JAVA Bean和XML之间的相互转换 - XStream简单入门

JAVA Bean和XML之间的相互转换 - XStream简单入门

• 背景介绍
• XStream的简介
• 注解简介
• 应用实例

背景介绍

我们在工作中经常 遇到文件解析为数据或者数据转化为xml文件的情况,之前我一直采用的方式都是手动的来解析或拼接XML文件,这个做法固然是可以的,但是代码部分会显得非常臃肿,所以就查找了相关的资料,发现了一个名为XStream的类库可以做这件事,下面我们来看一下.

XStream的简介

官网地址:http://x-stream.github.io/

从官网介绍我们能看到以下几个特性:

• 易用
• 不需要Mapping文件

  不需要额外提供Mapping文件即可完成映射

• 高性能

  高速且低内存消耗

• 整洁的XML文件

  生成的XML的相当简洁

• 不需要修改对象

  可以序列化private修饰的属性,且不需要提供get/set方法

• 完整的对象结构支持

  支持循环引用情况下的输出

• 兼容其他的XML API

  可以对任何的树形结构进行序列化或反序列化

• 可以自定义的转换策略

  可以通过策略的注册,允许自定义特定类型的转化为XML的样式

• 安全的框架

  对未分组的类型进行精细化的控制,防止输入错误而导致的安全问题

• 良好的异常反馈

  当XML文件格式错误的时候,能够提供诊断信息帮助处理

• 多样的输出格式

  不止是XML他还支持JSON及其变种

注解简介

从XStream的官网我们了解到,XStream不需要Mapping文件就能完成JavaBean和XML之间的转变,但大部分时候我们需要对生成的XML文件进行定制,name我们需要了解XStream提供的注解

注解	作用	适用范围
@XStreamAlias	设置别名	类或属性
@XStreamImplicit	忽略属性	集合类型的属性
@XStreamAsAttribute	将JavaBean转换成节点属性	属性
@XStreamOmitField	忽略属性	属性
@XStreamConverter	注入转换器	类

应用实例

首先在我们的项目中加入依赖:

<dependency>
    <groupId>com.thoughtworks.xstream</groupId>
    <artifactId>xstream</artifactId>
    <version>1.4.11.1</version>
</dependency>

假定环境为Computer和CPU两个类:

public class Computer implements Serializable {

    private static final long serialVersionUID = 567119860357020081L;

    private String name;
    private String brand;
    private List<CPU> processors;

    public Computer() {
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getBrand() {
        return brand;
    }

    public void setBrand(String brand) {
        this.brand = brand;
    }

    public List<CPU> getProcessors() {
        return processors;
    }

    public void setProcessors(List<CPU> processors) {
        this.processors = processors;
    }
}

public class CPU implements Serializable {

    private static final long serialVersionUID = -718438777162957779L;

    private String name;
    private String generation;

    public CPU() {
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getGeneration() {
        return generation;
    }

    public void setGeneration(String generation) {
        this.generation = generation;
    }
}

写一个测试方法:

import com.hykj.facheck.entity.CPU;
import com.hykj.facheck.entity.Computer;
import com.thoughtworks.xstream.XStream;
import com.thoughtworks.xstream.io.xml.DomDriver;

import java.util.ArrayList;
import java.util.List;

public class XStreamTest {

    public static void main(String[] args) {

        List<CPU> cpuList = new ArrayList<>();
        CPU cpu1 = new CPU();
        cpu1.setGeneration("8-i5-K");
        cpu1.setName("第一个");
        cpuList.add(cpu1);

        CPU cpu2 = new CPU();
        cpu2.setGeneration("8-i5-U");
        cpu2.setName("第二个");
        cpuList.add(cpu2);

        Computer computer = new Computer();
        computer.setBrand("huawei");
        computer.setName("wej-laptop");
        computer.setProcessors(cpuList);

        XStream xstream = new XStream(new DomDriver());
        xstream.ignoreUnknownElements();
        xstream.processAnnotations(Computer.class);

        //javabean to xml
        String xml = xstream.toXML(computer);
        System.out.println(xml);

        //xml to javabean
        Computer computerFromXml = (Computer) xstream.fromXML(xml);

        System.out.println(computer.getName());

    }
}

运行程序,控制台打结果如下:

Connected to the target VM, address: '127.0.0.1:53977', transport: 'socket'
<com.hykj.facheck.entity.Computer>
  <name>wej-laptop</name>
  <brand>huawei</brand>
  <processors>
    <com.hykj.facheck.entity.CPU>
      <name>第一个</name>
      <generation>8-i5-K</generation>
    </com.hykj.facheck.entity.CPU>
    <com.hykj.facheck.entity.CPU>
      <name>第二个</name>
      <generation>8-i5-U</generation>
    </com.hykj.facheck.entity.CPU>
  </processors>
</com.hykj.facheck.entity.Computer>
Security framework of XStream not initialized, XStream is probably vulnerable.
wej-laptop
Disconnected from the target VM, address: '127.0.0.1:53977', transport: 'socket'

