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RDB2RDF Implementation from Antidot
/*
* Copyright 2011 Antidot [email protected]
* https://github.com/antidot/db2triples
*
* DB2Triples is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License as
* published by the Free Software Foundation; either version 2 of
* the License, or (at your option) any later version.
*
* DB2Triples is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see extractColumnNamesFromStringTemplate(
String stringTemplate) {
Set result = new HashSet();
// Curly braces that do not enclose column names MUST be
// escaped by a backslash character (“\”).
stringTemplate = stringTemplate.replaceAll("\\\\\\{", "");
stringTemplate = stringTemplate.replaceAll("\\\\\\}", "");
if (stringTemplate != null) {
StringTokenizer st = new StringTokenizer(stringTemplate, "{}", true);
boolean keepNext = false;
String next = null;
while (st.hasMoreElements()) {
String element = st.nextElement().toString();
if (keepNext)
next = element;
keepNext = element.equals("{");
if (element.equals("}") && element != null) {
log.debug("[R2RMLToolkit:extractColumnNamesFromStringTemplate] Extracted column name "
+ next + " from string template " + stringTemplate);
result.add(next);
next = null;
}
}
}
return result;
}
/**
* Every pair of unescaped curly braces in the inverse expression is a
* column reference in an inverse expression. The string between the braces
* MUST be a valid column name.
*
* @param value
* @return
*/
public static Set extractColumnNamesFromInverseExpression(
String inverseExpression) {
Set result = new HashSet();
if (inverseExpression != null) {
StringTokenizer st = new StringTokenizer(inverseExpression, "{}");
while (st.hasMoreElements()) {
String element = st.nextElement().toString();
int index = inverseExpression.indexOf(element);
if (index > 0
&& index < inverseExpression.length()
&& inverseExpression.charAt(index - 1) == '{'
&& (inverseExpression.charAt(index + element.length()) == '}')) {
// result.add(deleteBackSlash(element));
result.add(ColumnIdentifierImpl.buildFromR2RMLConfigFile(element));
}
}
}
return result;
}
/**
* Returns the result of replacing each column reference c in the inverse
* expression with : - the quoted and escaped data value of column c in r,
* if c is a referenced column in the term map - the column name of column
* c, otherwise
*
* @param stringTemplate
* @param dbValues
* @param columnReferences
* @param dbTypes
* @return
* @throws R2RMLDataError
* @throws SQLException
* @throws UnsupportedEncodingException
* @throws MalformedURLException
*/
public static String extractColumnValueFromInverseExpression(
String inverseExpression,
Map dbValues,
Set columnReferences) throws R2RMLDataError, SQLException,
UnsupportedEncodingException {
// Let result be the template string
String result = inverseExpression;
if (dbValues == null)
return null;
for (ColumnIdentifier column : dbValues.keySet()) {
// A quoted and escaped data value is any SQL
// string that matches the or
// productions of [SQL2].
// This string can be used in a SQL query to specify a SQL data
// value.
String value = null;
if (dbValues.get(column) == null)
value = "NULL";
else {
// Extract db value
byte[] byteValue = dbValues.get(column);
// Apply cast to string to the SQL data value
value = new String(byteValue, "UTF-8");
}
result = column.replaceAll(result, "'" + value + "'");
// Test backslashes result =
/*
* result.replaceAll("\\{\\\"" + column + "\\\"\\}", "'" + result +
* "'"); result = result.replaceAll("\\{\\'" + column + "\\'\\}",
* "'" + result + "'"); result = result.replaceAll("\\{\\`" + column
* + "\\`\\}", "'" + result + "'");
*/
}
// Replace curly braces of not referenced column references
for (ColumnIdentifier column : columnReferences) {
if (!dbValues.keySet().contains(column)) {
result = column.replaceAll(result, column.toString());
// result = result.replaceAll("\\{\\'" + columnStr + "\\'\\}", columnStr);
// result = result.replaceAll("\\{\\`" + columnStr + "\\`\\}", columnStr);
}
}
// Curly braces that do not enclose column names MUST be
// escaped by a backslash character (“\”).
result = result.replaceAll("\\\\\\{", "{");
result = result.replaceAll("\\\\\\}", "}");
return result;
}
@Deprecated
public static String deleteBackSlash(String value) {
String result = value;
// Check if column is "backslashed"
if (value.startsWith("\"") && value.endsWith("\"")) {
result = value.substring(1, value.length() - 1);
}
if (value.startsWith("'") && value.endsWith("'")) {
result = value.substring(1, value.length() - 1);
}
if (value.startsWith("`") && value.endsWith("`")) {
result = value.substring(1, value.length() - 1);
}
return result;
}
/**
* The template value of the term map for a given logical table row is
* determined as follows.
