Xstream 简明教程

Xstream - Quick Guide

XStream - Overview

XStream 是一个简单的基于 Java 的库，用于将 Java 对象序列化为 XML，反之亦然。

XStream is a simple Java-based library to serialize Java objects to XML and vice versa.

Features

Easy to use − XStream API provides a high-level facade to simplify common use cases.
No need to create mapping − XStream API provides default mapping for most of the objects to be serialized.
Performance − XStream is fast and is of low memory footprint, which is suitable for large object graphs or systems.
Clean XML − XStream produces clean and compact XML output that is easy to read.
Object modification not required − XStream serializes internal fields like private and final fields, and supports non-public and inner classes. Default constructor is not a mandatory requirement.
Full object graph support − XStream allows to maintain duplicate references encountered in the object-model and also supports circular references.
Customizable conversion strategies − Custom strategies can be registered in order to allow customization of a particular type to be represented as XML.
Security framework − XStream provides a fair control over unmarshalled types to prevent security issues with manipulated input.
Error messages − When an exception occurs due to malformed XML, it provides detailed diagnostics to fix the problem.
Alternative output format − XStream supports other output formats like JSON and morphing.

Common Uses

Transport − XML is a text representation of object and can be used to transport objects over the wire independent of the serialization / deserialization techniques used.
Persistence − Objects can be persisted as XML in databases and can be marshalled/unmarshalled as and when required.
Configuration − XML is self-explanatory and is heavily used to define configurations. Objects can also be used for configuration purpose after converting them to XML representation.
Unit Tests − XStream API is JUnit compatible and can be used to enhance unit testing of application modules.

XStream - Environment Setup

在本章，我们将讨论为 Java 设置宜人环境的事物的不同方面。

In this chapter, we will discuss on the different aspects of setting up a congenial environment for Java.

Local Environment Setup

如果您想为 Java 编程语言设置您的环境，那么本部分将说明如何在计算机上下载和设置 Java。请按照下列步骤设置您的 Java 环境。

If you want to set up your environment for Java programming language, then this section explains how to download and set up Java on your machine. Please follow the steps given below to set up you Java environment.

Java SE 可以从此链接免费下载：

Java SE can be downloaded for free from the link −

Download Java 。

Download Java.

按照说明下载 Java 并运行 .exe 以在计算机上安装 Java。在您的计算机上安装 Java 后，您需要设置环境变量来指向正确的安装目录：

Follow the instructions to download Java and run the .exe to install Java on your machine. Once you have installed Java on your machine, you would need to set the environment variables to point to correct installation directories −

Setting Up the Path for Windows 2000/XP

假设你已将 Java 安装在 c:\Program Files\java\jdk 目录中 −

Assuming you have installed Java in c:\Program Files\java\jdk directory −

Right-click on 'My Computer' and select 'Properties'.
Click the 'Environment variables' button under the 'Advanced' tab.
Alter the 'Path' variable so that it also contains the path to the Java executable. For example, if the path is currently set to 'C:\WINDOWS\SYSTEM32', then change your path to read 'C:\WINDOWS\SYSTEM32;c:\Program Files\java\jdk\bin'.

Setting Up the Path for Windows 95/98/ME

假设你已将 Java 安装在 c:\Program Files\java\jdk 目录中 −

Assuming you have installed Java in c:\Program Files\java\jdk directory −

Edit the 'C:\autoexec.bat' file and add the following line at the end − 'SET PATH = %PATH%;C:\Program Files\java\jdk\bin'

Setting Up the Path for Linux, UNIX, Solaris, FreeBSD

环境变量 PATH 应设置为指向已安装 Java 二进制文件的位置。如果你在这方面遇到问题，请参阅 shell 文档。

Environment variable PATH should be set to point to where the Java binaries have been installed. Refer to your shell documentation if you have trouble doing this.

