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xStream框架
xStream可以轻易的将Java对象和xml文档相互转换，而且可以修改某个特定的属性和节点名称，而且也支持json的转换；
前面有介绍过json-lib这个框架，在线博文：http://www.cnblogs.com/hoojo/archive/2011/04/21/2023805.html
以及Jackson这个框架，在线博文：http://www.cnblogs.com/hoojo/archive/2011/04/22/2024628.html
它们都完美支持JSON，但是对xml的支持还不是很好。一定程度上限制了对Java对象的描述，不能让xml完全体现到对Java对象的描述。这里将会介绍xStream对JSON、XML的完美支持。xStream不仅对XML的转换非常友好，而且提供annotation注解，可以在JavaBean中完成对xml节点、属性的描述。以及对JSON也支持，只需要提供相关的JSONDriver就可以完成转换。
一、准备工作
1、 下载jar包、及官方资源
xStream的jar下载地址：
http://download.csdn.net/detail/u013791374/9636008
官方的示例很全，官方参考示例：http://xstream.codehaus.org/tutorial.html
添加xstream-1.3.1.jar文件到工程中，就可以开始下面的工作；
2、 测试用例代码
通过XStream对象的toXML方法就可以完成Java对象到XML的转换，toXML方法还有2个相同签名的方法，需要传递一个流。然后通过流来完成xml信息的输出。
3、 需要的JavaBean
package com.hoo.entity;
package com.cn.test.objecttoxml;
运行后结果如下：
------------Bean->XML------------
<xml>
2、 将List集合转换成xml文档
/**
* <b>function:</b>将Java的List集合转换成XML对象
* @author hoojo
* @createDate Nov 27, 2010 12:20:07 PM
*/
public static void main(String[] args) { System.out.println(setBean()); } public static String setBean(){ List<Student> list = new ArrayList<Student>(); Student sd = new Student(); sd.setId(1); sd.setName("张无忌");
sd.setEmail("zhangwuji@sina.com"); sd.setAddress("皖六安"); list.add(sd); Student sd2 = new Student(); sd2.setId(1); sd2.setName("张无忌2"); sd2.setEmail("zhangwuji@sina.com2"); sd2.setAddress("皖六安2");
list.add(sd2); return beanToXml(list); } public static String beanToXml(Object obj){ XStream xst = new XStream(); //xstream list转xml 设置<list>标签别名 xstream.alias("xxx", List.class); xst.alias("xml",List.class);
//aliasPackage 设置包别名 xst.aliasPackage("list", "com.cn.test.objecttoxml"); return xst.toXML(obj); }
上面的代码运行后，结果如下：
----------List-->XML----------
<xml>
如果不加xstream.addImplicitCollection(ListBean.class, "list");
这个设置的话，会出现一个List节点包裹着Student节点元素。添加addImplicitCollection可以忽略这个list节点元素。那么上面的list节点就不存在，只会在beans元素中出现name、student这2个xml元素标签；
setMode是设置相同的对象的引用方式，如果设置XStream.NO_REFERENCES就是不引用，会输出2分相同的Student元素。如果是XStream.ID_REFERENCES会引用相同的那个对象的id属性，如果是XStream.XPATH_ABSOLUTE_REFERENCES引用，那么它将显示xpath路径。上面采用的id引用，<student reference="3"/>这个引用了id=3的那个student标签元素；
useAttributeFor是设置某个节点显示到父节点的属性中，也就是将指定class中的指定属性，在这个class元素节点的属性中显示。
如：<student><name>hoojo</name></student>
设置好后就是这样的结果：<student name=”hoojo”></student>
aliasAttribute是修改属性名称。
3、 Map集合转换xml文档
/**
* <b>function:</b>Java Map集合转XML
* @author hoojo
* @createDate Nov 27, 2010 1:13:26 PM
*/
@Test
public void writeMap2XML() {
try {
Map<String,Student> map = new HashMap<String,Student>();
} catch (Exception e) {
e.printStackTrace();
}
}
public static String beanToXml(Object obj){
XStream xst = new XStream();
//不需要设置MAP.CLASS
//xst.alias("xml",Map.class);
xst.alias("student", Student.class);
xst.alias("key", String.class);
xst.useAttributeFor(Student.class, "id");
//aliasPackage 设置包别名
return xst.toXML(obj);
}
运行后结果如下：
---------Map --> XML---------
<map>
5、 用OutStream输出流写XML
/**
* <b>function:</b>用OutStream输出流写XML
* @author hoojo
* @createDate Nov 27, 2010 1:13:48 PM
*/
@Test
public void writeXML4OutStream() {
try {
out = xstream.createObjectOutputStream(System.out);
