org.apache.derby.iapi.types
Class XML

java.lang.Object
  extended by org.apache.derby.iapi.types.DataType
      extended by org.apache.derby.iapi.types.XML
All Implemented Interfaces:
java.io.Externalizable, java.io.Serializable, java.lang.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
private static int BASE_MEMORY_USAGE
           
private  boolean containsTopLevelAttr
           
private  SqlXmlUtil tmpUtil
           
protected static short UTF8_IMPL_ID
           
static int XML_DOC_ANY
           
static int XML_SEQUENCE
           
private static java.lang.String xmlReqCheck
           
private  SQLChar xmlStringValue
           
static short XQ_EMPTY_ON_EMPTY
           
static short XQ_NULL_ON_EMPTY
           
static short XQ_PASS_BY_REF
           
static short XQ_PASS_BY_VALUE
           
static short XQ_RETURN_CONTENT
           
static short XQ_RETURN_SEQUENCE
           
private  int xType
           
 
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
 
Constructor Summary
  XML()
          Default constructor.
private XML(SQLChar val, int xmlType, boolean seqWithAttr, boolean materialize)
          Private constructor used for the cloneValue method.
 
Method Summary
static void checkXMLRequirements()
          See if the required JAXP and Xalan classes are in the user's classpath.
 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.
 java.lang.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.
 java.lang.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(java.io.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.
 java.io.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(java.io.InputStream newStream)
          sets the on-disk stream state for the object.
 void setValueFromResultSet(java.sql.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(java.io.ObjectOutput out)
          Write an XML value.
 BooleanDataValue XMLExists(SqlXmlUtil sqlxUtil)
          The SQL/XML XMLExists operator.
 XMLDataValue XMLParse(java.lang.String text, 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(XMLDataValue result, SqlXmlUtil sqlxUtil)
          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 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, getNationalString, 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, 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, typeToBigDecimal
 

Field Detail

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 java.lang.String xmlReqCheck

containsTopLevelAttr

private boolean containsTopLevelAttr

tmpUtil

private SqlXmlUtil tmpUtil
Constructor Detail

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 Detail

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 java.lang.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 java.lang.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 java.io.IOException
Description copied from interface: DataValueDescriptor
Read the DataValueDescriptor from the stream.

Initialize the data value by reading it's values from the ArrayInputStream. This interface is provided as a way to achieve possible performance enhancement when reading an array can be optimized over reading from a generic stream from readExternal().

Specified by:
readExternalFromArray in interface DataValueDescriptor
Parameters:
in - The array stream positioned at the beginning of the byte stream to read from.
Throws:
java.io.IOException - Usual error is if you try to read past limit on the stream.
See Also:
DataValueDescriptor.readExternalFromArray(org.apache.derby.iapi.services.io.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(org.apache.derby.iapi.types.DataValueDescriptor)

setValueFromResultSet

public final void setValueFromResultSet(java.sql.ResultSet resultSet,
                                        int colNumber,
                                        boolean isNullable)
                                 throws java.sql.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:
java.sql.SQLException - Error accessing the result set
See Also:
DataValueDescriptor.setValueFromResultSet(java.sql.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(org.apache.derby.iapi.types.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(java.io.ObjectInput in)
                  throws java.io.IOException
Read an XML value from an input stream.

Specified by:
readExternal in interface java.io.Externalizable
Parameters:
in - The stream from which we're reading.
Throws:
java.io.IOException

writeExternal

public void writeExternal(java.io.ObjectOutput out)
                   throws java.io.IOException
Write an XML value.

Specified by:
writeExternal in interface java.io.Externalizable
Parameters:
out - The stream to which we're writing.
Throws:
java.io.IOException

returnStream

public java.io.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(java.io.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(java.io.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(java.lang.String text,
                             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:
text - 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(XMLDataValue result,
                             SqlXmlUtil sqlxUtil)
                      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:
result - The result of a previous call to this method; null if not called yet.
sqlxUtil - Contains SQL/XML objects and util methods that facilitate execution of XML-related operations
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:
java.lang.Exception - thrown on error (and turned into a StandardException by the caller).
StandardException

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.

Built on Thu 2012-03-29 21:53:33+0000, from revision ???

Apache Derby V10.6 Internals - Copyright © 2004,2007 The Apache Software Foundation. All Rights Reserved.