例如，如果你使用 bash 作为 shell，则需要在“‘.bashrc: export PATH=/path/to/java:$PATH’”的末尾添加以下行

For example, if you use bash as your shell, then you would add the following line at the end of your '.bashrc: export PATH=/path/to/java:$PATH'

Popular Java Editors

要编写 Java 程序，您需要一个文本编辑器。市场上有更加复杂的 IDE。但是现在，您可以考虑以下一项：

To write Java programs, you will need a text editor. There are even more sophisticated IDEs available in the market. But for now, you can consider one of the following −

Notepad − On Windows, you can use any simple text editor like Notepad (Recommended for this tutorial) or TextPad.
Netbeans − It is a Java IDE that is free and can be downloaded from https://www.netbeans.org/index.html.
Eclipse − It is also a Java IDE developed by the eclipse open-source community and can be downloaded from https://www.eclipse.org/.

Download XStream Archive

从 XStream download page 下载 XStream jar 文件的最新版本。在本教程的编写时，我们已经下载了 xstream-1.4.18.jar 并将其复制到 C:\>XStream 文件夹。

Download the latest version of XStream jar file from XStream download page. At the time of writing this tutorial, we have downloaded xstream-1.4.18.jar and copied it into C:\>XStream folder.

Archive name

Windows

xstream-1.4.18.jar

Linux

xstream-1.4.18.jar

Mac

xstream-1.4.18.jar

Set XStream Environment

设置 XStream_HOME 环境变量，以指向存储在计算机上的 xstream jar 的基本目录位置。以下表格显示了如何在 Windows、Linux 和 Mac 上设置 XStream 环境，假设我们在 XStream 文件夹中解压了 xstream-1.4.18.jar。

Set the XStream_HOME environment variable to point to the base directory location where xstream jar is stored on your machine. The following table shows how to set the XStream environment on Windows, Linux, and Mac, assuming we’ve extracted xstream-1.4.18.jar in the XStream folder.

Sr.No.

OS & Description

Windows Set the environment variable XStream_HOME to C:\XStream

Linux export XStream_HOME=/usr/local/XStream

Mac export XStream_HOME=/Library/XStream

Set CLASSPATH Variable

设置 CLASSPATH 环境变量来指向 XStream jar 位置。以下表格演示了如何在 Windows、Linux 和 Mac 系统上设置 CLASSPATH 变量，假设我们已将 xstream-1.4.18.jar 存储在 XStream 文件夹中。

Set the CLASSPATH environment variable to point to the XStream jar location. The following table shows how to set the CLASSPATH variable on Windows, Linux, and Mac system, assuming we’ve stored xstream-1.4.18.jar in the XStream folder.

Sr.No.

OS & Description

Windows Set the environment variable CLASSPATH to %CLASSPATH%;%XStream_HOME%\xstream-1.4.18.jar;

Linux export CLASSPATH=$CLASSPATH:$XStream_HOME/xstream-1.4.18.jar;

Mac export CLASSPATH=$CLASSPATH:$XStream_HOME/xstream-1.4.18.jar;

XStream - First Application

在深入了解 XStream 库之前，让我们看一个应用程序的实际使用情况。在此示例中，我们创建了 Student 和 Address 类。我们将创建一个学生对象，然后将其序列化为 XML 字符串。然后对相同的 XML 字符串进行反序列化，以获取回学生对象。

Before going into the details of the XStream library, let us see an application in action. In this example, we’ve created Student and Address classes. We will create a student object and then serialize it to an XML String. Then de-serialize the same XML string to obtain the student object back.

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

Create a java class file named XStreamTester in C:\>XStream_WORKSPACE.

File: XStreamTester.java

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.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();

      //Object to XML Conversion
      String xml = xstream.toXML(student);
      System.out.println(formatXml(xml));

      //XML to Object Conversion
      Student student1 = (Student)xstream.fromXML(xml);
      System.out.println(student1);
   }

   private Student getStudentDetails() {

      Student student = new Student();
      student.setFirstName("Mahesh");
      student.setLastName("Parashar");
      student.setRollNo(1);
      student.setClassName("1st");

