com.adobe.xmp.XMPPathFactory Maven / Gradle / Ivy
// =================================================================================================
// ADOBE SYSTEMS INCORPORATED
// Copyright 2006-2007 Adobe Systems Incorporated
// All Rights Reserved
//
// NOTICE: Adobe permits you to use, modify, and distribute this file in accordance with the terms
// of the Adobe license agreement accompanying it.
// =================================================================================================
package com.adobe.xmp;
import com.adobe.xmp.impl.Utils;
import com.adobe.xmp.impl.xpath.XMPPath;
import com.adobe.xmp.impl.xpath.XMPPathParser;
/**
* Utility services for the metadata object. It has only public static functions, you cannot create
* an object. These are all functions that layer cleanly on top of the core XMP toolkit.
*
* These functions provide support for composing path expressions to deeply nested properties. The
* functions XMPMeta such as getProperty(),
* getArrayItem() and getStructField() provide easy access to top
* level simple properties, items in top level arrays, and fields of top level structs. They do not
* provide convenient access to more complex things like fields several levels deep in a complex
* struct, or fields within an array of structs, or items of an array that is a field of a struct.
* These functions can also be used to compose paths to top level array items or struct fields so
* that you can use the binary accessors like getPropertyAsInteger().
*
* You can use these functions is to compose a complete path expression, or all but the last
* component. Suppose you have a property that is an array of integers within a struct. You can
* access one of the array items like this:
*
*
*
*
* String path = XMPPathFactory.composeStructFieldPath (schemaNS, "Struct", fieldNS,
* "Array");
* String path += XMPPathFactory.composeArrayItemPath (schemaNS, "Array" index);
* PropertyInteger result = xmpObj.getPropertyAsInteger(schemaNS, path);
*
*
*
You could also use this code if you want the string form of the integer:
*
*
*
* String path = XMPPathFactory.composeStructFieldPath (schemaNS, "Struct", fieldNS,
* "Array");
* PropertyText xmpObj.getArrayItem (schemaNS, path, index);
*
*
*
*
* Note: It might look confusing that the schemaNS is passed in all of the calls above.
* This is because the XMP toolkit keeps the top level "schema" namespace separate from
* the rest of the path expression.
* Note: These methods are much simpler than in the C++-API, they don't check the given
* path or array indices.
*
* @since 25.01.2006
*/
public final class XMPPathFactory
{
/** Private constructor */
private XMPPathFactory()
{
// EMPTY
}
/**
* Compose the path expression for an item in an array.
*
* @param arrayName The name of the array. May be a general path expression, must not be
* null or the empty string.
* @param itemIndex The index of the desired item. Arrays in XMP are indexed from 1.
* 0 and below means last array item and renders as [last()].
*
* @return Returns the composed path basing on fullPath. This will be of the form
* ns:arrayName[i], where "ns" is the prefix for schemaNS and
* "i" is the decimal representation of itemIndex.
* @throws XMPException Throws exeption if index zero is used.
*/
public static String composeArrayItemPath(String arrayName, int itemIndex) throws XMPException
{
if (itemIndex > 0)
{
return arrayName + '[' + itemIndex + ']';
}
else if (itemIndex == XMPConst.ARRAY_LAST_ITEM)
{
return arrayName + "[last()]";
}
else
{
throw new XMPException("Array index must be larger than zero", XMPError.BADINDEX);
}
}
/**
* Compose the path expression for a field in a struct. The result can be added to the
* path of
*
*
* @param fieldNS The namespace URI for the field. Must not be null or the empty
* string.
* @param fieldName The name of the field. Must be a simple XML name, must not be
* null or the empty string.
* @return Returns the composed path. This will be of the form
* ns:structName/fNS:fieldName, where "ns" is the prefix for
* schemaNS and "fNS" is the prefix for fieldNS.
* @throws XMPException Thrown if the path to create is not valid.
*/
public static String composeStructFieldPath(String fieldNS,
String fieldName) throws XMPException
{
assertFieldNS(fieldNS);
assertFieldName(fieldName);
XMPPath fieldPath = XMPPathParser.expandXPath(fieldNS, fieldName);
if (fieldPath.size() != 2)
{
throw new XMPException("The field name must be simple", XMPError.BADXPATH);
}
return '/' + fieldPath.getSegment(XMPPath.STEP_ROOT_PROP).getName();
}
/**
* Compose the path expression for a qualifier.
*
* @param qualNS The namespace URI for the qualifier. May be null or the empty
* string if the qualifier is in the XML empty namespace.
* @param qualName The name of the qualifier. Must be a simple XML name, must not be
* null or the empty string.
* @return Returns the composed path. This will be of the form
* ns:propName/?qNS:qualName, where "ns" is the prefix for
* schemaNS and "qNS" is the prefix for qualNS.
* @throws XMPException Thrown if the path to create is not valid.
