XStream註解
XStream支持註釋做同樣的任務，正如我們在前面的章節中是自動配置，而不是代碼1所做的。在前面的章節中，我們已經看到了下面的代碼配置。
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");
下面的代碼片段來說明使用annoations更容易的方式做同樣的工作。
@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; }
讓我們使用XStream測試上面的註釋。
創建一個Java類名爲XStreamTester文件在 C:\>XStream_WORKSPACE\com\yiibai\xstream.
File: XStreamTester.java
package com.yiibai.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; } }
驗證結果
使用javac編譯器編譯如下類：
C:\XStream_WORKSPACE\com\yiibai\xstream>javac XStreamTester.java
現在運行XStreamTester看到的結果：
C:\XStream_WORKSPACE\com\yiibai\xstream>java XStreamTester
驗證結果
<student name="Mahesh">
爲了告訴XStream框架來處理註釋，需要XML序列化之前添加下面的命令。
xstream.processAnnotations(Student.class);
或者
xstream.autodetectAnnotations(true);