XStream-----把JavaBean转换为xml的工具

1. 什么作用

　　可以把JavaBean转换为（序列化为）xml

2. XStream的jar包
　　核心JAR包：xstream-1.4.7.jar；
　　必须依赖包：xpp3_min-1.1.4c（XML Pull Parser，一款速度很快的XML解析器）；

3. 使用步骤
　　XStream xstream = new XStream();
　　String xmlStr = xstream.toXML(javabean);

4. 使用细节
　　别名：把类型对应的元素名修改了
　　　　xstream.alias("china", List.class)：让List类型生成的元素名为china
　　　　xstream.alias("province", Province.class)：让Province类型生成的元素名为province
　　使用为属性：默认类的成员，生成的是元素的子元素！我们希望让类的成员生成元素的属性
　　　　xstream.useAttributeFor(Province.class, "name")：把Province类的名为name成员，生成<province>元素的name属性
　　去除Collection类型的成名：我们只需要Collection的内容，而不希望Collection本身也生成一个元素
　　　　xstream.addImplicitCollection(Province.class, "cities")：让Province类的名为cities(它是List类型的，它的内容还会生成元素)的成名不生成元素
　　去除类的指定成名，让其不生成xml元素
　　　　xstream.omitField(City.class, "description")：在生成的xml中不会出现City类的名为description的对应的元素！

应用实例：

import java.util.ArrayList;
import java.util.List;
import org.junit.Test;
import com.thoughtworks.xstream.XStream;
/**
 * 演示XStream
 */
public class Demo1 {
    // 返回javabean集合
    public List<Province> getProinvceList() {
        Province p1 = new Province();
        p1.setName("北京");
        p1.addCity(new City("东城区", "DongChengQu"));
        p1.addCity(new City("昌平区", "ChangPingQu"));
        Province p2 = new Province();
        p2.setName("辽宁");
        p2.addCity(new City("沈阳", "shenYang"));
        p2.addCity(new City("葫芦岛", "huLuDao"));
        List<Province> provinceList = new ArrayList<Province>();
        provinceList.add(p1);
        provinceList.add(p2);
        return provinceList;
    }
    @Test
    public void fun1() {
        List<Province> proList = getProinvceList();
        /*
         * 创建XStream对象
         * 调用toXML把集合转换成xml字符串
         */
        XStream xstream = new XStream();
        String s = xstream.toXML(proList);
        System.out.println(s);
    }
    /*
     * 别名(alias)
     * 希望：
     * * 默认List类型对应<list>元素，希望让List类型对应<china>元素
     * * 默认Province类型对应<cn.itcast.demo1.Province>，希望让它对应<province>
     * * 默认City类型对应<cn.itcast.demo1.City>，希望它对应<city>元素
     */
    @Test
    public void fun2() {
        List<Province> proList = getProinvceList();
        XStream xstream = new XStream();
        /*
         * 给指定的类型指定别名
         */
        xstream.alias("china", List.class);//给List类型指定别名为china
        xstream.alias("province", Province.class);//给Province指定别名为province
        xstream.alias("city", City.class);//给City类型指定别名为city
        String s = xstream.toXML(proList);
        System.out.println(s);
    }
    /*
     * 默认javabean的属性都会生成子元素，而现在希望生成元素的属性
     */
    @Test
    public void fun3() {
        List<Province> proList = getProinvceList();
        XStream xstream = new XStream();
        xstream.alias("china", List.class);//给List类型指定别名为china
        xstream.alias("province", Province.class);//给Province指定别名为province
        xstream.alias("city", City.class);//给City类型指定别名为city
        /*
         * 把Province类型的name属性，生成<province>元素的属性
         */
        xstream.useAttributeFor(Province.class, "name");
        String s = xstream.toXML(proList);
        System.out.println(s);        
    }
    /*
     * 去除List类型的属性，只把list中的元素生成xml元素
     */
    @Test
    public void fun4() {
        List<Province> proList = getProinvceList();
        XStream xstream = new XStream();
        xstream.alias("china", List.class);//给List类型指定别名为china
        xstream.alias("province", Province.class);//给Province指定别名为province
        xstream.alias("city", City.class);//给City类型指定别名为city
        xstream.useAttributeFor(Province.class, "name");//把Province类型的name属性，生成<province>元素的属性
        /*
         * 去除<cities>这样的Collection类型的属性
         * 去除Provice类的名为cities的List类型的属性！
         */
        xstream.addImplicitCollection(Province.class, "cities");
        String s = xstream.toXML(proList);
        System.out.println(s);        
    }
    /*
     * 去除不想要的javabean属性
     * 就是让某引起javabean属性，不生成对应的xml元素！
     */
    @Test
    public void fun5() {
        List<Province> proList = getProinvceList();
        XStream xstream = new XStream();
        xstream.alias("china", List.class);//给List类型指定别名为china
        xstream.alias("province", Province.class);//给Province指定别名为province
        xstream.alias("city", City.class);//给City类型指定别名为city
        xstream.useAttributeFor(Province.class, "name");//把Province类型的name属性，生成<province>元素的属性
        xstream.addImplicitCollection(Province.class, "cities");//去除Provice类的名为cities的List类型的属性！
        /*
         * 让City类的，名为description属性不生成对应的xml元素
         */
        xstream.omitField(City.class, "description");
        String s = xstream.toXML(proList);
        System.out.println(s);        
    }
}

