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。

XStream converters are the key components of the XStream library, which are responsible to convert an object to XML and vice versa. XStream provides numerous converters for common types such as primitives, String, File, Collections, arrays, and Dates.

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。

Let us use a SingleValueConvertor whose purpose is to convert an object into a single string. We will use SingleValueConvertor to write an object as attribute string.

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);
   }
}

Register a Converter

xstream.registerConverter(new NameConverter());

Example without Converter

让我们首先在 XStream 中测试没有转换器的代码。

Let us first test the code without converter in XStream.

在 C:\>XStream_WORKSPACE\com\tutorialspoint\xstream 中创建一个名为 XStreamTester 的 java 类文件。

Create a java class file named 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.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：

Compile the classes using javac compiler as follows −

C:\XStream_WORKSPACE\com\tutorialspoint\xstream>javac XStreamTester.java

现在，运行 XStreamTester 以查看结果 −

Now run the XStreamTester to see the result −

C:\XStream_WORKSPACE\com\tutorialspoint\xstream>java XStreamTester

验证输出如下所示 −

Verify the output as follows −

<?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。

Let us now test the code with converter in XStream.