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:
"+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:
"+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:
"+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);
    }
}