public class City {
    private String name;//市名
    private String description;//描述
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public String getDescription() {
        return description;
    }
    public void setDescription(String description) {
        this.description = description;
    }
    @Override
    public String toString() {
        return "City [name=" + name + ", description=" + description + "]";
    }
    public City() {
        super();
        // TODO Auto-generated constructor stub
    }
    public City(String name, String description) {
        super();
        this.name = name;
        this.description = description;
    }
}

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

public class Province {
    private String name;// 省名
    private List<City> cities = new ArrayList<City>();

    public String getName() {
        return name;
    }

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

    public List<City> getCities() {
        return cities;
    }

    public void setCities(List<City> cities) {
        this.cities = cities;
    }

    public void addCity(City city) {
        cities.add(city);
    }
}

fun1输出结果：

<list>
  <Province>
    <name>北京</name>
    <cities>
      <City>
        <name>东城区</name>
        <description>DongChengQu</description>
      </City>
      <City>
        <name>昌平区</name>
        <description>ChangPingQu</description>
      </City>
    </cities>
  </Province>
  <Province>
    <name>辽宁</name>
    <cities>
      <City>
        <name>沈阳</name>
        <description>shenYang</description>
      </City>
      <City>
        <name>葫芦岛</name>
        <description>huLuDao</description>
      </City>
    </cities>
  </Province>
</list>

fun2输出结果：

<china>
  <province>
    <name>北京</name>
    <cities>
      <city>
        <name>东城区</name>
        <description>DongChengQu</description>
      </city>
      <city>
        <name>昌平区</name>
        <description>ChangPingQu</description>
      </city>
    </cities>
  </province>
  <province>
    <name>辽宁</name>
    <cities>
      <city>
        <name>沈阳</name>
        <description>shenYang</description>
      </city>
      <city>
        <name>葫芦岛</name>
        <description>huLuDao</description>
      </city>
    </cities>
  </province>
</china>

fun3输出结果：

<china>
  <province name="北京">
    <cities>
      <city>
        <name>东城区</name>
        <description>DongChengQu</description>
      </city>
      <city>
        <name>昌平区</name>
        <description>ChangPingQu</description>
      </city>
    </cities>
  </province>
  <province name="辽宁">
    <cities>
      <city>
        <name>沈阳</name>
        <description>shenYang</description>
      </city>
      <city>
        <name>葫芦岛</name>
        <description>huLuDao</description>
      </city>
    </cities>
  </province>
</china>

fun4输出结果：

<china>
  <province name="北京">
    <city>
      <name>东城区</name>
      <description>DongChengQu</description>
    </city>
    <city>
      <name>昌平区</name>
      <description>ChangPingQu</description>
    </city>
  </province>
  <province name="辽宁">
    <city>
      <name>沈阳</name>
      <description>shenYang</description>
    </city>
    <city>
      <name>葫芦岛</name>
      <description>huLuDao</description>
    </city>
  </province>
</china>

fun5输出结果：

<china>
  <province name="北京">
    <city>
      <name>东城区</name>
    </city>
    <city>
      <name>昌平区</name>
    </city>
  </province>
  <province name="辽宁">
    <city>
      <name>沈阳</name>
    </city>
    <city>
      <name>葫芦岛</name>
    </city>
  </province>
</china>