XStream的简单使用

XStream

XStream是一个java对象和xml相互转换的工具

1. 创建XStream对象：XStream stream = new XStream()
2. Java对象转换成xml：stream .toXML(...)
3. xml转换成Java对象：stream .fromXML(...)

转换装配方式

1. DomDriver方式：new XStream(new DomDriver());
2. StaxDriver方式：new XStream(new StaxDriver());
3. XppDriver，默认方式，但是xpp方式经常解析xml会出错

Java转XML

1.导入jar

1. xmlpull_1_0_5.jar
2. xpp3_min-1.1.4c.jar
3. xstream-1.4.4.jar

2.测试类

 public class TestC {
     /**
      * 控制台：
      *         xml:
      *         <list>
      *             <city id="1">
      *             <pid>1</pid>
      *             <cname>合肥</cname>
      *          </city>
      *          <city id="2">
      *            <pid>1</pid>
      *            <cname>芜湖</cname>
      *          </city>
      *          <city id="3">
      *            <pid>1</pid>
      *            <cname>蚌埠</cname>
      *          </city>
      *          <city id="4">
      *            <pid>1</pid>
      *            <cname>淮北</cname>
      *          </city>
      *        </list>
      */
     @Test
     public void test1() {//java--->xml
         List<City> list = new ArrayList<>();
         list.add(new City(1,1,"合肥"));
         list.add(new City(2,1,"芜湖"));
         list.add(new City(3,1,"蚌埠"));
         list.add(new City(4,1,"淮北"));

         XStream stream = new XStream(new DomDriver());//DomDriver装配方式

         //设置id为City.class标签的属性<com.qf.pojo.City id="">
         stream.useAttributeFor(City.class, "id");

         //使用别名city代替City.class    <com.qf.pojo.City> ----> <city>
         stream.alias("city", City.class);

         //list转换为xml字符串
         String xml = stream.toXML(list);

         System.out.println("xml:\n"+xml);
     }

     /**
      * 控制台：com.thoughtworks.xstream.io.StreamException: Cannot create XmlPullParser
      */
     @Test
     public void test2() {//xml--->java
         List<City> list = new ArrayList<>();
         list.add(new City(1,1,"合肥"));
         list.add(new City(2,1,"芜湖"));
         list.add(new City(3,1,"蚌埠"));
         list.add(new City(4,1,"淮北"));

         //默认装配方式,使用的其实是XppDriver
         XStream stream = new XStream();
         //会抛出异常：com.thoughtworks.xstream.io.StreamException: Cannot create XmlPullParser
         String xml = stream.toXML(list);

         stream.processAnnotations(List.class);
         Object fromXML = stream.fromXML(xml);
         List city = List.class.cast(fromXML);
         System.out.println("city:\n"+city);
     }

     /**
      * 控制台：
      * city:
      * [City [id=1, pid=1, cname=合肥], City [id=2, pid=1, cname=芜湖], City [id=3, pid=1, cname=蚌埠], City [id=4, pid=1, cname=淮北]]
      */
     @Test
     public void test3() {//xml--->java
         List<City> list = new ArrayList<>();
         list.add(new City(1,1,"合肥"));
         list.add(new City(2,1,"芜湖"));
         list.add(new City(3,1,"蚌埠"));
         list.add(new City(4,1,"淮北"));

         XStream stream = new XStream(new DomDriver());
         String xml = stream.toXML(list);

         stream.processAnnotations(List.class);
         Object fromXML = stream.fromXML(xml);
         List city = List.class.cast(fromXML);
         System.out.println("city:\n"+city);
     }
 }

xpp装配方式创建XStream对象解析xml经常会出错：com.thoughtworks.xstream.io.StreamException: Cannot create XmlPullParser

Java转JSON

xStream对JSON也有非常好的支持，它提供了2个模型驱动可以完成Java对象到JSON的相互转换

1.使用JettisonMappedXmlDriver驱动，可以将Java对象转换成json，也可以将json转换为Java对象，需要添加jettison.jar

 package com.qf.Test;

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

 import org.junit.Test;

 import com.qf.pojo.City;
 import com.thoughtworks.xstream.XStream;
 import com.thoughtworks.xstream.io.json.JettisonMappedXmlDriver;

