/* Copyright 2004 The Apache Software Foundation
*
* Licensed 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.xmlbeans.samples.xquery;
import org.apache.xmlbeans.XmlCursor;
import org.apache.xmlbeans.XmlObject;
/**
* This class demonstrates how to use the execQuery method to execute XQuery
* expressions. Compare the code here with the code in the SelectPath class.
* That class uses the selectPath method to execute XPath expressions.
* <p/>
* You can call the execQuery method from either an XmlObject or XmlCursor
* instance. Calling from XmlObject returns an XmlObject array. Calling
* from XmlCursor returns a new XmlCursor instance positioned at the root
* of a fragment containing copies of the XML queried against. Results of the
* query (if any) are sibling children of the fragment's root.
*/
public class ExecQuery
{
final static String m_namespaceDeclaration =
"declare namespace xq='http://xmlbeans.apache.org/samples/xquery/employees';";
/**
* Uses XQuery to retrieve work <phone> elements from the incoming XML, then
* changes the number in the results.
*
* This method demonstrates the following characteristics of the execQuery method:
*
* - it supports XQuery.
* - the XML it returns is a copy of the XML queried against; contrast this with
* the selectPath method, which returns a portion of the original document.
* Changes to returned XML do not impact the XML queried against.
* - execQuery called from an XmlCursor returns a cursor positioned at
* the STARTDOC token of a new XML fragment. Contrast this with the
* XmlCursor.selectPath method, which stores results as "selections" in
* the cursor used to execute the query.
*
* @param empDoc The incoming XML.
* @return <code>true</code> if the XPath expression returned results;
* otherwise, <code>false</code>.
*/
public boolean updateWorkPhone(XmlObject empDoc)
{
boolean hasResults = false;
// A cursor instance to query with.
XmlCursor empCursor = empDoc.newCursor();
empCursor.toNextToken();
// The expression: Get the <employee> elements with <state> elements whose
// value is "WA".
String queryExpression =
"for $e in $this/xq:employees/xq:employee " +
"let $s := $e/xq:address/xq:state " +
"where $s = 'WA' " +
"return $e//xq:phone[@location='work']";
// Execute the query. Results, if any, will be available at
// the position of the resultCursor in a new XML document.
XmlCursor resultCursor =
empCursor.execQuery(m_namespaceDeclaration + queryExpression);
System.out.println("The query results, <phone> element copies made " +
"from the received document: \n");
System.out.println(resultCursor.getObject().toString() + "\n");
// If there are results, the results will be children of the fragment root
// where the new cursor is positioned. This statement tests for children
// and moves the cursor if to the first if it exists.
if (resultCursor.toFirstChild())
{
hasResults = true;
// Use the cursor to loop through the results, printing each sibling
// <employee> element returned by the query.
int i = 0;
do
{
// Change the phone numbers.
XmlCursor editCursor = resultCursor.newCursor();
editCursor.toLastAttribute();
editCursor.toNextToken();
editCursor.removeXml();
editCursor.insertChars("(206)555-1234");
} while (resultCursor.toNextSibling());
resultCursor.toStartDoc();
System.out.println("The query results after changes: \n");
System.out.println(resultCursor.getObject().toString() + "\n");
System.out.println("The received document -- note that it is unchanged. " +
"Changes were made to the copy created by the execQuery method. \n");
System.out.println(empDoc + "\n");
}
return hasResults;
}
/**
* Uses XQuery to retrieve work <zip> elements from the incoming XML, adding the
* elements as children to a <zip-list> element.
*
* This method demonstrates the following characteristics of the execQuery method:
*
* - it supports XQuery.
* - execQuery called from an XmlObject returns an array of XmlObject instances.
* These are bound to copies of the received XML.
*
* @param empDoc The incoming XML.
* @return <code>true</code> if the XPath expression returned results;
* otherwise, <code>false</code>.
*/
public boolean collectZips(XmlObject empDoc)
{
// The query is designed to return results, so return
// true if it does.
boolean hasResults = false;
// The expression: Get the <zip> elements and return them as children
// of a new <zip-list> element.
String queryExpression =
"let $e := $this/xq:employees " +
"return " +
"<zip-list> " +
"{for $z in $e/xq:employee/xq:address/xq:zip " +
"return $z} " +
"</zip-list>";
// Execute the query. Results will be copies of the XML queried against,
// stored as members of an XmlObject array.
XmlObject[] results =
empDoc.execQuery(m_namespaceDeclaration + queryExpression);
// Print the results.
if (results.length > 0)
{
hasResults = true;
System.out.println("The query results: \n");
System.out.println(results[0].toString() + "\n");
}
return hasResults;
}
}