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/**
* eobjects.org MetaModel
* Copyright (C) 2010 eobjects.org
*
* This copyrighted material is made available to anyone wishing to use, modify,
* copy, or redistribute it subject to the terms and conditions of the GNU
* Lesser General Public License, as published by the Free Software Foundation.
*
* This program 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 Lesser General Public License
* for more details.
*
* You should have received a copy of the GNU Lesser General Public License
* along with this distribution; if not, write to:
* Free Software Foundation, Inc.
* 51 Franklin Street, Fifth Floor
* Boston, MA 02110-1301 USA
*/
package org.eobjects.metamodel.xml;
import java.io.File;
import java.io.InputStream;
import java.util.HashMap;
import java.util.LinkedHashMap;
import java.util.Map;
import javax.xml.parsers.SAXParser;
import javax.xml.parsers.SAXParserFactory;
import org.eobjects.metamodel.MetaModelException;
import org.eobjects.metamodel.QueryPostprocessDataContext;
import org.eobjects.metamodel.data.DataSet;
import org.eobjects.metamodel.data.RowPublisher;
import org.eobjects.metamodel.data.RowPublisherDataSet;
import org.eobjects.metamodel.query.SelectItem;
import org.eobjects.metamodel.schema.Column;
import org.eobjects.metamodel.schema.ColumnType;
import org.eobjects.metamodel.schema.ImmutableSchema;
import org.eobjects.metamodel.schema.MutableColumn;
import org.eobjects.metamodel.schema.MutableSchema;
import org.eobjects.metamodel.schema.MutableTable;
import org.eobjects.metamodel.schema.Schema;
import org.eobjects.metamodel.schema.Table;
import org.eobjects.metamodel.util.Action;
import org.eobjects.metamodel.util.FileResource;
import org.eobjects.metamodel.util.Ref;
import org.eobjects.metamodel.util.Resource;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.xml.sax.Attributes;
import org.xml.sax.InputSource;
import org.xml.sax.SAXException;
import org.xml.sax.XMLReader;
import org.xml.sax.helpers.DefaultHandler;
/**
* XML datacontext which uses SAX parsing for fast and memory effecient reading
* of XML files.
*
* The DataContext requires the user to specify a set of (simplified) XPaths to
* define which elements are row delimitors and which elements or attributes are
* value/column definitions.
*
* @author Kasper Sørensen
*/
public class XmlSaxDataContext extends QueryPostprocessDataContext {
private static final Logger logger = LoggerFactory.getLogger(XmlSaxDataContext.class);
public static final String COLUMN_NAME_ROW_ID = "row_id";
private final Ref _inputSourceRef;
private final Map> _valueXpaths;
private String _schemaName;
private XmlSaxTableDef[] _tableDefs;
/**
* Constructs an XML DataContext based on SAX parsing.
*
* @param inputSourceRef
* a factory reference for the input source to read the XML from.
* The ref will be repeatedly called for each access to the file!
* @param tableDefs
* an array of table definitions, which provide instructions as
* to the xpaths to apply to the document.
*
* @see XmlSaxTableDef
*/
public XmlSaxDataContext(Ref inputSourceRef, XmlSaxTableDef... tableDefs) {
_inputSourceRef = inputSourceRef;
_tableDefs = tableDefs;
_valueXpaths = new HashMap>();
_schemaName = null;
for (XmlSaxTableDef tableDef : tableDefs) {
LinkedHashMap xpathMap = new LinkedHashMap();
_valueXpaths.put(tableDef, xpathMap);
String[] valueXpaths = tableDef.getValueXpaths();
for (String valueXpath : valueXpaths) {
xpathMap.put(getName(tableDef, valueXpath), valueXpath);
}
}
}
public XmlSaxDataContext(final Resource resource, XmlSaxTableDef... tableDefs) {
this(createInputSourceRef(resource), tableDefs);
}
public XmlSaxDataContext(final File file, XmlSaxTableDef... tableDefs) {
this(createInputSourceRef(new FileResource(file)), tableDefs);
}
private static Ref createInputSourceRef(final Resource resource) {
return new Ref() {
@Override
public InputSource get() {
final InputStream in = resource.read();
return new InputSource(in);
}
};
}
@Override
protected Schema getMainSchema() throws MetaModelException {