      Address address = new Address();
      address.setArea("H.No. 16/3, Preet Vihar.");
      address.setCity("Delhi");
      address.setState("Delhi");
      address.setCountry("India");
      address.setPincode(110012);

      student.setAddress(address);
      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;
      }
   }
}

class Student {
   private int rollNo;
   private String firstName;
   private String lastName;
   private String className;
   private Address address;

   public String getFirstName() {
      return firstName;
   }

   public void setFirstName(String firstName) {
      this.firstName = firstName;
   }

   public String getLastName() {
      return lastName;
   }

   public void setLastName(String lastName) {
      this.lastName = lastName;
   }

   public int getRollNo() {
      return rollNo;
   }

   public void setRollNo(int rollNo) {
      this.rollNo = rollNo;
   }

   public String getClassName() {
      return className;
   }

   public void setClassName(String className) {
      this.className = className;
   }

   public Address getAddress() {
      return address;
   }

   public void setAddress(Address address) {
      this.address = address;
   }

   public String toString() {
      StringBuilder stringBuilder = new StringBuilder();

      stringBuilder.append("Student [ ");
      stringBuilder.append("\nfirstName: ");
      stringBuilder.append(firstName);
      stringBuilder.append("\nlastName: ");
      stringBuilder.append(lastName);
      stringBuilder.append("\nrollNo: ");
      stringBuilder.append(rollNo);
      stringBuilder.append("\nclassName: ");
      stringBuilder.append(className);
      stringBuilder.append("\naddress: ");
      stringBuilder.append(address);
      stringBuilder.append(" ]");

      return stringBuilder.toString();
   }
}

class Address {
   private String area;
   private String city;
   private String state;
   private String country;
   private int pincode;

   public String getArea() {
      return area;
   }

   public void setArea(String area) {
      this.area = area;
   }

   public String getCity() {
      return city;
   }

   public void setCity(String city) {
      this.city = city;
   }

   public String getState() {
      return state;
   }

   public void setState(String state) {
      this.state = state;
   }

   public String getCountry() {
      return country;
   }

   public void setCountry(String country) {
      this.country = country;
   }

   public int getPincode() {
      return pincode;
   }

   public void setPincode(int pincode) {
      this.pincode = pincode;
   }

   public String toString() {

      StringBuilder stringBuilder = new StringBuilder();

      stringBuilder.append("\nAddress [ ");
      stringBuilder.append("\narea: ");
      stringBuilder.append(area);
      stringBuilder.append("\ncity: ");
      stringBuilder.append(city);
      stringBuilder.append("\nstate: ");
      stringBuilder.append(state);
      stringBuilder.append("\ncountry: ");
      stringBuilder.append(country);
      stringBuilder.append("\npincode: ");
      stringBuilder.append(pincode);
      stringBuilder.append(" ]");

      return stringBuilder.toString();
   }
}

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>javac XStreamTester.java

现在，运行 XStreamTester 以查看结果 −

Now run the XStreamTester to see the result −

C:\XStream_WORKSPACE>java XStreamTester

Verify the output as follows

<?xml version = "1.0" encoding = "UTF-8"?>
<Student>
   <firstName>Mahesh</firstName>
   <lastName>Parashar</lastName>
   <rollNo>1</rollNo>
   <className>1st</className>
   <address>
      <area>H.No. 16/3, Preet Vihar.</area>
      <city>Delhi</city>
      <state>Delhi</state>
      <country>India</country>
      <pincode>110012</pincode>
   </address>
</Student>

Student [
   firstName: Mahesh
   lastName: Parashar
   rollNo: 1
   className: 1st
   address:
   Address [
      area: H.No. 16/3, Preet Vihar.
      city: Delhi
      state: Delhi
      country: India
      pincode: 110012
   ]
]

Steps to Remember

以下是需要考虑的重要步骤。

Following are the important steps to be considered here.

Step 1 − Create an XStream Object

通过传递 StaxDriver 创建一个 XStream 对象。StaxDriver 使用 Stax pull 解析器（在 Java 6 中可用），是一种快速的 xml 解析器。

Create an XStream object by passing it a StaxDriver. StaxDriver uses Stax pull parser (available from java 6) and is a fast xml parser.

XStream xstream = new XStream(new StaxDriver());

Step 2 − Serialize the Object to XML

使用 toXML() 方法来获取对象的 XML 字符串表示形式。

Use toXML() method to get the XML string representation of the object.

//Object to XML Conversion
String xml = xstream.toXML(student);

Step 3 − De-serialize XML to Get the Object

使用 fromXML() 方法从 XML 中获取对象。

Use fromXML() method to get the object from the XML.

