(InputStream)

loadStream

public void loadStream()
                throws StandardException

Description copied from interface: StreamStorable

Set the value by reading the stream and converting it to an object form.

Specified by:

loadStream in interface StreamStorable

Throws:

StandardException - on error

See Also:

• StreamStorable.loadStream()

XMLParse

public XMLDataValue XMLParse(StringDataValue stringValue,
 boolean preserveWS,
 SqlXmlUtil sqlxUtil)
                      throws StandardException

Method to parse an XML string and, if it's valid, store the _serialized_ version locally and then return this XMLDataValue.

Specified by:

XMLParse in interface XMLDataValue

Parameters:

stringValue - The string value to check.

preserveWS - Whether or not to preserve ignorable whitespace.

sqlxUtil - Contains SQL/XML objects and util methods that facilitate execution of XML-related operations

Returns:

If 'text' constitutes a valid XML document, it has been stored in this XML value and this XML value is returned; otherwise, an exception is thrown.

Throws:

StandardException - Thrown on error.

XMLSerialize

public StringDataValue XMLSerialize(StringDataValue result,
 int targetType,
 int targetWidth,
 int targetCollationType)
                             throws StandardException

The SQL/XML XMLSerialize operator. Serializes this XML value into a string with a user-specified character type, and returns that string via the received StringDataValue (if the received StringDataValue is non-null and of the correct type; else, a new StringDataValue is returned).

Specified by:

XMLSerialize in interface XMLDataValue

Parameters:

result - The result of a previous call to this method, null if not called yet.

targetType - The string type to which we want to serialize.

targetWidth - The width of the target type.

targetCollationType - The collation type of the target type.

Returns:

A serialized (to string) version of this XML object, in the form of a StringDataValue object.

Throws:

StandardException - Thrown on error

XMLExists

public BooleanDataValue XMLExists(SqlXmlUtil sqlxUtil)
                           throws StandardException

The SQL/XML XMLExists operator. Checks to see if evaluation of the query expression contained within the received util object against this XML value returns at least one item. NOTE: For now, the query expression must be XPath only (XQuery not supported) because that's what Xalan supports.

Specified by:

XMLExists in interface XMLDataValue

Parameters:

sqlxUtil - Contains SQL/XML objects and util methods that facilitate execution of XML-related operations

Returns:

True if evaluation of the query expression stored in sqlxUtil returns at least one node for this XML value; unknown if the xml value is NULL; false otherwise.

Throws:

StandardException - Thrown on error

XMLQuery

public XMLDataValue XMLQuery(SqlXmlUtil sqlxUtil,
 XMLDataValue result)
                      throws StandardException

Evaluate the XML query expression contained within the received util object against this XML value and store the results into the received XMLDataValue "result" param (assuming "result" is non-null; else create a new XMLDataValue).

Specified by:

XMLQuery in interface XMLDataValue

Parameters:

sqlxUtil - Contains SQL/XML objects and util methods that facilitate execution of XML-related operations

result - The result of a previous call to this method; null if not called yet.

Returns:

An XMLDataValue whose content corresponds to the serialized version of the results from evaluation of the query expression. Note: this XMLDataValue may not be storable into Derby XML columns.

Throws:

StandardException - thrown on error

setXType

public void setXType(int xtype)

Set this XML value's qualified type.

Specified by:

setXType in interface XMLDataValue

getXType

public int getXType()

Retrieve this XML value's qualified type.

Specified by:

getXType in interface XMLDataValue

markAsHavingTopLevelAttr

public void markAsHavingTopLevelAttr()

Take note of the fact this XML value represents an XML sequence that has one or more top-level attribute nodes.

Specified by:

markAsHavingTopLevelAttr in interface XMLDataValue

hasTopLevelAttr

public boolean hasTopLevelAttr()

Return whether or not this XML value represents a sequence that has one or more top-level attribute nodes.

Specified by:

hasTopLevelAttr in interface XMLDataValue

checkXMLRequirements

public static void checkXMLRequirements()
                                 throws StandardException

See if the required JAXP and Xalan classes are in the user's classpath. Assumption is that we will always call this method before instantiating an instance of SqlXmlUtil, and thus we will never get a ClassNotFound exception caused by missing JAXP/Xalan classes. Instead, if either is missing we should throw an informative error indicating what the problem is. NOTE: This method only does the checks necessary to allow successful instantiation of the SqlXmlUtil class. Further checks (esp. the presence of a JAXP _implementation_ in addition to the JAXP _interfaces_) are performed in the SqlXmlUtil constructor.

Throws:

StandardException - thrown if the required classes cannot be located in the classpath.

checkJAXPRequirement

private static boolean checkJAXPRequirement()

Check if we have a JAXP implementation installed.

Returns:

true if JAXP is installed, or false otherwise

checkXPathRequirement

private static boolean checkXPathRequirement()

Check if XPath is supported on this platform.

Returns:

true if XPath is supported, or false otherwise