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;
     }
 }

City

 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);
     }
 }

Province

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>

fun1

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>

fun2

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>

fun3

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>

fun4

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>

fun5