XStream - Convertitore personalizzato
XStream consente di scrivere un convertitore da zero, in modo che lo sviluppatore possa scrivere un'implementazione completamente nuova su come serializzare un oggetto in XML e viceversa. Un'interfaccia del convertitore fornisce tre metodi:
canConvert - È un controllo per la serializzazione del tipo di oggetto supportato.
marshal - Serializza un oggetto in XML.
unmarshal - De-serializza un oggetto da XML.
Passaggio 1: implementare l'interfaccia del convertitore
class StudentConverter implements Converter {
public boolean canConvert(Class object) {
return object.equals(Student.class);
}
public void marshal(Object value, HierarchicalStreamWriter writer, MarshallingContext context) {
Student student = (Student) value;
writer.startNode("name");
writer.setValue(student.getName().getFirstName() + "," + student.getName().getLastName());
writer.endNode();
}
public Object unmarshal(HierarchicalStreamReader reader, UnmarshallingContext context) {
reader.moveDown();
String[] nameparts = reader.getValue().split(",");
Student student = new Student(nameparts[0],nameparts[1]);
reader.moveUp();
return student;
}
}
Passaggio 2: registrare il convertitore
xstream.registerConverter(new StudentConverter());
Proviamo ora a testare il codice con il convertitore in 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 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.annotations.XStreamAlias;
import com.thoughtworks.xstream.converters.Converter;
import com.thoughtworks.xstream.converters.MarshallingContext;
import com.thoughtworks.xstream.converters.UnmarshallingContext;
import com.thoughtworks.xstream.io.HierarchicalStreamReader;
import com.thoughtworks.xstream.io.HierarchicalStreamWriter;
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());
Student student = tester.getStudentDetails();
xstream.autodetectAnnotations(true);
xstream.registerConverter(new StudentConverter());
//Object to XML Conversion
String xml = xstream.toXML(student);
System.out.println(formatXml(xml));
}
private Student getStudentDetails() {
Student student = new Student("Mahesh","Parashar");
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;
}
}
}
@XStreamAlias("student")
class Student {
@XStreamAlias("name")
private Name studentName;
public Student(String firstName, String lastName) {
this.studentName = new Name(firstName, lastName);
}
public Name getName() {
return studentName;
}
}
class Name {
private String firstName;
private String lastName;
public Name(String firstName, String lastName) {
this.firstName = firstName;
this.lastName = lastName;
}
public String getFirstName() {
return firstName;
}
public String getLastName() {
return lastName;
}
}
class StudentConverter implements Converter {
public void marshal(Object value, HierarchicalStreamWriter writer,
MarshallingContext context) {
Student student = (Student) value;
writer.startNode("name");
writer.setValue(student.getName().getFirstName() + "," + student.getName().getLastName());
writer.endNode();
}
public Object unmarshal(HierarchicalStreamReader reader,
UnmarshallingContext context) {
reader.moveDown();
String[] nameparts = reader.getValue().split(",");
Student student = new Student(nameparts[0],nameparts[1]);
reader.moveUp();
return student;
}
public boolean canConvert(Class object) {
return object.equals(Student.class);
}
}
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
Verificare l'output come segue:
<?xml version = "1.0" encoding = "UTF-8"?>
<student>
<name>Mahesh,Parashar</name>
</student>