XStream - Aliasing di collezioni implicite

L'aliasing implicito delle raccolte viene utilizzato quando una raccolta deve essere rappresentata in XML senza visualizzare le radici. Ad esempio, nel nostro caso, dobbiamo visualizzare ciascuna nota una per una ma non nel nodo radice "note". Modifichiamo di nuovo il nostro esempio e aggiungiamo il codice seguente.

xstream.addImplicitCollection(Student.class, "notes");

Testiamo la serializzazione degli oggetti sopra usando XStream.

Crea un file di classe java denominato XStreamTester in C:\>XStream_WORKSPACE\com\tutorialspoint\xstream.

File: XStreamTester.java

package com.tutorialspoint.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.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;
   }     
}

Verifica il risultato

Compila le classi usando javac compilatore come segue -

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

Ora esegui XStreamTester per vedere il risultato -

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

Verifica l'output come segue:

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

Nel risultato sopra, possiamo vedere che il nome sta arrivando come nodo figlio e ne abbiamo bisogno come attributo del nodo radice. Per sostituirlo, segui la sezione successiva.