Xstream 简明教程
XStream - Converters
XStream 转换器是 XStream 库的关键组件,它们负责将对象转换为 XML,反之亦然。XStream 为常用类型(如基本类型、String、File、Collections、数组和 Dates)提供了许多转换器。
Using Converter
让我们使用一个 SingleValueConvertor,其目的是将对象转换为单个字符串。我们将使用 SingleValueConvertor 将对象写入为属性字符串。
Create a Converter
class NameConverter implements SingleValueConverter {
public Object fromString(String name) {
String[] nameparts = name.split(",");
return new Name(nameparts[0], nameparts[1]);
}
public String toString(Object name) {
return ((Name)name).getFirstName() + "," + ((Name)name).getLastName();
}
public boolean canConvert(Class type) {
return type.equals(Name.class);
}
}
Example without Converter
让我们首先在 XStream 中测试没有转换器的代码。
在 C:\>XStream_WORKSPACE\com\tutorialspoint\xstream 中创建一个名为 XStreamTester 的 java 类文件。
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.annotations.XStreamAsAttribute;
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);
//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")
@XStreamAsAttribute
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;
}
}
Verify the Result
使用以下 javac 编译器编译类:
C:\XStream_WORKSPACE\com\tutorialspoint\xstream>javac XStreamTester.java
现在,运行 XStreamTester 以查看结果 −
C:\XStream_WORKSPACE\com\tutorialspoint\xstream>java XStreamTester
验证输出如下所示 −
<?xml version = "1.0" encoding = "UTF-8"?>
<student>
<name>
<firstName>Mahesh</firstName>
<lastName>Parashar</lastName>
</name>
</student>
Example with Converter
现在让我们用 XStream 中的转换器测试代码。
在 C:\>XStream_WORKSPACE\com\tutorialspoint\xstream 中创建一个名为 XStreamTester 的 java 类文件。
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.annotations.XStreamAsAttribute;
import com.thoughtworks.xstream.converters.SingleValueConverter;
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 NameConverter());
//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")
@XStreamAsAttribute
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 NameConverter implements SingleValueConverter {
public Object fromString(String name) {
String[] nameparts = name.split(",");
return new Name(nameparts[0], nameparts[1]);
}
public String toString(Object name) {
return ((Name)name).getFirstName() + "," + ((Name)name).getLastName();
}
public boolean canConvert(Class type) {
return type.equals(Name.class);
}
}
Verify the Result
使用以下 javac 编译器编译类:
C:\XStream_WORKSPACE\com\tutorialspoint\xstream>javac XStreamTester.java
现在,运行 XStreamTester 以查看结果 −
C:\XStream_WORKSPACE\com\tutorialspoint\xstream>java XStreamTester
验证输出如下所示 −
<?xml version = "1.0" encoding = "UTF-8"?>
<student name = "Mahesh,Parashar"/>