Package org.apache.derby.iapi.types
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
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:
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Field Summary
FieldsModifier and TypeFieldDescriptionprivate static final int
private boolean
private SqlXmlUtil
protected static final short
static final int
static final int
private static String
private SQLChar
static final short
static final short
static final short
static final short
static final short
static final short
private int
Fields inherited from interface org.apache.derby.iapi.types.DataValueDescriptor
UNKNOWN_LOGICAL_LENGTH
Fields inherited from interface org.apache.derby.iapi.types.Orderable
ORDER_OP_EQUALS, ORDER_OP_GREATEROREQUALS, ORDER_OP_GREATERTHAN, ORDER_OP_LESSOREQUALS, ORDER_OP_LESSTHAN
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Constructor Summary
Constructors -
Method Summary
Modifier and TypeMethodDescriptionprivate static boolean
Check if we have a JAXP implementation installed.static void
See if the required JAXP and Xalan classes are in the user's classpath.private static boolean
Check if XPath is supported on this platform.cloneValue
(boolean forceMaterialization) Clone this DataValueDescriptor.int
compare
(DataValueDescriptor other) Compare two XML DataValueDescriptors.int
Estimate the memory usage in bytes of the data value and the overhead of the class.int
Gets the length of the data value.Get a new null value of the same type as this data value.Gets the value in the data value descriptor as a String.int
Get a universally unique identifier for the type of this object.Get the SQL name of the datatypeint
getXType()
Retrieve this XML value's qualified type.boolean
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
Set the value by reading the stream and converting it to an object form.void
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
Read an XML value from an input stream.void
Read the DataValueDescriptor from the stream.void
Restore this object to its (SQL)null value.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
Each built-in type in JSQL has a precedence.void
Write an XML value.XMLExists
(SqlXmlUtil sqlxUtil) The SQL/XML XMLExists operator.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.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).XMLSerialize
(StringDataValue result, int targetType, int targetWidth, int targetCollationType) The SQL/XML XMLSerialize operator.Methods inherited from class org.apache.derby.iapi.types.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 java.lang.Object
clone, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
Methods inherited from interface org.apache.derby.iapi.types.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
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Field Details
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UTF8_IMPL_ID
protected static final short UTF8_IMPL_ID- See Also:
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BASE_MEMORY_USAGE
private static final int BASE_MEMORY_USAGE -
XQ_PASS_BY_REF
public static final short XQ_PASS_BY_REF- See Also:
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XQ_PASS_BY_VALUE
public static final short XQ_PASS_BY_VALUE- See Also:
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XQ_RETURN_SEQUENCE
public static final short XQ_RETURN_SEQUENCE- See Also:
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XQ_RETURN_CONTENT
public static final short XQ_RETURN_CONTENT- See Also:
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XQ_EMPTY_ON_EMPTY
public static final short XQ_EMPTY_ON_EMPTY- See Also:
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XQ_NULL_ON_EMPTY
public static final short XQ_NULL_ON_EMPTY- See Also:
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XML_DOC_ANY
public static final int XML_DOC_ANY- See Also:
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XML_SEQUENCE
public static final int XML_SEQUENCE- See Also:
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xType
private int xType -
xmlStringValue
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xmlReqCheck
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containsTopLevelAttr
private boolean containsTopLevelAttr -
tmpUtil
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Constructor Details
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XML
public XML()Default constructor. -
XML
Private constructor used for thecloneValue
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
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Method Details
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cloneValue
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 ifforceMaterialization
is set tofalse
. An example is if you need to access the value you just read usingcloneValue
after the current transaction has ended, or after the source result set has been closed.- Specified by:
cloneValue
in interfaceDataValueDescriptor
- Parameters:
forceMaterialization
- any streams representing the data value will be materialized iftrue
, the data value will be kept as a stream if possible iffalse
- Returns:
- A clone of the
DataValueDescriptor
with the same initial value as this. - See Also:
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getNewNull
Description copied from interface:DataValueDescriptor
Get a new null value of the same type as this data value.- Specified by:
getNewNull
in interfaceDataValueDescriptor
- See Also:
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getTypeName
Description copied from interface:DataValueDescriptor
Get the SQL name of the datatype- Specified by:
getTypeName
in interfaceDataValueDescriptor
- Returns:
- The SQL name of the datatype
- See Also:
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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 interfaceDataValueDescriptor
- Overrides:
typePrecedence
in classDataType
- Returns:
- The precedence of this type.