*/
public static String composeQualifierPath(
String qualNS,
String qualName) throws XMPException
{
assertQualNS(qualNS);
assertQualName(qualName);
XMPPath qualPath = XMPPathParser.expandXPath(qualNS, qualName);
if (qualPath.size() != 2)
{
throw new XMPException("The qualifier name must be simple", XMPError.BADXPATH);
}
return "/?" + qualPath.getSegment(XMPPath.STEP_ROOT_PROP).getName();
}
/**
* Compose the path expression to select an alternate item by language. The
* path syntax allows two forms of "content addressing" that may
* be used to select an item in an array of alternatives. The form used in
* ComposeLangSelector lets you select an item in an alt-text array based on
* the value of its xml:lang qualifier. The other form of content
* addressing is shown in ComposeFieldSelector. \note ComposeLangSelector
* does not supplant SetLocalizedText or GetLocalizedText. They should
* generally be used, as they provide extra logic to choose the appropriate
* language and maintain consistency with the 'x-default' value.
* ComposeLangSelector gives you an path expression that is explicitly and
* only for the language given in the langName parameter.
*
* @param arrayName
* The name of the array. May be a general path expression, must
* not be null or the empty string.
* @param langName
* The RFC 3066 code for the desired language.
* @return Returns the composed path. This will be of the form
* ns:arrayName[@xml:lang='langName'], where
* "ns" is the prefix for schemaNS.
*/
public static String composeLangSelector(String arrayName,
String langName)
{
return arrayName + "[?xml:lang=\"" + Utils.normalizeLangValue(langName) + "\"]";
}
/**
* Compose the path expression to select an alternate item by a field's value. The path syntax
* allows two forms of "content addressing" that may be used to select an item in an
* array of alternatives. The form used in ComposeFieldSelector lets you select an item in an
* array of structs based on the value of one of the fields in the structs. The other form of
* content addressing is shown in ComposeLangSelector. For example, consider a simple struct
* that has two fields, the name of a city and the URI of an FTP site in that city. Use this to
* create an array of download alternatives. You can show the user a popup built from the values
* of the city fields. You can then get the corresponding URI as follows:
*
*
*
*
* String path = composeFieldSelector ( schemaNS, "Downloads", fieldNS,
* "City", chosenCity );
* XMPProperty prop = xmpObj.getStructField ( schemaNS, path, fieldNS, "URI" );
*
*
*
*
* @param arrayName The name of the array. May be a general path expression, must not be
* null or the empty string.
* @param fieldNS The namespace URI for the field used as the selector. Must not be
* null or the empty string.
* @param fieldName The name of the field used as the selector. Must be a simple XML name, must
* not be null or the empty string. It must be the name of a field that is
* itself simple.
* @param fieldValue The desired value of the field.
* @return Returns the composed path. This will be of the form
* ns:arrayName[fNS:fieldName='fieldValue'], where "ns" is the
* prefix for schemaNS and "fNS" is the prefix for fieldNS.
* @throws XMPException Thrown if the path to create is not valid.
*/
public static String composeFieldSelector(String arrayName, String fieldNS,
String fieldName, String fieldValue) throws XMPException
{
XMPPath fieldPath = XMPPathParser.expandXPath(fieldNS, fieldName);
if (fieldPath.size() != 2)
{
throw new XMPException("The fieldName name must be simple", XMPError.BADXPATH);
}
return arrayName + '[' + fieldPath.getSegment(XMPPath.STEP_ROOT_PROP).getName() +
"=\"" + fieldValue + "\"]";
}
/**
* ParameterAsserts that a qualifier namespace is set.
* @param qualNS a qualifier namespace
* @throws XMPException Qualifier schema is null or empty
*/
private static void assertQualNS(String qualNS) throws XMPException
{
if (qualNS == null || qualNS.length() == 0)
{
throw new XMPException("Empty qualifier namespace URI", XMPError.BADSCHEMA);
}
}
/**
* ParameterAsserts that a qualifier name is set.
* @param qualName a qualifier name or path
* @throws XMPException Qualifier name is null or empty
*/
private static void assertQualName(String qualName) throws XMPException
{
if (qualName == null || qualName.length() == 0)
{
throw new XMPException("Empty qualifier name", XMPError.BADXPATH);
}
}
/**
* ParameterAsserts that a struct field namespace is set.
* @param fieldNS a struct field namespace
* @throws XMPException Struct field schema is null or empty
*/
private static void assertFieldNS(String fieldNS) throws XMPException
{
if (fieldNS == null || fieldNS.length() == 0)
{
throw new XMPException("Empty field namespace URI", XMPError.BADSCHEMA);
}
}
/**
* ParameterAsserts that a struct field name is set.
* @param fieldName a struct field name or path
* @throws XMPException Struct field name is null or empty
*/
private static void assertFieldName(String fieldName) throws XMPException
{
if (fieldName == null || fieldName.length() == 0)
{
throw new XMPException("Empty f name", XMPError.BADXPATH);
}
}
}