Student stu = new Student();
stu.setName("jack");
Classes c = new Classes("一班", bean, stu);
c.setNumber(2);
failRed("---------ObjectOutputStream # JavaObject--> XML---------");
out.writeObject(stu);
out.writeObject(new Birthday("2010-05-33"));
out.write(22);//byte
out.writeBoolean(true);
out.writeFloat(22.f);
out.writeUTF("hello");
} catch (Exception e) {
e.printStackTrace();
}
}
使用输出流后，可以通过流对象完成xml的构建，即使没有JavaBean对象，你可以用流来构建一个复杂的xml文档，运行后结果如下：
---------ObjectOutputStream # JavaObject--> XML---------
<object-stream>
<com.hoo.entity.Student>
<id>0</id>
<name>jack</name>
</com.hoo.entity.Student>
<com.hoo.entity.Birthday>
<birthday>2010-05-33</birthday>
</com.hoo.entity.Birthday>
<byte>22</byte>
<boolean>true</boolean>
<float>22.0</float>
<string>hello</string>
</object-stream>
三、XML内容转换Java对象
1、 将xml文档转换成Java对象
/**
* <b>function:</b>将XML字符串转换成Java对象
* @author hoojo
* @createDate Nov 27, 2010 2:39:06 PM
*/
@Test
public void readXml2Object() {
try {
Student sd = new Student();
sd.setId(1);
sd.setName("张无忌");
sd.setEmail("zhangwuji@sina.com");
sd.setAddress("皖六安");
xst.alias("xml",obj.getClass());
String xmlStr = xst.toXML(obj);
System.out.println("java对象转xml："+xmlStr);
Student sdt = (Student)xst.fromXML(xmlStr);
System.out.println("对象转换xml方法："+sdt.toString());
} catch (Exception e) {
e.printStackTrace();
}
}
运行后结果如下：
-----------Xml >>> Bean--------------java对象转xml：<xml> <id>1</id> <name>张无忌</name> <email>zhangwuji@sina.com</email> <address>皖六安</address></xml>对象转换xml方法：Student[id=1,name=张无忌,email=zhangwuji@sina.com,address=皖六安]
怎么样，成功的完成XML到JavaBean、List、Map的转换，更多对象转换还需要大家一一尝试。用法类似~这里就不一样赘述。
四、XStream对JSON的支持
xStream对JSON也有非常好的支持，它提供了2个模型驱动。用这2个驱动可以完成Java对象到JSON的相互转换。使用JettisonMappedXmlDriver驱动，将Java对象转换成json，需要添加jettison.jar
1、 用JettisonMappedXmlDriver完成Java对象到JSON的转换
/**
* <b>function:</b>XStream结合JettisonMappedXmlDriver驱动，转换Java对象到JSON
* 需要添加jettison jar
* @author hoojo
* @createDate Nov 27, 2010 1:23:18 PM
*/
@Test
public void writeEntity2JETTSON() {
failRed("=======JettisonMappedXmlDriver===JavaObject >>>> JaonString=========");
xstream = new XStream(new JettisonMappedXmlDriver());
xstream.setMode(XStream.NO_REFERENCES);
xstream.alias("student", Student.class);
fail(xstream.toXML(bean));
}
运行后结果如下：
=======JettisonMappedXmlDriver===JavaObject >>>> JaonString=========
{"student":{"id":1,"name":"jack","email":"jack@email.com","address":"china","birthday":[{},"2010-11-22"]}}
JSON的转换和XML的转换用法一样，只是创建XStream需要传递一个参数，这个参数就是xml到JSON映射转换的驱动。这里会降到两个驱动，分别是JettisonMappedXmlDriver、JsonHierarchicalStreamDriver。
2、 JsonHierarchicalStreamDriver完成Java对象到JSON的转换
/**
* <b>function:</b>用XStream结合JsonHierarchicalStreamDriver驱动
* 转换java对象为JSON字符串
* @author hoojo
* @createDate Nov 27, 2010 1:16:46 PM
*/
@Test
public void writeEntiry2JSON() {
failRed("======JsonHierarchicalStreamDriver====JavaObject >>>> JaonString=========");
xstream = new XStream(new JsonHierarchicalStreamDriver());
//xstream.setMode(XStream.NO_REFERENCES);
xstream.alias("student", Student.class);
failRed("-------Object >>>> JSON---------");
fail(xstream.toXML(bean));
//failRed("========JsonHierarchicalStreamDriver==删除根节点=========");