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getString
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 interfaceDataValueDescriptor
- Returns:
- The data value as a String.
- Throws:
StandardException
- Thrown on error- See Also:
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getLength
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 interfaceDataValueDescriptor
- Returns:
- The length of the data value
- Throws:
StandardException
- On error- See Also:
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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 interfaceDataValueDescriptor
- Returns:
- the estimated memory usage
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readExternalFromArray
Description copied from class:DataType
Read the DataValueDescriptor from the stream. The default implementation callsreadExternal()
, which accesses theArrayInputStream
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 interfaceDataValueDescriptor
- Overrides:
readExternalFromArray
in classDataType
- 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:
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setFrom
Description copied from class:DataType
Set the value of this DataValueDescriptor based on the value of the specified DataValueDescriptor.- Overrides:
setFrom
in classDataType
- Parameters:
theValue
- The DataValueDescriptor that holds the value to which we want to set this DataValueDescriptor's value.- Throws:
StandardException
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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 interfaceDataValueDescriptor
- 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:
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compare
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 interfaceDataValueDescriptor
- 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:
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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 interfaceDataValueDescriptor
- Overrides:
normalize
in classDataType
- Parameters:
desiredType
- The type to normalize the source column tosource
- The value to normalize- Throws:
StandardException
- Thrown if source is not XML_DOC_ANY.
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getTypeFormatId
public int getTypeFormatId()Description copied from interface:TypedFormat
Get a universally unique identifier for the type of this object.- Specified by:
getTypeFormatId
in interfaceTypedFormat
- Returns:
- The identifier. (A UUID stuffed in an array of 16 bytes).
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isNull
public boolean isNull()Description copied from interface:Storable
Return whether the value is null or not. -
restoreToNull
public void restoreToNull()Description copied from interface:Storable
Restore this object to its (SQL)null value.- Specified by:
restoreToNull
in interfaceStorable
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readExternal
Read an XML value from an input stream.- Specified by:
readExternal
in interfaceExternalizable
- Parameters:
in
- The stream from which we're reading.- Throws:
IOException
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writeExternal
Write an XML value.- Specified by:
writeExternal
in interfaceExternalizable
- Parameters:
out
- The stream to which we're writing.- Throws:
IOException
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returnStream
Description copied from interface:StreamStorable
Return the on-disk stream state of the object.- Specified by:
returnStream
in interfaceStreamStorable
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setStream
Description copied from interface:StreamStorable
sets the on-disk stream state for the object.- Specified by:
setStream
in interfaceStreamStorable
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loadStream
Description copied from interface:StreamStorable
Set the value by reading the stream and converting it to an object form.- Specified by:
loadStream
in interfaceStreamStorable
- Throws:
StandardException
- on error- See Also:
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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 interfaceXMLDataValue
- 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.
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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 interfaceXMLDataValue
- 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
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XMLExists
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 interfaceXMLDataValue
- 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
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XMLQuery
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 interfaceXMLDataValue
- Parameters:
sqlxUtil
- Contains SQL/XML objects and util methods that facilitate execution of XML-related operationsresult
- 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
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setXType
public void setXType(int xtype) Set this XML value's qualified type.- Specified by:
setXType
in interfaceXMLDataValue
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getXType
public int getXType()Retrieve this XML value's qualified type.- Specified by:
getXType
in interfaceXMLDataValue
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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 interfaceXMLDataValue
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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 interfaceXMLDataValue
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checkXMLRequirements
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.
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checkJAXPRequirement
private static boolean checkJAXPRequirement()Check if we have a JAXP implementation installed.- Returns:
true
if JAXP is installed, orfalse
otherwise
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checkXPathRequirement
private static boolean checkXPathRequirement()Check if XPath is supported on this platform.- Returns:
true
if XPath is supported, orfalse
otherwise
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