//XML to Object Conversion
Student student1 = (Student)xstream.fromXML(xml);

XStream - Aliasing

别名化是在 XStream 中定制生成的 XML 或使用特定格式化 XML 的一种技术。我们假设是要使用以下 XML 格式来序列化/反序列化 Student 对象。

Aliasing is a technique to customize the generated XML or to use a particular formatted XML using XStream. Let’s suppose the following XML format is to be used to serialize/de-serialize the Student object.

<student name = "Suresh">
   <note>
      <title>first</title>
      <description>My first assignment.</description>
   </note>

   <note>
      <title>second</title>
      <description>My second assignment.</description>
   </note>
</student>

基于上面的 XML 格式，我们来创建模型类。

Based on the above XML format, let’s create model classes.

class Student {
   private String studentName;
   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;
   }
}

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;
   }
}

让我们使用 XStream 测试上述对象的序列化。

Let’s test the above objects serialization using 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 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.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();

      //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."));

      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;
      }
   }
}

class Student {
   private String studentName;
   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;
   }
}

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;
   }
}

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"?>
<com.tutorialspoint.xstream.Student>
   <studentName>Mahesh</studentName>
   <notes>
      <com.tutorialspoint.xstream.Note>
         <title>first</title>
         <description>My first assignment.</description>
      </com.tutorialspoint.xstream.Note>

      <com.tutorialspoint.xstream.Note>
         <title>second</title>
         <description>My Second assignment.</description>
     </com.tutorialspoint.xstream.Note>
   </notes>
</com.tutorialspoint.xstream.Student>

在上述结果中，Student 对象名称是完全限定的。要将其替换为 student 标签，请按照下一部分操作。

In the above result, the Student object name is fully qualified. To replace it as student tag, follow the next section.

XStream - Annotations

XStream 支持注释，类似于自动配置，而不是编码。在上节中，我们在代码中看到了以下配置。

XStream supports annotations similarly like automatic configuration instead of coding. In the previous chapter, we’ve seen the following configurations in code.

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");

下面的代码片段说明了使用注释以更简单的方式完成相同工作的用法。

The following code snippet illustrates the use of annotations to do the same work in a much easier way.

@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;
}

让我们使用 XStream 测试上述注释。

Let us test the above annotation using 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 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;
   }
}

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 = "Mahesh">
   <note>
      <title>first</title>
      <description>My first assignment.</description>
   </note>

   <note>
      <title>second</title>
      <description>My Second assignment.</description>
   </note>
</student>

为了指示 XStream 框架处理注释，您需要在序列化 XML 之前添加以下命令。

In order to instruct the XStream framework to process annotation, you need to add the following command before serializing xml.

xstream.processAnnotations(Student.class);

或

xstream.autodetectAnnotations(true);

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.

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.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：

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 = "Mahesh,Parashar"/>

Custom Converter

XStream - Object Streams

XStream 提供了 java.io.ObjectInputStream 和 java.io.ObjectOutputStream 的替代实现，以便可以从 XML 序列化或反序列化对象流。当要处理大量对象集时，一次只保留一个对象在内存中时，这特别有用。

XStream provides alternative implementations of java.io.ObjectInputStream and java.io.ObjectOutputStream so that streams of objects can be serialized or deserialized from XML. This is particularly useful when large sets of objects are to be processed, keeping one object in memory at a time.

Syntax: createObjectOutputStream()

ObjectOutputStream objectOutputStream = xstream.createObjectOutputStream(
   new FileOutputStream("test.txt"));

Syntax: createObjectInputStream()

ObjectInputStream objectInputStream = xstream.createObjectInputStream(
   new FileInputStream("test.txt"));

现在让我们用 XStream 中的对象流测试代码。

Let us now test the code with object streams 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.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;

import com.thoughtworks.xstream.XStream;
import com.thoughtworks.xstream.annotations.XStreamAlias;
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());

      xstream.autodetectAnnotations(true);

      Student student1 = new Student("Mahesh","Parashar");
      Student student2 = new Student("Suresh","Kalra");
      Student student3 = new Student("Ramesh","Kumar");
      Student student4 = new Student("Naresh","Sharma");

      try {

         ObjectOutputStream objectOutputStream = xstream.createObjectOutputStream(
            new FileOutputStream("test.txt"));

         objectOutputStream.writeObject(student1);
         objectOutputStream.writeObject(student2);
         objectOutputStream.writeObject(student3);
         objectOutputStream.writeObject(student4);
         objectOutputStream.writeObject("Hello World");

         objectOutputStream.close();