//删除根节点
xstream = new XStream(new JsonHierarchicalStreamDriver() {
public HierarchicalStreamWriter createWriter(Writer out) {
return new JsonWriter(out, JsonWriter.DROP_ROOT_MODE);
}
});
//xstream.setMode(XStream.NO_REFERENCES);
xstream.alias("student", Student.class);
fail(xstream.toXML(bean));
}
运行后结果如下：
======JsonHierarchicalStreamDriver====JavaObject >>>> JaonString=========
-------Object >>>> JSON---------
{"student": {
"id": 1,
"name": "jack",
"email": "jack@email.com",
"address": "china",
"birthday": {
"birthday": "2010-11-22"
}
}}
{
"id": 1,
"name": "jack",
"email": "jack@email.com",
"address": "china",
"birthday": {
"birthday": "2010-11-22"
}
}
使用JsonHierarchicalStreamDriver转换默认会给转换后的对象添加一个根节点，但是在构建JsonHierarchicalStreamDriver驱动的时候，你可以重写createWriter方法，删掉根节点。
看上面的结果，一个是默认带根节点的JSON对象，它只是将类名作为一个属性，将对象作为该属性的一个值。而另一个没有带根属性的JSON就是通过重写createWriter方法完成的。
3、 将List集合转换成JSON字符串
@Test
public void writeList2JSON() {
failRed("======JsonHierarchicalStreamDriver====JavaObject >>>> JaonString=========");
JsonHierarchicalStreamDriver driver = new JsonHierarchicalStreamDriver();
xstream = new XStream(driver);
//xstream = new XStream(new JettisonMappedXmlDriver());//转换错误
//xstream.setMode(XStream.NO_REFERENCES);
xstream.alias("student", Student.class);
List<Student> list = new ArrayList<Student>();
list.add(bean);//add
bean = new Student();
bean.setAddress("china");
bean.setEmail("tom@125.com");
bean.setId(2);
bean.setName("tom");
Birthday day = new Birthday("2010-11-22");
bean.setBirthday(day);
list.add(bean);//add
bean = new Student();
bean.setName("jack");
list.add(bean);//add
fail(xstream.toXML(list));
//failRed("========JsonHierarchicalStreamDriver==删除根节点=========");
//删除根节点
xstream = new XStream(new JsonHierarchicalStreamDriver() {
public HierarchicalStreamWriter createWriter(Writer out) {
return new JsonWriter(out, JsonWriter.DROP_ROOT_MODE);
}
});
xstream.alias("student", Student.class);
fail(xstream.toXML(list));
}
运行后结果如下
======JsonHierarchicalStreamDriver====JavaObject >>>> JaonString=========
##{"list": [
{
"id": 1,
"name": "jack",
"email": "jack@email.com",
"address": "china",
"birthday": {
"birthday": "2010-11-22"
}
},
{
"id": 2,
"name": "tom",
"email": "tom@125.com",
"address": "china",
"birthday": {
"birthday": "2010-11-22"
}
},
{
"id": 0,
"name": "jack"
}
]}
#[
{
"id": 1,
"name": "jack",
"email": "jack@email.com",
"address": "china",
"birthday": {
"birthday": "2010-11-22"
}
},
{
"id": 2,
"name": "tom",
"email": "tom@125.com",
"address": "china",
"birthday": {
"birthday": "2010-11-22"
}
},
{
"id": 0,
"name": "jack"
}
]
上面的list1是使用JsonHierarchicalStreamDriver 转换的，当然你也可以使用JettisonMappedXmlDriver驱动进行转换；用JettisonMappedXmlDriver转换后，你会发现格式不同而且没有根属性。
4、 Map转换json
@Test
public void writeMap2JSON() {
failRed("======JsonHierarchicalStreamDriver==== Map >>>> JaonString=========");
xstream = new XStream(new JsonHierarchicalStreamDriver());
//xstream = new XStream(new JettisonMappedXmlDriver());
xstream.alias("student", Student.class);
Map<String, Student> map = new HashMap<String, Student>();
map.put("No.1", bean);//put
bean = new Student();
bean.setAddress("china");