Process finished with exit code 0

也就是说这样就可以用了,很棒棒
但是这个XML和我们的需求不太一样,我们加上注解,代码变成了这样:

import com.thoughtworks.xstream.annotations.XStreamAlias;

import java.io.Serializable;
import java.util.List;

@XStreamAlias("my")
public class Computer implements Serializable {

    private static final long serialVersionUID = 567119860357020081L;

    private String name;
    private String brand;
    @XStreamAlias("cpuList")
    private List<CPU> processors;

    public Computer() {
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getBrand() {
        return brand;
    }

    public void setBrand(String brand) {
        this.brand = brand;
    }

    public List<CPU> getProcessors() {
        return processors;
    }

    public void setProcessors(List<CPU> processors) {
        this.processors = processors;
    }
}

import com.thoughtworks.xstream.annotations.XStreamAlias;

import java.io.Serializable;

@XStreamAlias("oneCpu")
public class CPU implements Serializable {

    private static final long serialVersionUID = -718438777162957779L;

    private String name;
    private String generation;

    public CPU() {
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getGeneration() {
        return generation;
    }

    public void setGeneration(String generation) {
        this.generation = generation;
    }
}

测试方法不变,结果如下:

Connected to the target VM, address: '127.0.0.1:54181', transport: 'socket'
<my>
  <name>wej-laptop</name>
  <brand>huawei</brand>
  <cpuList>
    <oneCpu>
      <name>第一个</name>
      <generation>8-i5-K</generation>
    </oneCpu>
    <oneCpu>
      <name>第二个</name>
      <generation>8-i5-U</generation>
    </oneCpu>
  </cpuList>
</my>
Security framework of XStream not initialized, XStream is probably vulnerable.
wej-laptop
Disconnected from the target VM, address: '127.0.0.1:54181', transport: 'socket'

Process finished with exit code 0

这个XML就很舒服啦.
我们载试一下循环引用的情况吧,代码如下:

import com.thoughtworks.xstream.annotations.XStreamAlias;

import java.io.Serializable;
import java.util.List;

@XStreamAlias("my")
public class Computer implements Serializable {

    private static final long serialVersionUID = 567119860357020081L;

    private String name;
    private String brand;
    @XStreamAlias("cpuList")
    private List<CPU> processors;

    public Computer() {
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getBrand() {
        return brand;
    }

    public void setBrand(String brand) {
        this.brand = brand;
    }

    public List<CPU> getProcessors() {
        return processors;
    }

    public void setProcessors(List<CPU> processors) {
        this.processors = processors;
    }
}

import com.thoughtworks.xstream.annotations.XStreamAlias;

import java.io.Serializable;

@XStreamAlias("oneCpu")
public class CPU implements Serializable {

    private static final long serialVersionUID = -718438777162957779L;

    private String name;
    private String generation;
    private Computer computer;

    public CPU() {
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getGeneration() {
        return generation;
    }

    public void setGeneration(String generation) {
        this.generation = generation;
    }

    public Computer getComputer() {
        return computer;
    }

    public void setComputer(Computer computer) {
        this.computer = computer;
    }
}

import com.thoughtworks.xstream.XStream;
import com.thoughtworks.xstream.io.xml.DomDriver;

import java.util.ArrayList;
import java.util.List;

public class XStreamTest {

    public static void main(String[] args) {

        Computer computer = new Computer();
        computer.setBrand("huawei");
        computer.setName("wej-laptop");

        List<CPU> cpuList = new ArrayList<>();
        CPU cpu1 = new CPU();
        cpu1.setGeneration("8-i5-K");
        cpu1.setName("第一个");
        cpu1.setComputer(computer);
        cpuList.add(cpu1);

        CPU cpu2 = new CPU();
        cpu2.setGeneration("8-i5-U");
        cpu2.setName("第二个");
        cpuList.add(cpu2);
        cpu1.setComputer(computer);
        computer.setProcessors(cpuList);

        XStream xstream = new XStream(new DomDriver());
        xstream.ignoreUnknownElements();
        xstream.processAnnotations(Computer.class);

        //javabean to xml
        String xml = xstream.toXML(computer);
        System.out.println(xml);

        //xml to javabean
        Computer computerFromXml = (Computer) xstream.fromXML(xml);

        System.out.println(computer.getName());

    }
}

运行一下,先查看是否构成循环引用:

确认有循环引用,继续运行代码,控制台打印如下:

Connected to the target VM, address: '127.0.0.1:54221', transport: 'socket'
<my>
  <name>wej-laptop</name>
  <brand>huawei</brand>
  <cpuList>
    <oneCpu>
      <name>第一个</name>
      <generation>8-i5-K</generation>
      <computer reference="../../.."/>
    </oneCpu>
    <oneCpu>
      <name>第二个</name>
      <generation>8-i5-U</generation>
    </oneCpu>
  </cpuList>
</my>
Security framework of XStream not initialized, XStream is probably vulnerable.
wej-laptop
Disconnected from the target VM, address: '127.0.0.1:54221', transport: 'socket'

Process finished with exit code 0

可以看到生成的XML中采用类似路径的reference属性来标识了位置,实际上我们一般是需要忽略这个属性的,采用@XStreamOmitField注解就好了.