XStream - Chú thích
XStream hỗ trợ các chú thích tương tự như cấu hình tự động thay vì mã hóa. Trong chương trước, chúng ta đã thấy các cấu hình sau trong mã.
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");
Đoạn mã sau minh họa việc sử dụng các chú thích để thực hiện công việc tương tự theo cách dễ dàng hơn nhiều.
@XStreamAlias("student") //define class level alias
class Student {
@XStreamAlias("name") //define field level alias
@XStreamAsAttribute //define field as attribute
private String studentName;
@XStreamImplicit //define list as an implicit collection
private List<Note> notes = new ArrayList<Note>();
@XStreamOmitField //omit a field to not to be a part of XML
private int type;
}
Hãy để chúng tôi kiểm tra chú thích trên bằng XStream.
Tạo tệp lớp java có tên XStreamTester trong C:\>XStream_WORKSPACE\com\tutorialspoint\xstream.
Tệp: 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.annotations.XStreamAlias;
import com.thoughtworks.xstream.annotations.XStreamAsAttribute;
import com.thoughtworks.xstream.annotations.XStreamImplicit;
import com.thoughtworks.xstream.annotations.XStreamOmitField;
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.processAnnotations(Student.class);
//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."));
student.setType(1);
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")
@XStreamAsAttribute
private String studentName;
@XStreamImplicit
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;
}
@XStreamOmitField
private int type;
public int getType() {
return type;
}
public void setType(int type) {
this.type = type;
}
}
@XStreamAlias("note")
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;
}
}
Xác minh kết quả
Biên dịch các lớp bằng cách sử dụng javac trình biên dịch như sau -
C:\XStream_WORKSPACE\com\tutorialspoint\xstream>javac XStreamTester.java
Bây giờ hãy chạy XStreamTester để xem kết quả -
C:\XStream_WORKSPACE\com\tutorialspoint\xstream>java XStreamTester
Xác minh kết quả đầu ra như sau:
<?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>
Để hướng dẫn khung XStream xử lý chú thích, bạn cần thêm lệnh sau trước khi tuần tự hóa xml.
xstream.processAnnotations(Student.class);
Hoặc là
xstream.autodetectAnnotations(true);