bean.setEmail("tom@125.com");
bean.setId(2);
bean.setName("tom");
bean.setBirthday(new Birthday("2010-11-21"));
map.put("No.2", bean);//put
bean = new Student();
bean.setName("jack");
map.put("No.3", bean);//put
fail(xstream.toXML(map));
//failRed("========JsonHierarchicalStreamDriver==删除根节点=========");
//删除根节点
xstream = new XStream(new JsonHierarchicalStreamDriver() {
public HierarchicalStreamWriter createWriter(Writer out) {
return new JsonWriter(out, JsonWriter.DROP_ROOT_MODE);
}
});
xstream.alias("student", Student.class);
fail(xstream.toXML(map));
}
运行后结果如下：
======JsonHierarchicalStreamDriver==== Map >>>> JaonString=========
{"map": [
[
"No.3",
{
"id": 0,
"name": "jack"
}
],
[
"No.1",
{
"id": 1,
"name": "jack",
"email": "jack@email.com",
"address": "china",
"birthday": {
"birthday": "2010-11-22"
}
}
],
[
"No.2",
{
"id": 2,
"name": "tom",
"email": "tom@125.com",
"address": "china",
"birthday": {
"birthday": "2010-11-21"
}
}
]
]}
[
[
"No.3",
{
"id": 0,
"name": "jack"
}
],
[
"No.1",
{
"id": 1,
"name": "jack",
"email": "jack@email.com",
"address": "china",
"birthday": {
"birthday": "2010-11-22"
}
}
],
[
"No.2",
{
"id": 2,
"name": "tom",
"email": "tom@125.com",
"address": "china",
"birthday": {
"birthday": "2010-11-21"
}
}
]
]
5、 将JSON转换java对象
/**
* <b>function:</b>JsonHierarchicalStreamDriver可以将简单的json字符串转换成java对象，list、map转换不成功；
* JsonHierarchicalStreamDriver读取JSON字符串到java对象出错
* @author hoojo
* @createDate Nov 27, 2010 1:22:26 PM
* @throws JSONException
*/
@Test
public void readJSON2Object() throws JSONException {
String json = "{\"student\": {" +
"\"id\": 1," +
"\"name\": \"haha\"," +
"\"email\": \"email\"," +
"\"address\": \"address\"," +
"\"birthday\": {" +
"\"birthday\": \"2010-11-22\"" +
"}" +
"}}";
//JsonHierarchicalStreamDriver读取JSON字符串到java对象出错，但JettisonMappedXmlDriver可以
xstream = new XStream(new JettisonMappedXmlDriver());
xstream.alias("student", Student.class);
fail(xstream.fromXML(json).toString());
//JettisonMappedXmlDriver转换List集合出错，但JsonHierarchicalStreamDriver可以转换正确
//JettisonMappedXmlDriver 转换的字符串 {"list":{"student":[{"id":1,"name":"haha","email":"email","address":"address","birthday":[{},"2010-11-22"]}]},"student":{"id":2,"name":"tom","email":"tom@125.com","address":"china","birthday":[{},"2010-11-22"]}}
json = "{\"list\": [{" +
"\"id\": 1," +
"\"name\": \"haha\"," +
"\"email\": \"email\"," +
"\"address\": \"address\"," +
"\"birthday\": {" +
"\"birthday\": \"2010-11-22\"" +
"}" +
"},{" +
"\"id\": 2," +
"\"name\": \"tom\"," +
"\"email\": \"tom@125.com\"," +
"\"address\": \"china\"," +
"\"birthday\": {" +
"\"birthday\": \"2010-11-22\"" +
"}" +
"}]}";
System.out.println(json);//用js转换成功
List list = (List) xstream.fromXML(json);
System.out.println(list.size());//0好像转换失败
}
运行后结果如下：
haha#1#address#2010-11-22#email
{"list": [{"id": 1,"name": "haha","email": "email","address": "address","birthday": {"birthday": "2010-11-22"}},
{"id": 2,"name": "tom","email": "tom@125.com","address": "china","birthday": {"birthday": "2010-11-22"}}]}
0
JSON到Java的转换是fromXML方法。
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原文地址：http://blog.csdn.net/u013791374/article/details/52608091
