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Tip of the Day
Language: Java
Expertise: Advanced
Dec 11, 2007

Wrap the Result of an XQuery Query into an XML Document

Wrapping the result of an XQuery query into an XML document is very useful if you're working with atomic values. The following Java program uses the net.sf.saxon.om.SequenceIterator and net.sf.saxon.query.QueryResult classes to do this:

/*
The resulted document : C:\Data_Local\xml\docs\wrap.xml
*/

//Java
import java.io.File;
import java.io.OutputStream;
import java.io.FileOutputStream;
import java.util.Properties;
import javax.xml.transform.OutputKeys;
import javax.xml.transform.stream.StreamResult;

//Saxon
import net.sf.saxon.om.SequenceIterator;
import net.sf.saxon.query.QueryResult;
import net.sf.saxon.om.DocumentInfo;
import net.sf.saxon.Configuration;
import net.sf.saxon.query.DynamicQueryContext;
import net.sf.saxon.query.StaticQueryContext;
import net.sf.saxon.query.XQueryExpression;

public class XQueryWrapExample {
   public static void main(String[] args) {
      
      XQueryExpression exp=null; //used for compilation     
        
      //the XQuery query
      String query="for $i in (1, 2,3)"+"return ($i)";       
         
      //wrap.xml
      String xmlFileName="C://Data_Local//xml//docs//wrap.xml";
      File outFile=null;      
      OutputStream destStream=null;
                                 
      //create an instance of Configuration
      Configuration C=new Configuration();
        
      //create the static and dynamic contexts
      StaticQueryContext SQC=new StaticQueryContext(C);
      DynamicQueryContext DQC=new DynamicQueryContext(C);      
        
      //indentation
      Properties props=new Properties();
      props.setProperty(OutputKeys.METHOD,"xml");
      props.setProperty(OutputKeys.INDENT,"yes");

      try{
         //"prepare" the wrap.xml
         outFile=new File(xmlFileName);           
         destStream=new FileOutputStream(outFile);

         //compile the XQuery query
         exp=SQC.compileQuery(query);
         SQC=exp.getStaticContext(); 
         }catch(net.sf.saxon.trans.XPathException e)
            {System.err.println(e.getMessage());
         }catch(java.io.IOException e)
            {System.err.println(e.getMessage());}
          
      try{              
         //execute the query and wrap the result into wrap.xml
         SequenceIterator SI=exp.iterator(DQC);
          DocumentInfo DI=QueryResult.wrap(SI,C);
          QueryResult.serialize(DI,new 
                         StreamResult(destStream),props,C);
          destStream.close();
         }catch(net.sf.saxon.trans.XPathException e)
            {System.err.println(e.getMessage());
         }catch(java.io.IOException e)
            {System.err.println(e.getMessage());}                          
      }   
}

Result:

<?xml version="1.0" encoding="UTF-8"?>
<result:sequence xmlns:result=http://saxon.sf.net/xquery-results
                xmlns:xs=http://www.w3.org/2001/XMLSchema
                xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
   <result:atomic-value xsi:type="xs:integer">1</result:atomic-value>
   <result:atomic-value xsi:type="xs:integer">2</result:atomic-value>
   <result:atomic-value xsi:type="xs:integer">3</result:atomic-value>
</result:sequence>
Leonard Anghel
 
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