XStream转换器
XStream允许从无到有写入转换器，这样开发人员可以编写一个完全新的实现，如何对象序列化到XML，反之亦然。 转换器接口提供了三种方法。
- canConvert - 检查支持的对象类型的序列化。
- marshal - 序列化对象到XML。
- unmarshal - 从XML对象反序列化
第1步：实现转换器接口
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;
}
}
第2步：注册转换器。
现在，让我们XStream转换器的代码测试。 创建一个Java类名为XStreamTester文件在 C:\>XStream_WORKSPACE\com\yiibai\xstream. File: XStreamTester.javaxstream.registerConverter(newStudentConverter());
package cn.sxt.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);
}
}
验证结果
使用javac编译器编译如下类：
C:\XStream_WORKSPACE\cn\sxt\xstream>javac XStreamTester.java现在运行XStreamTester看到的结果：
C:\XStream_WORKSPACE\cn\sxt\xstream>java XStreamTester验证输出
<?xml version="1.0" encoding="UTF-8"?> <student> <name>Mahesh,Parashar</name> </student>
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