*
* @param stringTemplate
* @param dbValues
* @param dbTypes
* @return
* @throws R2RMLDataError
* @throws SQLException
* @throws UnsupportedEncodingException
* @throws MalformedURLException
*/
public static String extractColumnValueFromStringTemplate(
String stringTemplate,
Map dbValues,
ResultSetMetaData dbTypes) throws R2RMLDataError, SQLException,
UnsupportedEncodingException {
// Let result be the template string
String result = stringTemplate;
if (dbValues == null)
return null;
for (ColumnIdentifier dbValue : dbValues.keySet()) {
// For each pair of unescaped curly braces in result: if value is
// NULL, then return NULL
if (dbValues.get(dbValue) == null)
return null;
}
for (ColumnIdentifier column : dbValues.keySet()) {
// Extract db value
byte[] byteValue = dbValues.get(column);
// Extract RDF Natural form
SQLType sqlType = column.getSqlType();
// Apply cast to string to the SQL data value
String value;
if (sqlType != null) {
XSDType xsdType = SQLToXMLS.getEquivalentType(sqlType);
value = XSDLexicalTransformation.extractNaturalRDFFormFrom(
xsdType, byteValue);
}
else
{
value = new String(byteValue, "UTF-8");
}
result = column.replaceAll(result, getIRISafeVersion(value));
// Test backslashes result =
/*
* result.replaceAll("\\{\\\"" + column + "\\\"\\}",
* getIRISafeVersion(result)); result = result.replaceAll("\\{\\'" +
* column + "\\'\\}", getIRISafeVersion(result)); result =
* result.replaceAll("\\{\\`" + column + "\\`\\}",
* getIRISafeVersion(result));
*/
}
// Curly braces that do not enclose column names MUST be
// escaped by a backslash character (“\”).
result = result.replaceAll("\\\\\\{", "{");
result = result.replaceAll("\\\\\\}", "}");
return result;
}
/**
* The IRI-safe version of a string is obtained by applying the following
* transformation in [RFC3987].
*
* @throws R2RMLDataError
* @throws MalformedURLException
*/
public static String getIRISafeVersion(String value) {
// Any character that is not in the iunreserved production
// iunreserved = ALPHA / DIGIT / "-" / "." / "_" / "~" / ucschar
StringBuffer buff = new StringBuffer(value.length());
Set unreservedChars = new HashSet();
unreservedChars.add('-');
unreservedChars.add('.');
unreservedChars.add('_');
unreservedChars.add('~');
unreservedChars.add('*');
unreservedChars.add('\'');
unreservedChars.add('(');
unreservedChars.add(')');
unreservedChars.add('!');
unreservedChars.add('=');
for (int i = 0; i < value.length(); i++) {
char c = value.charAt(i);
if (!(Character.isDigit(c) || Character.isLetter(c) || unreservedChars
.contains(c))) {
// Percent-encode each octet
buff.append('%');
buff.append(Integer.toHexString(c).toUpperCase());
} else {
buff.append(c);
}
}
return buff.toString();
}
/**
* The URL-safe version of a string is obtained by an URL encoding to a
* string value.
*
* @throws R2RMLDataError
* @throws MalformedURLException
*/
public static String getURLSafeVersion(String value) throws R2RMLDataError {
if (value == null)
return null;
URL url = null;
try {
url = new URL(value);
} catch (MalformedURLException mue) {
// This template should be not a url : no encoding
return value;
}
// No exception raised, this template is a valid url : perform
// percent-encoding
try {
java.net.URI uri = new java.net.URI(url.getProtocol(),
url.getAuthority(), url.getPath(), url.getQuery(),
url.getRef());
String result = uri.toURL().toString();
// Percent encoding : complete with no supported char in this
// treatment
result = result.replaceAll("\\,", "%2C");
return result;
} catch (URISyntaxException e) {
throw new R2RMLDataError(
"[R2RMLToolkit:getIRISafeVersion] This value " + value
+ " can not be percent-encoded because "
+ e.getMessage());
} catch (MalformedURLException e) {
throw new R2RMLDataError(
"[R2RMLToolkit:getIRISafeVersion] This value " + value
+ " can not be percent-encoded because "
+ e.getMessage());
}
}
}
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