/*
Derby - Class org.apache.derbyDemo.vtis.core.XmlVTI
Licensed to the Apache Software Foundation (ASF) under one or more
contributor license agreements. See the NOTICE file distributed with
this work for additional information regarding copyright ownership.
The ASF licenses this file to You under the Apache License, Version 2.0
(the "License"); you may not use this file except in compliance with
the License. You may obtain a copy of the License at
http://www.apache.org/licenses/LICENSE-2.0
Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/
package org.apache.derbyDemo.vtis.core;
import java.io.*;
import java.lang.reflect.*;
import java.net.URL;
import java.sql.*;
import java.text.DateFormat;
import java.text.ParseException;
import javax.xml.parsers.*;
import org.w3c.dom.*;
/**
* <p>
* This is a VTI designed to read XML files which are structured like row sets.
* </p>
*
*/
public class XmlVTI extends StringColumnVTI
{
///////////////////////////////////////////////////////////////////////////////////
//
// CONSTANTS
//
///////////////////////////////////////////////////////////////////////////////////
///////////////////////////////////////////////////////////////////////////////////
//
// STATE
//
///////////////////////////////////////////////////////////////////////////////////
private String _rowTag;
private String _xmlResourceName;
private int _rowIdx = -1;
private int _rowCount = -1;
private String[] _currentRow;
private DocumentBuilder _builder;
private NodeList _rawRows;
///////////////////////////////////////////////////////////////////////////////////
//
// CONSTRUCTORS
//
///////////////////////////////////////////////////////////////////////////////////
/**
* <p>
* Build a XmlVTI given the name of an xml resource, the tag of the row
* element, and an array of attribute-names/element-tags underneath the row element
* </p>
*/
public XmlVTI( String xmlResourceName, String rowTag, String[] childTags )
{
super( childTags );
_xmlResourceName = xmlResourceName;
_rowTag = rowTag;
}
///////////////////////////////////////////////////////////////////////////////////
//
// DATABASE PROCEDURES
//
///////////////////////////////////////////////////////////////////////////////////
/**
* <p>
* Register all of the XMLRow table functions in a class. This method is exposed as a
* database procedure.
* </p>
*/
public static void registerXMLRowVTIs( String className )
throws Exception
{
// find public static methods which return ResultSet
Class theClass = Class.forName( className );
Method[] methods = theClass.getMethods();
int count = methods.length;
Method candidate = null;
XMLRow xmlRowAnnotation = null;
for ( int i = 0; i < count; i++ )
{
candidate = methods[ i ];
int modifiers = candidate.getModifiers();
if (
Modifier.isPublic( modifiers ) &&
Modifier.isStatic( modifiers ) &&
candidate.getReturnType() == ResultSet.class
)
{
xmlRowAnnotation = candidate.getAnnotation( XMLRow.class );
if ( xmlRowAnnotation != null )
{
VTIHelper.unregisterVTI( candidate );
registerVTI( candidate );
}
}
}
}
///////////////////////////////////////////////////////////////////////////////////
//
// StringColumnVTI BEHAVIOR TO BE IMPLEMENTED BY SUBCLASSES
//
///////////////////////////////////////////////////////////////////////////////////
/**
* <p>
* Get the string value of the column in the current row identified by the 1-based columnNumber.
* </p>
*/
protected String getRawColumn( int columnNumber ) throws SQLException
{
try {
return _currentRow[ columnNumber - 1 ];
} catch (Throwable t) { throw new SQLException( t.getMessage() ); }
}
///////////////////////////////////////////////////////////////////////////////////
//
// ResultSet BEHAVIOR
//
///////////////////////////////////////////////////////////////////////////////////
public void close() throws SQLException
{
_builder = null;
_rawRows = null;
}
public ResultSetMetaData getMetaData() throws SQLException
{
throw new SQLException( "Not implemented." );
}
public boolean next() throws SQLException
{
try {
if ( _rowIdx < 0 ) { readRows(); }
if ( ++_rowIdx < _rowCount )
{
parseRow( _rowIdx );
return true;
}
else { return false; }
} catch (Throwable t)
{
t.printStackTrace( System.out );
throw new SQLException( t.getMessage() );
}
}
///////////////////////////////////////////////////////////////////////////////////
//
// PUBLIC BEHAVIOR
//
///////////////////////////////////////////////////////////////////////////////////
/**
* <p>
* Register a method as a Derby Table Function. We assume the following:
* </p>
*
* <ul>
* <li>The method is public and static.</li>
* <li>The method returns a ResultSet.</li>
* <li>The method is annotated as an XMLRow.</li>
* </ul>
*
*/
public static void registerVTI( Method method )
throws Exception
{
XMLRow annotation = method.getAnnotation( XMLRow.class );
String methodName = method.getName();
String sqlName = methodName;
Class methodClass = method.getDeclaringClass();
Class[] parameterTypes = method.getParameterTypes();
int parameterCount = parameterTypes.length;
String[] columnNames = annotation.childTags();
String[] columnTypes = annotation.childTypes();
int columnCount = columnNames.length;
int typeCount = columnTypes.length;
StringBuilder buffer = new StringBuilder();
if ( columnCount != typeCount )
{
throw new Exception
(
"Bad XMLRow annotation for " +
methodName +
". The number of childTags (" +
columnCount +
") does not equal the number of childTypes (" +
typeCount +
")."