 /**
  * 测试用JettisonMappedXmlDriver实现与JSON的互相转换
  * @author 14505
  *
  */
 public class TestJson {
     /**
      * Java--->json
      * 控制台输出：
      *         {"list":[{"com.qf.pojo.City":[{"id":1,"pid":1,"cname":"合肥"},{"id":2,"pid":1,"cname":"芜湖"}]}]}
      */
     @Test
     public void test1() {
         List<City> list = new ArrayList<>();
         list.add(new City(1,1,"合肥"));
         list.add(new City(2,1,"芜湖"));

         XStream stream = new XStream(new JettisonMappedXmlDriver());

         stream.setMode(XStream.NO_REFERENCES);

         //list转换为Json字符串
         String json = stream.toXML(list);

         System.out.println(json);
     }

     /**
      * json--->Java
      * 控制台输出：
      *         [[City [id=1, pid=1, cname=合肥], City [id=2, pid=1, cname=芜湖]]]
      */
     @Test
     public void test2() {
         List<City> list = new ArrayList<>();
         list.add(new City(1,1,"合肥"));
         list.add(new City(2,1,"芜湖"));

         XStream stream = new XStream(new JettisonMappedXmlDriver());

         stream.setMode(XStream.NO_REFERENCES);

         //list转换为Json字符串
         String json = stream.toXML(list);

         Object obj = stream.fromXML(json);

         System.out.println(obj);
     }
 }

2.使用JsonHierarchicalStreamDriver驱动，只能将Java对象转换成json

 package com.qf.Test;

 import java.io.Writer;
 import java.util.HashMap;
 import java.util.Map;

 import org.junit.Test;

 import com.qf.pojo.City;
 import com.thoughtworks.xstream.XStream;
 import com.thoughtworks.xstream.io.HierarchicalStreamWriter;
 import com.thoughtworks.xstream.io.json.JsonHierarchicalStreamDriver;
 import com.thoughtworks.xstream.io.json.JsonWriter;

 /**
  * 测试用JsonHierarchicalStreamDriver实现java转换成JSON
  * @author 14505
  *
  */
 public class TestJson {
     /**
      * Java--->json
      * 控制台输出：
      *         JSON：{"map": [
      *              [
      *                "city1",
      *                {
      *                  "id": 1,
      *                  "pid": 1,
      *                  "cname": "合肥"
      *                }
      *              ],
      *              [
      *                "city2",
      *                {
      *                  "id": 2,
      *                  "pid": 1,
      *                  "cname": "芜湖"
      *                }
      *              ]
      *            ]}
      *默认会给转换后的对象添加一个根节点，可以通过重写JsonHierarchicalStreamDriver的createWriter方法进行设置删除额外添加的根节点
      */
     @Test
     public void test1() {
         City city1 = new City(1,1,"合肥");
         City city2 = new City(2,1,"芜湖");
         Map<String, City> map = new HashMap<>();
         map.put("city1", city1);
         map.put("city2", city2);

         XStream xStreamJ = new XStream(new JsonHierarchicalStreamDriver());

         String json = xStreamJ.toXML(map);
         System.out.println("JSON："+ json);
     }

     /**
      * Java--->json
      * 控制台输出：
      *         {"map": [
      *              [
      *                "city1",
      *                {
      *                  "id": 1,
      *                  "pid": 1,
      *                  "cname": "合肥"
      *                }
      *              ],
      *              [
      *                "city2",
      *                {
      *                  "id": 2,
      *                  "pid": 1,
      *                  "cname": "芜湖"
      *                }
      *              ]
      *            ]
      *        }
      */
     @Test
     public void test2() {
         City city1 = new City(1,1,"合肥");
         City city2 = new City(2,1,"芜湖");
         Map<String, City> map = new HashMap<>();
         map.put("city1", city1);
         map.put("city2", city2);

         //默认会给转换后的json添加一个根节点JSON,重写JsonHierarchicalStreamDriver的createWriter方法可以设置删除根节点
         XStream xStreamJ = new XStream(new JsonHierarchicalStreamDriver() {
             @Override
             public HierarchicalStreamWriter createWriter(Writer out) {
                 return new JsonWriter(out,JsonWriter.DROP_ROOT_MODE);
             }
         });

         String json = xStreamJ.toXML(map);
         System.out.println("JSON："+ json);
     }
 }