         ObjectInputStream objectInputStream = xstream.createObjectInputStream(
            new FileInputStream("test.txt"));

         Student student5 = (Student)objectInputStream.readObject();
         Student student6 = (Student)objectInputStream.readObject();
         Student student7 = (Student)objectInputStream.readObject();
         Student student8 = (Student)objectInputStream.readObject();

         String text = (String)objectInputStream.readObject();

         System.out.println(student5);
         System.out.println(student6);
         System.out.println(student7);
         System.out.println(student8);
         System.out.println(text);

      } catch (IOException e) {
         e.printStackTrace();

      } catch (ClassNotFoundException e) {
         e.printStackTrace();
      }
   }
}

@XStreamAlias("student")
class Student {

   private String firstName;
   private String lastName;

   public Student(String firstName, String lastName) {
      this.firstName = firstName;
      this.lastName = lastName;
   }

   public String getFirstName() {
      return firstName;
   }

   public String getLastName() {
      return lastName;
   }

   public String toString() {
      return "Student [ firstName: "+firstName+", lastName: "+ 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 −

Student [ firstName: Mahesh, lastName: Parashar ]
Student [ firstName: Suresh, lastName: Kalra ]
Student [ firstName: Ramesh, lastName: Kumar ]
Student [ firstName: Naresh, lastName: Sharma ]
Hello World

查看 C:\>XStream_WORKSPACE\com\tutorialspoint\xstream 文件夹中的 test.txt 的内容。

Look at the content of the test.txt present at C:\>XStream_WORKSPACE\com\tutorialspoint\xstream folder.

<?xml version = "1.0" ?>
<object-stream>
   <student>
      <firstName>Mahesh</firstName>
      <lastName>Parashar</lastName>
   </student>

   <student>
      <firstName>Suresh</firstName>
      <lastName>Kalra</lastName>
   </student>

   <student>
      <firstName>Ramesh</firstName>
      <lastName>Kumar</lastName>
   </student>

   <student>
      <firstName>Naresh</firstName>
      <lastName>Sharma</lastName>
   </student>
   <string>Hello World</string>
</object-stream>

XStream - Writing JSON using XStream

XStream 通过使用适当的驱动程序初始化 XStream 对象来支持 JSON。XStream 目前支持 JettisonMappedXmlDriver 和 JsonHierarchicalStreamDriver。

XStream supports JSON by initializing XStream object with an appropriate driver. XStream currently supports JettisonMappedXmlDriver and JsonHierarchicalStreamDriver.

现在让我们用 XStream 中的 json 处理测试代码。

Let us now test the code with json handling 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.Writer;

import com.thoughtworks.xstream.XStream;
import com.thoughtworks.xstream.annotations.XStreamAlias;
import com.thoughtworks.xstream.io.HierarchicalStreamWriter;
import com.thoughtworks.xstream.io.json.JsonHierarchicalStreamDriver;
import com.thoughtworks.xstream.io.json.JsonWriter;

public class XStreamTester {

   public static void main(String args[]) {

      XStreamTester tester = new XStreamTester();
      XStream xstream = new XStream(new JsonHierarchicalStreamDriver() {

         public HierarchicalStreamWriter createWriter(Writer writer) {
            return new JsonWriter(writer, JsonWriter.DROP_ROOT_MODE);
         }
      });

      Student student = new Student("Mahesh","Parashar");

      xstream.setMode(XStream.NO_REFERENCES);
      xstream.alias("student", Student.class);

      System.out.println(xstream.toXML(student));
   }
}

@XStreamAlias("student")
class Student {

   private String firstName;
   private String lastName;

   public Student(String firstName, String lastName) {
      this.firstName = firstName;
      this.lastName = lastName;
   }

   public String getFirstName() {
      return firstName;
   }

   public String getLastName() {
      return lastName;
   }

   public String toString() {
      return "Student [ firstName: "+firstName+", lastName: "+ 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 −

{
   "firstName": "Mahesh",
   "lastName": "Parashar"
}