);
}
VTIHelper.registerVTI( method, columnNames, columnTypes, false );
}
/**
* <p>
* Create a VTI ResultSet. It is assumed that our caller is an
* XMLRow-annotated method with one String argument. It
* is assumed that ResultSet is an instance of vtiClass and that
* vtiClass extends XmlVTI and has a constructor with the same
* arguments as the constructor of XmlVTI.
* </p>
*
*/
public static ResultSet instantiateVTI( String xmlResourceName )
throws SQLException
{
try {
// look up the method on top of us
StackTraceElement[] stack = (new Throwable()).getStackTrace();
StackTraceElement caller = stack[ 1 ];
Class<?> callerClass = Class.forName( caller.getClassName() );
String methodName = caller.getMethodName();
Method method = callerClass.getMethod
( methodName, new Class[] { String.class } );
XMLRow annotation = method.getAnnotation( XMLRow.class );
String rowTag = annotation.rowTag();
String[] childTags = annotation.childTags();
String vtiClassName = annotation.vtiClassName();
Class<?> vtiClass = Class.forName( vtiClassName );
Constructor constructor = vtiClass.getConstructor
( new Class[] { String.class, String.class, String[].class } );
return (ResultSet) constructor.newInstance( xmlResourceName, rowTag, childTags );
} catch (Throwable t) { throw new SQLException( t.getMessage() ); }
}
///////////////////////////////////////////////////////////////////////////////////
//
// MINIONS
//
///////////////////////////////////////////////////////////////////////////////////
//////////////////////////
//
// XML MINIONS
//
//////////////////////////
/**
* <p>
* Fault in the list of rows.
* </p>
*/
private void readRows() throws Exception
{
DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
_builder = factory.newDocumentBuilder();
URL url = new URL( _xmlResourceName );
InputStream is = url.openStream();
Document doc = _builder.parse( is );
Element root = doc.getDocumentElement();
_rawRows = root.getElementsByTagName( _rowTag );
_rowCount = _rawRows.getLength();
is.close();
}
/**
* <p>
* Parse a row into columns.
* </p>
*/
private void parseRow( int rowNumber ) throws Exception
{
Element rawRow = (Element) _rawRows.item( rowNumber );
String[] columnNames = getColumnNames();
int columnCount = columnNames.length;
_currentRow = new String[ columnCount ];
for ( int i = 0; i < columnCount; i++ )
{
// first look for an attribute by the column name
String columnName = columnNames[ i ];
String contents = rawRow.getAttribute( columnName );
// if there is not attribute by that name, then look for descendent elements by
// that name. concatenate them all.
if ( (contents == null) || "".equals( contents ) )
{
NodeList children = rawRow.getElementsByTagName( columnName );
if ( (children != null) && (children.getLength() > 0) )
{
int childCount = children.getLength();
StringBuffer buffer = new StringBuffer();
for ( int j = 0; j < childCount; j++ )
{
Element child = (Element) children.item( j );
// separate values with spaces.
if (j != 0)
buffer.append(" ");
buffer.append( squeezeText( child ) );
}
contents = buffer.toString();
}
}
_currentRow[ i ] = contents;
}
}
/**
* <p>
* Squeeze the text out of an Element.
* </p>
*/
private String squeezeText( Element node )
throws Exception
{
String text = null;
Node textChild = node.getFirstChild();
if ( textChild != null ) { text = textChild.getNodeValue(); }
return text;
}
}