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XStream – Package Aliasing

XStream - Package Aliasing

Xstream Package aliasing is used to create an alias of a fully qualified name of a class in XML to a new qualified name. Let us modify our example again and change the following code.

xstream.alias("student", Student.class);
xstream.alias("note", Note.class);

Above code is changed as follows −

xstream.aliasPackage("my.company.xstream", "com.adglob.xstream");

Let us test the above object’s serialization using XStream.

Create a java class file named XStreamTester in C:\>XStream_WORKSPACE\com\adglob\xstream.

File: XStreamTester.java

package com.adglob.xstream;

import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.util.ArrayList;
import java.util.List;

import javax.xml.transform.OutputKeys;
import javax.xml.transform.Source;
import javax.xml.transform.Transformer;
import javax.xml.transform.sax.SAXSource;
import javax.xml.transform.sax.SAXTransformerFactory;
import javax.xml.transform.stream.StreamResult;

import org.xml.sax.InputSource;

import com.thoughtworks.xstream.XStream;
import com.thoughtworks.xstream.io.xml.StaxDriver;

public class XStreamTester {
   public static void main(String args[]) {
   
      XStreamTester tester = new XStreamTester();
      XStream xstream = new XStream(new StaxDriver());
      
      xstream.alias("student", Student.class);
      xstream.alias("note", Note.class);
      
      xstream.useAttributeFor(Student.class, "studentName");
      xstream.aliasField("name", Student.class, "studentName");
      xstream.addImplicitCollection(Student.class, "notes");
      
      Student student = tester.getStudentDetails();
      
      //Object to XML Conversion
      String xml = xstream.toXML(student);
      System.out.println(formatXml(xml));		
   }	

   private Student getStudentDetails() {
      Student student = new Student("Mahesh");
      
      student.addNote(new Note("first","My first assignment."));
      student.addNote(new Note("second","My Second assignment."));
      
      return student;
   }

   public static String formatXml(String xml) {
   
      try {
         Transformer serializer = SAXTransformerFactory.newInstance().newTransformer();
         
         serializer.setOutputProperty(OutputKeys.INDENT, "yes");
         serializer.setOutputProperty("{http://xml.apache.org/xslt}indent-amount", "2");
         
         Source xmlSource = new SAXSource(new InputSource(
            new ByteArrayInputStream(xml.getBytes())));
         StreamResult res =  new StreamResult(new ByteArrayOutputStream());            
         
         serializer.transform(xmlSource, res);
         
         return new String(((ByteArrayOutputStream)res.getOutputStream()).toByteArray());
         
      } catch(Exception e) {
         return xml;
      }
   }
}

class Student {
   private String studentName;
   private List<Note> notes = new ArrayList<Note>();
   
   public Student(String name) {
      this.studentName = name;
   }
   
   public void addNote(Note note) {
      notes.add(note);
   }
   
   public String getName() {
      return studentName;
   }
   
   public List<Note> getNotes() {
      return notes;
   }
}

class Note {
   private String title;
   private String description;
   
   public Note(String title, String description) {
      this.title = title;
      this.description = description;
   }
   
   public String getTitle() {
      return title;
   }
   
   public String getDescription() {
      return description;
   }     
}

Verify the Result

Compile the classes using javac compiler as follows −

C:\XStream_WORKSPACE\com\asglob\xstream>javac XStreamTester.java

Now run the XStreamTester to see the result −

C:\XStream_WORKSPACE\com\adglob\xstream>java XStreamTester

Verify the output as follows −

<?xml version = "1.0" encoding = "UTF-8"?>
<student name = "Mahesh">
   <note>
      <title>first</title>
      <description>My first assignment.</description>
   </note>
   
   <note>
      <title>second</title>
      <description>My Second assignment.</description>
   </note>
</student>

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