final MutableSchema schema = new MutableSchema(getMainSchemaName());
for (XmlSaxTableDef tableDef : _tableDefs) {
final String rowXpath = tableDef.getRowXpath();
final MutableTable table = new MutableTable(getTableName(tableDef)).setSchema(schema)
.setRemarks("XPath: " + rowXpath);
final MutableColumn rowIndexColumn = new MutableColumn(COLUMN_NAME_ROW_ID, ColumnType.INTEGER).setColumnNumber(0)
.setNullable(false).setTable(table).setRemarks("Row/tag index (0-based)");
table.addColumn(rowIndexColumn);
for (String valueXpath : tableDef.getValueXpaths()) {
final MutableColumn column = new MutableColumn(getName(tableDef, valueXpath)).setRemarks("XPath: " + valueXpath);
if (valueXpath.startsWith("index(") && valueXpath.endsWith(")")) {
column.setType(ColumnType.INTEGER);
} else {
column.setType(ColumnType.VARCHAR);
}
column.setTable(table);
table.addColumn(column);
}
schema.addTable(table);
}
return new ImmutableSchema(schema);
}
private XmlSaxTableDef getTableDef(Table table) {
for (XmlSaxTableDef tableDef : _tableDefs) {
if (getTableName(tableDef).equals(table.getName())) {
return tableDef;
}
}
throw new IllegalArgumentException("No table def found for table " + table);
}
private String getTableName(XmlSaxTableDef tableDef) {
String xpath = tableDef.getRowXpath();
int lastIndexOf = xpath.lastIndexOf('/');
if (lastIndexOf != -1) {
xpath = xpath.substring(lastIndexOf);
}
return xpath;
}
private String getName(XmlSaxTableDef tableDef, String xpath) {
String rowXpath = tableDef.getRowXpath();
if (xpath.startsWith(rowXpath)) {
xpath = xpath.substring(rowXpath.length());
}
return xpath;
}
@Override
protected String getMainSchemaName() throws MetaModelException {
if (_schemaName == null) {
// when querying the schema name for the first time, pick the first
// element of the document.
try {
SAXParserFactory saxFactory = SAXParserFactory.newInstance();
SAXParser saxParser = saxFactory.newSAXParser();
XMLReader xmlReader = saxParser.getXMLReader();
xmlReader.setContentHandler(new DefaultHandler() {
@Override
public void startElement(String uri, String localName, String qName, Attributes attributes)
throws SAXException {
if (qName != null && qName.length() > 0) {
_schemaName = '/' + qName;
throw new XmlStopParsingException();
}
}
});
xmlReader.parse(_inputSourceRef.get());
} catch (XmlStopParsingException e) {
logger.debug("Parsing stop signal thrown");
} catch (Exception e) {
logger.error("Unexpected error occurred while retrieving schema name", e);
if (e instanceof RuntimeException) {
throw (RuntimeException) e;
}
throw new IllegalStateException(e);
}
}
return _schemaName;
}
@Override
protected DataSet materializeMainSchemaTable(Table table, Column[] columns, int maxRows) {
final XmlSaxTableDef tableDef = getTableDef(table);
final String[] valueXpaths = new String[columns.length];
final SelectItem[] selectItems = new SelectItem[columns.length];
for (int i = 0; i < columns.length; i++) {
final Column column = columns[i];
selectItems[i] = new SelectItem(column);
valueXpaths[i] = getXpath(tableDef, column);
}
final Action rowPublisherAction = new Action() {
@Override
public void run(RowPublisher rowPublisher) throws Exception {
SAXParserFactory saxFactory = SAXParserFactory.newInstance();
SAXParser saxParser = saxFactory.newSAXParser();
XMLReader xmlReader = saxParser.getXMLReader();
xmlReader.setContentHandler(new XmlSaxContentHandler(tableDef.getRowXpath(), rowPublisher, valueXpaths));
try {
xmlReader.parse(_inputSourceRef.get());
} catch (XmlStopParsingException e) {
logger.debug("Parsing stop signal thrown");
} catch (Exception e) {
logger.warn("Unexpected error occurred while parsing", e);
throw e;
} finally {
rowPublisher.finished();
}
}
};
return new RowPublisherDataSet(selectItems, maxRows, rowPublisherAction);
}
private String getXpath(XmlSaxTableDef tableDef, Column column) {
String columnName = column.getName();
if (COLUMN_NAME_ROW_ID.equals(columnName)) {
return "index(" + tableDef.getRowXpath() + ")";
}
String result = _valueXpaths.get(tableDef).get(columnName);
if (result == null) {
return columnName;
}
return result;
}
}
